Parkinsonism predicts schizophrenia cognitive course

Oct 3 2013

By Eleanor McDermid, Senior medwireNews Reporter

Parkinsonism is common in patients with first-episode psychosis and is predictive of cognitive impairment, say researchers.

“These results emphasize the relevance of the assessment of parkinsonism signs prior to starting to administer antipsychotic drugs,” write lead study author Manuel Cuesta (Complejo Hospitalario de Navarra, Pamplona, Spain) and colleagues in Schizophrenia Bulletin.

The team detected parkinsonism in 15 (19.5%) of 77 patients with first-episode psychosis who had never taken antipsychotic medication. Parkinsonism was defined as a score of 4 points or more on the Simpson-Angus Scale.

At baseline, patients with parkinsonism tended to perform slightly worse than those without on a range of neuropsychologic variables, although the difference was significant only for the Verbal Paired Associates subscale of the Wechsler Memory Scale (WMS).

The patients were retested at 1 and 6 months, and over this time parkinsonism significantly correlated with several measures of memory, executive functioning, and attention. At 6 months, patients with parkinsonism had poorer scores than those without for several tests; for example, 54.1 versus 62.7 for the WMS total, and 10.7 versus 7.4 for the Wisconsin Card Sorting Test Perseverative Errors.

“These cognitive impairments seem to represent core manifestations and be the most critical determinants of functioning and quality of life in schizophrenia and other psychoses, and it has been hypothesized that they may have common psychological and neurobiological substrates,” say the researchers.

However, the changes in scores between baseline and 6 months were not significantly different between the groups; the differences at 6 months arose from slight differences at baseline combined with slightly different rates of change during follow-up.

The relationship between parkinsonism and neurocognition was not affected by the type of antipsychotic patients were given during follow-up.

Cuesta et al suggest that their findings fit with the dopamine hypothesis of schizophrenia, saying that “psychotic patients with prominent [spontaneous parkinsonism] might have a coexistence of presynaptic striatal hyperdopaminergia to explain psychosis with some kind of striatal or subcortical hypodopaminergia that would express parkinsonian signs such as hypokinesia and cognitive dysfunction.”

Consistent with this, hypokinesia and rigidity were more strongly linked to cognitive impairment than was tremor, notes the team.

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