Myelopathy: chameleons and mimics.

The diagnosis of spinal cord disease may be delayed or missed if the presentation does not conform to the expected pattern of a symmetrical spastic paraparesis with sphincter dysfunction and a sensory level. This may occur when a myelopathy has yet to evolve fully, or is highly asymmetrical, as in Brown-Séquard syndrome. Other potential distractions include fluctuating symptoms, as may accompany spinal cord demyelination, and pseudoneuropathic features, as seen acutely in spinal shock and in the chronic setting with some high cervical cord lesions. A second pathology, such as a polyneuropathy or polyradiculopathy, can mask the presence of a myelopathy. The converse situation, of non-myelopathic disease mimicking a cord lesion, arises typically when symptoms and/or signs approximate bilateral symmetry. This may happen with certain diseases of the brain, or of the peripheral nerves, with functional disorders and even occasionally with non-neurological disease. These sources of diagnostic difficulty assume clinical importance when they delay the recognition of conditions that require urgent treatment.