What historical features are most useful in the differential diagnosis of pain?
Acute pure spinal cord lesions are typically not painful, although occasionally painful extensor or flexor muscle spasms will occur. Nerve root compression commonly produces pain and paresthesias in the affected nerve distribution. Peripheral nerve disease is often manifested by numbness and paresthesias; weakness can be seen when motor nerves are involved (e.g., Guillain–Barré syndrome). Neuromuscular junction lesions are not painful.
Myopathies may or may not be painful. In sorting them out, the following concepts are useful:
• Inflammatory myopathies are usually dominated by weakness, not pain. The exception to this rule is when the inflammatory myopathy has a fulminant onset, when pain may be a dominant feature.
• Muscle pain on exertion is suggestive of vascular insufficiency or diseases of muscle metabolism.