Cognition in children and young adults with myoclonus dystonia - A case control study

In adult patients with myoclonus dystonia (MD), cognitive deficits regarding information processing speed and executive functioning have been demonstrated, but it is unclear whether cognition is also affected in young MD patients. The present study investigates cognition in young MD patients and the role of an SGCE mutation.

In this case control study 20 young MD patients (9 children (5.75-12.58 years) and 11 adolescents/young adults (13.5-25.42 years)) were included and compared to an age-, IQ- and gender-matched healthy control group (n = 40). Within the patient group, we compared patients with (n = 12) and without (n = 8) an SGCE mutation (SGCE+/-). All participants completed neuropsychological tests for memory, attention/processing speed, executive functioning, social cognition and language.

Overall, patients performed in the (low) average range, comparable to healthy controls. Only on a semantic fluency test, patients scored significantly lower. SGCE + patients had lower emotion recognition scores (a social cognition test) compared to SGCE-patients.

We could not demonstrate cognitive deficits as found in adult MD patients in our younger group. Patients performed on the same level as healthy controls, with only a small difference in semantic fluency. We did not find executive deficits that were manifest in adult SGCE + patients, but we did find an association of an SGCE mutation and lower scores on a social cognition test. Similar to executive functioning, social cognition is a prefrontally regulated function, but had not been tested in adult MD. Hence, social cognition may precede executive problems in adulthood, suggesting growing into deficit.