Rock Around the Clock Drawing Task

So, recently one of the psychiatry residents, Dr. Eric Boyum, gave a presentation about the Clock Drawing Task (CDT) at one of our weekly Clinical Problems in Consultation Psychiatry (CPCP). The CDT is also a part of the Mini-Cog, a very brief, 3 minute cognitive screening tool for cognitive impairment. For a quick review and demonstration of the Mini-Cog, see the web link to my blog post, Lightning Fast Mini-Cog: Video Featuring Drs. Paul Thisayakorn and Alex Gamble « The Practical Psychosomaticist: James Amos, M.D.And another very thorough video presentation from the Hartford institute is also posted at Mini-Cog Video « The Practical Psychosomaticist: James Amos, M.D.

Anyway, it turns out the CDT has been around a lot longer than I thought. Karl Kliest was a German neurologist and psychiatrist who first wrote about impaired clock drawing back in 1912. He called this “constructional apraxia.”

Dr. Boyum described the various tasks and brain systems involved in what is a deceptively simple task:

1.  Language and auditory system: The patient must demonstrate that he or she understands instructions such as “draw a clock” and provide the required numbers in the drawing.

2.  Memory for the visuospatial features of a clock and the ability to access that memory are also important. Further, memory is required for the instruction of time setting after the clock is drawn.

3.  Visuoperceptual and visuomotor processes are required to translate memory into a “motor program” for drawing a clock.

4.  Visual perception is also needed to guide the spatial layout of the features of the clock being drawn and to monitor motor output.

5.  Hemiattention is also needed to ensure that features are represented on both sides of the drawing.

6.  Executive functioning must be intact in order to guide corrections to the drawing as it is being made, and to organize attention to multiple simultaneous processes as noted above.

Therefore, the CDT is a sensitive screening tool for disruption of cognition generally, but it is not specific to any particular brain lesion. So, for a seemingly simple task, it can be a very helpful tool for estimating cognitive impairment generally.

And a direct quote from Dr. Boyum:

And for the “practical” non-neuropsychology consultant, a dichotomous “normal versus abnormal” approach is probably sufficient, focusing on the placement or other indication of the time setting. A patient correctly setting the time of “ten after eleven,” even if the clock and numbers had been drawn for them by the examiner, proved to have a very high negative predictive value (0.99)–at least for Alzheimer’s dementia– in the study undertaken by the authors of the referenced book. This high negative predictive value (if one believes it is able to be generalized to delirium) can be highly useful for evaluating a patient in the general hospital when one of the main distinctions is whether the patient is suffering from a primary psychiatric illness or a delirium related to an underlying medical problem.

Much of the background information for the CDT was culled from one our neuropsychologists books, which is available from Amazon.com at link, Amazon.com: Clock Drawing: A Neuropsychological Analysis (9780195059069): Morris Freedman, Larry Leach, Edith Kaplan, Gordon Winocur, Kenneth Shulman, Dean C. Delis: Books.

Furthermore, one study showed that the CDT indicates “underlying subcortical pathology and deficiencies in executive function important for self-care” [1].

So for a simple task, it can be a very important tool for the consulting psychiatrist, the internist, the geriatrician, or the nurse. While it is not a test for delirium, it can make the Confusion Assessment Method (CAM) a better tool for detecting delirium.

1. Samton, J. B., S. J. Ferrando, et al. (2005). “The clock drawing test: diagnostic, functional, and neuroimaging correlates in older medically ill adults.” The Journal of neuropsychiatry and clinical neurosciences 17(4): 533-540.
This study evaluated the clock drawing test (CDT), a screening test sensitive to executive function, in 70 elderly psychiatric consultation patients. The CDT was compared to the Mini-Mental Status Examination (MMSE) on associations with psychiatric diagnoses, disposition status and radiographic findings. CDT and MMSE were correlated, and scores differed across psychiatric subgroups. In multivariate analysis, only age and CDT predicted disposition status. A lower CDT score correlated with a higher intercaudate ratio, indicating greater caudate atrophy. These findings suggest that the CDT indicates underlying subcortical pathology and deficiencies in executive function important for self-care.

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