- Email: [email protected]
Memory Testing: No Thermometers Available
604
patients with definitely abnormal PV ( < 80 % of the predicted normal), and those with a high normal RCM (113-125% of the predicted normal) also had higher or more persistently elevated PCV values on repeated measurement, as compared with those in a third group, who had minimal changes in RCM and PV values; these patients were labelled as transient pseudopolycythaemics and probably overlap with the third group described by Pearson et al. A useful practical suggestion emerged from this study: Marsh et al recommended that, in borderline cases, repeated measurements of PCV may, when this value declines, obviate the need for blood volume measurement. The PCV figure itself does not decisively distinguish between true and pseudopolycythaemia, except with figures of 0-60 or more." Moreover, it is not always easy to distinguish patients with a high normal RCM from those with mild forms of secondary polycythaemia, or those in the early stages of proliferative polycythaemia;14 experience has shown that the latter may occasionally present with a solitary erythrocytosis.4 Clearly, these patients must be kept under review. How should patients with established pseudopolycythaemia be managed? In those with PCVs of more than 0-54, regular small volume venesections of, say, 250 ml have been recommended, and seem prudent in the light of recent observations that a persistently raised PCV, with its associated increase in whole blood viscosity, causes a reduction in cerebral blood flow and may predispose to vascular occlusive episodes.15 However, in patients with PCV values between 0-51-0-54, it is not known whether therapeutic venesections, aimed at keeping the PCV around 0-45, confer any benefit. It is precisely this question that the Polycythaemia Study Group of the Royal College of Physicians14 is currently addressing. It goes without saying that in such patients the underlying risk factors, such as hypertension, obesity, and cigarette smoking need equal attention.
Memory Testing: No Thermometers Available CLINICAL is
assessment
of
memory,
of the
as
now
from practised, inadequate. Many the practical need for a screening procedure to detect gross impairment and its implications in terms of cerebral pathophysiology; they are unrelated to current models of memory processes and are dependent on the experience and the acumen of the tests stem
examiner. Moreover, the terminology is confusing. Thus short-term memory may be interpreted, historically, as memory for recent (autobiographical) events preceding the illness or, more technically, as a system that is limited in capacity and of which the operation is observed and measured over seconds, not hours or days. Misunderstandings can be avoided if the neurologists’ terms "recent" and "remote" refer to a time-span in the patient’s premorbid life whereas "short-term" and "long-term" are regarded as properties of dissociable memory systems that can be experimentally tested with new material. In general, there has been a failure to appreciate the wide spectrum of memory disorders. Digit repetition, recall of a name and address, and a correct answer to a question about a contemporary television serial provide but a coarse and limited screen. They are insufficient for diagnosis, research, or medico-legal assessment. A patient with prosopagnosia and/or topographical memory loss might pass such tests without difficulty whereas an aphasic patient could fail, without the opportunity to display intact memory for faces, places, autobiographical events, or general
(semantic) knowledge. The conceptual framework required for evaluation of memory processes is still evolving. Forty years ago, memory tests were designed in relation to a unitary (outmoded) brain damage, to be differentiated from functional (eg, depressive) disorders. The next stage was appreciation of hemispheric asymmetries of function and the notion of verbal and non-verbal memory deficits, associated with dominant and nondominant hemisphere lesions, respectively. Further dissection of memory mechanisms,’,’ prompted by the fractionations of disease, now emphasises the need for models of memory processes that incorporate the dissociable channels (visual, auditory, sensorimotor), mental representations, and output modes that are involved in registration, storage, and retrieval of information.
Contemporary neuropsychological examination, therefore, requires a more precise definition of intact and impaired mechanisms and skills in the patient. The emerging patterns fulfil several needs. For the clinician, they help to define syndromes in relation to the aetiology and ontogeny of the disorder, and they offer clues for remedial management of the individual patient. They also provide material for the continual testing and updating of memory models. A basic distinction has to be made between the so-called pure amnesias (sometimes observed in Korsakoffpsychosis, herpes simplex encephalitis, and ventricular tumours) and memory disorders that occur within a setting of more diffuse cognitive deterioration (the degenerative diseases, including 1. Shallice T. Neuropsychological research and the fractionation of
Wetherley-Mem G, Pearson TC, Bumey PGJ, Morris RW. Polycythaemia study: a project of the Royal College of Physicians Research Unit 1. Objectives, background and design. J R Coll Physns Lond 1987; 21: 7-16. 15. Humphrey PRD, Du Boulay GH, Marshall J, et al. Cerebral blood flow and viscosity in relative polycythaemia. Lancet 1979; ii: 873-77.
14.
memory systems In Nilsson LG, ed. Perspectives in memory research. Hillsdale, New Jersey: Erlbaum, 1979: 257-77.
2. Schacter DL.
Multiple forms of memory in humans and animals. In: Weinberger NM, McGaugh JL, Lynch G, eds. Memory systems of the brain. New York Guildford Press, 1985: 351-79.
605
Alzheimer, Huntington, and Creutzfeldt-Jacob diseases, and multi-infarct dementia). A wellstandardised mini-dementia scale may initially help to identify the latter groups, but a comprehensive
neuropsychological examination of language, perception, and spatial orientation is eventually required. (heterogeneous) group of "pure" is amnesias, there a typical pattern of intact short-term verbal memory (as measured by the conventional digit span test) and grossly impaired long-term memory (usually marked by difficulty with spontaneous recall of new material-short stories, unfamiliar faces, and new routes). The long-term memory defect in amnesia involves both retention of premorbid events (retrograde amnesia) and learning of new material (anterograde amnesia). It has been suggested that at least two components in long-term memory are differentially affected in amnesia-relative sparing of semantic memory (conceptual knowledge of the world, including language) and grossly impaired "episodic" memory (retention of personal experiences within their temporal context).33 This apparent difference may reflect overleaming of semantic information rather than two separate memory systems, but a case-report4 of the converse patternimpairment of semantic memory with relatively preserved autobiographical memory—argues the case for a genuine functional distinction. Some forms of learning are spared in pure amnesia.5 Amnesic patients may learn and retain various skills, including assembly work, typing, and routine work with computers. A characteristic feature of all preserved learning in amnesia is that patients have no conscious recollection of the previous learning episodes: hence the distinction between procedural and declarative memory in amnesia, originally expressed in the form of knowing how and knowing that.6 Declarative memory contains data-based information which can be explicitly accessed. Procedural learning is taken to involve the reorganisation of existing processing structures (procedures); the content of procedural memory cannot be accessed explicitly but can be expressed only through reactivation of the particular processing structures. The ability of the amnesic patient to learn new skills is clearly important in rehabilitation? In progressive dementing disorders, such as Huntington’s and Alzheimer’s diseases, memory impairment is one of the earliest and most prominent Within the
3 Cermak LS. The episodic-semantic distinction in
amnesia. In: Squire LR, Butters N, eds. Neuropsychology of memory. New York: Guildford Press, 1984: 55-62. 4 De Renzi E. Discussion of case reports of autobiographical and/or semantic amnesia. Presented at annual meeting of International Neuropsychological Symposium,
Sintra, Portugal, June 22-26, 1987. NJ. Preserved learning capacity in amnesia: evidence for multiple memory systems. In: Squire LR, Butters N, eds. Neuropsychology of memory. New York:
5 Cohen
Guilford Press, 1984: 83-103. NJ, Squire LR. Preserved learning and retention of pattern analyzing skill in amnesia: dissociation of "knowing how" and "knowing that". Science 1980; 210: 207-10. 7 Newcombe F. Rehabilitation in clinical neurology: neuropsychological aspects. In. Frederiks JAM, ed. Handbook of clinical neurology, vol 2. Amsterdam Elsevier, 1985: 609-642. 6 Cohen
symptoms,8-1° but it is qualitatively different from that occurring in more pure forms of amnesia. For example, in Huntington’s disease (unlike pure amnesia), procedural skill learning may be compromised, whereas verbal recognition memory may be relatively spared despite severe defects in verbal recallY,12 In contrast to the
global amnesic disorders, more material-specific impairments of memory occur in patients who have undergone unilateral temporal lobectomy for the treatment of intractable epilepsy.l3 Left temporal resection (involving the hippocampus) leads to impaired learning and memory for verbal material (although young patients are often able to compensate by using external aids), whereas memory for non-verbal stimuli remains intact. The converse pattern obtains for right temporal lobectomy, although the non-verbal impairment can be discerned only by sensitive tasks and is not an obvious handicap in everyday life. A comprehensive examination of memory circumscribed
functions
cannot be conducted at the bedside or brief outpatient appointment; evaluation of an individual patient is at least as complex as photomicroscopy or a comprehensive biochemical assay and none of these assessments should be undertaken by amateurs. In practice, a three-tier process is rational. At the screening level, with limits on time and skill, the clinicians’ resort to digit span and a short paragraph is defensible as a probe of verbal short-term and long-term memory, respectively. At the second level, a full neuropsychological examination is required to establish which memory processes are deficient and whether other cognitive skills are impaired. Here the neuropsychologist will make selective use of Wechsler’s intelligence and memory scales, supplemented by further tasks of attention, problem-solving, and praxis. Global memory quotients are misleading;14 they combine performance on different tasks (orientation, verbal memory, and constructional ability) in a single figure and provide no precise information about the nature of the memory impairment. The story recall sections of such scales, however, are robust measures of long-term verbal memory (particularly when delayed recall, without forewarning, is tested) and they correlate well with relatives’ ratings of real-life memory function-at least for patients with closed
during
a
8. Miller E. Abnormal aging: the psycholoogy of senile and presenile dementia. New York: Wiley, 1977. 9. Butters N, Sax D, Montgomery K, Tarlow S. Comparison of neuropsychological deficits associated with early and advanced Huntington’s disease. Arch Neurol 1978; 35: 585-89. 10. Katzman R, Terry RD, Bick KL, eds. DAT disease, senile dementia and related disorders. New York: Raven, 1978. 11. Martone M, Butters N, Payne M, Becker JT, Sax DS. Dissociations between skill learning and verbal recognition memory in amnesia and dementia. Arch Neurol 1984; 41: 965-70. 12. Moss MB, Albert MS, Butters N, Payne M. Differential patterns of memory loss with Alzheimer’s disease, Hunungton’s disease, and alcoholic Korsakoff syndrome. Arch Neurol 1986; 43: 239-46. 13. Milner B. Interhemispheric differences in the localization of psychological processes in man Br Med Bull 1971; 27: 272-77. 14. Loring DW, Papanicolaou AC Memory assessment m neuropsychology: theoretical considerations and practical utility. J Clin Expil Neuropsychol 1987, 9: 340-58.
606 and that simple food hygiene will eliminate any risk that exists. They suggest that the priority is not to identify carriers but to improve hygiene practice and to exclude food handlers who are actually ill. Moreover, as they rightly point out, insistence on screening or bacteriological clearance after any gastrointestinal upset will make catering workers less likely to report acute illness. In practical terms, Cruickshank and Humphrey stand by difficulty, multiple-choice recognition procedures can the guidance on the control of human sources of be used--eg, Benton’s visual retention task 17 (which gastrointestinal infections given by the Public Health requires the patient to recognise one of four Laboratory Service in 1983.2 These guidelines state that most symptomless food handlers recovering from nongeometrical designs) or Warrington’s unfamiliar face and typhoid salmonella infection should be allowed to work, and task.18 Patients with severe speech recognition that three negative stool specimens should be required only motor problems can readily respond by nodding or for defined high-risk categories. However, the need to judge pointing. A third level of inquiry is needed if any individual cases on merit, and particularly the capability of substantial advances are to be expected in the theory the individual to wash his hands adequately, is emphasised. and management of memory disorders. This step If employers in the catering industry follow this advice, involves fine-grain analysis of and intact and if employees are therefore more willing to admit to acute skills to identify the processes involved and to explore illness, British consumers may expect a small decrease in the special conditions in which individual patients can food poisoning risks. However, in a survey of the causes of 566 outbreaks of salmonella food poisoning in the UK, acquire and retain information in a real-life setting. 19.20 infection of a food handler was implicated in only z The great majority of outbreaks were attributed, either directly or indirectly through cross-contamination, to infected food. This is not only a problem of food hygiene but also an indictment of the methods of food production. According to FOOD HANDLERS AND SALMONELLA FOOD the Food Hygiene Laboratory, salmonellae can be grown POISONING from 79% of frozen chickens, 12% of pork sausages, and 7-5% of minced meat (and, incidentally, from occasional AT a time when many people return from holidays samples of frogs’ legs, turtle meat, and herbal teas).3 The abroad, and when warm weather has exposed the weakness source of this endemic infection is imported animal probable in kitchen hygiene, numerous food handlers will be told that food-stuffs. A report from the Central Veterinary they have been infected by non-typhoid salmonellae. These that present controls are less than Laboratory suggests individuals will have the misery of their physical illness and one consequence is the equally important and effective,4 compounded by restrictions placed on their work. The still uncontrolled problem of-inappropriate antibiotic use in mythology of the "salmonella carrier", which is based on an animals. In Britain, the Government appears to be as unproven extrapolation from the epidemiology of typhoid ineffectual in dealing with commercial interests in this in All is health attitudes. fever, deeply engrained public sphere as it is in the prevention of lung cancer and manner of rituals have been practised, including routine cardiovascular disease-a view supported by the continuing screening of catering staff returning from overseas, occurrence of outbreaks of salmonellosis associated with the antibiotic treatment of healthy carriers, and collection of sale of unpasteurised milk. stool samples in various numbers and at various intervals. The scientific evidence suggests that non-typhoid Victimisation by convention has no place in modem public salmonella infection is very different in its epidemiology . health practice. from enteric fever. The illness is usually mild, the infective Cruickshank and Humphrey have now challenged such dose is high, carriage is rare beyond three months, and rituals with a healthy dose of scientific criticism. These due to carriers are seldom documented. outbreaks workers reviewed the evidence for the contention that food the public health risk from non-typhoid Consequently, poisoning is spread by apparently healthy food handlers salmonellae will be minimised if most food handlers with who carry non-typhoid strains of salmonella bacterial They diarrhoea are excluded from work, but are allowed to return concluded that the carrier state is rare, that except in the as soon as they are free of symptoms. Stool specimens should immediate convalescent stage of an acute illness the amount be required only if they fall into a high-risk group, by virtue of bacteria carried is below that needed to transmit illness, of their capability of delivering a high dose of bacteria (eg, handlers of food not to be cooked further), of their contact with individuals who are at risk of infection from a low dose 15. Baddeley A, Sunderland A, Harris J. How well do laboratory-based psychological tests of bacteria (eg, nurses on a geriatric ward), or of a history predict patients’ performance outside the laboratory. In: Corkin S, David KL, Growdon JH, Usdin E, Wurtman RJ, eds. Alzheimer’s disease: a report of progress which suggests that they might be carrying Salmonella typhi (Aging, vol 19). New York: Raven, 1982. 16. Sunderland A, Harris JE, Baddeley AD. Do laboratory tests predict everyday or S paratyphi.
head injury.15,16 However, non-verbal visual memory is seldom measured appropriately. Traditional tasks require a patient to draw geometrical designs from memory. Constructional apraxia confounds the interpretation of poor performance of such tasks which, in any case, correlate highly with visuoperceptual and motor skills. To overcome this
.
impaired
A neuropsychological study. J Verb Learn Verbal Behav 1983; 22: 341-57. 17. Benton AL. The visual retention test as a constructional praxis task. Confin Neurol
memory?
1962; 22: 141-55. 18. Warrington EL. Recognition memory test. Windsor: NFER-Nelson, 1984. 19. Schacter DL, Rich SA, Stampp MS. Remediation of memory disorders: experimental evaluation of the spaced-retrieval technique. J Clin Exptl Neuropsychol 1985; 1:
79-96. 20. Wilson BA. Rehabilitation of Memory. New York: Guildford Press, 1987. 1. Cruickshank JG, Humphrey TJ. The carrier food handler and non-typhoid salmonellosis. Epidem Inf 1987; 98: 223-30.
2. PHLS Salmonella Sub-committee. Notes
on
the control of human
sources
of
gastro-intestinal infections and bacterial intoxications m the United Kingdom. Commun Dis Rep 1983 (supplement 1) 3. Gilbert RJ, Roberts D. Food hygiene aspects and laboratory methods. Salmonella special: March 1987 revision of PHLS Microbiology Digest 1986; 3: 9-11. 4 Kirby D, Wray C. Veterinary aspects and laboratory methods. Salmonella special: March 1987 revision of PHLS Microbiology Digest 1986, 3: 12-13.
patients with definitely abnormal PV ( < 80 % of the predicted normal), and those with a high normal RCM (113-125% of the predicted normal) also had higher or more persistently elevated PCV values on repeated measurement, as compared with those in a third group, who had minimal changes in RCM and PV values; these patients were labelled as transient pseudopolycythaemics and probably overlap with the third group described by Pearson et al. A useful practical suggestion emerged from this study: Marsh et al recommended that, in borderline cases, repeated measurements of PCV may, when this value declines, obviate the need for blood volume measurement. The PCV figure itself does not decisively distinguish between true and pseudopolycythaemia, except with figures of 0-60 or more." Moreover, it is not always easy to distinguish patients with a high normal RCM from those with mild forms of secondary polycythaemia, or those in the early stages of proliferative polycythaemia;14 experience has shown that the latter may occasionally present with a solitary erythrocytosis.4 Clearly, these patients must be kept under review. How should patients with established pseudopolycythaemia be managed? In those with PCVs of more than 0-54, regular small volume venesections of, say, 250 ml have been recommended, and seem prudent in the light of recent observations that a persistently raised PCV, with its associated increase in whole blood viscosity, causes a reduction in cerebral blood flow and may predispose to vascular occlusive episodes.15 However, in patients with PCV values between 0-51-0-54, it is not known whether therapeutic venesections, aimed at keeping the PCV around 0-45, confer any benefit. It is precisely this question that the Polycythaemia Study Group of the Royal College of Physicians14 is currently addressing. It goes without saying that in such patients the underlying risk factors, such as hypertension, obesity, and cigarette smoking need equal attention.
Memory Testing: No Thermometers Available CLINICAL is
assessment
of
memory,
of the
as
now
from practised, inadequate. Many the practical need for a screening procedure to detect gross impairment and its implications in terms of cerebral pathophysiology; they are unrelated to current models of memory processes and are dependent on the experience and the acumen of the tests stem
examiner. Moreover, the terminology is confusing. Thus short-term memory may be interpreted, historically, as memory for recent (autobiographical) events preceding the illness or, more technically, as a system that is limited in capacity and of which the operation is observed and measured over seconds, not hours or days. Misunderstandings can be avoided if the neurologists’ terms "recent" and "remote" refer to a time-span in the patient’s premorbid life whereas "short-term" and "long-term" are regarded as properties of dissociable memory systems that can be experimentally tested with new material. In general, there has been a failure to appreciate the wide spectrum of memory disorders. Digit repetition, recall of a name and address, and a correct answer to a question about a contemporary television serial provide but a coarse and limited screen. They are insufficient for diagnosis, research, or medico-legal assessment. A patient with prosopagnosia and/or topographical memory loss might pass such tests without difficulty whereas an aphasic patient could fail, without the opportunity to display intact memory for faces, places, autobiographical events, or general
(semantic) knowledge. The conceptual framework required for evaluation of memory processes is still evolving. Forty years ago, memory tests were designed in relation to a unitary (outmoded) brain damage, to be differentiated from functional (eg, depressive) disorders. The next stage was appreciation of hemispheric asymmetries of function and the notion of verbal and non-verbal memory deficits, associated with dominant and nondominant hemisphere lesions, respectively. Further dissection of memory mechanisms,’,’ prompted by the fractionations of disease, now emphasises the need for models of memory processes that incorporate the dissociable channels (visual, auditory, sensorimotor), mental representations, and output modes that are involved in registration, storage, and retrieval of information.
Contemporary neuropsychological examination, therefore, requires a more precise definition of intact and impaired mechanisms and skills in the patient. The emerging patterns fulfil several needs. For the clinician, they help to define syndromes in relation to the aetiology and ontogeny of the disorder, and they offer clues for remedial management of the individual patient. They also provide material for the continual testing and updating of memory models. A basic distinction has to be made between the so-called pure amnesias (sometimes observed in Korsakoffpsychosis, herpes simplex encephalitis, and ventricular tumours) and memory disorders that occur within a setting of more diffuse cognitive deterioration (the degenerative diseases, including 1. Shallice T. Neuropsychological research and the fractionation of
Wetherley-Mem G, Pearson TC, Bumey PGJ, Morris RW. Polycythaemia study: a project of the Royal College of Physicians Research Unit 1. Objectives, background and design. J R Coll Physns Lond 1987; 21: 7-16. 15. Humphrey PRD, Du Boulay GH, Marshall J, et al. Cerebral blood flow and viscosity in relative polycythaemia. Lancet 1979; ii: 873-77.
14.
memory systems In Nilsson LG, ed. Perspectives in memory research. Hillsdale, New Jersey: Erlbaum, 1979: 257-77.
2. Schacter DL.
Multiple forms of memory in humans and animals. In: Weinberger NM, McGaugh JL, Lynch G, eds. Memory systems of the brain. New York Guildford Press, 1985: 351-79.
605
Alzheimer, Huntington, and Creutzfeldt-Jacob diseases, and multi-infarct dementia). A wellstandardised mini-dementia scale may initially help to identify the latter groups, but a comprehensive
neuropsychological examination of language, perception, and spatial orientation is eventually required. (heterogeneous) group of "pure" is amnesias, there a typical pattern of intact short-term verbal memory (as measured by the conventional digit span test) and grossly impaired long-term memory (usually marked by difficulty with spontaneous recall of new material-short stories, unfamiliar faces, and new routes). The long-term memory defect in amnesia involves both retention of premorbid events (retrograde amnesia) and learning of new material (anterograde amnesia). It has been suggested that at least two components in long-term memory are differentially affected in amnesia-relative sparing of semantic memory (conceptual knowledge of the world, including language) and grossly impaired "episodic" memory (retention of personal experiences within their temporal context).33 This apparent difference may reflect overleaming of semantic information rather than two separate memory systems, but a case-report4 of the converse patternimpairment of semantic memory with relatively preserved autobiographical memory—argues the case for a genuine functional distinction. Some forms of learning are spared in pure amnesia.5 Amnesic patients may learn and retain various skills, including assembly work, typing, and routine work with computers. A characteristic feature of all preserved learning in amnesia is that patients have no conscious recollection of the previous learning episodes: hence the distinction between procedural and declarative memory in amnesia, originally expressed in the form of knowing how and knowing that.6 Declarative memory contains data-based information which can be explicitly accessed. Procedural learning is taken to involve the reorganisation of existing processing structures (procedures); the content of procedural memory cannot be accessed explicitly but can be expressed only through reactivation of the particular processing structures. The ability of the amnesic patient to learn new skills is clearly important in rehabilitation? In progressive dementing disorders, such as Huntington’s and Alzheimer’s diseases, memory impairment is one of the earliest and most prominent Within the
3 Cermak LS. The episodic-semantic distinction in
amnesia. In: Squire LR, Butters N, eds. Neuropsychology of memory. New York: Guildford Press, 1984: 55-62. 4 De Renzi E. Discussion of case reports of autobiographical and/or semantic amnesia. Presented at annual meeting of International Neuropsychological Symposium,
Sintra, Portugal, June 22-26, 1987. NJ. Preserved learning capacity in amnesia: evidence for multiple memory systems. In: Squire LR, Butters N, eds. Neuropsychology of memory. New York:
5 Cohen
Guilford Press, 1984: 83-103. NJ, Squire LR. Preserved learning and retention of pattern analyzing skill in amnesia: dissociation of "knowing how" and "knowing that". Science 1980; 210: 207-10. 7 Newcombe F. Rehabilitation in clinical neurology: neuropsychological aspects. In. Frederiks JAM, ed. Handbook of clinical neurology, vol 2. Amsterdam Elsevier, 1985: 609-642. 6 Cohen
symptoms,8-1° but it is qualitatively different from that occurring in more pure forms of amnesia. For example, in Huntington’s disease (unlike pure amnesia), procedural skill learning may be compromised, whereas verbal recognition memory may be relatively spared despite severe defects in verbal recallY,12 In contrast to the
global amnesic disorders, more material-specific impairments of memory occur in patients who have undergone unilateral temporal lobectomy for the treatment of intractable epilepsy.l3 Left temporal resection (involving the hippocampus) leads to impaired learning and memory for verbal material (although young patients are often able to compensate by using external aids), whereas memory for non-verbal stimuli remains intact. The converse pattern obtains for right temporal lobectomy, although the non-verbal impairment can be discerned only by sensitive tasks and is not an obvious handicap in everyday life. A comprehensive examination of memory circumscribed
functions
cannot be conducted at the bedside or brief outpatient appointment; evaluation of an individual patient is at least as complex as photomicroscopy or a comprehensive biochemical assay and none of these assessments should be undertaken by amateurs. In practice, a three-tier process is rational. At the screening level, with limits on time and skill, the clinicians’ resort to digit span and a short paragraph is defensible as a probe of verbal short-term and long-term memory, respectively. At the second level, a full neuropsychological examination is required to establish which memory processes are deficient and whether other cognitive skills are impaired. Here the neuropsychologist will make selective use of Wechsler’s intelligence and memory scales, supplemented by further tasks of attention, problem-solving, and praxis. Global memory quotients are misleading;14 they combine performance on different tasks (orientation, verbal memory, and constructional ability) in a single figure and provide no precise information about the nature of the memory impairment. The story recall sections of such scales, however, are robust measures of long-term verbal memory (particularly when delayed recall, without forewarning, is tested) and they correlate well with relatives’ ratings of real-life memory function-at least for patients with closed
during
a
8. Miller E. Abnormal aging: the psycholoogy of senile and presenile dementia. New York: Wiley, 1977. 9. Butters N, Sax D, Montgomery K, Tarlow S. Comparison of neuropsychological deficits associated with early and advanced Huntington’s disease. Arch Neurol 1978; 35: 585-89. 10. Katzman R, Terry RD, Bick KL, eds. DAT disease, senile dementia and related disorders. New York: Raven, 1978. 11. Martone M, Butters N, Payne M, Becker JT, Sax DS. Dissociations between skill learning and verbal recognition memory in amnesia and dementia. Arch Neurol 1984; 41: 965-70. 12. Moss MB, Albert MS, Butters N, Payne M. Differential patterns of memory loss with Alzheimer’s disease, Hunungton’s disease, and alcoholic Korsakoff syndrome. Arch Neurol 1986; 43: 239-46. 13. Milner B. Interhemispheric differences in the localization of psychological processes in man Br Med Bull 1971; 27: 272-77. 14. Loring DW, Papanicolaou AC Memory assessment m neuropsychology: theoretical considerations and practical utility. J Clin Expil Neuropsychol 1987, 9: 340-58.
606 and that simple food hygiene will eliminate any risk that exists. They suggest that the priority is not to identify carriers but to improve hygiene practice and to exclude food handlers who are actually ill. Moreover, as they rightly point out, insistence on screening or bacteriological clearance after any gastrointestinal upset will make catering workers less likely to report acute illness. In practical terms, Cruickshank and Humphrey stand by difficulty, multiple-choice recognition procedures can the guidance on the control of human sources of be used--eg, Benton’s visual retention task 17 (which gastrointestinal infections given by the Public Health requires the patient to recognise one of four Laboratory Service in 1983.2 These guidelines state that most symptomless food handlers recovering from nongeometrical designs) or Warrington’s unfamiliar face and typhoid salmonella infection should be allowed to work, and task.18 Patients with severe speech recognition that three negative stool specimens should be required only motor problems can readily respond by nodding or for defined high-risk categories. However, the need to judge pointing. A third level of inquiry is needed if any individual cases on merit, and particularly the capability of substantial advances are to be expected in the theory the individual to wash his hands adequately, is emphasised. and management of memory disorders. This step If employers in the catering industry follow this advice, involves fine-grain analysis of and intact and if employees are therefore more willing to admit to acute skills to identify the processes involved and to explore illness, British consumers may expect a small decrease in the special conditions in which individual patients can food poisoning risks. However, in a survey of the causes of 566 outbreaks of salmonella food poisoning in the UK, acquire and retain information in a real-life setting. 19.20 infection of a food handler was implicated in only z The great majority of outbreaks were attributed, either directly or indirectly through cross-contamination, to infected food. This is not only a problem of food hygiene but also an indictment of the methods of food production. According to FOOD HANDLERS AND SALMONELLA FOOD the Food Hygiene Laboratory, salmonellae can be grown POISONING from 79% of frozen chickens, 12% of pork sausages, and 7-5% of minced meat (and, incidentally, from occasional AT a time when many people return from holidays samples of frogs’ legs, turtle meat, and herbal teas).3 The abroad, and when warm weather has exposed the weakness source of this endemic infection is imported animal probable in kitchen hygiene, numerous food handlers will be told that food-stuffs. A report from the Central Veterinary they have been infected by non-typhoid salmonellae. These that present controls are less than Laboratory suggests individuals will have the misery of their physical illness and one consequence is the equally important and effective,4 compounded by restrictions placed on their work. The still uncontrolled problem of-inappropriate antibiotic use in mythology of the "salmonella carrier", which is based on an animals. In Britain, the Government appears to be as unproven extrapolation from the epidemiology of typhoid ineffectual in dealing with commercial interests in this in All is health attitudes. fever, deeply engrained public sphere as it is in the prevention of lung cancer and manner of rituals have been practised, including routine cardiovascular disease-a view supported by the continuing screening of catering staff returning from overseas, occurrence of outbreaks of salmonellosis associated with the antibiotic treatment of healthy carriers, and collection of sale of unpasteurised milk. stool samples in various numbers and at various intervals. The scientific evidence suggests that non-typhoid Victimisation by convention has no place in modem public salmonella infection is very different in its epidemiology . health practice. from enteric fever. The illness is usually mild, the infective Cruickshank and Humphrey have now challenged such dose is high, carriage is rare beyond three months, and rituals with a healthy dose of scientific criticism. These due to carriers are seldom documented. outbreaks workers reviewed the evidence for the contention that food the public health risk from non-typhoid Consequently, poisoning is spread by apparently healthy food handlers salmonellae will be minimised if most food handlers with who carry non-typhoid strains of salmonella bacterial They diarrhoea are excluded from work, but are allowed to return concluded that the carrier state is rare, that except in the as soon as they are free of symptoms. Stool specimens should immediate convalescent stage of an acute illness the amount be required only if they fall into a high-risk group, by virtue of bacteria carried is below that needed to transmit illness, of their capability of delivering a high dose of bacteria (eg, handlers of food not to be cooked further), of their contact with individuals who are at risk of infection from a low dose 15. Baddeley A, Sunderland A, Harris J. How well do laboratory-based psychological tests of bacteria (eg, nurses on a geriatric ward), or of a history predict patients’ performance outside the laboratory. In: Corkin S, David KL, Growdon JH, Usdin E, Wurtman RJ, eds. Alzheimer’s disease: a report of progress which suggests that they might be carrying Salmonella typhi (Aging, vol 19). New York: Raven, 1982. 16. Sunderland A, Harris JE, Baddeley AD. Do laboratory tests predict everyday or S paratyphi.
head injury.15,16 However, non-verbal visual memory is seldom measured appropriately. Traditional tasks require a patient to draw geometrical designs from memory. Constructional apraxia confounds the interpretation of poor performance of such tasks which, in any case, correlate highly with visuoperceptual and motor skills. To overcome this
.
impaired
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