Sensory reinnervation of myocutaneous flaps revealed by infrared laser evoked sensations and brain potentials

The aim of this study was to examine the recovery of sensory function in myocutaneous flaps comparing 2 test methods. Eight flaps in 7 patients were examined by using clinical neurological test procedures (CNT) in comparison with psychophysics and evoked brain potentials (LEP) following infrared laser stimuli. The authors found that only 3 out of 8 flaps in 7 patients exhibited signs of reinnervation when tested with CNT. Three grades of reinnervation appeared in 7 flaps when tested with the laser. Grade 1 indicated the recovery of unmyelinated C-fiber function in 7 flaps accounting for the ability to discriminate laser intensities by different degrees of warmth. Grade 2 appeared in 3 of these flaps and was characterized by the additional ability to sense pinprick pain and the elicitation of late components of LEP mediated by thinly myelinated A delta-nociceptors. Grade 3 involved the additional sensibility for superficial touch indicating the recovery of thickly myelinated A beta-fibers noted in 2 of these flaps. The authors conclude that the LEP method is more sensitive than standard neurological test procedures to objectively document early signs of reinnervation after reconstructive flap surgery. This result is promising to investigate greater patient populations comparing different surgical techniques in future studies.