Neuromuscular Disorders - Erlanger · PDF file•In myasthenic exacerbation / crisis, ......
Transcript of Neuromuscular Disorders - Erlanger · PDF file•In myasthenic exacerbation / crisis, ......
Objectives
• Identify common clinical presentations of Guillain-Barré syndrome and myasthenia gravis
• Develop an appropriate treatment strategy for neuromuscular emergencies
• Determine appropriate monitoring parameters for respiratory dysfunction of neuromuscular origin
• Describe common chronic neuromuscular conditions
Case presentationHistory
• 56-year-old male
• Three-week history of progressive limb weakness and dysphagia progressing to the point of being unable to safely swallow.
• He feels that his symptoms are worse as the day progresses.
Subacute progressiveNeuromuscular disorders• i.e. “Neuromuscular Emergencies”
• Myasthenia Gravis
• Guillain-Barré syndrome (GBS)• Acute inflammatory demyelinating
polyradiculoneuropathy (AIDP)
Myasthenia Gravis
• Chronic autoimmune disorder affecting the post-synaptic neuromuscular junction
• Fluctuating and fatigable weakness
• Typically ocular onset
• Acetylcholine receptor antibody positivity is not required and does not correlate with disease severity
• Evaluate for thymic pathology
• Very treatable
AIDP
• Monophasic autoimmune disorder affecting the peripheral nerves
• Preceding immunologic trigger
• Subacute progression of neurological deficits localizable to the peripheral nerves
• Typical pattern is ascending sensory loss and weakness
• CSF cytoalbuminologic dissociation occurs within several days of symptom onset
Case Presentation Neurological Examination
• Cranial nerves• Mild left ptosis• Normal pupillary reactivity• Diplopia with right lateral gaze• Mild weakness with eye closure• Severe weakness with cheek puff and tongue protrusion
• Strength examination• Moderate neck flexor weakness (MRC 4/5)• Mild to moderate weakness in the limb musculature
• Deltoids, triceps, finger extensors• Hip flexors, ankle dorsiflexors
• Normal sensory examination• Normal deep tendon reflexes (2 to 2+)
Evaluation
• MRI Brain• Mestinon Trial (Tensilon test)• Laboratory evaluation:
• CK• CBC• Quantitative immunoglobulins• CMP• TSH• (Acetylcholine receptor antibodies)
• Respiratory evaluation• FVC, NIF
• Consider lumbar puncture for CSF analysis
Treatment of Neuromuscular Emergencies• Plasmapheresis
• IVIg
• Corticosteroids• DO NOT USE
• In myasthenic exacerbation / crisis, useful as a bridging therapy AFTER onset of efficacy of rescue therapy
• Mestinon• High doses cause weakness (cholinergic crisis)
• Cholinergic side effects = sialorrhea
Supportive Care
• Monitoring respiratory function• Assess measures of respiratory force (FVC, NIF)• Ensure good seal during assessment• Consider endotracheal intubation when FVC reaches 15
mL/kg.• Hypercapnea / oxygen desaturation = imminent respiratory
failure
• Enteral feeding• NPO Speech Therapy consultation• May need NGT placement• Very limited role for PEG placement
• Cardiac monitoring• Autonomic dysfunction is common in AIDP
Myasthenia Gravis variants
• Patterns of myasthenia:• Ocular• Generalized – bulbar• Generalized – limb
• MuSK• Female (80%), typically 30-50 years old• Neck flexor weakness / bulbar impairment• Crisis is more common
• Exacerbation or Crisis?
AIDP variants
• Miller-Fisher syndrome• Triad of ataxic, areflexia, ophthalmoparesis
• GQ1b antibodies
• Pharyngeal-cervical-brachial• GT1a antibodies
• Acute motor axonal neuropathy (AMAN)• GM1, GD1a antibodies
• Other variants
Chronic Neuromuscular DisordersSecondary disorders
• Most peripheral neuropathies• Diabetes mellitus• B12 deficiency• Hypo / hyperthyroidism• Renal failure• Monoclonal gammopathies• Alcoholism• Toxic neuropathies• Connective tissue disease
• Structural radiculopathies
• Entrapment neuropathies
Treat the underlying disorder
Chronic Neuromuscular DisordersPrimary disorders
• Treatable disorders = autoimmune• Neuropathies
• Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)
• Multifocal motor neuropathy (MMN)
• Myopathies• Dermatomyositis
• Polymyositis
• Neuromuscular junction disorders• Myasthenia gravis
Chronic Neuromuscular DisordersPrimary disorders
• Untreatable disorders (i.e. supportive measures only)• Charcot-Marie-Tooth disorder
• Inherited polyneuropathy• Rarely life-threatening
• Amyotrophic Lateral Sclerosis (ALS)• Upper + lower motor neuron dysfunction
• Muscular dystrophy• Duchenne’s / Becker’s • Limb-Girdle• Myotonic dystrophy• Cardiac involvement / arrhythmias
• Inclusion body myositis
Summary
1. Does the presentation suggest a neuromuscular disorder?
2. What is the time course (chronic vs. subacute)?• Subacute progressive = probable role for IVIg /
plasmapheresis
3. Supportive measures• Respiratory
• Swallowing
• Cardiac
Sources
• Mahadeva B, Phillips LH, Juel VC. Autoimmune disorders of neuromuscular transmission. Semin Neurol 2008 Apr;28(2):212-27.
• Juel VC. Myasthenia gravis: Management of myasthenic crisis and perioperative care. Semin Neurol 2004 Mar;24(1):75-81.
• Yuki N, Hartung HP. Guillain-Barré syndrome. N Engl J Med 2012;366:2294-304.
• Burns TM. Guillain-Barré syndrome. Semin Neurol 2008 Apr;28(2):152-67.
• Merrigioli MN, Sanders DB. Myasthenia gravis: diagnosis. Semin Neurol2004 Mar;24(1):31-9.