Diagnostic and Statistical Manual-5 and dementia: Fine print, finer points.

Abstract

Byline: K. Jacob Introduction The Diagnostic and Statistical Manual (DSM) revolution has marched on with the unveiling of its most recent achievement, the DSM-5. [sup][1] However, many questions and controversies raised [sup][2] call for introspection into its many diagnostic categories and their implementation in practice. The limitations of phenomenological diagnoses and clinical classifications and the complexity of the diagnostic process, frequently misunderstood, demand review. This editorial attempts to appraise clinical reality, diagnostic guidelines, and medical practice in relation to neurocognitive disorders (NCD). Changes in DSM-5 The DSM-5 has made many changes to the section on cognitive disorders. [sup][1] It has expanded cognitive domains, which now include complex attention, executive function, learning and memory, language, perceptual-motor, and social cognition. It changed the name dementia to major NCD, which now subsumes dementia and amnestic disorder. It introduced the category of mild NCD, for mild cognitive impairment. Common etiological diagnoses, which result in neurocognitive presentations, have operational diagnostic criteria. Clinical information and the results of neuropsychological tests are now required for a definitive diagnosis of NCD. DSM-5 demands comparison of the person's individual performance on neuropsychological tests with population norms, adjusted for age, education, and cultural background. It provides for bedside cognitive tests, for objective assessments. Fine print, finer points Diagnostic and laboratory tests support the operational criteria and categories for cognitive disorders in DSM-5. The criteria are more rigorous and are on firmer etiopathological evidence base than most other diagnoses in the manual. However, the DSM-5 acknowledges, in the text, many caveats and cautionary statements, which call for a nuanced understanding and cautious interpretation. Clinical dimensions The DSM-5 clearly acknowledges that cognitive decline is more appropriately mapped on a dimension from deficits commonly seen in older people without disability, to those with mild cognitive impairment to frank and severe cognitive deterioration. Despite its mathematical and clinical convenience, dichotomous demarcations often misrepresent clinical reality, which often lie on a spectrum, [sup][3] leading to errors. The continuum of cognition and cognitive decline makes categorical diagnosis complex, making the placement of a diagnostic threshold, in stone, difficult. Nevertheless, clinical medicine and psychiatry have preferred diagnostic categories, even while identifying and managing clinical phenomena, which usually lie on a continuum with a gradual change from normal to abnormal/pathological and without definitive threshold. DSM-5 does acknowledge that the current categorization of NCD, into major and mild, as arbitrary. Surrogate indicators of pathology The evidence generated by medical procedures contributes different weights to diagnosis. Certain procedures, such as biopsies, often produce definitive evidence. Other procedures, such as the brain imaging in patients with significant cognitive decline, provide contributory evidence. When combined with a history, clinical examination and neuropsychological data, the results of the test can lead to a diagnostic decision. Nevertheless, the scenario is complex, particularly in the context of dementia. The inability to biopsy brains of people with cognitive impairment forces us to employ surrogate clinical markers for diagnosis. However, the use of surrogate markers is complicated by the limited correlation between the clinical continuum and the spectrum of pathology. The Nun study clearly documents the presence of pathological changes even among those who did not demonstrate clinical evidence of dementia. [sup][4] Consequently, the disconnect or rather the lack of lock step, between pathological and clinical dimensions make diagnostic decision-making using surrogate clinical markers difficult. …