Neuroscience Flashcards
Dsyfunction of Broca vs. Wernicke areas (dominant hemisphere)
Dysfunction of Broca’s area → expressive/motor aphasia characterized by slow speech consisting primarily of nouns and verbs (agrammatism) and preserved speech comprehension; patients are often frustrated because they are aware of their problem
Dysfunction of Wernicke’s area → receptive/sensory aphasia characterized by impaired comprehension and fluent aphasia (speech flows readily but is meaningless); patients often lack insight into their problem
Embryonic derivation of microglia cells?
Mesoderm
Embryonic derivation of CNS vs. PNS structures
CNS neurons, ependymal cells, oligodendroglia, and astrocytes → neuroectoderm
PNS neurons, Schwann cells → neural crest
Embryologic derivation of optic nerve and tract
Neural ectoderm → diencephalon
What bones are formed from pharyngeal arch I?
Maxilla
Part of temporal bone
Mandible
Malleus
Incus
Sphenomandibular ligament
What bones are formed from pharyngeal arch II?
Upper part of hyoid
Stapes
Styloid
Stylohyoid ligament
What bones are formed from pharyngeal arch III?
Rest of hyoid
What bones are formed from pharyngeal arch IV and VI?
Laryngeal cartilages
What muscles are formed from pharyngeal arch I?
Muscles of mastication
Mylohyoid
Anterior belly of digastric
Tensor tympani
Tensor veli palatini
What muscles are formed from pharyngeal arch II?
Muscles of facial expression
Stapedius
Stylohyoid
Posterior belly of digastric
What muscles are formed from pharyngeal arch III?
Stylopharyngeus
What muscles are formed from pharyngeal arch IV?
Pharyngeal constrictors
Salpingopharyngeus
Palatopharyngeus
Levator veli palatini
Palatoglossus
Cricothyroid
What muscles are formed from pharyngeal arch VI?
Remaining laryngeals (except cricothyroid)
Which nerve innervates pharyngeal arch I?
CN V3 (mandibular nerve)
Which nerve innervates pharyngeal arch II?
CN VII (facial nerve)
Which nerve innervates pharyngeal arch III?
CN IX (glossopharyngeal nerve)
Which nerve innervates pharyngeal arch IV?
CN X (vagus nerve)
Which nerve innervates pharyngeal arch VI?
CN X (recurrent laryngeal nerve of vagus nerve)
Pharyngeal pouches
1st → auditory tube
2nd → tonsillar crypt
3rd → inferior parathyroids, thymus
4th → superior parathyroids, C cells of thyroid
Innervation of the tongue
Anterior tongue → V3 (sensation), VII (taste)
Middle tongue → IX (sensation and taste)
Posterior tongue → X (sensation and taste)
Motor → XII
Acoustic neuroma
Benign proliferation of Schwann cells
Typically located in internal acoutic meatus (CN VIII)
If bilateral, strongly associated with neurofibromatosis type 2
Oligodendrocytes vs. Schwann cells
Oligodendrocytes → myelinates multiple axons in the CNS; degeneration causes MS, PML, leukodystrophies
Schwann cells → myelineates one axon in the periphery; denegeneration causes Guillain-Barre
Epidural vs. subdural hematoma
Epidural hematoma → biconvex blood collection that doesn’t cross suture lines, rupture of middle meningeal artery
Subdural hematoma → crescent-shaped hemorrhage that crosses suture lines, midline shifts, rupture of bridging veins
Normal pressure hydrocephalus
Decreased CSF absorption by arachnoid granulations → communicating hydrocephalus
Imaging: ventriculomegaly out of proportion to or without corresponsding sulci enlargement
Triad: urinary incontinence (stretching of descending cortical fibers → decreased inhibitory control of bladder contractions), ataxia, cognitive dysfunction (“wet, wobbly, and whacky”)
Tx: removal of CSF
Where to place the needle for lumbar puncture?
Between L3 and L5
(“To keep the cord alive, keep the spinal needle between L3 and L5”)
Lower vs. upper motor neuron lesions
Lower motor neuron lesions
Flaccid paralysis
Fasciculations
Reduced muscle tone
Reduced myotatic reflex
Rapid atrophy
Upper motor neuron lesions
Spastic paralysis
Increased muscle tone
Exaggerated myotatic reflex
Increased resistance to passive stretch
Babinski sign
Slow atrophy
Poliomyelitis
Lesions in spinal anterior horns → ipsilateral lower motor neuron signs
Similar features seen in spinal muscular atrophy (Werdnig-Hoffman disease) → “floppy baby” with hypotonia and tongue fasciculations
What causes spinal anterior horn lesions?
Poliomyelitis
West Nile
Spinal muscular atrophy
Amyotrophic lateral sclerosis
ALS AKA Lou Gehrig disease is caused by a defect in superoxide dismutase I
Riluzole modestly increases survival by decreasing presynaptic glutamate release
Lesions in lateral corticospinal tract and anterior horns → combined UMN and LMN signs → fasiculations with eventual atrophy and weakness of the hands
What cranial nerves traverse the cavenous sinus?
CN III
CN IV
CN VI
CN V1
CN V2
What goes through the optic canal?
CN II (optic nerve) Ophthalmic artery
What goes through the superior orbital fissure?
CN III (occulomotor nerve)
CN IV (trochlear nerve)
CN V1 (ophthalmic nerve)
CN VI (abducens nerve)
Ophthalmic vein
What goes through the foramen rotundum?
CN V2 (maxillary nerve)
What goes through the foramen ovale?
CN V3 (mandibular nerve)
What goes through the foramen spinosum?
Middle meningeal artery Meningeal nerve (V3)
What goes through the internal acoustic meatus?
CN VII (facial nerve)
CN VIII (vestibulocochlear nerve)
What goes through the jugular foramen?
CN IX (glossopharyngeal nerve)
CN X (vagus nerve)
CN XI (spinal accessory nerve) exits
Inferior petrosal sinus
Jugular bulb
What goes through the hypoglossal canal?
CN XII (hypoglossal nerve)
What goes through the foramen magnum?
Brain stem/spinal cord junction
CN XI (spinal accessory nerve) enters
Vertebral arteries
Lesion of the angular gyrus of the dominant parietal lobe (often left lobe)
Supplied by MCA
Gerstmann syndrome: agraphia, acalculia, finger agnosia, left-right disorientation
Cranial nerve most likely to be affected by lesion at the middle cerebellar peduncles
CN V
Where is the lesion that causes hemiballism
Lesion (e.g. lacunar stroke) in contralateral subthalamic nucleus
Hemiballism - sudden, wild flailing of one arm ± ipsilateral leg
Wernicke encephalopathy and Korsakoff syndrome
Wernicke encephalopathy = ataxia, nystagmus, opthalmoplegia, anterograde amnesia
Korsakoff syndrome (temporal lobes) = anterograde and retrograde amnesia (usually permanent), apathy, lack of insight, confabulation
Caused by thiamine deficiency (often secondary to chronic alcoholism and malnutrition) → administration of dextrose can exacerbate thiamine deficiency so always supplement first (thiamine is a cofactor for glycolytic enzymes pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, transketolase)
A/w necrosis of mammillary bodies
Dx: low erythrocyte transketolase activity
Chronic alcoholism may also cause cerebellar atrophy/degeneration → wide-based gait ataxia, truncal instability, intention tremor
Interventricular hemorrhage
Hemorrhage of the germinal matrix into the lateral ventricles as a complication of premature birth
Symptoms may include bulging anterior fontanelle, hypotension, decerebrate posturing, tonic-clonic seizures, irregular respirations, coma
Lesions of the cerebellum
Lateral cerebellum → ipsilateral dysdiadochokinesia, limb dsmetria, intension tremor, propensity to fall towards injured side
Medial cerebellum (vermis) → bilateral truncal ataxia, nystagmus, head tilting, wide-based gait
Dopaminergic pathways in the brain
Mesolimbic (ventral tegmental area to limbic system) → ↑ D2 activity leads to positive symptoms of schizophrenia
Mesocortical (ventral tegmental area to cortex) → ↓ dopaminergic activity leads to negative symptoms of schizophrenia
Nigrostriatal (substantia nigra to the caudate nucleus and putamen) → ↓ dopaminergic activity leads to Parkinsons
Tuberoinfundibular (hypothalamus to pituitary) → ↓ D2 activity leads to hyperprolatinemia
Principles sites of norepinephrine, serotonin, and dopamine synthesis
Norepinephrine → locus ceruleus (posterior rostral pons)
Serotonin → raphe nucleus (pons, medulla, midbrain)
Dopamine → ventral tegmental area, substantia nigra pargs compacta (midbrain)
Innervation of the eye muscles
LR6SO4R3
CN VI (abducens): lateral rectus
CN IV (trochlear): superior oblique
CN III (oculomotor): medial rectus, superior rectus, inferior rectus, inferior oblique
Palsies of the cranial nerves involved in eye movements
CN III (oculomotor) palsy → vertical and horizontal diplopia, ptosis, enlarged and nonreactive pupil, eye is “down and out”
CN VI (abducens) palsy → weakness of lateral rectus → horizontal diplopia
CN IV (trochlear) palsy → weakness of superior oblique → verticle diplopia worse when towards the nose, patient may tilt head away from affected eye
Alzheimers disease
Widespread cortical atrophy (narrowing of gyri and widening of sulci) with decreased acetylcholine levels 2/2 deficiency of choline acetyltransferase
Early onset risk factors (before age 60)
Down Syndrome (extra amyloid precursor protein gene on chromosome 21), presenilin 1 gene (chromosome 14), presenilin 2 gene (chromosome 1) → all promote production of Aβ amyloid
Late onset risk factors (after age 60)
ε4 allele of apolioprotein E → senile plaques?
Protective factors
ε2 allele of apolioprotein E
Huntington disease
AD caused by CAG trinucleotide repeats (chromosome 4) → huntingtin protein → increased histone deacetylation → transcriptional silencing of genes necessary for neuronal survival
Characterized by choreiform movements, aggression, depression, and dementia
Decreased levels of GABA and acetylcholine
Atrophy of the caudate nuclei
Arnold-Chiari malformation
Arnold-Chiari I: small cerebellar tonsillar ectopia, may be asymptomatic or cause headaches, associated with syringomyelia
Arnold-Chiari II: significant herniation of the cerebellar tonsils and the vermis through the foramen magnum with aqueductal stenosis and hydrocephalus
Dandy-Walker
Agenesis of cerebellar vermis with cystic enlargement of the 4th ventricle
Syringomyelia
Cystic cavity within the spinal cord
Anterior spinal commissural fibers damaged → “cape-like” bilateral loss of pain and temperature sensation in upper extremities
A/w Chiari I malformation
Function of the supraoptic nucleus of the hypothalamus
Makes ADH
Function of the paraventricular nucleus of the hypothalamus
Makes oxytocin and anterior pituitary hormones (CRH, TRH)
Function of the ventromedial nucleus of the hypothalamus
Mediates satiety → stimulated by leptin
Destruction causes hyperphagia
(“Zap the ventromedial nucleus and you’ll grow ventrally”)
Function of the lateral nucleus of the hypothalamus
Mediates hunger → inhibited by leptin
Destruction causes anorexia, failure to thrive
(“If you zap the lateral nucleus, you shrink laterally”)
Function of the anterior nucleus of the hypothalamus
Mediates cooling (parasympathetic)
Destruction leads to hyperthermia
(“Anterior nucleus = A/C”)
Function of the posterior nucleus of the hypothalamus
Mediates heating (sympathetic)
Destruction leads to hypothermia
Function of the suprachiasmatic nucleus of the hypothalamus
Circadian rhythm regulation and pineal gland function
Function of the arcuate nucleus of the hypothalamus
Secretion of dopamine, GHRH, GRH
Parkinsons disease
Loss of dopaminergic neurons in the substantia nigra pars compacta
Characterized by resting tremors (pill-rolling), cogwheel rigidity, bradykinesia/akinesia, postural instability, shuffling gait
Associated with Lewy bodies (α-synuclein intracellular eosinophilic inclusions)
Kluver-Bucy syndrome
Bilateral amygdala damage
Characterized by hyperorality, hypersexuality, disinhibited behavior
Associated with HSV-1
Lesion of the angular gyrus of the non-dominant parietal lobe (often right lobe)
Spatial neglect syndrome (agnosia of the contralateral side of the world)
Central pontine myelinolysis
Axonal demyelination in the pontine white matter tracts secondary to osmotic forces and edema
Characterized by acute paralysis, dysarthria, dysphagia, diplopia, loss of consciousness, “locked-in” syndrome
Caused by rapid correction of hyponatremia
Rapid correction of hypernatremia = cerebral edema
Berry aneurysms
Anterior communicating > posterior communicating (a/w CN III palsy)
Associated with ADPKD, Marfan syndrome, Ehlers-Danlos
Brown-Sequard sequence
Caused by hemisection of the spinal cord
Ipsilateral impaired motor function, proprioception, vibration
Contralateral impaired pain and temperature sensation
Nerve roots associted with clinical reflexes
S1, 2 buckle my shoe (Achilles)
L3, 4 kick the door (patellar)
C5, 6 pick up sticks (biceps)
C7, 8 lay them strait (triceps)
S3, 4 anal wink
L1, 2 cremaster
Describe the tonotopy of the cochlea?
High frequency heard best at the base of the choclea near the oval window
Low frequency heard best at the apex near the helicotrema
Visual field deficits
Frontotemporal dementia (Picks disease)
Characterized by dementia, asphasia, parkinsonian features, change in personality
Associated with frontotemporal atrophy, pick bodies (tau protein aggregates)
Lewy body dementia
Characterized by parkinsonian symptoms, dementia, visual hallucinations
Associated with α-synuclein defect
Multiple sclerosis
Autoimmune inflammation and demyelination of the CNS
Characterized by neurologic deficits separated by space and time (relapsing and remitting course)
Symptoms may include scanning speech, intention tremor, incontinence, internuclear ophthalmoplegia, nystagmus, optic neuritis
Dx: oligoclonal IgG in CSF, periventricular plaques on MRI (lipid laden macrophages containing the products of myeline breakdown, loss of myelin sheaths, depletion of oligodendrocytes)
Tx: IFN-β, immunosuppression, natalizumab
Guillain-Barre
Acute inflammatory demyelinating polyradiculopathy caused by autoimmune destruction of Schwann cells that causes demyelination of peripheral nerves with endoneural inflammatory infiltration
Characterized by symmetric ascending muscle weakness/paralysis beginning in the lower extremities
Associated with URI or GI infection (esp. Campylobacter jejuni and CMV)
Progressive multifocal leukoencephalopathy
Demyelination of CNS due to destruction of oligodendrocytes
Associated with JC virus and AIDS
Metachromatic leukodystrophy
Autosomal recessive lysosomal storage disease due to arylsulfatase A deficiency
Characterized by central and peripheral demyelination with ataxia and dementia due to build-up of sulfatide which impairs producion of the myelin sheath
Krabbe disease
Autosomal recessive lysosomal storage disease due to deficiency of galactocerebrosidase
Build of up galactocerebroside and psychosine destroys myelin
Characterized by peripheral neuropathy, developmental delay, optic atrophy, and globoid cells
Adrenoleukodystrophy
X-linked disease due to impaired metabolism of long chain fatty acids
Accumulation damages white matter and adrenal glands
Glioblastoma multiforme (grade IV astrocytoma)
Malignant tumor of astrocytes (GFAP +)
Gross features: can cross corpus callosum (“butterfly glioma”)
Histologic features: “Pseudopalasading”
Prognosis: poor
Pilocytic astrocytoma
Benign tumor of astrocytes (GFAP +)
Gross features: well circumscribed, often found in posterior fossa, cystic + solid
Histologic features: Rosenthal fibers (eosinophilic, corkscrew fibers)
Prognosis: good
Meningioma
Benign tumor of arachnoid cells
Gross features: dural attachment (“tail”),
Histologic features: Spindle cells concentrically arranged in a whorled pattern, psamomma bodies
Oligodendroglioma
Tumor of oligodendrocytes (GFAP +)
Gross features: most often in frontal lobes, often calcified
Histologic features: “Fried egg” cells with round nuclei and clear cytoplasm
Schwannoma
Tumor of Schwann cells (S-100+)
Gross features: usually found at the cerebellopontine angle, often localized to CN VIII (acoustic neuroma)
Histology: highly cellular areas with palisading (Antoni A) interspersed with nuclear-free zones (Verocay body) intermixed with myxoid regions of low cellularity (Antoni B)
Bilateral acoustic neuroma (tinnitus, vertigo, sensorineural hearing loss) associated with neurofibromatosis type II
Medulloblastoma
Malignant tumor of primitive neuroectoderm
Gross features: located in the cerebellum, can compress 4th ventricle causing hydrocephalus, can send drop metastases to the spinal cord
Histologic features: Homer-Wright rosettes, small blue cells
Ependymoma
Tumor of ependymal cells (GFAP +)
Gross features: often found in the 4th ventricle and can cause hydrocephalus
Histologic features: perivascular rosettes, rod-shaped blepharoplasts (basal ciliary bodies) found near nucleus
Prognosis: poor
Craniopharyngioma
Benign tumor of the remnants of Rathke’s pouch
Gross features: cysts filled with brownish-yellow fluid composed of protein and cholesterol crystals, calcification is common (“enamel-like”)
Histologic features: cysts lined by cords/nests of stratified squamous epithalium with peripheral palisading and niternal areas of lamellar “wet” keratin
Gross and histological changes associated with HIV-associated dementia
Subcortical atrophy and groups of microglial nodules around small areas of necrosis that may fuse to form multinucleated giant cells
Creutzfeldt-Jakob disease
Abnormal folding of proteins from α-helices to β-pleated sheets (reorganization of hydrogen bonds) that are resistant to degradation by proteases → PrP accumulates in extracellular space
Characterized by rapidly progressive dementia and myoclonic jerks
Mostly iatrogenic (contaminated corneal transplants, implantable electrodes, growth hormones)
On histology, spongiform encephalopathy (vacuoles in the cytoplasm of neutrophils and neurons → cysts)
Types of seizures
Focal seizures (involves one hemisphere at onset)
Simple: no loss of consciousness or postictal state
Complex: loss of consciousness and postictal state, may have automatisms (e.g. lip smacking)
Generalized seizures (involves both hemispheres at onset)
Tonic-clonic: loss of consciousness and postictal state, diffuse muscle contraction of limbs (tonic) followed by rhythmic jerking (clonic)
Myoclonic: no loss of consciousness or postictal state, brief jerking movements
Absence: brief loss of consciousness (e.g. blank stare), may have automatism, usually no postictal state
Lacunar infarcts vs. Charcot-Bouchard aneurysms
Lacunar infarcts: small ishchemic infarct (< 15 mm) involving deep brain structures associated with chronic HTN which promotes lipohyalinosis, microatheroma formation → hypertensive arteriolar sclerosis
Charcot-Bouchard aneurysms: caused by chronic hyprtension involving the same penetrating arterioles as lacunar strokes but typically lead to intraparenchymal hemorrhage in deep brain structures
Most common cause of intracranial hemorrhage in children vs. elderly
Children: AV malformation
Elderly: cerebral amyloid angiopathy, most often affects occipital and parietal lobes
Autonomic nervous system receptors and neurotransmitters
All preganglionic receptors are nicotinic and use ACh as a neurotransmitter (including adrenal medulla)
Parasympathetic postganglionic receptors are muscarinic and use ACh as a neurotransmitter
Most sympathetic postganglion receptors are α or β and use norepinephrine as a neurotransmitter (eccrine sweat glands are the exception; they have muscarinic receptors and use ACh as a neurotransmitter)
Drug used to prevent vasospasm following a subarachnoid hemorrhage
Nimodipine (calcium-channel blocker)
Parinaud syndrome
Upward gaze palsy, absent pupillary light reflec, impaired conversion
Can be caused by mass effect (e.g. pinealoma) affecting the superior colliculus
Pseudotumor cerebri (idiopathic intracranial hypertension)
Increased ICP in the absense of a tumor or other disease
Typically presents in young obese women with daily headache, bilaterally symmetric papilledema, and transient visual disturbances related to impaired cerebral venous outflow and elevated intracranial pressure. Build-up in pressure compresses the optic nerve impairing axoplasmic flow.
Symptoms are worse during Valsalva as ICP increases
Decerebrate vs. decorticate posturing
