Schizotypal personality disorder (SPD) shares social deficits and cognitive impairment with schizophrenia, but is not typically characterized by frank psychosis. Because striatal size and functional activity have both been shown to be associated with psychotic symptoms, we carried out the first study of SPD to assess the caudate and putamen for comparison with findings in schizophrenia.
Patients with SPD (n = 16), schizophrenic patients (n = 42), and age- and sex-matched normal control subjects (n = 47) were assessed with magnetic resonance imaging. All of the patients with SPD and subsamples of the schizophrenic patients (n = 27) and control subjects (n = 32) were also assessed with positron emission tomography using fluorodeoxyglucose F-18.
The relative size of the putamen in controls was significantly larger than in patients with SPD and significantly smaller than in schizophrenic patients, while the relative size of the caudate was similar in all 3 groups. Compared with control values, relative glucose metabolic rate in the ventral putamen was significantly elevated in patients with SPD and reduced in schizophrenic patients. When subsamples of schizophrenic patients (n = 10) and patients with SPD (n = 10) both of whom never received medication were compared, this pattern was more marked, with the highest value for the putamen being found in patients with SPD for the ventral slice and the lowest value for the right dorsal putamen.
Patients with SPD showed reduced volume and elevated relative glucose metabolic rate of the putamen compared with both schizophrenic patients and controls. These alterations in volume and activity may be related to the sparing of patients with SPD from frank psychosis.