Flashcards in Neurology UWorld Deck (86)
Fulminant meningococcemia resulting in bilateral adrenal hemorrhage.
What does the internal capsule do?
Anterior limb: separates caudate nucleus from globus pallidus and carries some thalamocortical fibers
Genu: carries corticobulbar fibers
Posterior limb: separates thalamus from putamen and globus pallidus and carries corticospinal motor and sensory fibers, visual fibers and auditory fibers.
Genetic associations with Alzheimer's disease
APP on chromosome 21 - Down's syndrome
Presenelin 1 on chromosome 14 - early onset
Presenelin 2 on chromosome 1 - early onset
ApoE4 - late onset
Gabapentin mechanism of action in treatment of seizures
Inhibits pre-synaptic voltage-gated Ca2+ channel and prevents vesicle release
Levatiracetam mechanism of action in treatment of seizures
Disrupts neurotransmitter vesicle fusion
Phenytoin and carbamazepine mechanism of action in treatment of seizures
Prevent action potential generation in the axon hillock and propagation down the axon by inhibiting voltage-gated Na+ channels
A patient presents with mental retardation and low serum levels of serotonin and dopamine and high serum phenylalanine. How should you treat this patient?
Dihydropteridine reductase deficiency results in decreased synthesis of serotonin due to reduced conversion of BH2 to BH4 by dihydropteridine reductase for the enzyme tryptophan hydroxylase. There is also reduced dopamine because phenylalanine hydroxylase and tyrosine hydroxylase need BH4 to convert Phe to tyrosine and tyrosine to DOPA, respectively. This child should avoid Phe-containing foods and receive BH4 supplementation.
Enzyme involved in formation of GABA
Glutamate decarboxylase (from glutamate)
Enzyme involved in formation of glutamate
Glutaminase (from glutamine)
Superior vs. inferior gluteal nerve injuries
Superior = Trendelenberg gait from paralysis of medius and minimus
Inferior = difficulty rising from a chair or climbing stairs due to paralysis of gluteus maximus
Enzyme involved in joining Okazaki fragments on the lagging strand
Lamotrigine side effect
How does toxin from Clostridium tetani cause unregulated firing of primary motor neurons?
Tetanospasmin migrates up motor neurons by retrograde axonal transport to the medulla and spinal cord where it is cleaved and inhibits inhibitory release of GABA and glycine from the spinal inhibitory neurons that results in increased activation of lower motor neurons.
A patient presents after head trauma, unable to grab something palpated by his left hand with his right hand. He is otherwise normal. What structure is most likely affected in this patient?
Corpus callosum lesions can cause split brain syndrome, as seen in this patient.
3 domains of frontal lobe syndrome
Disinhibition, apathy and disorganization
Microscopic features in a patient with Guillain-Barre
Segmental demyelination and endoneural inflammation with lymphocytes and macrophages.
Pathophysiology of Fragile X syndrome
Mutation of FMR1 gene on chromosome X -> 200 CGG repeats -> hypermethylation of DNA -> gene inactivation.
Use of edrophonium
Diagnosis of myasthenia gravis. Condition should improve immediately with this AChE inhibitor. Treat with neostigmine or physostigmine.
What would happen if there were CSF obstruction at the foramen of Monro?
Enlargement of only the one lateral ventricle that drains through that foramen
How does isoniazid cause peripheral neuropathy?
It competes with B6 (pyridoxine) for binding sites in synthesis of multiple neurotransmitters. It also increases excretion of B6, resulting in vitamin deficiency.
Carbamazepine side effects
Marrow suppression, hepatotoxicity and SIADH
Ethosuximide mechanism of action and use
Blocks T-type Ca2+ channels, 1st line for absence seizures.
Cholinergic agonist use in medicine
Bethanochol: used for post-operative ileus and urinary retention
Carbachol and pilocarpine: miosis causes the iris to move further from the cornea, used in treatment of glaucoma
Pupillary light reflex
Light -> CN II -> bilateral pretectal nuclei in superior colliculus of midbrain -> bilateral Edinger-Westphal nuclei -> pre-ganglionic parasympathetic fibers in CN III -> Ciliary ganglion -> post-gangiolonic parasympathetic fibers -> pupillary constriction
Fish toxins that inhibit voltage gated Na+ influx? Ones that keep voltage gated Na+ channels persistently open?
Inhibit influx: tetrodotoxin (pufferfish) and saxitoxin (red tide)
Persistently open: ciguatoxin (eels) and batrachotoxin (frogs)
Valproic acid mechanism of action in seizure treatment
Blocks NMDA receptors, increases K+ efflux, blocks Na+ channels and potentiates GABA receptors.
How does a globus pallidus externus lesion differ from an internus lesion?
In normal physiology, DA binding to D2 -> inhibition of GPe -> disinhibits STN -> GPi stimulation -> thalamic inhibition. A GPe lesion would cause bradykinesia because the STN would never be inhibited -> GPi constitutively activated -> constant thalamic inhibition.
In normal physiology, DA binding to D1 -> inhibition of GPi -> disinhibition of thalamus. A GPi lesion would result in continuous thalamus activation and increased movement.
Symptoms of internal capsular stroke
Contralateral pure facial, UE and LE weakness with UMN lesion signs
What is responsible for the majority of side effects associated with 1st generation anti-histamines?
Anticholinergic, anti-serotonergic and alpha-blocking effects