An Addition to the Neurological Examination?
Abstract & Commentary
By Barbara A. Phillips, MD, MSPH, Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington. Dr. Phillips is a consultant to Cephalon and Ventus and serves on the speakers bureaus of Cephalon and Boehringer Ingelheim.
Synopsis: When an older patient lies obliquely (at an angle) when asked to lie on a bed, he or she may be developing dementia.
Source: Kraft P, et al. Lying obliquely a clinical sign of cognitive impairment: Cross sectional observational study. BMJ 2009;339:b5273.
Over a period of about a year, these German neurologists asked inpatients who were age 60 or older to lie down on an examination bed. They photographed the position of the patients in the bed, and calculated the body axis angle as the angle between the patient's body axis and the longitudinal axis of the bed. To define which body axis angles are perceived as oblique, they showed photographs of a man positioned in bed at 14 different angles to 23 neurologists, and asked them to classify the orientation of the body axis as either "reasonably straight" or "oblique." The smallest angle that was identified by 90% of the neurologists was considered the angle for obliqueness in this study; this turned out to be 7°.
To evaluate cognition, the investigators performed cognitive testing (the Mini-Mental State Examination [MMSE], the DemTect, and the clock drawing test) on the same day as the calculation of the angle of the body in the bed. They defined dementia as a MMSE score < 24 or a DemTect score < 9. They defined mild cognitive impairment as a MMSE score between 24 and 26 or a DemTect score between 9 and 12. Results of the clock drawing test were considered abnormal when the score was < 5 on a scale of 1-6.
They were able to include 109 patients in this study. After assuming their initial position (which was photographed), all patients were eventually able to achieve a straight orientation of the body axis when asked to do so (so they weren't impaired in their physical ability to get straight in the bed). There wasn't any difference in the angle of obliqueness, regardless of the side the patients approached the bed. The absolute value of the angle of the body axis orientation for all patients ranged from 0° to 23° with a median of 3°.
Of 109 patients who completed all the testing in the protocol, 24 had MMSE scores suggesting mild cognitive impairment, and 8 had scores below the dementia cut-off. For the DemTect test, cognitive impairment was suggested in 34 patients, with 11 of them having scores indicating dementia. Cognitive impairment was suggested in 33 patients by the clock drawing test.
Patients who positioned their body at an oblique angle (≥ 7°) from the longitudinal axis of the bed often had cognitive impairment. Larger angles were associated with greater severity of cognitive impairment on all three cognitive test scores. Linear regression analysis showed that the degree of variation of the photographed body position from the axis of the bed correlated significantly with all three neuropsychological tests, even after controlling for age. Indeed, the body axis angles of patients reaching dementia scores were significantly larger than those with normal scores. Relationships persisted after re-analysis excluding those 4 patients who were noted to be wearing shoes when they lay down.
Use of assuming an oblique angle (≥ 7°) as a screen for dementia had a specificity of more than 80% in predicting impaired cognition in all tests, with sensitivities between 27% and 50%. The authors conclude, "... lying down obliquely may be regarded as a simple clinical sign ('oblique sign'), which may prompt further formal assessment."
Commentary
Dementia is a scary thing for doctors and their patients, and we are often asked to assess our older patients' cognitive function. Formal testing is expensive and sometimes not very accessible, and even simple screens (such as those used in this study) are time-consuming. This paper offers a simple screen that can be included as part of the physical examination; this assessment does not require any additional tools or time beyond noticing whether the patient lies down at an angle (≥ 7°) on the examination table. It probably is advisable to ask the patients to remove their shoes before lying down, as the authors note that some patients may be uncomfortable about putting their shoes on the exam table. This technique may be better at suggesting if dementia is present (80% specificity) than at ruling it out (sensitivity below 50%), but it is a starting place in determining whether to proceed with further evaluation.
The authors speculate that since their instructions to the patients did not suggest lying straight, cognitively healthy adults naturally adopt a fairly vertical position when lying down in bed. This is different from the behavior of infants and children, and could have the ecological advantage of preventing falling out of bed. They also note that the inability to detect the orientation of an object in relation to others has been observed in Alzheimer's disease,1 suggesting that impaired spatial relationships may be part of dementia. Further, impaired perception of the upright position may be related to falls in older people,2 so impaired position sense may be a poor prognostic sign in general.
This study was done in a highly selected population (inpatients age 60 or older with neurological disorders, but no known vascular dementia or dementia associated with hypokinetic movement disorders), and needs to be replicated in a more general population. However, it does suggest a very quick and easy screen that may prompt more specific testing for our older patients who are at risk for dementia.
References
1. Caterini F, et al. Object recognition and object orientation in Alzheimer's disease. Neuropsychology 2002;16:146-155.
2. Tobis JS, et al. Visual perception of verticality and horizontality among elderly fallers. Arch Phys Med Rehabil 1981; 62:619-622.
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