Neuropsychological testing in the locked-in syndrome: preliminary results from a feasability study

The locked-in syndrome (LIS) is characterised by complete loss of voluntary motor output but preserved sensory input and consciousness, as a result of a ventral pontine lesion. Communication is only possible via spared vertical eye movements and/or eyelid blinking. The aim of this study was to adapt standard neuropsychological tests to an eye-response mode for use in LIS patients. We assessed five patients in LIS for 3–6 years (age 24–57 years) and 10 controls with a modified version of the direct and backwards digit span (working memory), the Doors and People Test (episodic memory [1]), the Wisconsin Card Sorting Test (executive functioning [2]), the LEXIS (phonological and lexico-semantic processing [3]), the EVIP (vocabulary knowledge [4]) and two new tests designed to measure sustained and selective attention for auditory stimuli. Like the LIS patients, the control subjects had to respond via eye movements. The results showed that the patients' performance was in the normal range for most measures. However, differences of performance between subjects have been found. This study demonstrates the feasibility of a complete neuropsychological testing in chronic LIS survivors. It re-emphasises the fact that LIS patients recover a globally intact cognitive potential. Nevertheless, inter-individual differences observed suggest the interest of this battery to detect some deficits and then to maximize the communication between the family, the medical staff and the patients in LIS.