Because the neurologic manifestations of post-polio syndrome are primarily those of a lower motor neuron or motor axonopathy, the differential diagnosis primarily encompasses diseases manifesting lower motor neuron or peripheral nerve involvement. These diseases are adult onset spinal muscular atrophy (Harding and Thomas 1980; Norris 1991), multifocal motor neuropathy (Van den Berg-Vos et al 2000), chronic inflammatory polyradiculopathy (Bouchard et al 1999), plasma cell dyscrasias (Latov 1982), motor neuropathy and monoclonal gammopathy (Brannagan and Latov 1999), hexosamiadase deficiency (Johnson 1982), thyrotoxicosis (Rowland 1982), parathyroid disorders (Patten and Engel 1982), and heavy metal toxicity (Conradi et al 1982). Other entities in the differential might include lumbar spinal stenosis (Hall et al 1985; Onel et al 1993), chronic disc degeneration and lumbar spondylosis (Ehni 1975), cauda equina syndromes (Shapiro 1993), and lumbar-sacral cord tumors (Schutta 1994). Occasionally, involvement of a single extremity or nerve may be included in the differential, eg, monomelic atrophy (Donofrio 1994), diabetic amyotrophy (Barohn et al 1991), radiculopathies, and entrapment neuropathies (Dawson et al 1999).
For the rare post-polio patient with upper motor neuron signs, amyotrophic lateral sclerosis (Rowland 2001), cervical spondylosis (Stark et al 1981), foramen magnum tumors (Endtz and Fresay 1980), and tumors of the cervical and thoracic cord (Schutta 1994) are part of the differential diagnosis.
Because fatigue is such a prominent feature of the post-polio syndrome, diseases that frequently cause this complaint such as myasthenia gravis (Engel 1999), myasthenic syndrome (Engel 1999), and some myopathies (Norris et al 1980) and medical diseases (cardiac, hematologic, endocrine, cancer, chronic systemic infections) must be excluded. A number of unusual entities, manifested primarily by muscle pain, cramps, and fasciculations (Hudson et al 1978; Coers et al 1981; Ashizawa et al 1983) also should be excluded. A syndrome of acute asymmetric flaccid paralysis has been described in numerous patients with West Nile virus infection (Leis et al 2003). This resembles the paralysis of the anterior horn cell poliomyelitis seen in polio victims and is often associated with disabling fatigue and frequently hinders rehabilitation efforts.