Abnormal tactile discrimination and somatosensory plasticity in familial primary hyperhidrosis

Abnormal sensory processing seems to be involved in hyperhidrosis. To test this hypothesis, we investigated tactile acuity and cortical plastic changes in patients with primary hyperhidrosis (PH) and their asymptomatic relatives. We studied thirteen subjects belonging to two families with PH and thirteen age-matched healthy controls using Johnson-Van Boven-Phillips domes before and after 45min of transient visual deafferentation. Spatial discrimination thresholds (SDTs) were lower in controls than in the familial group (1.08+/-0.25 vs 1.59+/-0.71; p=0.0032). After 45min of light deprivation and blindfolding, SDTs decreased significantly in controls (0.83+/-0.3; p=0.003), but not in patients (1.4+/-0.62; p=0.108). Interestingly, two subjects without clinical complaints of hyperhidrosis had abnormal SDTs behavior after short term visual deprivation. This study demonstrates that sensory processing is abnormal in PH, with a lack of plastic cortical somatosensory changes regardless of clinical condition. These modulatory abnormalities would affect gating processes in the somatosensory cortex which may play a role in maintaining hyperhidrosis.