“The motor paradox”: Abnormal postural sway and gait disturbances in schizophrenia spectrum disorders

Abstract

Subtle motor abnormalities have been described in schizophrenic patients since the first descrip- tions of the disease [1,2] and are now properly conceptualized as early endo-phenotypes of schizo- phrenia. [3] Despite the role of psycho-motor disturbances as endo-phenotipic markers of schizophre- nia spectrum disorders, very few studies have investigated the locomotor pattern of gait in schizo- phrenia. The present study aimed to detect the presence of gait disturbances and postural anomalies by means of “Gait Analysis System”, in order to identify specific underlying endophenotipic deficits in motor control . 21 patients and 14 healthy subjects have been analyzed in gait and postural sway by classic full Gait Analysis system. Schizophrenic patients showed a longer gait cycle compared to controls (cycle duration sx=1,11±0,09 vs 1,04±0,06; cycle duration dx=1,10±0,09 vs 1,04±0,06). This dif- ference (sx 0.065, 95%CI [0.12-0.05]) (dx 0.065,95%CI [0.12-0.003]) was significant (sx t(35)2.2,p=0.03) (dx t(35)2.15,p=0.03). Moreover, schizophrenic group had greater sway area with open eyes (swayarea OE 107,5±89.8 vs 57,2±31.8). This differences (51.54, 95%CI [97.28-5.20]) was significant (t(35)=2.3, p=0.03). Finally, patients had more postural stability following the removal of visual input, as demon- strated by more length of the curve(464.9±180.68 vs 345.4±54.17)(difference 119.43, 95%CI[95.18+9.4]; t(35)=2.7,p=0.01) with no significative differences in the sway area, compared to controls.

According with current evidence, schizophrenic patients show a different locomotor pattern and specific postural sway abnormalities compared to controls. [4,5,6] Particularly, the present study found a “motor paradox” in the control of posture and balance in schizophrenia: notably, patients exhibit more postural instability with open eyes, as due to an interference of visual input; with pos- tural stabilization following the removal of visual input.

The present findings would support the hypothesis of an information processing disorder, as a core feature of schizotaxic vulnerability, associated to subtle deficits in basic motor control of postural stability. [4]