IMPAIRED PERIPHERAL SOMATOSENSORY FUNCTION IN CHILDREN WITH PRADER-WILLI-SYNDROME

The Prader-Willi syndrome (PWS) is associated with a tendency to self- injury and a reduced sensitivity to painful stimuli. Somatosensory fun ctions were studied in 5 children aged 11-13 years with PWS. Tactual p erception in the hands (stereognosis) was apparently normal in 4 of th em. Sensory nerve conduction velocities in the median nerve and latenc ies for sensory evoked potentials were similar in the PWS subjects and in 10 healthy controls indicating a preserved myelinisation of sensor y nerve fibers in PWS. Sensory nerve action potential amplitudes in th e PWS group were on an average only 40-50% of normal size (p = 0.03), suggesting a reduced number of normal axons in the median nerve. The r esults may be relevant for the impaired pain sensitivity in PWS becaus e similar neurographic findings and a low density of peripheral nerve fibers have been reported in patients with hereditary or congenital in sensitivity to pain.