AM Report 3/27/17: Weakness

Myasthenia Gravis: autoimmune – directed against post-synaptic NM junction; look for bulbar muscle involvement that gets worse with activity.

Sign/Symptoms:

  1. Ocular: ptosis/diplopia, EOM involvement, no pupillary involvement
  2. Bulbar: dysarthria, dysphagia, fatigue with chewing
  3. Weakness: proximal limb weakness, facial/neck weakness
  4. Respiratory muscle weakness ⇒ Myasthenia crisis

Tests:

Bedside

  • Ice-pack test – improved ptosis with ice pack administration
  • Tensilon (edraphnium) – acetylchoinesterase inhibitor with rapid onset/short duration; NOT SPECIFIC

Serologic

  • Acetylecholine receptor antibody
  • Muscle specific tyrosine kinase antibody (Anti-MUSK)

Electrophysiologic

  • Repetitive nerve stimulation: ↓ amplitude with repetitive stimulation ~75% have thymic abnormalities (85% thymic hyperplasia, 15% thymoma)

GBS: ascending motor and sensory involvement, symmetric

Timing: <4 weeks

Pathophysiology: Due to molecular mimicry → immune response to preceding infection cross reacts to peripheral nerve

Common trigger: Campylobacter Jejuni (most common), CMV, EBV, HIV, VZV, mycoplasma, Zika

Physical Exam:

  • Absent/depressed DTRs (90%)
  • Ascending weakness (~90%)
  • Paresthesias (80%)
  • Facial weakness/bulbar signs (55%)

LP: Albumino-cytologic dissociation

Miller Fisher Variant

  • Ophthalmoplegia
  • Ataxia
  • Areflexia

Botulism: bulbar involvement – spread in craniocaudal direction ~ “descending paralysis” with CN/eye involvement

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