- Heterogeneous group of disorders causing demyelination of peripheral nerves
- Most common mode of inheritance is autosomal dominant
Relevant physical signs
- Inspection
- Guttering of dorsal interossei (UL and LL)
- Claw hands (advanced cases, hyperextension of MCPJs with fixed flexion of IPJs)
- Inverted champagne bottle appearance (distal wasting, most often affecting the anterolateral compartment of the leg. Classically stops at distal third of thigh)
- Pes cavus (increased height and curvature of medial longitudinal arch, with medially angulated heel. High arch does not flatten with weight-bearing)
- Fasciculations, especially of distal muscles
- Foot drop (usually bilateral)
- Walking aids
- Tone usually flaccid
- Reflexes typically absent of greatly diminished
- Confirm absent reflexes by Jendrassik manoeuvre
- Power
- Symmetrically affected
- Distal weakness usually predominates
- Plantarflexion relatively spared compared to dorsiflexion
- Proximal weakness typically only in severe cases
- Coordination normal, unless impaired by weakness
- Sensation
- May be spared until later on in disease
- Sensory loss to pinprick and proprioception in a length-dependent manner (glove and stocking)
- Demonstrate length-dependent loss by running sharp object up the limb
- Gait: high steppage, may have sensory ataxia
- Positive Rhomberg’s sign as disease progresses
Differential diagnosis
- Diabetic neuropathy
- Hereditary neuropathy with pressure palsy
- Drugs
- Isoniazid
- Zidovudine
- Vincristine
- Amiodarone
- Metronidazole
- Dapsone
- Toxins
- Lead (predominantly motor)
- Alcohol
- Metabolic
- B12 deficiency (usually associated with UMN signs as well)
- Porphyria (predominantly motor)
- Inflammatory
- Guillain-Barre syndrome
- Acute inflammatory demyelinating polyneuropathy
- Chronic inflammatory demyelinating polyneuropathy
- Sarcoidosis
- Vasculitis causing mononeuritis multiplex (typically asymmetrical)
- Churg-Strauss syndrome
- Polyarteritis nodosa
- Wegner’s granulomatosis
- Sjögren’s syndrome
- Systemic lupus erythematosus
- Amyloidosis
- Infections
- Human immunodeficiency virus
- Lyme disease
- Leprosy
- Neoplastic
- Paraneoplastic phenomenon
Investigations
- Nerve conduction studies to look for slowing of conduction velocities
- Consider genetic testing
- Fasting plasma glucose, HbA1c, B12, folate levels
- Detailed drug history
- Consider HIV testing, Borrelia serology
- Consider nerve biopsy in amyloidosis, leprosy, vasculitis, and CIDP
Management
- Multidisciplinary team approach
- Patient education
- Physiotherapy and occupational therapy to preserve and maximize function
- Analgesia for pain
- Orthotics / walking aids as necessary
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