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Background: Prader Willi syndrome (PWS) is a genetic developmental disorder, mostly caused by a deletion on the paternal chromosome 15 or by a maternal unipa rental disomy 15. Some PWS clinical and neurochemical features suggest an involv ement of the corticospinal motor structures. Objective: To explore the corticosp inal physiology of PWS by transcranial magnetic stimulation. Setting: A communit y based hospital. Methods: We studied motor evoked potentials in the first dors al interosseous muscle of 21 young adult patients with PWS. Thirteen patients h ad a deletion at chromosome 15; 8 had a uniparental disomy. We measured the foll owing variables: relaxed motor threshold, central motor conduction time, duratio n 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, ce ntral silent period, and F waves were normal. Intracortical facilitation was red uced significantly (P<.001). Patients with PWS and a deletion had a weaker intra cortical inhibition as compared with patients with PWS and a uniparental disomy (P<.05). Conclusions: Transcranial magnetic stimulation changes in patients with PWS suggested a hypoexcitability of the motor cortical areas. Defective neuroge nesis of the cortical tissue and multiple transmitter alterations are the putati ve causes. Impaired intracortical inhibition might represent an electrical marke r for a deletion defect.
Background: Prader Willi syndrome (PWS) is a genetic developmental disorder, mostly caused by a deletion on the paternal chromosome 15 or by a maternal unipa rental disomy 15. Some PWS clinical and neurochemical features suggest an involvment of the corticospinal motor structures. Objective Setting: A communit y based hospital. Methods: We studied motor evoked potentials in the first dors al interosseous muscle of 21 young adult patients with PWS. Thirteen patients h ad a deletion at chromosome 15; 8 had a uniparental disomy. We measured the foll owing variables: relaxed motor threshold, central motor conduction time, duratio n of the central silent period, and short interval intracortical inhibition and facilitation. We also recorded F waves in the first We had 11 normal controls. Results: In the whole PWS group, motor threshold was higher as compared with controls (P <. The central motor conduction time, ce Central silent period, and F waves were normal. Intracortical facilitation was red uced significantly (P <.001). Patients with PWS and a deletion had a weaker intra cortical inhibition as compared with patients with PWS and a uniparental disomy (P <.05). Conclusions: Transcranial magnetic stimulation changes in patients with PWS suggested a hypoexcitability of the motor cortical areas. Defective neuroge nesis of the cortical tissue and multiple transmitter alterations are the putati ve causes. Impaired intracortical inhibition may represent an electrical marke r for a deletion defect.