Abdominal adhesions =Post-polio syndrome (PPS) is acondition that affects polio survivors years after recovery from an initialacute attack of the poliomyelitis virus. PPS is mainly characterized by newweakening in muscles that were previously affected by the polio infection and inmuscles that seemingly were unaffected. Symptoms include slowly progressivemuscle weakness, unaccustomed fatigue (both generalized and muscular), and, attimes, muscle atrophy. Pain from joint degeneration and increasingskeletal deformities such as scoliosis are common. Some patients experience onlyminor symptoms. While less common, others may develop visible muscle atrophy, orwastingPPS is rarely life-threatening. However, untreated respiratory muscleweakness can result in underventilation, and weakness in swallowing muscles canresult in aspiration pneumonia.The severity of residual weakness and disabilityafter acute poliomyelitis tends to predict the development of PPS. Patients whohad minimal symptoms from the original illness will most likely experience onlymild PPS symptoms. People originally hit hard by the poliovirus and who attaineda greater recovery may develop a more severe case of PPS with a greater loss ofmuscle function and more severe fatigue. It should be noted thatmany polio survivors were too young to remember the severity of their originalillness and that accurate memory fades over time.According to estimates by theNational Center for Health Statistics, more than 440,000 polio survivors in theUnited States may be at risk for PPS. Researchers are unable to establish a firmprevalence rate, but they estimate that the condition affects 25 percent to 50percent of these survivors, or possibly as many as 60 percent, depending on howthe disorder is defined and which study is quoted.Patients diagnosed with PPSsometimes are concerned that they are having polio again and are contagious toothers. Studies have shown that this does not happen. The cause is unknown. However, the newweakness of PPS appears to be related to the degeneration of individual nerveterminals in the motor units that remain after the initial illness. A motor unitis a nerve cell (or neuron) and the muscle fibers it activates. The poliovirusattacks specific neurons in the brainstem and the anterior horn cells of thespinal cord. In an effort to compensate for the loss of these neurons, ones thatsurvive sprout new nerve terminals to the orphaned muscle fibers. The result issome recovery of movement and enlarged motor units. Years of high use of theseenlarged motor units adds stress to the neuronal cell body, which then may notbe able to maintain the metabolic demands of all the new sprouts, resulting inthe slow deterioration of motor units. Restoration of nerve function may occurin some fibers a second time, but eventually nerve terminals malfunction andpermanent weakness occurs. |
