Motor perseveration is a well-documented clinical sign of neurological dysfunction, though there is limited research regarding its diagnostic utility for identifying mild neurocognitive disorder and dementia.

A five-step motor command from the Commands subtest of the Boston Diagnostic Aphasia Examination (“Tap each shoulder twice with two fingers keeping your eyes shut”) was administered to 157 consecutive patients (M _AGE = 68) referred for neuropsychological evaluation in the context of suspected cognitive decline. The motor perseveration sign was considered positive when patients repeated any step of the command or the entire sequence. The motor perseveration sign was considered as a measure of mild neurocognitive disorder and dementia and compared with the final diagnosis. Analysis included calculations of sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios, and diagnostic odds ratio.

In our sample of 157 patients, 50 (32%) exhibited the motor perseveration sign, 49 of whom had psychometrically defined cognitive impairment. In 45 cases of dementia, 25 (56%) demonstrated the sign. In 83 cases of mild neurocognitive disorder, 24 (29%) demonstrated it. The motor perseveration sign as a diagnostic marker of cognitive impairment had a specificity of 0.97 and sensitivity of 0.38. The positive predictive value was 0.98 and the negative predictive value was 0.26. Positive and negative likelihood ratios were 11.1 and 0.64, respectively. The diagnostic odds ratio was 17.37.

The motor perseveration sign is a highly specific marker of mild neurocognitive disorder and dementia. Despite low sensitivity, its brevity makes it a valuable asset in the neurological toolkit. When positive, the motor perseveration sign could be considered the smoking gun of cognitive impairment in brief mental status examinations.