Original ArticleEarly Cognitive Impairment: Role of Clock Drawing Test
Introduction
The potential of clock drawing test (CDT) as a screening tool for cognitive impairment has long been a matter of great interest. A completely normal clock suggests that a number of functions are intact [1]. Clock drawing involves comprehension, perception, memory, gross motor function, visual spatial organization, concentration, numerical knowledge, concept of time and inhibition of distracting stimuli. Though it appears simple, drawing of a clock correlates to a complex goal directed behaviour in an abstract environment [1, 2].
Routine tests of cognition such as the Folstein's test or Mini Mental Status Examination (MMSE) often fail to identify executive dysfunction even if severe. There are neuropsychological and extensive bedside tests available to evaluate executive function, but most of them are time consuming. We undertook this study to determine the value of CDT as a simple bed side tool to identify cognitive dysfunction and to assess its utility as an adjunct to MMSE in identifying potential executive dysfunction in a clinical setting [3, 4].
Alzheimer's disease is a typical primary degenerative dementia characterised by defective declarative memory and impaired anterograde learning. However, disturbance of executive function often occurs before the memory decline and can cause problems in day-to-day activities. For example, patients retain their ability to dress but are unable to initiate the task or choose appropriate clothes. The challenge is to identify executive cognitive dysfunction in such patients. Early diagnosis of cognitive deficits in primary degenerative dementia facilitates planning (e.g. execution of will, precautions and advanced directives) while the patient is still capable of taking important decisions [5]. Besides Alzheimer's, various neurological diseases are also known to affect cognition e.g. cerebrovascular accidents (CVA), space occupying lesions (SOL) and infections.
Inability to complete a CDT in a busy outpatient department (OPD) does not establish a diagnosis of dementia but indicates further testing is needed [1, 2, 3, 4, 5, 6, 7, 8]. A normal or equivocal MMSE result doesn't exclude the diagnosis of dementia. However, addition of CDT with careful selection of instructions and time to be depicted can be a useful adjunct [11, 12]. In screening for dementia, CDT proves superior to MMSE [13]. CDT is not designed to be the only form of cognitive evaluation and should be an adjunct to the MMSE [6, 10, 14].
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Material and Methods
A total of 81 patients and 81 control subjects were recruited for the study. The study was carried out in the internal medicine outpatient department (OPD) of AFMC, neurology OPD of Command Hospital (Southern Command) and old age homes located in Pune. Informed consent was taken and confidentiality assured. Age, sex and education matched controls were also studied to minimize the confounding effect. Both cases and controls were exposed to CDT (1 and 2) and MMSE tests.
The survivors of stroke,
Results
In this study, age group of patients varied from 20-79 years and male to female ratio was 58:23. The subjects were divided into groups according to the aetiology (Table 1).
Examples of clocks drawn are shown in Table 2. Since the data is in terms of scores given to individuals (cases and controls), non parametric Mann-Whitney U test was applied. The hypothesis was to test whether there is any significant difference between the cases and controls with respect to their mean scores (Table 3).
All
Discussion
In this study we have found that a CDT can be administered which is strongly associated with an executive function measure. We found that CDT when combined with MMSE is a sensitive tool for detection of cognitive and executive function deficits in various neurological conditions (p value= 0.00), which is in agreement with other studies by Royall et al [3].
When the MMSE score is abnormal and suspicion of cognitive impairment high, abnormal CDT reinforces the diagnosis of cognitive impairment.
Conflicts of Interest
None identified
Intellectual Contribution of Authors
Study Concept : Col SP Gorthi
Drafting & Manuscript Revision : C Mittal
Statistical Analysis : C Mittal, Col S P Gorthi
Study Supervision : Maj Gen S Rohatgi, vsm
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