CNS non tumor
Infections
Rabies

Authors: Kymberly A. Gyure, M.D. (see Authors page)

Revised: 29 November 2016, last major update November 2016

Copyright: (c) 2005-2016, PathologyOutlines.com, Inc.

PubMed Search: cns rabies
Cite this page: Rabies. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/cnsrabies.html. Accessed March 27th, 2017.
Definition / General
  • Zoonotic disease caused by rabies virus, which is usually transmitted to humans by animal bites
Essential Features
  • Rabies is an almost uniformly fatal neurologic illness caused by rabies virus which is typically transmitted by a bite from a rabid animal
  • Two main clinical forms, encephalitic and paralytic
  • Characteristic pathologic features include Negri bodies, which are intracytoplasmic, eosinophilic inclusions found in neurons of the hippocampus and cerebellum
Epidemiology
  • ~ 60,000 human rabies deaths per year worldwide
  • More common in developing countries where rabies is endemic in dogs
  • Rabies in bats is an important risk factor in North America
Sites
  • Hippocampi and cerebellum
Pathophysiology
  • Rabies virus is secreted in the saliva of infected animals and is inoculated into tissue at the bite site
  • Virus then spreads via the peripheral nerves to the brainstem or spinal cord and disseminates throughout the central nervous system along neuroanatomical connections and selectively injures neuronal processes (axons and dendrites) without producing neuronal death
Etiology
  • Caused by rabies virus, a negative strand RNA virus in the family Rhabdoviridae
Clinical Features
  • Nonspecific, flu-like prodrome
  • Paresthesia, pain or itching at the site of the bite
  • Encephalitic ("furious") form (80% of cases): brain involvement predominates; acute neurologic illness characterized by hyperactivity, disorientation, bizarre behavior, hallucinations and autonomic dysfunction
  • Hydrophobia (pharyngeal / laryngeal spasm when attempting to drink) is characteristic but present in only 50% - 80% of patients
  • Paralytic form: spinal cord and peripheral nerve / nerve root involvement predominates; less common variant with weakness in the bitten limb followed by progression to quadriparesis with facial weakness
Laboratory
  • CSF pleocytosis in 60% of cases
  • Diagnosis can be confirmed by detecting anti rabies virus antibodies in serum or cerebrospinal fluid and rabies virus antigen or RNA in tissue (nuchal skin biopsy) or fluids
Radiology Description
  • Normal or increased signal of gray matter structures on T2 weighted images
Prognostic Factors
  • Almost always fatal in nonimmunized patients
Case Reports
Treatment
  • Post exposure prophylaxis: wound cleansing and administration of rabies vaccine and rabies immune globulin
Gross Description
  • Brain and spinal cord are grossly normal in most cases
Micro Description
  • Negri and lyssa bodies: round to oval, eosinophilic intracytoplasmic inclusions in the pyramidal cells of the hippocampus and cerebellar Purkinje cells
  • Perivascular chronic inflammation, microglial nodules and neuronophagia
Micro Images

Images hosted on PathOut server:

Contributed by Dr. Kymberly Gyure, West Virginia University School of Medicine (USA)

Differential Diagnosis
  • Guillain-BarrĂ© syndrome
  • Bat acquired cases are more likely to be misdiagnosed due to the lack a bite history