Magnetic resonance imaging and posttraumatic Lhermitte's sign.

Two patients developed Lhermitte's sign after cervical spine fractures. The patients were otherwise without evidence of spinal cord dysfunction. Both patients were studied with magnetic resonance scans of the cervical spine. The magnetic resonance scans were normal. The possible etiology of Lhermitte's sign in these patients is discussed. The differential diagnosis including cervical spondylosis, combined systems degeneration, multiple sclerosis, neoplasm, and radiation myelopathy is reviewed. These patients should be carefully evaluated clinically, and flexion/extension lateral cervical spine films as well as a complete blood count and peripheral smear should be obtained. Magnetic resonance scanning may have an important role in evaluating these patients. Magnetic resonance is exquisitely sensitive in detecting demyelination; therefore, we speculate that subarachnoid scarring may be responsible for this symptom. Gadolinium-enhanced magnetic resonance scanning may confirm the presence of such scarring in the future.