Chronic Fatigue Syndrome
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J7ournal ofNeurology, Neurosurgery, and Psychiatry 1996;60:495-503 495 Memory, attention, and executive function in J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.60.5.495 on 1 May 1996. Downloaded from chronic fatigue syndrome Eileen Joyce, Stephen Blumenthal, Simon Wessely Abstract tive impairment in information processing Objectives-To examine cognitive func- speed, whereas Smith'0 and Smith et al" have tion in chronic fatigue syndrome. shown deficits in psychomotor function and Methods-Twenty patients with chronic selective and sustained attention as well as fatigue syndrome recruited from primary wide ranging memory deficits. Two studies care and 20 matched normal controls have examined memory and information pro- were given CANTAB computerised tests cessing while measuring evoked potentials and of visuospatial memory, attention, and again the results are contradictory as one study executive function, and verbal tests oflet- found distinct abnormalites in the P300 cogni- ter and category fluency and word associ- tive evoked response'4 whereas the other did ation learning. not.'5 Results-Patients with chronic fatigue One explanation of these discrepant find- syndrome were impaired, predominantly ings concerns sample selection. Most studies in the domain of memory but their pat- have been of patients with chronic fatigue syn- tern of performance was unlike that of drome recruited in specialist settings. These patients with amnesic syndrome or patients tend to have long durations of illness dementia. They were normal on tests of and high rates of psychiatric morbidity both of spatial and pattern recognition memory, which might confound neuropsychological simultaneous and delayed matching to performance and produce variable data. The sample, and pattern-location association role of expectancy and the controversial nature learning. They were impaired on tests of of chronic fatigue syndrome might also exert spatial span, spatial working memory, an influence. We have attempted to overcome and a selective reminding condition of the the problem of subject selection bias by study- pattern-location association learning test. ing patients with chronic fatigue syndrome An executive test ofplanning was normal. recently identified prospectively in primary In an attentional test, eight subjects with care. chronic fatigue syndrome were unable to A second possible explanation for the dis- learn a response set; the remainder crepancies concerns differences in the sensitiv- exhibited no impairment in the executive ity of the neuropsychological tests used, both set shifting phase ofthe test. Patients with within and between studies. For example, sev- http://jnnp.bmj.com/ chronic fatigue syndrome were also eral of the studies have used clinical tests of impaired on verbal tests of unrelated memory and attention devised for the assess- word association learning and letter ment of brain damaged groups of patients, fluency. which may not be sensitive to more subtle Conclusion-Patients with chronic impairments. In this study we have used the fatigue syndrome have reduced atten- Cambridge automated neuropsychological test tional capacity resulting in impaired per- battery (CANTAB).16 This consists of com- on September 28, 2021 by guest. Protected copyright. formance on effortful tasks requiring puterised neuropsychological tests shown to planned or self ordered generation of be sensitive to mild cognitive abnormalities in Academic Department responses from memory. both psychiatric and neurological disorders. of Psychiatry, Charing Because no clear hypotheses concerning the Cross and (7 Neurol Neurosurg Psychiatry 1996;60:495-503) nature of the cognitive complaints in chronic Westminster Medical School, London, UK fatigue syndrome can be derived from existing E M Joyce publications and because these complaints Keywords: chronic fatigue syndrome; memory; atten- might be attributable to abnormalities in any Academic Department tion; cognition; effortful processing of Psychological one of several cognitive processes, we included Medicine, King's several tests of memory, attention, and execu- College Hospital Medical School, Patients with chronic fatigue syndrome often tive function. Finally, because these tests are London, UK complain of poor concentration and memory. all visual in nature, we also employed two ver- S Blumenthal Several studies have looked for objective evi- bal tasks for comparative purposes. S Wessely dence of cognitive dysfunction with a range of Correspondence to: Dr E M Joyce, Mental standardised neuropsychological tests but Health Unit, Queen Mary's have found only mild deficits, if any.'-6 Other Methods University Hospital, Roehampton Lane, London, studies have found significant impairments but PATIENTS SW15 5PN, UK. within these there is no consensus as to which All patients were identified at the final stage of Received 30 August 1995 cognitive processes are primarily affected.7-" a large prospective community based study of and in revised form 24 November 1995 For example, Riccio et al found a discrete chronic fatigue syndrome and its relation to Accepted 30 November 1995 memory deficit,7 DeLuca et al8 9 found a selec- viral infection.'7 18 A total of 2376 patients 49646oyce, Blumenthal, Wessely aged 18 to 45 were recruited from primary examined. There was no evidence that the J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.60.5.495 on 1 May 1996. Downloaded from care after a consultation with a general practi- patients with chronic fatigue syndrome were tioner for a viral infection. Of these, 1985 were more impaired on tests performed towards the followed up at six months and those scoring end of the test session. In fact, the most signif- above a predefined cut off on a scale measur- icant group differences were found on tests of ing fatigue'9 completed several questionnaires spatial span and spatial working memory, to establish the criteria for chronic fatigue syn- which were performed early in the session. drome and underwent a standardised psychi- atric assessment.20 Out of the original 2376, PROCEDURE 36 were identified as fulfilling the current Computerised tests United Kingdom criteria for chronic fatigue The CANTAB battery runs on a personal syndrome.2' These patients were spread across computer with an Intersolve LCD portable five general practices in the south of England. touch sensitive screen. Detailed descriptions Twenty nine were living in two practices close of these tests have been published elsewhere to our research team and these were invited to (see 16293436) and only a brief outline is given participate. Twenty patients agreed to be below. tested. Of those not tested, one refused and Pattern recognition memory-Subjects were the remainder failed to reply. Compared with shown 12 visual patterns one after another. the group of patients with chronic fatigue syn- They were then shown 12 successive pairs of drome tested, there were more men among the patterns of which one had been shown before patients not tested but no differences in sever- and the other was novel. They were asked to ity of disease. Controls were selected from the touch the familiar pattern. The procedure was same cohort study and were 20 patients who then repeated with 12 new patterns (maxi- had originally consulted with a viral infection mum score = 24). but were not chronically fatigued six months Spatial recognition memory-Subjects were later. Most of the fatigued patients did not shown five squares, one at a time, at different consider themselves to have chronic fatigue locations on the screen. They were then shown syndrome or myalgic encephalomyelitis and five successive pairs of squares of which one were not seeking help under these labels. was at a previous location and the other was at Table 1 shows that the two groups were a novel location. They were asked to touch the matched for age, sex ratio, and WAIS-R square at the location previously used. Four IQ estimated from the national adult reading blocks of five stimuli were presented in total test (NART).22 Patients were asked to (maximum score = 20). complete a 13 item fatigue questionnaire Simultaneous and delayed matching to sample- covering items relating to both physical and Subjects were shown a complex abstract pat- mental fatigue'9 and the hospital anxiety and tern and then asked to pick out this pattern depression scale 23, a well validated question- from an array of four similar patterns. In the naire which avoids using items concerning simultaneous condition, the sample pattern somatic symptoms including fatigue. A score remained on the screen while the choice stimuli of 1 1 or more designates pathological anxiety appeared. In the delayed condition, the sam- or depression. Table 1 shows the scores on ple pattern disappeared and the choice pat- these scales. The tests were given in the same terns appeared after a delay of 0, 4, or 12 http://jnnp.bmj.com/ order for each subject and the test session took seconds. There were 10 test trials at each of about three hours to complete. All controls the simultaneous and delay conditions, which and 15 patients with chronic fatigue syndrome were presented in a randomised order. completed the tests in one session. The Paired associates learning-Subjects were remaining patients performed the tests over required to learn the location of nine sets of two sessions because the development of sub- patterns individually placed in boxes on the curtailed the first session. screen. For each the was allowed