Functional assessment of Aδ and C fibers in patients with Fabry's disease

The pathophysiology of neuropathic pain in Fabry's disease (FD) is still largely unknown. Seven FD patients were studied by laser evoked potentials (LEPs) to assess the function of the Adelta and C fibers. Laser pulses were delivered on the skin of the hand and perioral region at painful intensity to record LEPs related to Adelta-fiber inputs and at nonpainful intensity to obtain LEPs related to C-fiber inputs. When the perioral region was stimulated, a vertex positive component was recorded with a mean latency of 260.3 ms and 376 ms after Adelta- and C-fiber stimulation, respectively. The mean Adelta-LEP amplitude was significantly lower in FD patients (N1/P1 mean values were 2.8 muV and 4.5 muV after hand and face stimulation, respectively, compared to 4 muV and 8.9 muV for controls; N2/P2 mean values were 8.2 muV and 11.1 muV after hand and face stimulation, respectively, and 16.7 muV and 22.3 muV in controls). Unlike the healthy subjects, 6 FD patients, suffering from neuropathic pain, showed a late positive potential related to C-fiber function (mean latency, 377.1 ms) also after facial stimulation at painful intensity, suggesting a relative overflow of C-fiber input, which may be relevant in the pathophysiology of pain in this disease.