MR imaging in human rabies

Mahidol University, Siayuthia, Bangkok, 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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    ABSTRACT: The developing world is still endemic to rabies, tetanus, leprosy, and malaria. Globally more than 55000 people die of rabies each year, about 95% in Asia and Africa. Annually, more than 10 million people, mostly in Asia, receive postexposure vaccination against the disease. World Health Organization estimated tetanus-related deaths at 163000 in 2004 worldwide. Globally, the annual detection of new cases of leprosy continues to decline and the global case detection declined by 3.54% during 2008 compared to 2007. Malaria is endemic in most countries, except the US, Canada, Europe, and Russia. Malaria accounts for 1.5-2.7 million deaths annually. Much of the disease burden related to these four infections is preventable.
    Full-text · Article · Dec 2014 · Handbook of Clinical Neurology
    • "A plausible scientific explanation is that post-mortem CSF represents sample at the terminal stage of illness in rabies, when the viral load in the central nervous system is known to be relatively high, as compared to the initial stages of infection wherein the viral load is lower. MR imaging studies in human rabies cases have demonstrated MR signal intensity changes in the early stages of illness, but enhancement is seen only in terminal stages once patient becomes comatose suggesting breach in blood brain barrier terminally[Laothamatas et al., 2003]. This could be responsible for the higher frequency of presence of viral RNA in CSF and hence high rates of positivity of PCR in postmortem samples. "
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    ABSTRACT: Rabies, a fatal zoonotic viral encephalitis remains a neglected disease in India despite a high disease burden. Laboratory confirmation is essential, especially in patients with paralytic rabies who pose a diagnostic dilemma. However, conventional tests for diagnosis of rabies have several limitations. In the present study the utility of a real-time TaqMan PCR assay was evaluated for antemortem/postmortem diagnosis of rabies. Human clinical samples received for antemortem rabies diagnosis (CSF, saliva, nuchal skin biopsy, serum), and samples obtained postmortem from laboratory confirmed rabies in humans (brain tissue, CSF, serum) and animals (brain tissue) were included in the study. All CSF and sera were tested for rabies viral neutralizing antibodies (RVNA) by rapid fluorescent focus inhibition test (RFFIT) and all samples (except sera) were processed for detection of rabies viral RNA by real-time TaqMan PCR. All the 29 (100%) brain tissues from confirmed cases of human and animal rabies, and 11/14 (78.5%) CSF samples obtained postmortem from confirmed human rabies cases were positive by real-time TaqMan PCR. Rabies viral RNA was detected in 5/11 (45.4%) CSF samples, 6/10 (60%) nuchal skin biopsies, and 6/7 (85.7%) saliva samples received for antemortem diagnosis. Real-time TaqMan PCR alone could achieve antemortem rabies diagnosis in 11/13 (84.6%) cases; combined with RVNA detection in CSF antemortem rabies diagnosis could be achieved in all 13 (100%) cases. Real-time TaqMan PCR should be made available widely as an adjunctive test for diagnosis of human rabies in high disease burden countries like India. J. Med. Virol. © 2013 Wiley Periodicals, Inc.
    No preview · Article · Oct 2014 · Journal of Medical Virology
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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.
    Full-text · Article · Feb 2013 · BMC Veterinary Research
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