CIPA Patients Exhibit No Dysfunction In PNS/CNS Encoding Tactile Sensation

Objectives: Congenital insensitivity to pain with anhidrosis (CIPA), also referred to as hereditary sensory and autonomic neuropathy type 4, is a rare autosomal-recessive disorder characterized by reduced sensitivity to pain and heat, an inability to sweat, and mental retardation of variable severity. This disease has been identified as a genetic disorder due to loss-of-function mutations in the high-affinity tyrosine kinase receptor encoding TrkA, a receptor tyrosine kinase for NGF. Although it has been reported that patients with CIPA lack A-delta/C neurons, cortical regulation in neuronal mechanisms for pain sensation remains to be clarified. In the present study, we investigated somatosensory-evoked magnetic fields from cortical neurons following electrical stimulation of the median nerve at the wrist in patients with CIPA. Methods: Somatosensory-evoked magnetic fields following electrical stimulation in the CIPA patients and healthy subjects were recorded using a 204 channel whole-head neuromagnetometer. Neuromagnetic responses were examined using time-varying multi-dipole analysis to estimate current dipoles which were superimposed in the individual MRI to determine the source locations. Results: Following stimulation, short latency (20 ms) cortical responses on the magnetic waveforms were observed. Between healthy subjects and CIPA patients, no differences were observed in: 1) latencies, 2) magnetic RMS amplitude for short latency (20 ms) cortical response, 3) three-dimensional coordinates of equivalent current dipoles, or 4) source strength of equivalent current dipoles. Conclusion: These results indicate that CIPA patients exhibit no dysfunction in the peripheral/central nervous system encoding tactile sensation.