Srikanth et al: Reversible dementias
Dementia prevalence in elderly individuals in Southern India is estimated to be 33.6 per 1000[3]. It is striking that nearly one fifth might have a reversible dementia. In fact, the true prevalence of reversible dementia may be even higher. Srikanth et al excluded patients with alcoholic dementia, depressive pseudodementia, intracranial tumours and subdural haematomas; these patients were referred to other departments for follow up. Furthermore serum B12 assays were only performed ‘as deemed necessary’, but the haematological and neurological features of B12 deficiency are often unrelated in such patients.[4] The advent of sensitive but expensive tests such as homocysteine and holotranscobalamin assays now makes it possible to detect such subtle deficiencies.[5] However, there is a difficult but important ‘cost/benefit’ issue to be addressed. Should every patient presenting with dementia be extensively investigated for potentially reversible causes with an inherent increase in diagnostic costs? Hence it is helpful that Srikanth et al describe a distinct clinical profile to alert physicians to the possible presence of reversibility. They found that a subcortical pattern of dementia in younger patients with a short duration of symptoms was suggestive of
an underlying reversible cause. Clearly more work is required to develop cost-effective clinical algorithms for the investigation of patients with cognitive disorders. As the authors note, this has special relevance for countries like India where reversible etiologies are likely to be common but diagnostic resources scarce. ‘Silence is golden’ but can we afford to listen?
Andrew McCaddon Department of General Practice, Wales College of Medicine, Wrexham, UK
Reference 1. 2. 3. 4.
5.
Bec, JC, Benson DF, Scheibel AB, Spar JE, Rubenstein LZ. Dementia in the Elderly. The Silent Epidemic. Ann Intern Med 1982;97:231-41. Srikanth S, Nagaraja AV. Prospective Study of Reversible Dementias - Frequency, Causes, Clinical Profile and Results of Treatment. Neurol India 2005;53:291-6 Shaji S, Bose S, Verghese A. Prevalence of Dementia in an Urban Population in Kerala, India. Br. J Psychiatry 2005;186:136-40. McCaddon A, Tandy S, Hudson P, Gray R, Davies G, Hill D, Duguid J. Absence of Macrocytic Anaemia in Alzheimer’s Disease. Clin Lab Haematol. 2004;26:25963. Hvas AM, Nexo E. Holotranscobalamin-a First Choice Assay for Diagnosing Early Vitamin B Deficiency? J Intern Med 2005;257:289-98.
Invited Comments
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 inves-
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tigations 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.[6] 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
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Srikanth et al: Reversible dementias
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.
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P. S. Mathuranath Cognition and Behavioural Neurology Center, Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum - 695 011, Kerala, India E-mail:
[email protected]
References 1. 2.
3.
4.
5.
Clarfield AM. The decreasing prevalence of reversible dementias: an updated meta-analysis. Arch Intern Med 2003;163:2219-29. Sempere AP, Callejo-Dominguez JM, Garcia-Clemente C, et al. [Cost effectiveness of the diagnostic study of dementia in an extra-hospital Neurology service]. Rev Neurol 2004;39:807-10. Takada LT, Caramelli P, Radanovic M, Anghinah R, Hartmann AP, Guariglia CC, et al. Prevalence of potentially reversible dementias in a dementia outpatient clinic of a tertiary university-affiliated hospital in Brazil. Arq Neuropsiquiatr 2003;61:925-9. Sundar U, Sharma A, Yeolekar ME. Presenile dementia—etiology, clinical profile and treatment response at four month follow up. J Assoc Physic India 2004;52:953-8. Jha S, Patel R. Some observations on the spectrum of dementia. Neurol India 2004;52:213-4.
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