questions 3

Diseases of Myelination

Topic updated on 02/07/17 5:11am

Guillain-Barré Syndrome
  • Introduction
    • acute inflammatory demyelinating polyradiculopathy (AIDP)
      • most common presentation
    • inflammatory demyelination of peripheral nerves
    • autoimmune attack of peripheral Schwann cells due to molecular mimicry
      • previous Campylobacter jejuni and Mycoplasma pneumoniae
        • may have an association with Zika virus infection
  • Presentation 
    • symptoms
      • symmetric weakness usually begins in distal limbs and moves proximally
        • can begin proximally or a combination of proximally and distally
    • physical exam
      • decreased or absent deep tendon reflexes
      • cranial nerve involvement common resulting in facial paralysis
      • autonomic dysfunction resulting in cardiac irregularities and fluctuations in blood pressure
  • Evaluation 
    • LP
      • albuminocytologic dissociation 
        • ↑ CSF protein with normal cell count
  • Treatment
    • almost all patients survive and achieve complete recovery in several weeks
    • respiratory support is critical until recovery
      • pulmonary function testing
    • plasmapheresis or IV immunoglobulin
      • equal efficacy; no additive benefit
  • Prognosis, prevention, and complications
    • prognosis
      • low mortality
    • complications
      • respiratory failure
Progressive Multifocal Leukoencephalopathy (PML)
  • Introduction 
    • widespread CNS demyelination due to destruction of oligodendrocytes
    • associations
      • latent JC virus reactivation
      • ↑ risk with natalizumab
      • ↑ risk with rituximab
    • seen in the immunosuppressed
      • HIV infection
        • < 200 per mm3
      • organ transplant patients
  • Presentation
    • subacute neurological deficits
      • e.g., hemiparesis, monoparesis, ataxia, altered mental status
  • Evaluation
    • clinical diagnosis with MRI imaging
      • MRI
        • symmetric or asymmetric lesions in multifocal areas
    • PCR of CSF for JC virus
    • brain biopsy
  • Treatment
    • patients with HIV
      • antiretroviral therapy
    • natalizumab-associated
      • stop agent
      • initiate plasma exchange
  • Prognosis, prevention, and complications
    • prognosis
      • HAART therapy improves survival in patients with HIV
    • prevention
      • improving CD4+ count in patients with HIV
    • complications
      • death
Acute Disseminated (Postinfectious) Encephalomyelitis
  • Introduction
    • autoimmune inflammatory demyelination of the CNS secondary to infection or vaccination
      • via infection
        • e.g., chickenpox and measles
      • via vaccinations
        • e.g., rabies and smallpox
  • Presentation
    • symptoms
      • acute and rapidly progressive development
        • multifocal neurological deficits
          • altered mental status
          • motor deficits
          • cranial nerve neuropathy
          • ataxia
          • sensory deficit
  • Evaluation
    • clinical diagnosis
  • Treatment
    • high-dose corticosteroids
      • IVIG or plasma exchange if poor response
    • acyclovir
  • Prognosis, prevention, and complications
    • prevention
      • no small pox vaccine before 12 months of age
    • complications
      • neurologic impairment
Metachromic Leukodystrophy
  • Introduction
    • autosomal recessive lysosomal storage disease due to deficient arylsulfatase A
    • inability to degrade sulfatides → sulfatide build up → myelin breakdown
  • Presentation
    • symptoms
      • diverse neurological impairment depending on subtype
        • e.g., motor skill regression in late infantile subtype
  • Evaluation
    • arylsulfatase enzyme activity in leukocytes
      • decreased
    • biopsy
      • neural tissue metachromatic lipid deposits
  • Treatment
    • no curative treatment
Charcot-Marie-Tooth Disease
  • Introduction
    • also known as hereditary motor and sensory neuropathy (HMSN)
    • group of disorders negatively affecting peripheral nerves and/or myelin
      • genetically distinct disorders
  • Presentation
    • symptoms
      • peroneal nerve neuropathy
        • lower leg atrophy
          • "inverted bottle" appearance
      • diminished or absent reflexes
      • decrease vibration and proprioception sense
      • pes cavus
  • Treatment
    • supportive
Central Pontine Myelinolysis (CPM)
  • Introduction
    • pontine demylination
      • loss of corticospinal and corticobulbar tracts
        • due to rapid correction of hyponatremia
        • can result in "locked-in syndrome"
  • Presentation
    • symptoms
      • pseudobulbar palsy with spastic quadriparesis
        • locked-in like presentation
          • can move eyes and blink
      • may also include cognitive function changes
  • Prognosis
    • often fatal


Qbank (2 Questions)

(M1.NE.12) A 74-year-old man was admitted to the hospital after falling down several stairs. He is a known alcoholic. He was started on IV fluids and received a head CT, which was negative. It was decided that he would be watched for one day before being discharged, after a negative work-up. Suddenly, he is unable to move his arms and legs in addition to experiencing difficulty chewing, swallowing, moving his face, and speaking. Which of the following electrolyte imbalances was most likely corrected too aggressively? Topic Review Topic

1. Hyponatremia
2. Hypernatremia
3. Hypokalemia
4. Hyperkalemia
5. Hypochloremia

(M1.NE.77) A 26-year-old man presents to his primary doctor with one week of increasing weakness. He reports that he first noticed difficulty walking while attending his sister's graduation last week, and yesterday he had difficulty taking his coffee cup out of the microwave. He remembers having nausea and vomiting a few weeks prior, but other than that has no significant medical history. On exam, he has decreased reflexes in his bilateral upper and lower extremities, with intact sensation. If a lumbar puncture is performed, which of the following results are most likely? Topic Review Topic

1. High neutrophils, high protein, low glucose, high opening pressure
2. High lymphocytes, normal protein, normal glucose, normal opening pressure
3. High lymphocytes, high protein, low glucose, high opening pressure
4. Normal cell count, high protein, normal glucose, normal opening pressure
5. Normal cell count, normal protein, normal glucose, normal opening pressure

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