Clinical Clues to Causes of Peripheral Nervous System* Disorders
Finding | Cause to Consider | |
|---|---|---|
Symmetric, diffuse deficits | Diffuse disorders (eg, toxic-metabolic, hereditary, infectious, or inflammatory disorders; most immune-mediated disorders) | |
Unilateral deficits | Focal disorders (eg, mononeuropathies, plexopathies) | |
Deficits localized to one or more peripheral nervous system structures (eg, nerve root, spinal nerve, nerve plexus, single peripheral nerve, ≥ 2 discrete nerves in separate areas [multiple mononeuropathy]) | One or more lesions in peripheral nervous system structures | |
Stocking-glove distribution of deficits | Diffuse peripheral polyneuropathies, probably axonal | |
Disproportionate weakness of proximal muscles (eg, difficulty climbing stairs or combing hair) with no sensory deficits | Diffuse muscle dysfunction, as occurs in diffuse myopathies Possibly disorders of the neuromuscular junction if eye movements are affected | |
Chronic, progressive weakness affecting mostly distal muscles with no sensory deficits | ||
Numbness, tingling, and/or paresthesias with motor weakness and decreased reflexes | ||
Profound proximal and distal motor weakness with minimal atrophy | ||
Deficient pain and temperature sensation; painful, often burning sensations Weakness proportional to atrophy; disproportionately mild reflex abnormalities, usually more distal than proximal | Vascular disorders (eg, vasculitis, ischemia, hypercoagulable states) | |
* Lower motor neuron disorders (eg, spinal muscular atrophies) technically involve the CNS because the cell body of the motor neuron (anterior horn cell) is located in the spinal cord. | ||
CNS = central nervous system. | ||