Poliomyelitis-like syndrome

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Poliomyelitis-like syndrome, or polio-like paralysis, is an uncommon myelitis that presents similar to polio, due to non-poliovirus pathologies which selectively involve the anterior horn cells of the spinal cord and result in an anterior horn syndrome. Although it usually has an infective etiology, there are rare non-infective etiologies too.

Clinical presentation

Patients with poliomyelitis-like syndrome present with selective neurological deficits due to anterior horn involvement; flaccid paralysis and areflexia of the involved limb without sensory impairment .

Pathology

There are many causes:

infective: enterovirus 71 considered a leading cause, but there are many other implicated viruses (e.g. coxsackie A9 and A23, coxsackie B viruses, West Nile virus, Japanese encephalitis virus, Epstein-Barr virus, Murray Valley encephalitis virus, respiratory syncytial virus, etc.)
post-vaccination
Hopkins syndrome: exceedingly rare myelitis following an asthma attack

Radiographic features

MRI of the spine is the modality of choice for assessing for signal abnormality of the anterior horn cells.

MRI

MRI typically reveals involvement of the ipsilateral anterior horn cells. If there is radioculomyelitis, there may be thickening of the ventral nerve roots of the cauda equina.

T2: hyperintense anterior horn cells
- on axial imaging this has the characteristic owl's eyes sign, which appears as thin anterior 'pencil like' linear T2 hyperintensities
T1 C+ (Gd): generally no enhancement unless there is radicular involvement

Depending on the underlying etiology, there may also be imaging findings related to concurrent encephalitis.

Differential diagnosis

The differential diagnosis is largely that of other causes of anterior horn syndrome or owl's eyes sign and includes:

anterior spinal artery ischemia: sudden onset, often with pain
neuromyelitis optica (NMO): uncommon