It has been suggested that late onset neurological deterioration after
poliomyelitis may be due in some cases to persistent poliovirus
infection of the central nervous system. In view of this, we decide to determine whether polioviruses and other enteroviruses can persist in the central nervous system. In a previous study, one of us (M.K.S.) reported serological evidence of persistent poliovirus
infection of the central nervous system (CNS) in a proportion of these patients. We have now studied cerebrospinal fluid (CSF) from these patients for the presence of enterovirus RNA sequences using the polymerase chain reaction (PCR). Enteroviral
RNA was detected in 3 of 24 patients with a clinical diagnosis of
post-polio syndrome, but in none of 36 patients with stable
poliomyelitis, and none of 36 patients with other neurological conditions of noninfective origin. All 3 patients in whom
viral RNA was detected had high intrathecal levels of poliovirus-specific
oligoclonal IgM bands. In a second study we examined
formalin-fixed postmortem CNS tissue from 7 patients with a history of paralytic
poliomyelitis. Enterovirus
RNA was detected in tissue from the spinal cord from 3 patients, but not in the cerebral cortex. We are now conducting a larger prospective, blind study of patients with evidence of late deterioration. Analysis of the first 30 patients studied revealed the presence of enterovirus
RNA in CSF of 1 of 4 patients with unexplained late-onset post-
polio weakness, 1 of 6 with some evidence of
clinical deterioration, but none of 20 without inexplicable signs of post-
polio weakness. Enteroviral
RNA was also detected in spinal cord from 2 of 3 patients who died from other causes during this study. These studies provide virological evidence that enteroviruses may persist in the CNS of man. Further study is required in order to understand fully the
biological and clinical significance of these findings.