Mohammed T. Abou-Saleh

282 PRINCIPLES AND PRACTICE OF GERIATRIC PSYCHIATRYdevelops: in contrast to the true modality-specific prosopagnosia,which occasionally complicates right occipitotemporal strokes,the deficit in semantic dementia is cross-modal, so that patientsare also impaired in the identification of names and voices 13 .In contrast to Alzheimer’s disease, patients with semanticdementia are well orientated and have good episodic (day-to-dayand autobiographical) memory, although recent studies haveshown that the preservation applies only to recent memories. Thatis to say, they show a reversal of the temporal gradient found inamnesia and Alzheimer’s disease 14 .Behavioural changes may be slight at presentation but withtime features identical to those seen in DFT emerge and may bestriking in patients with right-sided disease 15 .Neuropsychological FindingsThe impairment of knowledge is most apparent on tasks requiringa verbal output, such as category fluency tests (in which subjectsare asked to produce as many examples as possible from definedsemantic categories, such as animals, within 1 minute), picturenaming and the generation of verbal definitions to words andpictures. The pattern of errors reflects a loss of fine-grainedknowledge, with preservation of superordinate information: onnaming tasks, naming errors are initially category co-ordinates(‘‘elephant’’ for hippopotamus), then with time prototype responsesemerge, so that all animals are called ‘‘dog’’, then eventually theyare simply called ‘‘animal’’. Single-word comprehension is alsoaffected, as judged by tasks such as word–picture matching orsynonym tasks (e.g. which of the following is the odd one out,‘‘pond, lake or river’’). Non-verbal semantic knowledge is lesseasy to assess, but the Pyramids and Palm Trees Test in which thesubject is asked to judge the semantic relatedness of pictures,invariably reveals deficits 10,16 .In contrast to the profound semantic deficit, other aspects oflanguage competency (phonology and syntax) are strikinglypreserved. Although able to read and spell words with regularspelling-to-sound correspondence, virtually all cases have difficultyin reading and spelling irregular words (e.g. reading PINT torhyme with hint, flint, etc.). This pattern, known as surfacedyslexia (or dysgraphia), has been attributed to the loss ofsemantic support which is necessary for the correct pronunciationof irregular words. Patients perform normally on non-verbalproblem-solving tasks, such as Raven’s Matrices, and on tests ofperceptual and spatial ability.NON-FLUENT PROGRESSIVE APHASIAThe status of patients with the non-fluent form of progressiveaphasia within the spectrum of FTD is less certain. Changes inbehaviour are rare, but after a number of years global cognitivedecline occurs. Unlike the other syndromes, a number of nonfluentcases have Alzheimer pathology 17 .Patients present with complaints of speech dysfluency anddistortion or word-finding difficulty. Phonological errors areusually obvious in conversation. Comprehension is relatively wellpreserved, at least in the early stages, although as the diseaseprogresses there are problems with phoneme discrimination, whichthe patients invariably attribute to poor hearing. In the late stagespatients become mute and effectively ‘‘word deaf ’’. Day-to-daymemory is good and patients cope well in everyday life.Neuropsychological FindingsThe pattern of cognitive deficits in progressive non-fluent aphasiais the mirror image to that found in semantic dementia. Theyperform well on tests of semantic memory, except on thoserequiring a spoken output. Although conversational speech isseverely disrupted, the anomia is mild and the errors arephonological (efelant for elephant). Semantic category fluency isless affected than letter fluency. Word–picture matching, synonymtasks and other semantic tests are usually performed perfectly.They perform poorly on tests of phonological competence (suchas repetition of multisyllabic words and rhyming) and syntacticcomprehension 16 . In common with the other syndromes, however,performance on visuo-spatial and perceptual function is wellpreserved.NEURORADIOLOGICAL FINDINGS IN FTDCT scans are of limited value in diagnosis: the temporal lobes arepoorly seen due to bone artefacts but MRI with coronal images isextremely valuable, especially in cases with semantic dementiawho show focal atrophy of the polar region, fusiform and inferolateralgyri with relative sparing of the hippocampal formation.An asymmetric pattern is almost invariable, with the left temporallobe much more often involved than the right 18 . In non-fluentcases the changes are more subtle, with widening of the leftSylvian fissure. In dementia of frontal type, atrophy of theorbitofrontal cortex can be seen, but 99 Tc–HMPAO–SPECT ismore valuable: focal hypoperfusion is apparent before clearstructural changes are obvious 11,19 .MANAGEMENTThe management of patients and their families requires aspecialist multidisciplinary team approach with input from clinicalpsychology, genetics, psychiatry and neurology. Counselling,especially with regard to genetic implications and prognosis, areessential at an early stage. Although there are, at present, notherapies that will affect the course of the disease, many of thesymptoms can be helped. The stereotypical features, disinhibitionand overeating, may respond to serotonin reuptake blockers 20 .Neuroleptic drugs may be necessary to control aggressivebehaviour.REFERENCES1. Jackson M, Lowe J. The new neuropathology of degenerativefrontotemporal dementias. Acta Neuropathol 1996; 91: 127–34.2. Goedert M, Crowther RA, Spillantini MG. Tau mutations causefrontotemporal dementias. 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