Neuro 2 Flashcards
What do the muscle fibers of mitochondrial myopathies look like? Why do they look that way?
Gomori trichrome stain shows “ragged red” muscle fibers on biopsy. They have this appearance because abnormal mitochondria accumulate under their sarcolemma.
What defect is involved w/ Ataxia-telangiectasia? What does it predispose to?
This is an AR mutation of the ATM gene that’s involved w/ DNA break repair. It primarily causes IgA deficiency, w/c predisposes to sinopulmonary infections.
>Triad: cerebellar ataxia, telangiectasia, sinopulmo infections.
What is the pathogenesis of Malignant hyperthermia?
A defective Ryanodine receptor on the surface of the SR releases large amounts of Ca when exposed to an inhaled anesthetic or Succinylcholine. The excess Ca stimulates ATP-dependent reuptake of Ca, and ATP consumption generates heat. High temps damages muscle, causing release of K+ (hyperK), myoglobin, and creatine kinase.
What are the 2 ways to exacerbate Myasthenia gravis? How do you differentiate b/w the them?
> Myasthenic crisis: undertreatment means not enough ACh is available in the NMJ.
Cholinergic crisis: too much AChE inhibitor leads to excess ACh.
Edrophonium (Tensilon) test: a short-acting AChEi – improvement means patient is undertreated (myasthenic crisis).
What is the mechanism that causes impaired neural development in Fragile X syndrome?
The CGG repeat can cause FMR1 hyerpemethylation. DNA methylation inactivates transcription, so there’s no production of the Fragile X Mental Retardation protein, impairing neural development.
In transtentorial herniation, w/c structures may be compressed and how would it present?
> Ipslateral CN 3: oculomotor muscle paralysis.
Ipsilateral PCA: contralateral homonymous hemianopsia w/ macular sparing.
Cerebral peduncle: hemiparesis.
Brainstem hemorrhage or compression: fatal; Cushing triad.
What drug may be used to prevent secondary vasospasm associated w/ SAH?
Nimodipine is a selective cerebral CCB that prevents vasospasm. Secondary vasospasm found in patients who had SAH days (4-12 days) prior may be related to impaired brain autoregulation and blood breakdown.
What is a possible cause of Wallenberg syndrome? Presentation?
PICA occlusion causes Lateral medullary syndrome, and it can occur w/ cervical spinal trauma that dissects the vertebral artery.
>Loss of pain and temp from affected spinothalamic tract.
>Dysphagia, dysphonia from injured nucleus ambiguus.
What parts of the spinal cord are affected in Amyotrophic lateral sclerosis?
> Anterior horns - LMN lesion.
>Lateral corticospinal tract - UMN lesion.
How do you manage patients w/ Parkinson disease who have medically intractable ssx?
High-frequency deep brain stimulation of the globus pallidus internus or subthalamic nucleius. This inhibits firing of these nuclei, w/c promotes thalamo-cortical disinhibition w/ improved mobility.
Damage to which parts of the brainstem would cause Decerebrate or Decorticate posturing?
> Decerebrate: damage at or below level of the Red nucleus in the midbrain – loss of descending excitation of arm flexors, unopposed excitation of extensors.
Decorticate: damage above red nucleus – loss of descending inhibition from cortex, hyperactivity of UE flexors.
