Corticospinal physiology in patients with Prader-Willi syndrome: a transcranial magnetic stimulation study.
BACKGROUND
Prader-Willi syndrome (PWS) is a genetic developmental disorder, mostly caused by a deletion on the paternal chromosome 15 or by a maternal uniparental disomy 15. Some PWS clinical and neurochemical features suggest an involvement of the corticospinal motor structures.


OBJECTIVE
To explore the corticospinal physiology of PWS by transcranial magnetic stimulation.


METHODS
A community-based hospital.


METHODS
We studied motor evoked potentials in the first dorsal interosseous muscle of 21 young-adult patients with PWS. Thirteen patients had a deletion at chromosome 15; 8 had a uniparental disomy. We measured the following variables: relaxed motor threshold, central motor conduction time, duration of the central silent period, and short-interval intracortical inhibition and facilitation. We also recorded F waves in the first dorsal interosseous muscle. We had 11 normal controls.


RESULTS
In the whole PWS group, motor threshold was higher as compared with controls (P<.05). The central motor conduction time, central silent period, and F waves were normal. Intracortical facilitation was reduced significantly (P<.001). Patients with PWS and a deletion had a weaker intracortical inhibition as compared with patients with PWS and a uniparental disomy (P<.05).


CONCLUSIONS
Transcranial magnetic stimulation changes in patients with PWS suggested a hypo-excitability of the motor cortical areas. Defective neurogenesis of the cortical tissue and multiple transmitter alterations are the putative causes. Impaired intracortical inhibition might represent an electrical marker for a deletion defect.
Department of Medical Sciences, Section of Neurology, Università del Piemonte Orientale A. Avogadro, Novara, Italy.
Carlo
C
Civardi
Roberta
R
Vicentini
Graziano
G
Grugni
Roberto
R
Cantello
D000293:Adolescent; D000328:Adult; D004599:Electric Stimulation Therapy; D005071:Evoked Potentials / Q000502:physiology / Q000528:radiation effects; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology / Q000528:radiation effects; D011218:Prader-Willi Syndrome / Q000503:physiopathology* / Q000628:therapy; D011712:Pyramidal Tracts / Q000528:radiation effects*; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D012684:Sensory Thresholds / Q000502:physiology / Q000528:radiation effects; D050781:Transcranial Magnetic Stimulation