Postpolio syndrome and the late effects of poliomyelitis. Part 1. pathogenesis, biomechanical considerations, diagnosis, and investigations.

Postpolio syndrome (PPS) is characterized by new muscle weakness and/or muscle fatigability that occurs many years after the initial poliomyelitis illness. Many theories exist regarding the pathogenesis of PPS, which remains incompletely understood. In contrast, the late effects of poliomyelitis are often a consequence of biomechanical alterations that occur as a result of polio-related surgeries, musculoskeletal deformities, or weakness. Osteoporosis and fractures of the polio-involved limbs are common. A comprehensive clinical evaluation with appropriate investigations is essential to fulfilling the established PPS diagnostic criteria. PPS is a diagnosis of exclusion in which a key clinical feature required for the diagnosis is new muscle weakness and/or muscle fatigability that is persistent for at least 1 year. Electromyographic and muscle biopsy findings including evidence of ongoing denervation cannot reliably distinguish between patients with or without PPS. Muscle Nerve 58:751-759, 2018.