Schizophrenia is a clinical brain syndrome with neuroanatomical, biological and molecular complexities. A wide range of aberrant motor functioning has been reported in 40-80% of patients with schizophrenia and some do overlap with patients’ cognitive and negative symptoms.
Settings: A Department of Neurology and Psychiatry.
Case description: A 34-year-old male had schizophrenia characterized (in severe episodes) by apathy, negativism and auditory hallucinations. He had low intelligence (IQ = 68), schizoid personality traits and first degree relatives with schizophrenia. At the age of 27, he experienced stereotyped spitting behavior, bizarre facial grimacing and left persistent clenched fist posturing. Neurological evaluation revealed left-hand posturing, atrophy and nail injuries of the hand flesh with fungal infection and motor apraxia. Therapy with different antipsychotics, electroconvulsive therapy, and lorazepam resulted in partial clinical improvement but failed to improve hand posturing.
Assessment/Results: Transcranial magnetic stimulation (TMS) was delivered to M1 (right or left) using single-pulse paradigm. Cortical motor evoked potential (CMEP) was recorded from the contralateral abductor pollicis brevis (APB) muscle for determination of resting (rMT) and active (aMT) motor threshold stimulus intensities and cortical silent period (CSP) and from ipsilateral APB for determination of transcallosal inhibition (TCI or ipsilateral CSP). The results from the stimulation of the patient’s right and left motor cortices were compared. They showed: (1) Lower rMT and aMT from right M1. (2) CMEP had similar latencies and amplitudes on both sides. (3) Shorter CSP from right M1, (4) Altered inter-hemispheric conduction times (TCI).
Discussion: We suggest the following as possible pathophysiologic mechanisms of hand posturing: (1) Cortical disinhibition with hemispheric asymmetry (right > left), (2) Inter-hemispheric disconnection syndrome and motor apraxia. (3) Cognitive deficits with possible impaired cognitive control of movement, and (4) Neurodevelopmental deficits.

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