Kaplan Anatomy

How is the nervous system organized?

Into central and peripheral nervous systems

-CNS: neural tube
-PNS: neural crest

How is the peripheral nervous system divided?
It contains cranial and spinal nerves. Their cell bodies might be derived from neural tube (inside CNS) or neural crest (outside CNS, ganglion)
What are the 2 neuron cell types derived from neural crest?
Sensory neurons and postganglionic autonomic neurons
What are the 2 myelin forming cells?
Schwann cells (PNS) and oligodendrocytes (for axons in a tract-CNS)
What are the gaps between myelin segments of a nerve?
Node of Ranvier
What voltage-gated channels are concentrated at a Node of Ranvier?
Sodium channels to produce saltatory conduction
What happens to voltage gated sodium channels in demyelinating disease?
The sodium channels start spreading throughout the lenght of the nerve instead of being concentrated
What are the 2 most common demyelinating diseases?
-Multiple sclerosis (MS): CNS myelin only
-Guillain-Barre syndrome: PNS myelin only
What are the characteristics of multiple sclerosis?
-Symptoms are separated in space and time
-Vision loss (optic neuritis)
-Internuclear ophtalmoplegia (MLF)
-Motor/sensory deficits
-Vertigo
-Neuropsyquiatric problems
What is the only PNS nerve myelinated by oligodendrocytes?
Optic nerve
What are the characteristics of Guillain-Barre?
-Mostly motor
-Acute symmetric ascending inflammatory neuropathy of PNS myelin
-Weakness begins in lower limbs and ascends
-Respiratory failure in severe cases
-Autonomic dysfunction may be prominent
-Cranial nerve involvement is common
-Sensory loss, pain and paresthesias rarely occur
-Reflexes invariably decreased or absent
What is gastrulation?
Is the phase early in the embryonic development during which the single-layered blastula is reorganized into a three-layered structure known as gastrula
What are the 3 layers of the gastrula?
-Ectoderm
-Mesoderm
-Endoderm
Which layer from the gastrula gives rise to the entire nervous system?
Ectoderm
What is the notochord?
It is a structure in the midline under the mesoderm which induces formation of the organ systems by producing inducing factors
What is Sonic Hedgehog?
It is one of the factors produced by the notochord that induces the creation of the nervous system
Where are the nerves initially produced?
The future dorsal midline which will become the back
What is the first neural structure formed?
The neural plate
Which part of the neural tube closes first?
The middle part at day 22-23, followed by the rostral end (day 25) and the caudal end (day 27)
When is Alpha feto-protein elevated?
With any body wall defect
What are 2 classic examples of ventral wall defects?
-Gastroschisis
-Omphalocele
When can AFP be low in pregnancy?
Down syndrome fetus
What marker is specific for open neural tube defect?
Acetylcholinesterase
What are the 2 common neural tube defects?
-Anencephaly (presents with polyhydramnios)
-Spina bifida
What are the 3 primary vesicles of the brain?
-Forebrain
-Midbrain
-Hindbrain
Which are the 5 secondary vesicles of the brain?
-Telencephalon (forebrain)
-Diencephalon (forebrain)
-Mesencephalon (midbrain)
-Metencephalon (hindbrain)
-Myelencephalon (hindbrain)
What structures are derived from the telencephalon?
-Cerebral hemispheres
-Most basal ganglia
-Lateral ventricles (remnants)
What structures are derived from the diencephalon?
-Thalamus
-Hypothalamus
-Subthalamus
-Epithalamus (pineal gland, retina and optic nerve)
-Third ventricles (remnants)
What structures are derived from the mesencephalon?
-Midbrain
-Cerebral aqueduct
What structures are derived from the metencephalon?
-Pons
-Cerebellum
-Fourth ventricle (together with myelencephalon) (remnants)
What structures are derived from the myelencephalon?
-Medulla
-Fourth ventricle (together with metencephalon) (remnants)
What does the thalamus do?
Filter and relay information to the cortical area in the brain
What does the hypothalamus do?
Major controller of the organism’s autonomic and endocrine functions
What is the epithalamus?
It is another name for the pineal gland
What is the subthalamus?
It is the basal ganglia
What are the characteristics of anencephaly?
-Failure of the anterior neuropore to close
-No brain development
-Incompatible with life
-Increased AFP during pregnancy
-Increased AChE
-Polyhydramnious
What are the types of spina bifida?
-Spina bifida occulta (AFP is normal)
-Spina bifida cystica with meningocele (AFP increased)
-Spina bifida cystica with meningomyelocele (AFP increased)
-Spina bifida with myeloschisis (AFP and AChE increased)
What is spina bifida?
It is the failure of the neural tube to induce bone to form the vertebral arch resulting in missing spinous processes
What are the characteristics of spina bifida occulta?
-Failure of the posterior neuropore to close, or to induce bone growth around it
-Mildest form
-Vertebrae fail to form around the spinal cord
-No increase in AFP
-It is asymptomatic
-There is a tuft of hair over the defect (pathonogmonic)
What is the main characteristic of spina bifida with meningocele?
Meninges protrude through vertebral defect (AFP is increased)
What is the main characteristic of spina bifida with meningomyelocele?
Meninges and spinal cord protrude through the vertebral defect. It is seen with Arnold-Chiari type II
What is the main characteristic of spina bifida with myeloschisis?
It is the most severe form, the spinal cord can be seen externally
What are the differences between type I and type II Arnold-Chiari malformations?
-Type I
-Most common
-Mostly asymptomatic (later can develop syrinx)
-Downward displacement of cerebral tonsils onto the foramen
-Type II
-More often symptomatc
-Downward displacement of cerebral vermis and medulla
through foramen magnum
-Compression of 4th ventricle (obstructive hydrocephaly)
-Frequent lumbar meningomyelocele
-Frequent association with syringomyella (more in type I)
What causes Arnold-Chiari?
Downward protrusion of different parts of the cerebellum into the foramen magnum
What is the Dandy-Walker syndrome?
Congenital defect failing to open the foramina of Lushka and Magendie causing a dilation of the 4th ventricle. There is agenesis of cerebral vermis and splenium of the corpus
What is syrinx?
It is an enlargement of the central canal of the spinal cord
What is holoprosencephaly?
It is incomplete separation of cerebral hemispheres, there is only one ventricle in the telencephalon and it seen in trisomy 13 (Patau)
What are the 2 derivatives of ectoderm?
Neuroectoderm and surface ectoderm
What are the derivatives of surface ectoderm?
-Epidermis
-Hair
-Nails
-Inner and external ear
-Enamel of teeth
-Lens of the eye
-Anterior pituitary (Rathke pouch)
-Parotid gland
-Anal canal below pectinate line
What are the derivatives of neural tube neuroectoderm?
-CNS
-Retina and optic nerve
-Pineal gland
-Neurohypophysis
-Astrocytes
-Oligodendrocytes
What are the derivatives of the neural crest of the neuroectoderm?
-Adrenal medulla
-Ganglia: sensory (unipolar) and autonomic (postganglionic)
-Pigment cells (melanocytes)
-Schwann cells
-Meninges: pia and arachnoid matter
-Pharyngeal arch cartilage (first arch syndromes)
-Odontoblast
-Parafollicular (C) cells
-Aorticopumonary septum (Tetrallogy of Fallot)
-Endocardial cushions (Down Syndrome)
What are the derivatives of surface mesoderm?
-Muscle (smooth, cardiac and skeletal)
-Connective tissue
-All serous membranes
-Bone and cartilage
-Blood lymph and cardiovascular organs
-Adrenal cortex
-Gonads and internal reproductive organs
-Spleen
-Kidney and ureter
-Dura mater
What are the derivatives of surface endoderm?
-Epithelial lining of:
-GI tract (foregut, midgut and hindgut)
-Lower respiratory system (larynx, trachea, bronchi and lungs)
-GU system (urinary bladder, urethra and lower vagina)
-Pharyngeal pouches (auditory tube and middle ear, palatine
tonsils, parathyroid glands, thymus)
-Parenchyma of:
-Liver
-Pancreas
-Submandibular and sublingual glands
-Follicles of the thyroid glands
What is a craniopharyngioma?
It is a persistance or remnant of oral ectoderm (Rathke’s pouch)
Why is the adrenal medulla derived from the neural crest?
Because it is an autonomic ganglion
Where are melanocytes found?
In the basal layers of the epidermis
Where is the most common place for an individual to develop a Schannoma?
On the cerebellar pontine angle, myelinated axons of cranial nerve VIII
What are the functions of the autonomic nervous system?
It is responsible for the motor innervation of all smooth muscle, the heart and all the glands
What subdivisions make up the ANS?
Sympathetic and parasympathetic
Which 2 neurons make up the motor innervation?
-Preganglionic neuron (cell body inside CNS)
-Postganglionic neuron (cell body in a ganglion in the PNS)
What is the neurotransmitter and its receptor used in all preganglionic autonomic neuron?
ACh and Nicotinic (Nn) receptors
What array of receptors are in the cells innervated by postganglionic neurons?
Muscarinic (M) and different adrenergic receptors (NE alpha and beta)
What are the 4 cranial nerves that carry preganglionic parasympathetic axons out of the brain stem?
-Cranial nerves III, VII and IX (innervate glands and smooth muscle of the head)
-Cranial nerve X (innervate viscera of neck, thorax, foregut and midgut)
What sacral nerves carry preganglionic parasympathetic axons out of the brain stem?
Pelvic splanchnic nerves (S1,S3,S4) innervate hindgut and pelvic viscera (including bladder and erectile tissue)
What structures is the parasympathetic innervation limited to?
Visceral structures in or near body cavities not in the body wall or vascular smooth muscle
What 2 smooth muscles does CN III innervate?
-Pupillary sphincter
-Ciliary muscle
What are all of the parasympathetic functions of CN VII?
Glands (most clinically relevant is the lacrimal gland)
Where does CN IX parasympathetics lead to?
Parotid gland
What is Horner’s syndrome?
It is a pathology characterized by ipsilateral ptosis, miosis and anhydrosis
What are the types of Horner’s syndrome?
-Painful Horner’s (with internal carotid dissection)
-Central Horner’s (CNS lesion with tract sign)
What is a Pancoast tumor?
It is a tumor of the lung apex
Which nerves carry preganglionic sympathetic axons?
T1-L2
Where do the preganglionic sympathetic axons end up?
On the paravertebral ganglia
What is the main role of the sympathetic chain?
To innervate the body wall (sweat glands, vascular smooth muscle)
What part of the brain controls autonomic function?
Hypothalamus
Which 3 neurons are needed for sympathetic innervation?
-1st neuron in the hypothalamus
-2nd neuron in the thoracolumbar spinal cord
-3rd ganglion outside the spinal cord
What is the main sign to differentiate a central Horner’s and other types of Horner’s?
In central Horner’s there is a tract problem added to the typical Horner’s signs
What are the major glial cells that are found in the nervous system?
-Oligodendrocytes: form myelin (CNS)
-Astrocytes: maintains the blood-brain barrier with the foot processes
-Schwann cells: form myelin (PNS)
-Ependymal cells: ciliated neurons that line the ventricles and central canal of the spinal cord
-Microglia: form part of the mononuclear phagocyte system (target of HIV-1 in CNS)
What is the difference of Schwann cells and oligodendrocytes in respecto to the amount of cells they myelinate?
Scwann cells myelinate just one cell and oligodendrocytes myelinate many axons
How do cells communicate with other neurons or tissues?
Via neurotransmitters
Where is the neurotransmitter synthesized in the neuron?
Nissl substance (RER)
How is the neurotransmitter transported from the cell body to the synapse?
Via anterograde axonal transport
What are the specific organelles that facilitate both retrograde and anterograde transport?
Microtubules, facilitated by kinesin and dynein
What is kinesin?
Is an ATPase protein that carries organelles and vesicles along microtubules in an anterograde direction
What is dynein?
Is an ATPase protein that carries organelles and vesicles along microtubules in an retrograde direction
Which transport has more clinical significance in neurons, anterograde or retrograde?
Retrograde, because axons can pick up viruses and transport them to the cell bodies (herpes, polio, rabies and tetanus)
What is the speed of retrograde and anterograde transport in neurons?
-Retrograde: 200 mm/day
-Anterograde: 400 mm/day
What happens to a segmented axon distal of the injury site?
Anterograde (Wallerian) degeneration
What would be a predictor of the capacity of a severed neuron to regenerate?
Only axons that are myelinated by Schwann cells have the capacity to regenerate
What is the regeneration rate of a nerve?
1-3 mm per day
What is the endoneurium?
A delicate layer of connective tissue produced by Schwann cells that is required for a nerve to regenerate
What are the main brain neoplasms?
-Glioblastoma multiforme (most common)
-Astrocytoma
-Oligodendroglia
-Epyndimoma
-Medulloblastoma
-Meningioma (2nd most common)
-Schwanoma (3rd most common)
-Retinoblastoma
-Craniopharingioma
What is the most common highly malignant brain tumor?
Glioblastoma multiforme
What is the foramen of Monroe?
Is the foramen that connects the lateral ventricle with the 3rd ventricle
Where is the 4th ventricle located?
Between pons, medulla and cerebellum
What channel connects the 3rd and 4th ventricles?
Cerebral (Sylvius) aqueduct
What is the site of production of CSF?
Choroid plexus in all ventricles
Where is CSF reabsorbed?
Arachnoid granulations in the superior sagittal sinus
How does CSF communicate from the ventricles to the surrounding subarachnoid space?
Through Lushka (2) and Magendie (1) foramina
How much CFS is produced and secreted on a daily basis?
400-500 cc
How much CSF is contained in the ventricles and subarachnoid space?
100-150 cc at a time
What are the classic types of hydrocephalus?
-Noncommunicating (obstruction within ventricles)
-Communicating (impaired reabsorption)
-Normal pressure (chronic)
-Ex vacuo (excess fluid in zones where brain tissue has degenerated)
What typical triad is manifested in normal pressure hydrocephalus?
-Dementia
-Apraxic gait
-Urinary incontinence
How many spinal nerves are there?

31 pairs

-8 cervical
-12 thoracic
-5 lumbar
-5 sacral
-1 cocciygeal

What type of neurons are located in the dorsal and ventral horns of the spinal cord?
-Sensory: dorsal horn
-Motor: ventral horn
Where in the spinal cord are the brachial (C5-T1) and lumbar (L2-S3) plexus located?
In the cervical and lumbar enlargement respectively
What is located in the lateral horn or intermediate zone?
Preganglionic autonomic neurons and Clarke’s nucleus
What is Clarke’s nucleus?
It is a sensory nucleus that carries proprioception information to the cerebellum
What makes up a spinal nerve?
A dorsal (sensory) root and a ventral (motor) root
What is the difference in nomenclature between dorsal roots that come from muscle and those that come from skin?
Those that come from muscle are named with roman numerals (I, II, III, IV) and those that come from skin are named with greek letters (A-Beta, A-delta, C)
What kind of sensory receptors do we find in muscles?
-Muscle spindle (stretch receptors)
-Golgi tendon organ (force receptors) (inhibit muscles with excessive contraction)
Which are the thickest of the dorsal roots?
The ones that come from muscle
Which fibers carry propioception information via the dorsal roots?
Type Ia and Ib
Which sensory fibers do not enter through the dorsal horns?
The medial division. Propioceptive (Ia, Ib) and touch (II, A-beta) fibers
Which are the thinnest sensory neurons?
Pain and temperature fibers (lateral division)
Which fibers carry information about cold and sharp pain to the dorsal horn?
Type III and A-delta fibers
Which fibers carry information about heat and dull pain to the dorsal horn?
Type IV and C fibers
Which sensory fibers synapse in the ventral horn?
Propioception fibers
Which are the 2 kinds of motor neurons in the ventral horn?
-Alpha motor neurons (most important)
-Gamma motor neurons (innervate only muscle spindles to change its sensitivity)
What differentiates the spinal enlargements from the rest of the spinal medulla?
A larger ventral horn due to an increase in the number of motor neurons
What neurons from the ventral horn innervate proximal and distal muscles?
Medial and lateral part respectively
What are Renshaw cells?
Are small interneurons that inhibit alpha motor neurons to prevent muscle spasm. These are affected by tetanus toxin
Which to neurons are needed in order to generate a voluntary muscle contraction?
Upper motor neuron (UMN) and lower motor neuron (LMN)
Where are the UMN cell bodies found?
In the brain’s motor cortex on the contralateral side of the muscle it innervates
Where does the UMN cross to the opposite side?
In the pyramidal decussation in the brain stem at the medulla-spinal cord junction
What tract comprised from the axons of the UMN flows from the motor cortex to the LMN?
Corticospinal or pyramidal tract
Which 2 neurons are used in order to generate a reflex (involuntary) contraction?
Ia dorsal root fibers and LMN
What is the role of the UMN in an involuntary (reflex) contraction?
UMN have an inhibitory effect on reflex contraction
Which are the most commonly tested stretch reflexes?
-Knee or patellar (quads) L2-L4 femoral nerve
-Ankle (gastrocnemius) S1 tibial nerve
-Elbow (biceps) C5-C6 musculocutaneous nerve
-Elbow (triceps) C7-C8 radial nerve
-Forearm (brachioradialis) C5-C6 radial nerve
Where is the corticospinal tract located?
In the lateral side of the white matter throughout the whole spinal cord
What are the 2 main characteristics of all LMN lesions?
They are ipsilateral and affecting only at the level of the lesion
What are the 2 main characteristics of all UMN lesions?
They affect all innervation below the lesion and can be either ipsilateral (in spinal cord) and contralateral (medulla)
What are the signs of UMN lesions?
-Spastic paresis
-Hyperreflexia
-Banbinski sign present
-Increased muscle tone
-Clasp knife reflex
-Disuse muscle atrophy
-Decreased speed of voluntary muscles
-Large area of body involved
What are the signs of LMN lesions?
-Flaccid paralysis
-Areflexia
-Babinski sign absent
-Fasciculations
-Hypotonia or atonia
-Muscle atrophy
-Loss of voluntary movement
-Small area of the body affected
What does the Clasp Knife reflex determine?
A hyperactive Golgi tendon organ
How many pathways and neurons are in charge of conveying sensory information to the brain?
2 pathways with 3 neurons each
Which are the 3 sensory neurons that carry information into the brain?
-First order neuron (A dorsal root neuron) (ipsilateral)
-Second order neuron (medulla) (nucleus cunneatus and gracilis)(ipsilateral)
-Third order neuron (thalamus) (contralateral)
Where does the second order neuron crosses the midline?
At the same level it is located
In what region of the thalamus are the bodies of the third order neurons that carry all body wall sensations located?
Ventroposterolateral (VPL) nucleus
Which are the 2 pathways that carry sensory information into the brain?
-Dorsal column medial lemniscus system
-Anterolateral system (pain and temperature)
What kind of information of the 3 neurons in the DCML system convey?
-Conscious proprioception
-Fine touch
-Vibration
-Pressure
-Two-point discrimination
What tract carries the axons of the first order neurons?
Dorsal columns (fasciculus cuneatus and fasciculus gracilis)
What is the difference between fasciculus cuneatus and gracilis?
Fasciculus cuneatus carries information from above T5 and gracilis T6 and below
What tract is formed from the axons of the second order neurons after they cross the midline?
Medial lemniscus
What are the crossing fibers of the second order neurons called?
Internal arcuate fibers
Where is the body of second order neurons in the anterolateral system?
1-2 segments above and ipsilateral to first order neuron in the grey matter of the dorsal horn
What tract is formed by the crossing axons of second order neurons in the anterolateral system?
Spinothalamic tract
Which tract is longer, the medial lemniscus or the spinothalamic tract?
Spinothalamic tract
What is Lissauer’s tract?
It is formed by the axons of first order neurons of the anterolateral system
What is the ventral white commisure?
The crossing of the fibers of the second order neuron of the anterolateral system
What features can you look for to identify the level of a spinal cord segment?
-Presence of large ventral horn (C5-T1 or L2-S2)
-Presence of both dorsal columns (only above T5)
-Presence of lateral horn (only between T1-L2)
What are the most commonly USMLE tested spinal cord leions?
-Brown-Sequard
-Polio
-Tabes Dorsalis
-Amiotrophic Lateral Sclerosis (ALS)
-Anterior Spinal Artery (ASA) Occlusion
-Subacute Combined Degeneration
-Syringomyelia
What are the main characteristics of Polio?
-Flaccid paralysis
-Muscle atrophy
-Fasciculations
-Areflexia
-Common at lumbar levels
What are the main characteristics of Tabes Dorsalis?
-Demyelinating disease
-Paresthesia
-Pain
-Polyuria
-Sensory ataxia
-Associated with late stage syphilis plus Romberg sign
-Suppressed reflexes
-Argyll Robertson Pupils
-Common at lumbar levels
What are the main characteristics of Amyotrophic Lateral Sclerosis (ALS)?
-Progressive spinal muscular atrophy (ventral horn)
-Primary lateral sclerosis (corticospinal tract)
-Spastic paralysis in the lower limbs
-Increased tone and reflexes
-Flaccid paralysis in upper limbs
-Common in cervical enlargement
What are Argyll Robertson pupils?
Pupils that accommodate but don’t react
What is the main blood supply for the bulk of the spinal cord?
Anterior spinal artery
What are the characteristics of Anterior Spinal Artery Occlussion?
-Similar to ALS but with added sensory loss
-Everything is affected except dorsal columns
-Common at mid-thoracic levels
What are the characteristics of Subacute combined degeneration?
-Similar to Tabes Dorsaales with corticospinal tract affection
-Vit B12 deficiency, pernicious anemia
-Demyelination of the:
-Dorsal columns (central and peripheral myelin)
-Spinocerebellar tracts
-Corticospinal tracts
-Upper thoracic or lower cervical cord
What are the characteristics of Syringomyelia?
-Cavitation of the cord (usually cervical)
-Bilateral loss of pain and temperature at the level of the lesion
-Progresses to muscle weakness, then flaccid paralysis and upper limb atrophy
What are the characteristics of Brown-Sequard Syndrome?
-Affects one side of the spinal cord
-Dorsal columns: ipsilateral loss of position and vibratory senses at and below the level of the lesion
-Spinothalamic tract: contralateral loss of pain and temperature 1-2 segments below the lesion and ipsilateral at the level of the lesion
-CST: ipsilateral paresis below the level of the lesion
-LMN: flaccid paralysis at the level of the lesion
-Descending hypothalamic: ipsilateral horner syndrome (if above T1)
Mhat are the 3 parts of the brain stem?
-Midbrain
-Pons
-Medulla (upper and lower)
What distribution will the corticospinal tract have along the brain stem?
It will run medially and ventrally until the pyramidal decussation in the lower medulla
What is the main difference between a lesion anywhere in the spinal cord and in the brain stem?
All lesions of the tracts are contralateral
What cranial nerves are associated with the brain stem?

From III to XII with the exception of XI

-CN III and IV (midbrain)
-CN V, VI, VII, VIII (pons)
-CN IX, X, XII (upper medulla)

Which cranial nerves are closest to the midline of the brain stem?
CN III, IV, VI and XII (all motor)
Which cranial nerves are furthest from the midline of the brain stem?
CN V, VII, IX and X (all mixed)
What is the main cause of brain stem lesions?
Vascular syndromes
Where in the brain stem are the corticospinal tract, spinothalamic tract, the descending hypothalamic fibers and the medial lemniscus located?
-CST: always medial
-STT and DHF: always lateral
-ML: moves medial to lateral
Which nuclei contain the fibers for CN III?
Oculomotor nucleus and the Edinger-Westphal nucleus
What kind of neurons are in the nucleus of Edinger-Westphal?
Parasympathetic
What is the role of the medial longitudinal Fasciculus (MLF)?
To communicate CN III and VI and help with coordinate horizontal movement of the eyes
Which is the only dorsally exiting cranial nerve in the brain stem?
Trochlear
Which is the only TRUE pontine cranial nerve?
CN V, because it enters/exits through the middle of the pons
Which nuclei give rise to CN V?
The main sensory and the motor nucleus of V
What information do the sensory fibers of CN V carry?
Only facial touch
Which CN nerves exit or enter at the pons-medulla junction?
VI (medially), VII and VIII
Why does a lesion of the abducens nucleus also affects the facial nerve?
Because the facial nerve, as it exits its nucleus it loops closely around the abducens nucleus before exiting
Where does the medial lemniscus start to shift laterally?
At the lower pons level
What helps distinguish an upper medulla segment?
Olivary nucleus
What is the function of the solitary nucleus?
Visceral sensory nucleus that responds mainly to taste derived from CN VII and IX. It also helps regulate changes in blood pressure by receiving sensory information from the carotid body and the carotid sinus
What is the function of the ambiguous nucleus?
It contains lower motor neurons for CN IX and X
What are the 3 most common cranial nerve reflexes tested?
-Light
-Blink
-GagAlways bilateral

Which cranial nerves are sensorial, motor and mixed?
Some Say Marry Money But My Brother Says Big Brains Matter More
(pnemonic)
Which cranial nerves are in charge of moving the eye?
III, IV and VI
When is intortion and extortion of the eye performed?
Only involuntarily when head is tilted to the opposite side
What is the function of the oculomotor nerve in relation to skeletal muscles?
It innervates superior rectus, inferior rectus, medial rectus and inferior oblique. Look up and or in. It also innervates the levator palpebrae superioris (raises eyelids)
What is the function of the oculomotor nerve in relation to smooth muscle?
It innervates the sphincter pupillae (constrict pupils) and ciliary muscle (accommodation)
What is the function of the abducens?
Innervate lateral rectus (abducts)
What is the function of the trochlear nerve?
It innervates the superior oblique (depresses and abducts the eye and intorts involuntary)
What cranial nerve is being tested when the patient is asked to depress the abducted eye?
Trochlear
What are the signs of an oculomotor nerve lesion?
-External strabismus
-Ptosis
-Dilated pupil
-Loss of near response
If there is a compression on the lateral side of the oculomotor nerve, what will be the first sign presented?
Blown pupil, because parasympathetic fibers run on the outside of the nerve
What signs present in a lesion of the trochlear nerve?
-Weaknes looking down on adducted eye
-Trouble going down the stairs
-Head tilts away from lesioned side
What are the components of the trigeminal nerve?
-Ophtalmic (V1) sensory division of the optic nerve
-Maxillary (V2)
-Mandibular (V3)
What are the muscles of mastication?
-temporalis
-Masseter
-Medial pterygoid
-Lateral pterigoid (deficit shows deviation of jaw towards the side of the lesion)
What does the motor aspect of the trigeminal nerve innervate?
-Muscles of mastication
-Anterior belly of digastric
-Tensor palati
-Tensor tympani
-Mylohyoid
What are signs of a facial nerve lesion?
-Drooping corner of mouth
-Cannot wrinkle forehead
-Cannot close eye
-Loss of blink reflex
-Hyperacusis
-Bell’s palsy
-Pain behind ear
-Ageusia (alteration or loss of taste)
-Dry and red eye
What does the facial nerve innervate?
-Muscles of facial expression
-Posterior belly of digastric
-Stylohyoid
-Stapedius
-Submandibular and sublingual glands (salivation)
-Skin behind ear
-Taste (anterior 2/3 of tongue)
-Lacrimal gland (tears)
What is the function of the glossopharyngeal nerve?
-Oropharynx sensation
-Carotid sinus/body
-Parotid gland (salivation)
-Sensation of the posterior 1/3 of tongue (gag reflex with X)
-Stylopharyngeus (only motor function)
What is the function of the vagus nerve?
-Muscles of swallowing except tensor palati and stylopharyngeus
-Muscles of larynx (phonates)
-Sensory of larynx and laryngopharynx
-Sensory of GI tract
-GI tract smooth muscle and glands of foregut and midgut
What are the signs of a vagus nerve lesion?
-Nasal speech
-Nasal regurgitation
-Dysphagia
-Palate droop
-Uvula deviated away from the affected side
-Hoarseness/fixed vocal cord
-Loss of cough and gag reflex
What does the accessory nerve innervate?
-Sternocleidomastoid (head rotation to the opposite side)
-Trapezius (scapular elevation and rotation)
What muscles does the hypoglossal innervate?
-Styloglossus
-Hyoglossus
-Genioglossus
-Intrinsic tongue muscles
What nerve is in charge of tongue movement?
Hypoglossal (lesion causes tongue to point to affected side on protrusion)
What is the difference in the innervation of the 2/3 of the anterior part of the tongue between V3 and VII?
V3 carries information of touch while the facial nerve carries information about taste
Where is the body of the lower motor neuron of CN V located?
In the trigeminal motor nucleus of CN V in the middle of the pons
What is the difference between tactile and pain afferents from the sensory aspect of CN V?

The main difference is the location of the bodies of the second neurons.

-Tactile: main sensory nucleus of CN V near the motor nucleus
-Pain and temperature: spinal trigeminal nucleus below at the lower pons/upper medulla

Where are the bodies of the 3rd sensory neurons of CN V located?
At the ventral posterior medial (VPM) nucleus in the thalamus
What is the main function of the mesencephalic nucleus of CN V?
Jaw propioception
What are the upper motor neuron fibers called in cranial nerves?
Corticobulbar or corticonuclear axons
Which facial motor neurons don’t have bilateral innervation coming from the brain?
The ones that innervate the muscles of the lower half of the face (contralateral)
What are the segments of the ear?
-External ear
-Middle ear
-Inner ear
Which are the bones of the ear?
-Malleus
-Incus
-Stapes
What is the difference between conduction and a sensorineural hearing problem?
Sensorineural involves the inner ear (hair cells) and/or the nerve (VIII). Conduction involves the outer and or middle ear. Air conduction is better than bone conduction in sensorineural and viceversa.
What is the Organ of Corti?
It is the hearing organ that contains an array of hair cells that start at the base of the cochlea at the middle ear, extending all the way up to the apex of the cochlea
What are the different frequency response of hair cells at the base of the cochlea vs hair cells at the apex of the cochlea?
Hair cells at the base respond to the highest frequencies of sound whereas the ones at the apex respond to the lowest frequencies of sound
What is presbycusis?
it is an age related loss of hair cells at the base of the cochlea
What is the cause of hyperacusis?
CN VII
What is the Rinne test?
It is a test where a tuning fork is used to compare bone vs air conduction
What is the endolymph?
It is a specialized extracellular fluid that bathes the cochlear hair cells. It has high potassium and low sodium
What is the cause of Menieur’s disease?
A problem in the circulation of endolymph that increases its volume
Where in the inner ear are the receptors of gravity located?
In the saccule and utricle
Which receptors are located in each of the semicircular ducts?
Ampulla (responds to angular acceleration)
Where are the cell bodies of the cochlear nerve?
In the spiral ganglion
Where does the cochlear nerve enter the brain stem?
Pontocerebellar junction
Where are the 2nd sensory neuron bodies of the cochlear nerve?
Cochlear nucleus
Where is the first site of sound localization that receives information from both ears?
Superior olivary nucleus in the rostral pons
What are the 2 functions of the central auditory system?
-Convey a sound stimulus to cortex
-Help localize the source of a sound in space
Which are the neuronal relay stations above the olivary nucleus for the cochlear nerve?
-Inferior colliculus
-Medial geniculate body
What is the point at which the cochlear fibers cross the midline?
Trapezoid body
What is the vestibulo ocular reflex?
It is the reflex by which the position of the eyes remain constant when the head is moved
What is the mechanism for the vestibulo ocular reflex?
1. Head movements stimulates endolymph on the same side as the head turned
2. Endolymph stimulates hair cells
3. Stimulation of the vestibular nuclei
4. Fibers from vestibular nuclei cross the midline to join the abducens on one eye while other fibers stay ipsilateral and move along the medial longitudinal fasciculus to reach the oculomotor on the other eye
5. This causes a coordinated lateral movement to the opposite side of the head turning
What is nystagmus?
It is an irregular movement of one or both eyes in response mainly to pathology
What is the caloric test?

It is a test in which cold or warm water is poured into the external auditory meatus. Warm water stimulates the ear making the eyes move slowly to the opposite side and, if normal, the eye will quickly turn to the side the water was applied to. Cold water mimics a lesion, so the eyes first move slowly to the side that was stimulated and then quickly away.

COWS: Cold opposite Warm Same

What would an abnormal caloric test indicate?
If the eyes slowly move towards the stimulated side but don’t quickly return the lesion is in the cortex. If the eyes don’t move at all the problem is in the vestibular system.
What is a saccade?
It is a rapid conjugate eye movement
Where are the first motor neurons that generate eye movement?
On the cortex of the frontal lobe (area 8) contralateral to the side the eye moved. Then they cross the midline and synapse with the second motor neuron.
Where is the body of the second motor unit involved in conscious conjugate gaze?
In the paramedian pontine reticular formation (PPRF) in the caudal pons right next to the abducens nucleus
Where is the body of the third motor unit involved in voluntary horizontal conjugate gaze?
In the abducens nucleus
What is the trajectory of the third neuron of the adducting eye in a voluntary horizontal conjugate gaze?
It starts in the contralateral abducens nucleus and then the axons cross to the other side through the medial longitudinal fasciculus (MLF) and synapse with a fourth and last neuron found at the oculomotor nucleus
What is the internuclear ophtalmoplegia?
It is the demyelination of the medial longitudinal fasciculus which carries fibers between the abducens nucleus and the oculomotor nucleus. The patient cannot adduct the eye in lateral voluntary gaze
What is convergence?
It is the capacity of the eyes to adduct when focusing at an object that is moving near
What supplies the blood to the brain stem?
Two vertebral arteries on the ventral surface of the medulla
What are the branches of the vertebral arteries?
-Anterior spinal artery
-Posterior inferior cerebellar artery
What areas does the anterior spinal artery supply blood to?
-Ventrolateral 2/3 of the cervical spinal cord
-Ventromedial part of the medulla
What areas does the posterior inferior cerebellar artery supply blood to?
-Cerebellum
-Dorsolateral part of the medulla
What does the union of the 2 vertebral arteries form?
The basilar artery
What are the branches of the basilar artery?
-Anterior inferior cerebellar artery (lateral caudal pons)
-Paramedian artery (medial pons)
-Superior cerebellar (Rostral lateral pons)
-Posterior cerebellar
What arteries form the circle of Willis?
-Anterior communicating
-Anterior cerebral
-Internal carotid
-Posterior communicating
-Posterior cerebral (medial midbrain)
What are the main arteries that supply blood to the lateral pons and medulla?
-Posterior inferior cerebellar artery (PICA)
-Anterior inferior cerebellar artery (PICA)
-Superior cerebellar artery
What are main aspects of all medullary and brain vascular syndromes?
-It is impossible to have a brain stem vascular syndrome either medially or laterally that does not give a crossed tract sign
-The level can be determined by the motor cranial nerve affected
How can the level of a medial vascular syndrome be determined in the brainstem?

Determining what motor cranial nerve is affected.

-Midbrain (III)
-Pons (VI)
-Medullary (XII)

What are the signs of a vascular medial medullary syndrome in the brain stem (anterior spinal artery)?
-Pyramid: contralateral spastic paresis
-Medial lemniscus: contralateral los of touch and vibration
-XII nucleus/fibers: ipsilateral flaccid paralysis of tongue with deviation to lesion side on protrusion
What are the signs of a vascular lateral medullary syndrome in the brain stem (PICA/Wallenberg syndrome)?
-Inferior cerebellar peduncle: ipsilateral limb ataxia
-Vestibular nuclei: vertigo, nausea/vomiting, nystagmus away from lesion
-Nucleus ambiguous (CN IX,X): ipsilateral paralysis of larynx, pharynx, palate (dysarthria, dysphagia, loss of gag reflex)
-Spinal V: loss of ipsilateral pain and temperature of the face
-Spinothalamic tract:contralateral pain and temperature loss in the body
-Descending hypothalamics: ipsilateral Horner syndrome
What are the signs of a medial pontine syndrome (paramedian branches of the Basillar artery)?
-Corticospinal tract: contralateral spastic hemiparesis
-Medial lemniscus: contralateral loss of tactile/position/vibration sensation
-Fibers of V1: medial strabismus
What are the signs of a lateral pontine syndrome (AICA)?
-Middle cerebellar peduncle: ipsilateral ataxia
-Vestibular nuclei: vertigo, nausea and vomiting, nystagmus
-Facial nucleus and fibers: ipsilateral facial paralysis, loss of taste (anterior 2/3 of tongue), lacrimation, salivation and corneal reflex, hyperacusis
-Spinal trigeminal nucleus/tract: ipsilateral loss of pain and temperature in the face
-Spinothalamic tract: contralateral loss of pain and temperature in the body
-Cochlear nucleus/VIII fibers: ipsilateral hearing loss
-Descending hypothalamics: ipsilateral Horner syndrome
What are the signs of a dorsal midbrain (Parinaud) syndrome (pineal region tumor)?
-Superior colliculus/pretectal area: paralysis of upward gaze, various pupillary abnormalities
-Cerebral aqueduct: non-communicating hydrocephalus
What are the characteristics of a medial midbrain (Weber) syndrome (branches of PCA)?
-Fibers of III: ipsilateral oculomotor palsy (lateral strabismus, dilated pupils, ptosis)
-Corticospinal tract: contralateral spastic hemiparesis
-Corticobulbar tract: contralateral hemiparesis of lower face
What is the function of the cerebellum?
Planning and fine-tuning of skeletal muscle contractions by comparing intended vs. actual performance
Where is the cerebellum located?
Dorsal to the pons and medulla.
How is the cerebellum organized?
-Vermis: controls midline and proximal limbs
-Intermediate hemispheres: distal limbs
-Lateral hemispheres: motor planning
-Folliculonodular lobe: involved in control of balance and eye movements
What is the main function of the olives?
Sound localization (upper) and movement correction and learning (lower)
Where does the major input of the cerebellum travels through?
In the inferior cerebellar peduncle (ICP)(restiform body) and middle cerebellar peduncle (MCP)
Where does the major outflow of the cerebellum travels through?
In the superior cerebellar peduncle (SCP)
What are the 3 layers of the cerebellar cortex?
-Molecular layer
-Purkinje cell layer
-Granule cell layer
What is the most important neuron in the cerebellar cortex?
The purkinje cells. They are the largest cells in the brain and are the only axons that leave the cerebellar cortex
What neurotransmitter do Purkinje cells use?
GABA (inhibitory) (the whole outflow of the cerebellum is inhibitory)
What type of stimuli does the cerebellum receive which uses glutamate as a transmitter?
Excitatory stimulus
What are climbing fibers?
Fibers that synapse directly on Purkinje cells and come from the superior olive
What do climbing fibers do?
Offer information on errors in the execution of movement
What are Mossy fibers?
Are fibers that synapse with granule cells which then carry the excitatory information to Purkinje cells
Where do Purkinje cells synapse?
In the deep cerebellar nuclei (outside the cortex)
Which are the 4 deep cerebellar nuclei?
-Dentate nucleus (lateral hemisphere fibers) (most important)
-Emboliform nucleus (intermediate hemisphere fibers)
-Globose nucleus (intermediate hemisphere fibers)
-Fastigial nucleus (vermal hemisphere fibers)
What is the destination of fibers from the deep cerebellar nuclei?
Cerebral cortex contralateral to the nucleus to find upper motor neurons, synapsing first in tha thalamic motor nuclei (VL/VA)
Why do the signs appear to be ipsilateral to a lesion of the cerebellum if the fibers of the deep nuclei cross to the contralateral side of the cerebral cortex?
Because the upper motor neurons on the corticospinal tract cross again before reaching the lower motor neuron
What does the rubrospinal tract do?
It is a minor upper motor neuron component that controls flexors in the upper limb
What kind of motor problem occurs in a hemisphere cerebellar lesion?
Intent tremor (tremor with movement)
What is dysmetria?
It is difficulty measuring distance (fails finger-to-nose test)
What is the main sign of a patient with dysdiadochokinisia?
Problems performing rapid alternating movements like pronating-supinating hands
What is scanning dysarthria?
Is a disruption of melody in a speech due to asynergy of muscles involved in speech. Patient fragments words into syllables
What are signs of cerebellar problems?
-Intent tremor
-Dysmetria
-Dysdiadochokinisia
-Scanning dysarthria
-Gaze dysfunction (eyes drift off a target in a lateral gaze)
How is a cerebellar hemisphere lesion different from a vermal lesion?
Vermal lesions present problems in trunk and proximal limbs (gait ataxia, postural problems)
How can vermal lesions be differentiated from dorsal columns lesions?
Vermal lesions present problems in balance with eyes open and closed. Dorsal columns present loss of balance only with eyes closed
What is the anterior vermis typically suceptible to?
High alcohol levels cause gait disturbances
What are the typical causes for lesions in the posterior vermis?
Tumors (medulloblastomas and ependymomas) the present with truncal ataxia
What is the major function of the basal ganglia?
Initiate skeletal muscle contractions on desired movements and suppres all unwanted movements that interrupt the desired ones
What are the most important components of the basal ganglia?
-Striatum (telencephalon)
-External and internal segments of Globus Pallidus (telencephalon)
-Substantia Nigra (midbrain)
-Subthalamic Nucleus (diencephalon)
What does the striatum consist of?
Caudate nucleus and putamen
What are the 2 basal ganglia pathways?
-Direct relays in the internal segment of the globus pallidus initiating movement (driven by dopamine)
-Indirect: relays in the external segment of the globus pallidus supressing unwanted movements (driven by acetylcholine)
What is disinhibition phenomenom in the basal ganglia pathways?
It is the inhibition of a neuron that is inhibiting. This causes a net excitation
What is the deficit in Parkinson’s disease?
There is a problem with the direct pathway of the basal ganglia due to a loss of dopaminergic neurons (involuntary tremor)
What is the problem in Huntington’s disease?
GABA neuron loss in the caudate nucleus of the basal ganglia (involuntary tremor)
What are the signs of Parkinson’s disease?
-Bradykinesia
-Cogwheel rigidity
-Pill-rolling tremor
-Shuffling gait
-Stooped posture
-Masked face
-Depression
-Dementia
What are the signs of Huntington’s disease?
-Chorea (multiple, rapid, random movements)
-Athetosis (slow, writhing movements)
-Personality changes
-Dementia
-Onset between 20-40 years
What are Lewy bodies?
They are pinkish intracytoplasmic inclusions caused by a defect in protein folding resulting in an accumulation alpha-synuclein
What is the trinucleotide repeat in Huntington’s?

CAG

Note: remember pnemonic Caudate Atrophy of GABA neurons

What are the characteristics of Wilson’s Disease?
-Tremor (wing beating)
-Asterixis
-Parkinsonian symptoms
-Chorea
-Neuropsychiatric symptoms
-Hepatitis or liver cirrhosis
What is Wilson’s disease?
It is an autosomal recessive defect in copper transport. Copper accumulates in liver, brain and eyes
What are Kayser-Fleischer rings?
They are green-yellow ring around the iris sue to copper deposits in Decemet membrane
What is the treatment for Wilson’s disease?
Penicillamine (chelator) and zinc acetate (blocks absorption)
What is hemiballismus?
It is a movement disorder consisting of ballistic flinging repetitive movements of proximal limbs due to destruction of the contralateral subthalamic nucleus (lacunar stroke)
What makes up the diencephalon?
-Thalamus
-Hypothalamus
-Epithalamus (pinneal body)
-Subthalamus
Which are the thalamic nuclei?
-Ventral posterolateral (VPL)
-Ventral posteromedial (VPM)
-Ventral anterior/Ventral lateral (VA/VL)
-Lateral geniculate body (LGB)
-Medial geniculate body (MGB)
-Anterior nuclei (AN)
-Dorsomedial nuclei (MD)
-Pulvinar
What is the ventral posteromedial nucleus?
It is the thalamic relay for facial sensation and taste
What are the ventral anterior and ventral lateral nuclei?
They are the motor nuclei of the thalamus that relay information from cerebellum and basal ganglia
What is the difference between the lateral and medial geniculate bodies?
-Lateral relays visual information to cortex
-Medial relays auditory information to cortex
Which thalamic nucleus is affected in chronic alcoholics due to vitamin B1 (thiamine) deficiency?
Dorsomedial nucleus, causing memory loss. The mamillary bodies are also affected
Which are the 2 hypothalamic nuclei that project their axons onto the posterior pituitary?
Supraoptic and paraventricular nuclei
What controls the hormone secretion in the anterior pituitary?
The arcuate nucleus by production of releasing and inhibiting factors
Which are the hypothalamic nuclei?
-Lateral hypothalamic (feeding center)
-Ventromedial (fullness center)
-Suprachiasmatic (direct retinal input for circadian rythm)
-Supraoptic and paraventricular (vasopressin/oxitocyn production)
-Mamillary body (memory consolidation)
-Arcuate (produce/release inhibiting/releasing factors)
-Anterior region (temperature regulation)
-Posterior region (temperature regulation)
-Preoptic area (regulates the release of gonadotrophic hormones) (it is sexually dimorphic)
-Dorsomedial
-Epithalamic (releases melatonin)
-Subthalamic (part of indirect basal ganglia pathway)
What would be the consecuences of a tumor in the pineal gland?
Compression of the superior culliculus and pre-tectal area of the mid-brain
What would a compression of the superior colliculus cause?
Compromised vertical conjugate gaze
What would a compression of the pre-tectal area of the mid-brain cause?
Argyll-Robertson pupils and non-communicating hydrocephalus
What are the 3 layers that comprise most of the eye?
-Sclera (type I collagen)
-Choroid
-Retina
Why do patients with osteogenesis imperfecta have blue sclera?
Because sclera is made of type I collagen fibers which are affected in OI so there is thinning of the sclera allowing for the veins in the choroid to be seen
What is found in the choroid layer of the eye?
Retinal blood vessels that supply the eyeball and all innervation of the eye except the optic nerve
What are the 2 smooth muscles of the iris?
Dilator of the pupil (sympathetics) and the constrictor of the pupil (parasympathetics of CN III)
What structure suspends the lens of the eye?
Suspensory ligament that is attached to the ciliary muscle (CN III)
What structure divides the posterior and anterior chambers of the eye?
The pupil
Where is aqueous humor produced?
In the ciliary bodies in the posterior chamber
Where does the aqueous humor drain?
Through canal of Schlemm
What does the obstruction of drainage of the aqueous humor cause?
Increase in intra-ocular pressure that can lead to open-angle glaucoma
What is the most important part of the retina?
The fovea because it contains only cones and it is specialized in visual acuity
What does a patient with age-related macular degeneration (AMD) present?
Central scotoma (loss of central vision)
Which 4 neurons are involved in the pupillary light reflex?
-Optic nerve axons
-Pre-tectal neurons send axons to both Edinger-Westphal Nucleus
-Edinger-Westphal neurons send fibers with CN III to the ciliary ganglion
-Short ciliary nerve (from ciliary ganglion)
What is eye accommodation?
It is a change in the shape of the lens
What are the 3 elements of near response?
-Accommodation
-Convergence
-Pupilary constriction
What is a Marcus Gunn pupil?
It is a lesion of the afferent limb (optic nerve) of pupillary light reflex. In a swingin light test when light is shined in the non-affected eye the response is normal, when is shined on the affected eye the pupils don’t constrict normally, they will dilate back to normal
What is the swinging light test?
Test in which a light is shined on one eye, then on the other eye
What sign results when the pretectal area neuron (2nd in light reflex) is affected by compression or disease?
Argyll Robertson pupils, no reflex with intact accommodation and convergence (light-near dissociated)
What pupillary abnormality is found in lateral CN III compression?
A fixed and dilated pupil (blown) with anisocoria
Name 2 causes of lateral Edinger-Westphal axon compression?
A berry aneurism and transtentorial (uncal) herniation
What is an Adies pupils
It is a result of degeneration of neurons of the ciliary ganglion causing affected pupil to react sluggishly to light but better to accommodation (mono-ocular Agyll Robertson)
What is a Horner’s pupil?
It is a constricted pupil, accompanied by loss of facial sweating and ptosis (ipsilateral to lesion)
What are the 3 transparent media that light must traverse in order to reach the retina?
-Cornea
-Lens
-Vitreous body
Where are the photoreceptors of the retina located?
In the outermost layer
What are the 3 layers of the retina?
-Ganglion layer
-Inner nuclear layer (bipolar cells)
-Outer nuclear layer (nuclei of rods and cones)
What are the characteristics of photoreceptor rods?
-Achromatic
-Used in low light/night vision
-Track movement across visual space
What are the characteristics of cones?
-Chromatic
-Only sensitive in bright light
-They are sensitive
-Used in object recognition
What are the 3 type of cones in the retina?
-Green sensitive
-Blue sensitive
-Red sensitive
Where are the first 2 neurons of visual processing located?
In the retina
What are the 3 neurons involved in visual processing?
-Bipolar cells in the inner nuclear layer
-Ganglion cells (ganglion layer)(optic nerve)
-Neurons in the lateral geniculate body
Which are the fibers of the optic nerve that cross at the chiasm?
The fibers from the nasal retinal axons
What kind of visual loss will a patient with a pituitary tumor?
Temporal hemifield visual loss (tunnel vision)
What are the 2 divisions of the lateral geniculate body (LGB) fibers before they reach the visual cortex?
-Temporal (end up in the lingual gyrus)
-Parietal (end up in the cunneus gyrus)
What is the location of any lesion that causes homonymous anopsia?
Behind the optic quiasm and contralateral to the visual field affected
What are the 2 basic characteristics in relation to the anopsia caused by a lesion in the optic quiasm?
I would be bilateral and heteronymous
What is the main difference between a lesion before the lateral geniculate body and one after?
Before the LGB it would cause a contralateral hemianopsia with suppressed pupillary light reflex and after it would cause a contralateral quadrantanopsia and the pupillary light reflex will be intact
How can a lesion in the primary visual cortex be differentiated from other lesion in the visual pathway?
It will present as a contralateral homonymous hemianopsia with macular (central) sparing due to a dual blood supply to the macular cortex (PCA and MCA)
What are causes of lesions to the visual pathway?
-Optic neuritis
-Central retinal artery occlusion
-Internal carotid artery aneurysm
-Pituitary adenoma (begins as superior quadrantanopsia)
-Craniopharyngioma (begins as an inferior quadrantanopsia)
-Vascular
-Middle cerebral artery (MCA) occlusion
-Posterior cerebral artery occlusion
Where are the primary somatosensory and motor cortex located?
In the postcentral and precentral gyrus respectively
What vascular components supply the cerebral cortex?
-Posterior cerebral
-Middle cerebral (lateral aspect of the hemidphere)
-Anterior cerebral (medial aspect of the hemisphere)
Where is the most common site to get a berry aneurism?
In the circle of Willis it would be in the juncture between and anterior cerebral and an anterior communicatin artery, but in general it would be in the carotid, anterior circulation more than in posterior circulation
What brain hemisphere is dominant for language?
Left hemisphere which contain Broca and Wernicke area
Which are the language centers in the brain?
-Broca area (motor speech)
-Wernicke area (language comprehension)
-Angular gyrus (language comprehension)
What are the prosodic centers?
They are centers located in the right hemisphere of the brain which add emotional content to the speech and to comprehend the emotional content on someone’s speech
Which artery supplies the most part of the medial aspect of the brain hemisphere?
The anterior cerebral artery
Which artery supplies the most part of the lateral aspect of the brain hemisphere?
The middle cerebral artery
What is affected in a premotor cortex lesion?
Motor planning (apraxia: inability to perform a simple motor task in the abscence of weakness)
What are the Broadmann numbers for Broca and Wenicke?
44 and 22 respectively
What are characteristic signs of all afasia types?
-Agraphia
-Impaired ability to repeat
What type of afasia does a lesion in the left prefrontal cortex cause?
Motor, nonfluent or expressive afasia (Broca). They use single syllable words that cannot be used effectively in a sentence. Might present with lower face weakness and weakness in contralateral arm due to motor cortex proximity
What are the characteristics of Wernicke’s afasia?
It is a receptive or sensory afasia. Patients don’t understand what it is said. Their expression is normal but with the misuse of some words. Patients dont get frustrated because they think it is just a hearing problem
What would a lesion in the dominant parietal lobe at the angular gyrus (Gertsmann syndrome) cause?
They will present alexia with agraphia, finger agnosia, acalculia and right-left disorientation
What are characteristics of a lesion in the fiber bundle that connect Broca and Wernicke (arcuate fasciculus)?
-It is a conduction afasia
-Motor speech and understanding is relatively normal
-Can’t repeat
-Patients are aware and frustrated
What would a lesion in the right parietal lobe present?
Asomatognosia, which is a neglect of the contralateral half of the body (stop shaving or puting on make-up on the left side)
What is the importance of the internal capsule?
It carries all of the axons to and from each brain hemisphere
What is the arterial supply for the internal capsule?
-Medial striate branch of the anterior cerebral artery (anterior limb)
-Lenticulostriate branch of the middle cerebral artery (genu and posterior limb)
Which tracts go through each part of the internal capsule?
-Thalamocortical (anterior limb)
-Corticobulbar (genu)
-Corticospinal, all somatosensory thalamocortical projections (posterior limb)
What does the limbic system do?
It plays a role in memory consolidation, sex drive, learning, smell and behaviour
What are the main components of the limbic system?
-Hyppocampus (memory consolidation)
-Amygdala (emotional response center, might cause deja vu)
What is the only neuronal sensory system that can reach cerebral cortex without thalamic relay?
Olfactory system
What is the Papez circuit?
It is a closed neural circuit in the medial limbic system that starts and ends in the hippocampus
What are the parts of the Papez circuit?
-Hippocampus
-Mammilary bodies
-Anterior nucleus of the thalamus
-Cingulate gyrus
What is the hallmark deficit of a loss of hippocampus neurons?
Anterograde amnesia
What parts of the brain are affected in Wernicke-Korsakoff syndrome?
Mamillary bodies and dorsomedial nuclei of the thalamus causing retrograde amnesia with compensatory confabulations
What is the Kluver-Bucy syndrome?
It is a lesion of both sides of the amygdala and hippocampus
What are the characteristics of Kluver-Bucy syndrome?
-Placidity
-Psychic blindness (innapropiate treatment of objects in the visual fields)
-Hypermetamorphosis (visual stimuli are approached as if the were new)
-Increased oral exploratory behaviour
-Hypersexuality and loss of sexual preference
-Anterograde amnesia

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