USMLE Neuro
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- Parkinson's drug that selectively inhibits MAO-B
- selegiline
- epilepsy drug that can cause agranulocytosis
- carbamazepine
- what do you use to treat benzodiazepine overdose?
- flumazenil (competitive antagonist at GABA receptor)
- seizure drug that can cause SLE-like syndrome
- phenytoin
- what is the mechanism of dilantin/phenytoin?
- use-dependent blockade of Na+ channels
- chronic use of this anti-epileptic can cause gingival hyperplasia in kids, peripheral neuropathy, hirsutism, megaloblastic anemia, and malignant hyperthermia
- phenytoin
- mechanism of action of barbiturates?
- facilitate GABA action by increasing duration of Cl- channel opening, thus decreasing neuron firing
- what seizure drug is contraindicated in porphyria?
- barbiturates
- barbiturates do what to the P-450 system?
- induce it
- what epilepsy drug is associated with hepatotoxicity and neural tube defects?
- valproic acid
- what drug is used to treat neuroleptic malignant syndrome (rigidity, myoglobinuria, autonomic instability, hyperprexia)
- dantrolene and dopamine agonists
- tardive dyskinesia can result from long-term use of what class of drugs?
- neuroleptics (antipsychotics) - thioridazine, haloperidol, fluphenazine, chlorpromazine
- schizophrenia drug that can cause agranulocytosis
- clozapine
- side effects of lithium?
- polyuria (ADH antagonist causeing nephrogenic diabetes insipidus), hypothyrodism
- what is the mechanism of action of atypical antipsychotics (clozapine, olanzapine, risperidone)
- block 5-HT2 and dopamine receptors
- what is 'serotonin syndrome'?
- can occur when SSRIs are given with MAOI's - hperthermia, muscle rigidity, CV collapse
- fluoxetine, sertaline, paroxetine, and citalopram are what type of drugs?
- SSRIs
- how do TCAs work?
- block reuptake of NE and serotonin - imipramine, amitrptyline, desipramine, nortriptyline, clomipramine, doxepin
- what TCA can be used for bedwetting?
- imipramine
- which TCA is the least sedating?
- desipramine
- which class of antidepressants has convulsions, coma, arrythmias, respiratory depression as potential toxicities?
- tricyclics
- tricyclics can cause confusion and hallucinations in elderly due to anticholinergic side effects - what do you use?
- nortriptyline
- which of the SSRIs inhibits the P-450 system?
- fluvoxamine
- which atypical antipsychotic can also be used to treat OCD, GAD, depression, mania?
- olanzapine
- what is the mechanism of antipsychotic drugs?
- block dopamine D2 receptors
- this parkinson's drug agonizes dopamine receptors
- bromocriptine
- mechanism of action of amantadine? what is it used for?
- increased dopamine - parkinson's
- entacapone and tolcapone are parkinson's drugs that inhibit what?
- COMT - prevent dopamine breakdown
- this parkinson's drug curbs excess cholinergic activity
- benztropine - antimuscarinic, improves tremor and rigidity but has littel effect on bradykinesia
- mechanism of l-dopa
- increased level of dopamine in brain
- what is l-dopa administered with and why?
- carbidopa - a peripheral decarboxylase inhibitor - increases the bioavailability of l-dopa in the brain and to limit peripheral side effects
- what is sumatriptan and what is it used for?
- 5-HT1D agonist - causes vasoconstriction; used for acute migraine & cluster headache attacks
- sumatriptan is contraindicated in patients with what? why?
- can cause coronary vasospasm, so contraindiicated in pts. with CAD or prinzmental's angina
- which 2 epilepsy drugs can cause stevens-johnson syndrome?
- lamotrigine, ethosuximide
- what is the first line drug for absence seizures?
- ethosuximide
- what is the first line drug for acute status epilepticus?
- benzodiazepines (diazepam or lorazepam)
- what is the first line drug for prophylaxis of status epilepticus?
- phenytoin
- what is the first-line seizure drug for pregnant women, children?
- phenobarbital
- this drug is a first-line treatment for tonic-clonic seizures and trigeminal neuralgia
- carbamazepine
- what is the mechanism of action of benzodiazepines?
- facilitate GABAa action by increasing frequency of Cl- channel opening
- this class of antidepressants can cause sedation, alpha-blocking effects, atropine-like effects (tachycardia, urinary retention)
- TCAs
- what is the mechanism of action of venlafaxine?
- heterocyclic antidepressant - inhibits serotonin, NE, and dopamine reuptake
- mechanism of action of mirtazapine?
- alpha2 agonist - increases release of NE and serotonin, and potent 5-HT2 and 5-HT3 receptor antagonist
- this heterocyclic antidepressant blocks NE reuptake
- maprotiline
- what is the clinical use of MAOIs?
- atypical depression (i.e. with psychotic or phobic features(, anxiety, hypochondriasis
- MAOIs are contraindicated with what two classes of drugs?
- SSRIs and beta blockers (prevent serotonin syndrome)
- what is a sensitive indicator of alcohol use?
- serum gamma-glutamyltransferase
- disinhibition, emotional lability, slurred speech, ataxia, coma, and blackout are signs of what type of intoxication?
- alcohol
- tremor, tachycrdia, hypertension, malaise, nausea, seizures, agitation, hallucinations are signs of withdrawal from what?
- alcohol
- CNS depression, nausea and vomiting, constipation, pinpoint pupils, and seizures may be signs of what type of intoxication?
- opiods
- anxiety, insomnia, anorexia, sweating, dilated pupils, fever, rhinorrhea, piloerection, nausea, cramps, diarrhea, yawning are signs of withdrawal from what type of drug?
- opiods
- psychomotor agitation, impaired judgement, pupillary dilation, hypertension, tachycardia, euphoria, prolonged wakefulness and attention, cardiac arrythmias, delusions, hallucinations, and fever may be signs of what type of intoxication?
- amphetamines
- post use crash, including depression, lethargy, headache, stomach cramps, hunger, and hypersomnolence are characteristic of withdrawal from what?
- amphetamines
- euphoria, psychomotor agitation, impaired judgment, tachycardia, pupillary dilation, hypertension, hallucinations (including tactile), paranoid ideations, angina, and sudden cardiac death may be signs of intoxication with what drug?
- cocaine
- post use crash, including severe depression and suicidality, hpersomnolence, fatigue, malaise, severe psychologial craving are characteristic of withdrawal from what?
- cocaine
- belligerence, impulsiveness, fever, pschomotor agitation, vertical and horizontal nystagmus, tachycardia, ataxia, homicidality, psychosis, and delerium are indicative of intoxication with what drug?
- PCP
- recurrence of intoxication symptoms due to reabsorption in GI tract, sudden onset of severe, random, homicidal violence may occur with withdrawal from what substance?
- PCP
- what 2 drugs are not typically associated with withdrawal symptoms?
- marijuana, LSD
- marked anxiety or depression, delusions, visual hallucinations, flashbacks, and pupil dilation are characteristic of intoxication with what substance?
- LSD
- euphoria, anxiety, paranoid delusions, perception of slowed time, impaired judgment, social withdrawal, increased appetite, dry mouth, and hallucinations are characteristics of what type of substance use?
- marijuana
- which has a higher safety margin: barbiturates or benzodiazepines?
- benzodiazepines
- anxiety, seizures, delerium, life-threatening CV collapse are potential side effects of withdrawal from what?
- barbiturates
- what drug inhibits opiods?
- naltrexone
- this drug of abuse causes pupillary constriction/pinpoint pupils
- opiods
- these 3 drugs of abuse can cause pupillary dilation
- amphetamines, cocaine, LSD
- this drug of abuse can cause vertical and horizontal nystagmus
- PCP
- this drug of abuse can cause angina and sudden cardiac death
- cocaine
- which drug of abuse is associated wtih homicidality?
- PCP
- which epilepsy drug can cause kidney stones?
- topiramate
- name two MAOIs
- phenelzine, tranylcypormine
- what class of benzodiazepines are the most appropriate for acute insomnia and jet lag?
- short-acting, e.g. triazolam
- alpazolam is what type of benzodiazepine and what is it most often used for?
- intermediate-acting; panic attacks
- is secobarbital short- or long-acting?
- short
- what is xerostomia?
- dry mouth
- what type of drug is benztropine?
- anticholinergic - leads to anti-SLUDG side effects
- how do methamphetamine/amphetamine work?
- gain entrance to dopamine and NE nerve terminals, causing the release of these NTs via the uptake carriers; DA is a significant factor in the reinforcing effects of stimulants
- how does supatriptan work?
- serotonin1D agonist
- this type of cell is important for physical support & repair, K+ metabolism, and helps to maintain BBB
- astrocyte
- what are microglia responsible for?
- phagocytosis
- where are ependymal cells found?
- inner lining of ventricles
- from where do microglia originate?
- mesoderm (like macrophages; M)
- how many axons does each oligodendrocyte myelinate?
- multiple - up to 30 each
- what is the predominant type of glial cell in white matter?
- oligodendroglia
- how many axons do Schwann cells myelinate?
- only one each; also promote axonal regeneration
- what fuses to form multinucleated giant cells in CNS of HIV infected patients?
- HIV-infected microglia
- what peripheral nerve layer serves as a permeability layer?
- perineurium - must be rejoined in microsurgery for limb reattachment
- what layer surrounds the entire nerve (fascicles and blood vessles)?
- epineurium
- what peripheral nerve layer invests single nerve fibers?
- endoneurium
- these are found in dermis of palms, soles, and digits
- Meissner's corpuscles
- what is involved in light discriminaory touch of glabrous (hairless) skin?
- Meissner's corpuscles
- these are large, encapsulated nerve endings found in deeper layers of skin at ligamnts, joint capsusles, serous membranes, mesnteries
- pacinian corpuscles
- these are involved in pressure, coarse touch, vibration, and tension
- pacinian corpuscles
- these are cup-shaped nerve endings (tactile disks) in dermis of fingertips, hair follicles, and hard palate that are invovled in light, crude touch
- Merckel's corpuscles
- perilymph is rich in what?
- Na+ (peri- think outside the cell)
- endolymph is rich in what?
- K+ (endo-think inside the cell)
- what does the bony labyrinth include?
- filled with perilymph - cochlea, vestibule, semicircular canals
- what does the membranous labyrinth include?
- filled with endolymph - cochlear duct (within the cochlea), utricle and saccule (within the vestibule), and semicircular canals
- what frequency sound does the base of the cochlea pick up?
- narrow and stiff - picks up high-frequency
- what frequency sounds does the apex of the cochlea pick up?
- wide and flexible - picks up low-frequency
- what do the ampullae detect?
- angular acceleration
- how does hearing loss progress in the elderly?
- high frequency - low frequency
- what do the utricle and saccule contain and detect?
- maculae - detect linear acceleration
- what produces endolymph?
- stria vascularis
- what 3 structures form the blood-brain barrier?
- 1. tight junctions between nonfenestrated capillary membranes 2. basement membrane, 3. astrocyte process
- how do glucose and AA's cross the BBB?
- carrier-mediated transport mechanism
- which crosses the BBB more readily: nonpolar/lipid-soluble substances or polar/water-soluble substances?
- nonpolar/lipid soluble substances
- name 2 specialized brain regions with fenestrated capillaries and no BBB that allow molecules in the blood to affect function or neurosecretory products to enter circulation
- 1. area postrema- vomiting after chemo 2. neurohypophysis - ADH release
- what hypothalamic nucleus is responsible for thirst and water balance?
- supraoptic nucleus
- the neurohypophysis releases hormones that were synthesized where?
- hypothalamic nuclei
- destruction of what hypothalamic nucleus leads to anorexia and starvation?
- lateral nucleus
- destruction of what hypothalamic nucleus leads to hyperphagia and obesity?
- ventromedial (you grow ventrally and medially)
- what part of the hypothalamus regulates the parasympathetic NS?
- anterior
- what part of the hypothalamus regulates the sympathetic nervous system?
- posterior
- what part of the hypothalamus regulates circadian rhythms?
- suprachiasmatic nucleus
- what part of the hypothalamus regulates heat conservation and production when cold?
- posterior hypothalamus
- what part of the hypothalamus coordinates cooling when hot?
- anterior (A/C)
- what part of the hypothalamus controls sexual urges and emotions? (destruction of this nucleus leads to rage)
- septal nucleus (S-sexual/septal)
- the posterior pituitary recieves axonal projections from where?
- supraoptic (ADH) and periventricular (oxytocin) nuclei
- which thalamic nucleus is responsible for relaying visual information?
- lateral geniculate nucleus - (Lateral for Light)
- which thalamic nucleus is responsible for relaying auditory information?
- medial geniculate nucleus (M-music)
- which thalamic nucleus is responsible for relaying body sensation?
- VPL
- which thalamic nucleus is responsible for relaying facial sensation?
- VPM
- which thalamic nucleus is responsible for relaying motor information?
- VA/VL nuclei
- what is the limbic system responsible for?
- feeding, fighting, feeling, flight, and sex (famous 5 Fs)
- premotor area is what Broadman's area?
- 6
- principal motor area is what Broadman's area?
- 4
- principal sensory area is what Broadman's areas?
- 3, 1, 2
- principal visual cortex is what Broadman's area?
- 17
- associative auditory cortex/Wernicke's area is what Broadman's area?
- 22
- primary auditory cortex is what Broadman's area?
- 41, 42
- motor speech/Broca's area is what Broadman's area?
- 44, 45
- frontal eye fields are what Broadman's area?
- 8
- what is most notable in a frontal lobe lesion?
- lack of social judgment
- this supplies the medial surface of the brain, leg-foot area of motor and sensory cortices
- anterior cerebral artery
- what artery supplies the lateral apsect of the brain, trunk-arm-face area of motor and sensory cortices, and Broca's and Wernicke's areas?
- MCA
- what artery is the most common circle of Willis aneurysm; lesion may cause visual field defects?
- anterior communicating artery
- lesion of this artery causes CN III palsy
- posterior communicating artery - common area of aneurysm
- these are known as the 'arteries of stroke'
- lateral striate areries - divisions of MCA
- what do the lateral striate arteries supply?
- internal capsule, caudate, putamen, globus pallidus
- a stroke of what circle leads to general sensory and motor dysfunction and aphasia?
- anterior
- a stroke of what circle leads to cranial nerve deficits, coma, and cerebellar deficits?
- posterior
- cerebral veins drain into what?
- venous sinuses - internal jugular vein
- what is the main location of CSF return via arachnoid granulations?
- superior saggital sinus
- hemisection above TI presents with what?
- Horner's syndrome
- what waveform is present when awake with eyes open?
- beta
- awake with eyes closed - what waveform?
- alpha
- stage 1/light sleep - what waveform?
- theta
- stage 2/deeper sleep - what waveform?
- sleep spindles and K complexes
- stage 3-4/deepest, non-REM sleep, sleepwalking, night terrors, bed-wetting (slow-wave) - what waveform?
- delta - lowest frequency, highest amplitude
- in what stage of sleep is there dreaming, loss of motor tone, possibly a memory processing function, erections, increased brain O2 use?
- REM
- what waveform is associated with REM sleep?
- beta
- serotonergic predominance of raphe nucleus is key to initiating what?
- sleep
- what neurotransmitter reduces REM sleep?
- NE
- what is responsible for the extraocular movements seen during REM sleep?
- PPRF (paramedian pontine reticular formation/conjugate gaze center)
- what drugs shorten stage 4 sleep? what are they therefore useful for?
- benzodiazepines - night terrors and sleepwalking
- why is imipramine used to treat enuresis?
- because it decreases stage 4 sleep
- what happens to pulse and BP during REM sleep?
- increased and variable
- how often does REM sleep occur?
- every 90 minutes - duration increases throughout the night
- what is the principal neurotransmitter involved in REM sleep?
- ACh
- where's the lesion: motor (nonfluent/expressive) aphasia with good comprehension
- Broca's area
- where's the lesion: sensory (fluent/receptive) aphasia with poor comprehension
- Wernicke's area
- where's the lesion: conduction aphasia; poor repetition with good comprehension, fluid speech
- arcuate fasciculus
- where's the lesion: Kluver-Bucy syndrome (hyperorality, hypersexuality, disinhibited behavior)
- bilateral amygdala
- where's the lesion: personality changes and deficits in concentration, orientation, and judgement; may have reemergence of primitive reflexes
- frontal lobe
- where's the lesion: spatial neglect syndrome (agnosia of the contralateral side of the world)
- right parietal lobe
- where's the lesion: coma
- reticular activating system
- where's the lesion: Wernicke-Korsakoff syndrome
- bilateral mammilary bodies
- where's the lesion: tremor at rest, chorea, or athetosis
- basal ganglia
- where's the lesion: intention tremor, limb ataxia
- cerebellar hemisphere (laterally located, affect lateral limbs)
- where's the lesion: truncal ataxia, dysarthria
- cerebellar vermis (centrally located - affects central body)
- where's the lesion: contralateral hemiballismus
- subthalamic nucleus - loss of inhibition of thalamus through globus pallidus
- what do you call slow, writhing movements, especially of fingers? what are these characteristic of?
- athetosis; basal ganglia lesion
- where is Broca's area?
- inferior frontal gyrus
- where is Wernicke's area?
- superior temporal gyrus
- familial form of AD (10%) is associated with genes on what chromosomes?
- 1, 14, 19 - APOE4 allele (ch 21 pApp gene)
- intracellular, abnormally phosphorylated tau protein is associated with what?
- neurofibrillary tangles in AD
- dementia, aphasia, parkinsonian aspects & specificity for frontal and temporal lobes?
- Pick's disease
- intracellular, aggregated tau protein is associated with what?
- Pick bodies
- what disease is associated with Lewy bodies?
- Parkinson's
- what 2 degenerative diseases are associated with spinocerebellar atrophy?
- olivopontocerebellar atrophy, Friedreich's ataxia
- this disease is associated with degeneration of anterior horns
- Werdnig-Hoffman disease
- this disease presents at birth as a 'floppy baby'; tongue fasciculations are characteristic
- Werdnig-Hoffman disease
- how is Werdnig-Hoffman disease inherited; what is the median age of death?
- AR, 7 months
- polio is associated with degeneration of what?
- anterior horns - LMN destruction
- how is poliovirus transmitted?
- fecal-oral
- what are the CSF findings in poliomyelitis?
- lymphocytic pleocytosis with slight elevation of protein
- what is the classic triad associated with MS?
- scanning speech, intention tremor, nystagmus (SIN)
- what is the treatment for MS?
- beta-interferon or immunosuppressant therapy
- the prevalance of this disease increases with distance from equator
- MS
- what are periventricular plaques?
- areas of oligodendrocyte loss and reactive gliosis seen in MS (preservation of axons)
- patients with what disease can present with optic neuritis, MLF syndrome, hemiparesis, hemisensory symptoms, or bladder/bowel incontinence?
- MS
- what is progressive multifocal leukoencephalopathy associated with?
- JC virus - seen in 2-4% of AIDS patients (reactivation of latent virus)
- what is the treatment for Guillain Barre?
- respiratory support until recovery; plasmapheresis, IVIg
- symmetric ascending muscle weakness beginning in distal lower extremities is seen in what disease?
- Guillain Barre
- what are the CSF findings in Guillain Barre?
- elevated CSF protein with normal cell count - albuminocytologic dissociation; elevated protein leads to papilledema
- this disease is marked by inflammation and demyelination of peripheral nerves and motor fibers of ventral roots
- Guillain Barre - sensory effect is less severe than motor
- what are the causes of seizures in children?
- genetic, infection, congenital, trauma, metabolic
- what are the causes of seizures in adults?
- tumors, trauma, stroke, infection
- what are the causes of seizures in elderly?
- stroke, tumor, trauma, metabolic, infection
- this type of seizures involves one area of the brain
- partial
- rupture of middle meningeal artery causing an epidural hematoma is often secondary to what?
- fracture of temporal bone
- what does CT show in epidural hematoma?
- biconvex disk not crossing suture lines
- what kind of intracranial hemorrhage is most likely to be seen in a shaken baby, elderly person, or alcoholic?
- subdural hematoma - rupture of bridging veins
- this type of intracranial hemorrhage is caused by hypertension, amyloid angiopathy, DM, and tumor
- parenchymal hematoma
- what does CT show in the case of subdural hematoma?
- crescent-shaped hemorrhage that crosses suture lines
- what is the drug of choice for status epilepticus?
- diazepam
- what is the most common site of obstruction causing hydrocephalus?
- aqueduct of sylvius
- what is the underlying lesion in retinopathy of prematurity?
- inappropriate proliferation of vessels in the inner layers of the retina
- location at the junction of cortical gray and white matter is typical for what type of tumor?
- metastatic; round shape is also characteristic
- progressive dementia with diffuse loss of deep hemispheric white matter?
- subcortical leukoencephalopathy - Binswanger disease - one of the neurologic syndromes associated with hypertension
- what degenerative disorder is characterized by ophthalmoplegia, pseudobulbar palsy, axial dystonia, and bradykinesia?
- progressive supranuclear palsy - widespread neuronal loss and gliosis in subcortical sites with sparing of the cerebral and cerebellar cortices
- confusion, ataxia, vestibular dysfunction, sluggish pupillary light reflexes, anisocoria, and oculomotor dysfunction are acute sympmtoms as what?
- Wernicke's syndrome - thiamine deficiency usually second to chronic alcohol abuse (chornic form includes anterograde amnesia and confabulation and is called wernicke korsakoff)
- syringomyelia is often associated with what?
- Arnold-Chiari malformation, in which there is a congenital protrusion of the cerebellum and medulla through the foramen magnum
- this type of benign tumor often involves the lateral ventricles of young boys
- choroid plexus papilloma - can affect the caudate because it comprises part of the wall of the lateral ventricle
- atrophy of the caudate and putamen can make what look large on imaging?
- ventricles
- a pituitary tumor that expands laterally will first affect what?
- abducens nerve
- lesion of the right parietal lobe will cause what?
- sensory neglect syndrome of left side (most common pattern in right handed patients)
- what is the most common primary brain tumor?
- glioblastoma multiforme - grade IV astrocytoma
- what stains astrocytes?
- GFAP
- this type of tumor has 'pseudopalisading cells' that border central areas of necrosis and hemorrhage
- glioblastoma multiforme
- this type of brain tumor has spindle cells concentrically arranged in a whorled pattern' psammoma bodies (laminated calcifications)
- meningioma
- this is the second most common type of brain tumor - most often occurs in convexities of hemispheres and parasagittal region
- meningioma
- from what does a meningioma arise?
- arachnoid cells external to brain
- this is the third most common primary brain tumor - originates from Schwann cells
- Schwannoma - often localized to 8th nerve (acoustic neuroma)
- this tpe of tumor contains 'fried egg' cells
- oligodendroglioma - often calcified
- where are oligodendrogliomas most frequently found?
- frontal lobes
- the majority of adult primary tumors are located where?
- supratentorial
- the majory of childhood primary tumors are found where?
- infratentorial
- this tumor has a peak incidence in childhood - diffusely infiltrating glioma, most often found in posterior fossa; benign with good prognosis
- pilocytic (low-grade) astrocytoma
- this type of childhood peak incidence brain tumor has Rosenthal fibers - eosinophilic, corkscrew fibers
- pilocytic (low-grade) astrocytoma
- this is a highly malignant cerebellar tumor & a form of primitive neuroectodermal tumor (PNET); found primarily in children; can compress the 4th ventricle to cause hydrocephalus
- medulloblastoma
- this type of childhood tmor contains rosettes or perivascular pseudorosete pattern of cells & is radiosensitive
- medulloblastoma
- where are ependymomas most commonly found? what is the prognosis?
- 4th ventricle; poor prognosis
- foamy cells and high vascularity are characteristic of what type of childhood-predominant tumor?
- hemangioblastoma
- this type of brain tumor is associated with von Hippel-Lindau
- hemangioblastoma
- this type of tumor shows characteristic perivascular pseudorosettes; rod-shaped blepharoplasts are found near the nucleus
- ependymoma
- this type of child-predominant tumor can produce EPO, leading to secondary polycythemia
- hemangioblastoma
- this is a benign childhood tumor, confused with pituitary adenoma
- craniopharyngioma
- this is the most common childhood supratentorial tumor
- craniopharyngioma
- where does syringomyelia most commonly occur?
- C8-T1
- contralateral paralysis of lower face only
- lesion of motor cortex or connection between cortex and facial nucleus (UMN CN VII)
- cingulate herniation under falx cerebri can compress what?
- anterior cerebral artery
- what results with downward transtentorial (central) herniation?
- coma and death - if compress brainstem
- ipsilateral dilated pupil/ptosis in uncal herniation results from what?
- stretching of CN III
- contralateral homonymous hemianopia in uncal hernaition results from what?
- compression of ipsilatearal posterior cerebral artery
- ipsilateral paresis in uncal herniation results from what?
- compression of contralateral crus cerebri (Kernohan's notch)
- Duret hemorrhages - paraemdian artery rupture in uncal herniation results from what?
- caudal displacement of brain stem
- lesion in MLF results in what on attempted lateral gaze?
- medial rectus palsy; nystagmus is seen in the abducting eye; convergence is normal
- why are local anesthetics less effective in areas of infection?
- they are weak bases and are only effective at penetrating tissue in the unprotonated form - abscesses have lower pH and thus lidocane, etc. becomes protonated and poor anesthesia results
- transient global amnesia usually represents a variant of what?
- TIA (typically in the posterior cerebral territory): migraine and epileptic attacks have also been implicated in some cases of transient global amnesia