Prediction of Neurocognitive Deficits by Parkinsonian Motor Impairment in Schizophrenia: A Study in Neuroleptic-Naïve Subjects, Unaffected First-Degree Relatives and Healthy Controls From an Indigenous Population

Abstract

Background: Neurocognitive deficits are among the most debilitating and pervasive symptoms of schizophrenia, and are present also in unaffected first-degree relatives. Also, multiple reports reveal parkisonian motor deficits in untreated subjects with schizophrenia and in first-degree relatives of affected subjects. Yet, the relation between motor and cognitive impairment and its value as a classifier of endophenotypes has not been studied.

Aims: To test the efficacy of midbrain hyperechogenicity (MHE) and parkinsonian motor impairment (PKM) as predictors of neurocognitive impairment in subjects with or at risk for schizophrenia, that could be used to segregate them from first-degree relatives and healthy controls.

Method: Seventy-six subjects with chronic schizophrenia never exposed to antipsychotic medication, 106 unaffected first-degree relatives, and 62 healthy controls were blindly assessed for cognitive and motor function, and transcranial ultrasound.

Results: Executive function, fluid intelligence, motor planning, and hand coordination showed group differences. PKM and MHE were significantly higher in untreated schizophrenia and unaffected relatives. Unaffected relatives showed milder impairment, but were different from controls.

Conclusions: PKM and MHE predict cognitive impairment in neuroleptic-naive patients with schizophrenia and their unaffected first-degree relatives and may be used to segregate them from first-degree relatives and healthy controls.

Keywords: endophenotype; genetic risk; indigenous populations; literacy-independent neuropsychological testing; parkinsonism; schizotaxia; transcranial ultrasound.