A step toward an objective quantification of subtle neurological signs in schizophrenia

Numerous reports have emphasized the value of neurological soft signs (NSS) as endophenotypic markers in schizophrenia. NSS also appear as useful prognostic predictors for functional outcome, response and tolerance to antipsychotics. Although several standardized scales have been proposed and offer fair inter-rater reliability, they still rely on the experience and accuracy of the investigators. This study was designed to assess NSS objectively. We evaluated 27 patients who met the Diagnostic and Statistical Manual, fourth edition (DSM-IV) criteria for schizophrenia and 15 healthy controls using a standardized examination encompassing a 23-item NSS scale as well as an assessment of parkinsonism and dyskinesia. Movements were then recorded using inertia sensors while the patients were performing a selection of motor items from the aforementioned scale (balance tasks, rapid alternative movements, rigidity). To our knowledge, this study is the first to provide an objective assessment of specific NSS in schizophrenia using inertial sensors. The results objectively demonstrate impairments in patients with schizophrenia when balance relies on proprioceptive information, with specific differences in groups of patients based on their NSS scores. Inertia sensors are promising, inexpensive and 'easy-to-use' tools that could improve the assessment of motor and sensory impairments in patients with schizophrenia in daily clinical practice, especially when the dysfunction is subtle.