Neurological abnormalities in schizophrenic patients and their siblings.

OBJECTIVE: The aim of this study was to investigate the prevalence and type of neurological abnormalities in schizophrenic patients and their nonpsychotic siblings.
METHOD: A comprehensive neurological assessment, including evaluation of both hard and soft signs, was performed for 60 schizophrenic patients, 21 siblings, and 75 normal comparison subjects.
RESULTS: None of the comparison subjects scored higher than 6 on the neurological assessment scale, but a score of 7 or higher was given to 67% of patients and 19% of siblings. Both patients and siblings scored significantly higher than comparison subjects on total neurological abnormalities, hard signs, soft signs, primitive reflexes, integrative sensory functions, and motor functions. The most conspicuous abnormalities were motor coordination problems and involuntary movements in the patients and cranial nerve deviations and mirror movements in their siblings. Levels of neurological abnormality were positively correlated within patient-sibling pairs. The total battery and hard signs best discriminated patients from comparison subjects.
CONCLUSIONS: High levels of neurological abnormality characterize both schizophrenic patients and their siblings. The constellation of abnormalities and absence of overt psychopathology in siblings may represent the mildest form of disturbance within the schizophrenia spectrum. Levels of neurological abnormality covary positively in patients and siblings within the same family, suggesting common genetic and/or environmental pathogenic factors. An extended assessment battery provides optimal discrimination of patients from normal subjects, and hard signs are more differentially associated with schizophrenia than are soft signs. The neurological abnormality has no consistent localizing profile, and nearly all functional domains are involved.