Mohammed T. Abou-Saleh

Principles and Practice of Geriatric Psychiatry.Editors: Professor John R. M. Copeland, Dr Mohammed T. Abou-Saleh and Professor Dan G. BlazerCopyright & 2002 John Wiley & Sons LtdPrint ISBN 0-471-98197-4 Online ISBN 0-470-84641-0268 PRINCIPLES AND PRACTICE GERIATRIC PSYCHIATRYClinical Criteria for Dementia with Lewy BodiesI. G. McKeithNewcastle upon Tyne General Hospital, UKWhy are diagnostic criteria for dementia with Lewy body (DLB)important? There are many reasons, but the most significant are toproperly advise patients and carers, to minimize neurolepticprescribing and possibly to effectively target cholinesterase inhibitoruse. Also, since DLB is relatively common, it needs to be routinelyexcluded in the differential diagnosis of other dementia subtypes,particularly when a diagnosis of Alzheimer’s disease (AD) is beingconsidered. Several studies have now reported on either thesensitivity (proportion of cases positively identified) or specificity(proportion of negative cases correctly identified) of the InternationalConsensus criteria for DLB, against neuropathologicaldiagnosis. Most find ‘‘probable DLB’’ criteria to have a specificity40.8, a figure comparable with the best clinical criteria for AD andParkinson’s disease (PD). High specificity means that when adiagnosis of probable DLB is made, it is likely to be correct. Themore lenient ‘‘possible DLB’’ category should be useful as ascreening tool for identifying cases in the clinic, although manyfalse-positive diagnoses will be made.Sensitivity rates for probable DLB are more variable andgenerally lower. This may in part be due to retrospectiveapplication of the criteria to case records in most of these studies.Spontaneous documentation of fluctuation and detailed psychiatricphenomenology in case notes is notoriously incomplete,leading some to conclude that inter-rater reliability for individualdiagnostic items, especially ‘‘fluctuation’’, is unsatisfactory.Although a tighter operational definition, or a biological measure,of fluctuation would undoubtedly be useful, studies prospectivelyapplying the DLB diagnostic criteria generally find inter-raterreliability for individual items (including fluctuation) and for afinal diagnosis of DLB, to be acceptable (k40.6), allowing fordiagnostic sensitivities 40.8 to be achieved.Ancillary investigations will have an important future role inimproving the accuracy of clinical diagnosis of DLB. FP-CITSPECT brain imaging demonstrates a large reduction indopamine transport to the striatum in DLB, and this may beapparent before extrapyramidal signs are manifest. Nigrostriataldopaminergic depletion is only rarely seen in AD or vasculardementia. Relative lack of medial temporal lobe atrophy on CT/MRI is also characteristic of DLB compared to AD.The Second International Workshop on DLB recommendedthat the Consensus criteria should continue to be used in theircurrent format for recruiting cohorts of DLB patients for researchstudies and clinical trials. Depression and REM sleep behaviourdisorder were suggested as two additional features supporting thediagnosis.Accurate case detection will ultimately be best achieved byincreasing the index of suspicion for a diagnosis of DLB, notonly in dementia assessment clinics but also in any settingwhere elderly patients may present with delirium, movementdisorder, falls or syncope. Perhaps we might do better to framethe next revision of the diagnostic criteria within a broaderspectrum of Lewy body-related disorders or a-synucleinopathies,thereby acknowledging the links between PD, DLB andprimary autonomic failure, and breaking down some currentlyunhelpful boundaries between psychiatry, neurology and geriatricmedicine.