Post-Polio Syndrome Revisited

Abstract

Post-polio syndrome (PPS) is characterized by recrudescence or worsening of motor neuron disease symptoms decades after recovery from acute paralytic poliovirus infection, i.e., poliomyelitis. PPS afflicts between 25% and 40% of poliomyelitis survivors and mimics motor neuron diseases (MNDs), such as amyotrophic lateral sclerosis (ALS), due to its selective impairment, degeneration, or death of motor neurons in the brainstem and spinal cord. Herein, we report a case of PPS in a 68-year-old man with a remote history of bulbar and cervical cord involvement by poliomyelitis, review the relevant literature, and contrast the salient histopathologic features that distinguish our case of PPS from ALS.

Keywords: amyotrophic lateral sclerosis; motor neuron disease; post-polio syndrome.

Figure 1

Spinal ventral horn atrophy with neurodegeneration in PPS. Formalin-fixed, paraffin-embedded histological sections of thoracic spinal cord were (A–C) stained with Luxol fast blue, hematoxylin and eosin (LHE; 8 µm thick), or (D) immunostained for ubiquitin (4 µm thick). (A) Thoracic cord level showing absence of lateral and anterior corticospinal tract degeneration (note homogeneous Luxol fast blue staining of myelin). (B) Extensive neuronal loss in the ventral horn shown in Panel A. (C) Ventral horn cells are virtually replaced by glia. (D) Note the absence of ubiquitin-positive inclusions in residual anterior horn cells (examples of negative staining in neurons shown at arrow tips). (C) Scale bar = 30 µm; (D) Scale bar = 40 µm.

Figure 2

Ventral nerve root degeneration and skeletal muscle myofiber type grouping in PPS. Spinal ventral nerve roots (A) stained with LHE or (B) immunostained with antibodies to neurofilament show loss of myelinated fibers in A. For example, between arrows, asterisk marks normally myelinated fibers, and in (B), loss of axon is represented by the clear gaps among fibers. (C,D) Histological sections of quadriceps muscle immunostained to detect (C) fast or (D) slow myosin. Note clear grouping according to myofiber type, i.e., fast versus slow. Brown staining precipitates in (B–D) correspond to positive immunostaining results. (C,D) Scale bars = 100 µm.

Figure 3

Ventral horn neurodegeneration in ALS. Spinal thoracic ventral horn showing (A) subtotal loss of neurons and (B) extensive gliosis. (C) Many surviving anterior horn cells exhibit swelling and chromatolysis. (D) Bunina body cytoplasmic inclusions. The narrow arrow shows a classical Bunina body. The broad arrow shows a larger, diffusely pale cytoplasmic inclusion. Additional sections from the same block were immunostained with antibodies to (E) ubiquitin and (F) TDP-43, both of which detected discrete cytoplasmic Bunina bodies (dense brown staining). (E) Scale bar = 30 µm; (F) Scale bar = 25 µm.

Figure 4

Spinal cord (A,C) Lumbar and (B,D) thoracic ventral nerve root degeneration in ALS. Formalin-fixed paraffin-embedded LHE-stained sections in (A,B) show loss of myelinated fibers, e.g., between arrows (asterisk marks normally myelinated fibers). (C,D) Additional sections from the same blocks immunostained with antibodies to neurofilament to show loss of axon (gaps among fibers). Fiber degeneration and loss are greater in lumbar (A,C) compared with thoracic (B,D) cord levels. (A,B) Scale bars = 50 µm; (C,D) Scale bars = 35 µm.

Figure 5

Skeletal muscle (A,B) denervation atrophy with myofiber hypertrophy and myofiber type grouping in ALS. Histological sections stained with H&E show (A) small (circled) and (B) large group myofiber atrophy with no endomesial fibrosis in different areas of quadriceps muscle. Additional sections from the same blocks immunostained to detect (C) fast (Type 2) or (D) slow (Type 1) myosin show clear myofiber type grouping away from the regions with active denervation as shown in Panels (A,B). (A–D) Scale bars = 80 µm.