Long-term follow-up of patients with nonparalytic poliomyelitis

Objective: To examine patients with previous nonparalytic poliomyelitis in search of muscle atrophy, weakness, and other late symptoms of poliomyelitis. Design: A mailed questionnaire followed up with neurologic and neurophysiologic examinations of respondents who reported symptoms possibly related to the late sequelae of polio. Setting: Neurology department at a university hospital. Participants: Thirty-nine of 47 patients diagnosed with nonparalytic poliomyelitis and hospitalized at a Norwegian hospital between 1950 and 1954, during the Norwegian polio epidemic. Interventions: Not applicable. Main Outcome Measures: Electromyography to determine function of the anterior tibialis, vastus lateralis, and biceps brachii muscles; nerve conduction studies of the sural, peroneal, and tibial nerves; motor and sensory nerve conduction velocity, and compound muscle and sensory nerve action potentials, and distal latencies. Results: Twenty-five of 47 patients (53.2%) reported symptoms possibly related to the late sequelae of poliomyelitis. Eight of 20 examined symptomatic patients had normal neurologic and neurophysiologic findings, whereas 9 others had other medical conditions that could explain the symptoms. Three patients (6.7%) had neurologic and neurophysiologic findings and development of symptoms consistent with motoneuron damage. Conclusion: Some nonparalytic patients may have subclinical acute motoneuron damage with subsequent development and manifestation of motor weakness and neuromuscular symptoms many years later. These symptoms should be considered a differential diagnosis in patients who have a history of nonparalytic poliomyelitis.