January 11, 2018
A 19-year-old man with complaints of altered sensorium for the last 10 days; history of dog bite 40 days back, and dog died 2 days after incident; did not receive any postprophylaxis vaccination
Rabies Encephalomyelitis
- Background:
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Rabies virus belongs to the Rhabdoviridae family of neurotropic RNA viruses that cause an acute onset, progressive encephalitis.
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At the site of the dog bite, the virus multiplies in adjacent muscle cells and then spreads to the CNS through reverse axoplasmic transport.
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The incubation period ranges from 2 weeks to 6 years
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- Clinical Presentation:
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The neurologic symptoms caused by rabies virus are classified into 2 categories: encephalitic and paralytic.
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In the encephalitic form, there is autonomic and limbic dysfunction with associated autonomic stimulation signs.
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In the paralytic form, the patient presents with weakness of all 4 limbs; however, there is relative sparing of consciousness.
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- Key Diagnostic Features:
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Appropriate clinical history, along with laboratory exams and imaging findings, helps to diagnose rabies encephalomyelitis.
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MRI is the imaging modality of choice for diagnosing rabies encephalomyelitis.
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MR findings reveal bilateral T2/FLAIR hyperintensity in the basal ganglia, thalami, hippocampi, hypothalamus, brain stem, and spinal cord.
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- Differential Diagnoses:
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Acute disseminated encephalomyelitis: usually involves cortical and deep white matter; gray matter involvement is less commonly seen
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Viral meningoencephalitis: signals in spinal cord are absent; however, differentiation may be difficult from rabies infection
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- Treatment:
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There is no known effective treatment for rabies infection.
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Postexposure prophylaxis, human rabies immunoglobulin, ribavirin, and interferon are given after the bite.
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Rabies is almost invariably fatal after neurologic symptoms have developed.
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