Functional magnetic resonance imaging evidence of incomplete maternal imprinting in myoclonus-dystonia.

ABSTRACT

BACKGROUND: Myoclonus-dystonia is an autosomal dominantly inherited movement disorder, clinically characterized by myoclonic jerks and dystonic postures or movements. A previous functional magnetic resonance imaging study showed altered cortical activation patterns in clinically affected SGCE mutation carriers when compared with controls consistent with defective sensorimotor integration. Genetically, the disorder is characterized by the maternal imprinting mechanism; ie, patients who inherit the mutation from their fathers will develop symptoms. However, several clinically manifest patients with myoclonus-dystonia who inherited the mutation from their mother have been described. OBJECTIVE: To compare cerebral activation patterns of paternally inherited SGCE mutation carriers are with maternally inherited mutation carriers and a control group. DESIGN: Case-control study using functional magnetic resonance imaging. PARTICIPANTS: Eight paternally inherited SGCE mutation carriers, 8 asymptomatic or slightly affected (4 of 8) symptomatic maternally inherited mutation carriers, and 11 control subjects. INTERVENTIONS: Participants were studied using a 3-T functional magnetic resonance imaging scanner with a finger tapping task. RESULTS: When paternal and maternal gene mutation carriers were compared, hyperresponsiveness was seen in the contralateral secondary somatosensory cortex. When maternal mutation carriers and control subjects were compared, hyperresponsiveness of the ipsilateral cerebellum and supplementary motor area were found. Using a nonparametric analysis to study only the 4 clinically asymptomatic patients, no significant differences were found between groups. Contrast estimates were plotted for the known affected sensorimotor brain areas, showing intermediate activation in maternally inherited mutation carriers, even when this was performed for only the 4 clinically unaffected mutation carriers. CONCLUSIONS: The results suggest biased gene expression based on parent of origin rather than a strictly dichotomous maternal imprinting mechanism, consistent with clinical observations.