Mohammed T. Abou-Saleh

296 PRINCIPLES AND PRACTICE OF GERIATRIC PSYCHIATRYfew conditions of relevance in old age psychiatry, which will beoutlined briefly. Systemic carcinomas may produce effects in thebrain by several mechanisms through metabolic disturbances(such as excess secretion of adrenocorticotrophic hormone orantidiuretic hormone), through structural change (cerebralsecondaries or infections) or through remote effect (limbicencephalitis). This last condition is common in men, particularlywith oat cell carcinomas of the lung, and has a course of up to 24months. Affective changes dominate the picture, with amnesia theprimary (and occasionally the sole) abnormality. Diagnosis of thecondition is through attention to the physical condition of theindividual. Vitamin deficiencies (notably B 12 and folate) causemental impairment, but routine testing for their levels makes thediagnosis relatively easy. The same holds true for thyroiddysfunction and hypercalcaemia. Chronic excessive alcohol intakecan result in a dementia 24 .CREUTZFELDT–JAKOB DISEASEEarly features include fatigue and listlessness, elevated mood andimpaired memory and concentration. Motor abnormalities occurwith spasticity, ataxia and tremor. Myoclonic jerks and seizuresmay occur. The EEG is very abnormal, with characteristictriphasic waves superimposed on some suppression of thebackground rhythms. The course of the illness is very rapid andmost affected individuals are dead within 2 years 25 .SUMMARYThe differential diagnosis of dementia is a two-stage process: first,the differentiation of dementia from other causes of cognitiveimpairment; and second, if it is found to be a form of dementia,the elucidation of the aetiology. Alzheimer’s disease is thecommonest form of dementia, cerebrovascular disease is probablythe second commonest cause and Lewy body dementia isbecoming increasingly recognized. 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