MR imaging in human rabies

Department of Radiology, Ramathibodi Hospital, Bangkok 10400, Thailand.
American Journal of Neuroradiology (Impact Factor: 3.59). 06/2003; 24(6):1102-9.
Source: PubMed


Whether human rabies of different forms, encephalitic (furious) and paralytic (dumb), share similar MR imaging patterns is unknown. We assessed the diagnostic value of MR imaging in both forms of the disease and compared the clinical and neuroimaging findings.
Three patients with paralytic and two with encephalitic rabies were examined during preserved or deteriorated levels of consciousness. Six MR examinations of the brain, three of the spinal cord, and one of the brachial plexus were performed with a 1.5-T superconducting magnet.
No difference was noted between the MR findings in both clinical forms of human rabies. Nonenhancing, ill-defined, mild hyperintensity changes in the brain stem, hippocampi, hypothalami, deep and subcortical white matter, and deep and cortical gray matter were demonstrated on T2-weighted images in the noncomatose patients with rabies. Enhancement along the brachial plexus of the bitten arm was noted in one patient with encephalitic rabies who at that time had only local neuropathic pain symptoms. Enhancement with gadolinium-based contrast material was seen at the hypothalami, brain stem nuclei, spinal cord gray matter, and intradural cervical nerve roots only when the patients became comatose.
Both forms of human rabies share a similar MR imaging pattern. Such pattern and the lack of enhancement in a noncomatose patient with suspected encephalitis may differentiate rabies from other viral encephalitides.

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    • "gic studies of rabies that have shown maximal concentration of Negri bodies and antirabies antigen as revealed by immunohistochemistry ( Jogal et al . , 2000 ) . Contrast enhancement with gadolinium is seen at the hypothalami , brainstem nuclei , spinal cord gray matter , and intradural cervical nerve roots only when the patients become comatose ( Laothamatas et al . , 2003 ) ."
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    Handbook of Clinical Neurology 01/2014; 121:1501-20. DOI:10.1016/B978-0-7020-4088-7.00101-2
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    • "Although previous magnetic resonance imaging (MRI) studies in human rabies patients have revealed no differences between the two clinical forms [13], diffusion tensor imaging technique has demonstrated disruption of neural tract integrity at the brainstem level in dogs with the paralytic form of rabies [14]. A marked decrease in the mean diffusivity values, representing cytotoxic edema, was noted in the cerebral hemispheres without evidence of blood brain barrier leakage in paralytic dogs [14]. "
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    ABSTRACT: Background The mechanisms that differentiate rabies infections into furious and paralytic forms remain undetermined. There are no neuropathological features in human brains that distinguish furious and paralytic rabies. This could be due to methodology and/or examination of specimens late in the disease course. In this study, postmortem examination of brain (5 furious and 5 paralytic) and spinal cord (3 furious and 3 paralytic) specimens was performed in 10 rabies-infected dogs, sacrificed shortly after developing the illness. Rabies virus (RABV) antigen (percentage of positive neurons, average antigen area in positive neurons and average antigen area per neuron) and RNA were quantified at 15 different central nervous system (CNS) regions. The distribution and degree of inflammation were also studied. Results More RABV antigen was detected in furious rabies than paralytic in many of the CNS regions studied. Caudal-rostral polarity of viral antigen distribution was found in both clinical forms in order from greatest to least: spinal cord, brainstem, cerebellum, midline structures (caudate, thalamus), hippocampus, and cerebrum. In contrast, RABV RNA was most abundant in the cerebral midline structures. Viral RNA was found at significantly higher levels in the cerebral cortex, thalamus, midbrain and medulla of dogs with the furious subtype. The RNA levels in the spinal cord were comparable in both clinical forms. A striking inflammatory response was found in paralytic rabies in the brainstem. Conclusions These observations provide preliminary evidence that RABV antigen and RNA levels are higher in the cerebrum in furious rabies compared to the paralytic form. In addition, brainstem inflammation, more pronounced in paralytic rabies, may impede viral propagation towards the cerebral hemispheres.
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    • "The basal ganglia, cortical grey matter and white matter showed normal signal. The findings were considered consistent with those described in prior reports of rabies encephalitis.[1–3] "
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    ABSTRACT: Rabies encephalitis is an invariably fatal disease characterized by typical clinical symptoms. Although the diagnosis of this condition can be made on the basis of the patient's history and the classical clinical presentation, neuroimaging may still play a role, especially for establishing an early diagnosis in cases with atypical presentations or when the history of animal bite is not forthcoming. We report the MRI findings in a case of furious rabies encephalitis and describe the utility of diffusion imaging in its diagnosis.
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