An Unusual Case of Memory Decline
New variant Creutzfeldt-Jakob disease (nvCJD) is an acquired prion disease causally related to bovine spongiform encephalopathy that has occurred predominantly in young adults. All clinical cases studied have been methionine homozygotes at codon 129 of the prion protein gene (PRNP) with distinctive neuropathological findings and molecular strain type (PrP (Sc) type 4). Modeling studies in transgenic mice suggest that other PRNP genotypes will also be susceptible to infection with bovine spongiform encephalopathy prions but may develop distinctive phenotypes. New variant Creutzfeldt–Jakob disease (vCJD) was first identified in the UK in 1996, and was causally linked to bovine spongiform encephalopathy. Initially misnamed as ‘mad-cow disease’ it went as a taboo with beef eaters. However it has been identified as a prion disease with dissimilarities with classical CJD both clinically and radiologically throughout the world. Herein we report a case of possible nvCJD from India.
A 64-year-old man, Islam by faith, who had lived throughout his life at Calcutta, India. Presented with sub acute onset and progressive depression, irritability, personality change. He was first assessed by psychiatrist and antidepressants failed to arrest the course of illness. The clinical features extended to cause gait ataxia and cognitive impairment which made him seek neurological consultation. His initial MRI of the brain revealed minimal signal alterations around the thalami and he had a normal EEG. Routine blood reports were normal except marginally raised liver enzymes. However he continued to deteriorate and by 3 months he needed support for his Instrumental activities of daily living. She has by then developed myoclonic jerks in generalized fashion. This time EEG did show the typical appearance of of periodic complexes with a much slower background. His CSF study showed raised protein and normal sugar with mild Lymphocytic pleocytosis. However PCR for Tb was negative and fungal smear was also negative. Brain magnetic resonance imaging this time revealed high signal lesions involving bilateral caudate nuclei, left lentiform nucleus, bilateral dorsomedial thalami and pulvinar on fluid attenuation inversion recovery, T2- and diffusion-weighted imaging. The patient developed a kinetic mutism at 4 months and now after 6 months remains vegetative, completely bedbound. Presently she remains on Clonazepam, Sodium valproate and supportive care.
The clinical presentation and neuroimaging findings were compatible with the nvCJD cases reported since 1996 for probable nvCJD. A human disease thought due to the same infectious agent as bovine spongiform encephalopathy (BSE), or mad cow disease. Both the human and bovine disorders are invariably fatal brain diseases with unusually long incubation periods measured in years, and are caused by an unconventional transmissible agent, a prion, resulting in the deposition of amyloid tissue that causes a breakdown of brain tissue leaving the infected brain with a “spongy” (“spongiform”) appearance. The disease in humans is sometimes called variant Creutzfeldt-Jakob disease (nvCJD). The BSE agent has been identified in the brain, spinal cord, retina, dorsal root ganglia (nervous tissue located near the backbone), and the bone marrow of cattle experimentally infected with this agent by the oral route. In addition to cattle, sheep are susceptible to experimental infection with the BSE agent by the oral route. Thus, in countries where flocks of sheep and goats may have been exposed to the BSE agent through contaminated feed, there exists a theoretical risk that these animals may have developed infections caused by the BSE agent and that these infections have been maintained in the flocks, even in the absence of continued exposure to contaminated feed (for example, through maternal transmission). Everyone with nvCJD appears to have eaten beef and beef products at some time during their lives (but then so have most of the population). Investigation of a cluster of cases with nvCJD disclosed that most of the people were likely infected through their diet. Beef carcass meat appears to have been contaminated with the BSE agent in butchers’ shops where cattle heads were split.