Enterovirus 71 CNS Infection
- Background:
- Enterovirus 71 (EV-71) belongs to the RNA enterovirus family, which also includes poliovirus and EV-68. All have been reported to be neurotropic, either hematogenously or by axonal transport.
- EV-71 is 1 of the common pathogens leading to hand-foot-and-mouth disease (HFMD).
- CNS invasion in EV-71-related HFMD is rare, but when it occurs, it causes an immune response that leads to several types of neurologic disease.
- EV-71-related HFMD outbreaks with CNS manifestations were first described in 1975 in Bulgaria, but have since been reported worldwide, most commonly in southeast Asia.
- Larger published series describe presentation more often between April and August, though cases have been reported between February and December.
- Clinical Presentations:
- Patients are most often 1–4 years of age, and male predominance has been reported in some series.
- The most common presenting symptom is fever. HFMD rash is often described, but many patients present with no rash.
- Many neurologic syndromes have been described in various case series, including aseptic meningitis, brain stem encephalitis, cerebellitis/ataxia, myoclonus, and acute flaccid myelitis (AFM can also be referred to as acute flaccid paralysis, or AFP). There are many variations in how these syndromes have been defined and substantial overlap between these presentations.
- In severe cases, respiratory failure from pulmonary edema or hemorrhage can be fatal, making prompt diagnosis and recognition of the clinical syndrome critical.
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Key Diagnostic Features:
- Nonenhancing T2 hyperintensity of the midbrain tegmentum, dorsal pons, and dentate has been described in patients with brain stem encephalitis, though in our experience, this can also be seen with clinical syndromes of aseptic meningitis, cerebellitis, or myoclonus.
- Ill-defined, nonenhancing central spinal cord T2 hyperintensity can be seen early in the disease course, though it is inconsistently associated with AFM at this stage. Spinal cord imaging performed later in definite AFM cases can show more focal/cavitated areas of T2 hyperintensity, similar to what is described with EV-68 and poliovirus.
- Cranial nerve enhancement and spinal nerve root enhancement are also seen and inconsistently related to focal symptoms of cranial nerve dysfunction or AFM.
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Treatment:
- Treatment has often been supportive, though intravenous immunoglobulin and steroids have been used.
- Outcomes vary, with complete recovery fairly common in more recent series, though mortality from respiratory and brain stem complications has been as high as 14% in older series.
