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Neurology India, Vol. 53, No. 3, July-September, 2005, pp. 295-296 Invited Comments Invited Comments Mathuranath PS Cognition and Behavioural Neurology Center, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum - 695 011, Kerala Code Number: ni05102 Related article: ni05100, ni05101 The majority of dementing illnesses are degenerative or vascular. A proportion of them (2-30%), however, are fully or partially reversible. They have two underlying mechanisms, which may coexist.[1] The dementia is caused by a potentially treatable condition.[2] There is a potentially treatable co-morbid condition that amplifies the underlying dementia (or rarely mimics it). The latter commonly includes drugs (CNS stimulants/depressants), depression and septic/metabolic (or rarely endocrinal) encephalopathy. The former includes cerebral infections, nutritional deficiencies, toxins, brain irradiation, structural lesions (NPH, subdural hematomas, etc.), primary/secondary CNS vasculitis, metabolic/endocrinal disturbances (e.g., thyroid dysfunction), and primary/secondary brain tumors. The co-morbid conditions require a high index of clinical suspicion and very few investigations and treating them is often rewarding. In contrast, the causative conditions require an extensive diagnostic work-up. Even though beneficial in some individual cases, it is debatable if it is cost-effective in the diagnostic work-up of a syndrome, which in the majority of cases requires very limited investigations. Only systematic longitudinal follow-up studies of such patients can throw more light on the necessity, yield, and indications of various investigations in such reversible dementias. Systematic meta analysis of studies, mainly on the Western population, have shown that potentially reversible causes account for perhaps less than a 10th of the dementing syndromes, less than a 10th of which are actually reversed with appropriate treatment.[1] Depression accounts for the majority of reversible causes while investigations for other conditions are cost-ineffective.[2] Well-conducted studies from the developing countries, including India, are limited. A recent retrospective hospital-based study on 275 dementia patients (mean age ~ 75 years) in Brazil reported 8% prevalence of potentially reversible dementia of which only 9% reverted in full and 45% partially.[3] Two recent hospital-based reports from India provide unusually high rates of potentially reversible dementia, ~32% ( n = 76, age < 65 years)[4] and ~38% (traumas and tumors excluded, n = 124, age > 60 years).[5] Follow-up duration was insufficient for drawing meaningful conclusions. This issue carries a report of a hospital-based prospective 1-year follow-up study on reversible dementias. The methodology is sound and the analysis and reporting good. The authors find a prevalence of 18% in 129 consecutive patients (40 years of age) referred for cognitive complaints, which relates well with experience in memory clinics. They make three important observations. First, patients with reversible dementias are a decade younger (mean age 51 years) than those with vascular/degenerative dementias. Second, CNS infection (neurosyphilis, crypococcal or tuberculous meningitis, neurocysticercosis and HIV) and vitamin B12 deficiency, which accounted for the majority of these cases, were detected in >60% of patients only on investigations. Last, these patients showed significant cognitive improvement following treatment. In summary, this study suggests that the investigation of younger patients with cognitive complaints, for reversible dementia such as neuroinfections and B12 deficiency, is likely to be more yielding and treating them more rewarding. Data from such studies make important contribution to resolving the dilemma of when and how much to investigate for reversible dementia. References
Copyright 2005 - Neurology India |
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