Timothy J. Best

Walking track analysis : a long-term assessment of peripheral nerve recovery

Functional recovery following sciatic, tibial, and peroneal nerve injury was assessed over a 1-year period using walking track analysis in the rat. Internal neurolysis did not affect nerve function. Crush injury induced a temporary, but complete, loss of function that recovered to control levels by 4 weeks. Nerve transaction resulted in complete loss of function without any evidence of recovery. After nerve repair, functional recovery occurred, reaching near-optimal recovery by 12 weeks. The degree of functional recovery varied with the specific nerve involved. The sciatic nerve recovered 41 percent of function, whereas the tibial nerve recovered 54 percent of function. The peroneal nerve exhibited the highest degree of recovery, achieving functional levels similar to control values. Assessment of neural regeneration using walking track analysis appears to be a valuable addition to the traditional methods of histology and electrophysiology.

Strain differences in autotomy in rats undergoing sciatic nerve transection or repair

&NA; The degree of self‐mutilation (autotomy) following sciatic nerve injury was assessed in 6 rat strains. Experimental groups included sciatic nerve transection with and without repair and crush lesions. The degree of autotomy was measured using a standard grading system. There were statistically significant differences between the strains in the transected group in terms of both degree of autotomy and the time of onset of its appearance. The repair group showed a shorter mean time of onset, lower maximal scores, and lower percentage of affected animals. Autotomy was absent in the nerve crush group and in all Lewis rats. In experimental studies when the status of the foot is critical (e.g., to evaluate functional walking patterns) Lewis rats appear to be the most appropriate strain to utilize. These results suggest that there are definite strain differences in the degree of autotomy following nerve transection or repair.

Walking Track Analysis: Utilization of Individual Footprint Parameters

Functional assessment of rat sciatic, tibial, and peroneal nerve injuries was performed using walking track analysis. Individual walking print length (PL), toe spread (TS), and intermediate toe spread (ITS) values were measured up to 24 weeks after specific nerve transection, with or without repair. Sciatic and tibial nerve manipulation initially affected all footprint measurements, consistent with loss of intrinsic and extrinsic motor function. After sciatic repair, TS demonstrated partial recovery without any substantial recovery in PL or ITS, compared with sciatic transection values. By contrast, after tibial repair, PL values recovered dramatically, between 16 and 24 weeks, to levels not significantly different from control subjects. This was not observed after tibial transection without repair. TS recovered partially, whereas ITS recovered to control levels by 20 weeks after tibial repair. Peroneal transection resulted in multiple contractures, rendering this group unmeasurable at 4 weeks. After peroneal repair, only the PL reflected significant loss of function at 2 weeks, recovering to control values by 8 weeks. Manual TS measurements in nonwalking rats did not reflect functional nerve regeneration. Thus, individual PL measurements alone can be used to characterize functional recovery after tibial and peroneal nerve injury, whereas TS reflected recovery after sciatic nerve injury.

Merkel cell carcinoma of the scrotum

We report a rare case of Merkel cell carcinoma arising from the scrotal skin of an 84-year-old man. The tumor was treated by wide, local excision and radiation. The man died due to extensive metastatic disease 16 months after his surgery. The natural history, histology, and pathogenesis of Merkel cell carcinoma are discussed briefly.

Verification of a free vascularized nerve graft model in the rat with application to the peripheral nerve allograft.

We report a vascularized sciatic nerve graft in the rat, based upon the femoral popliteal superior muscular artery pedicle. The pedicle may be raised from the common femoral artery via the popliteal artery, with accompanying venous drainage to the femoral vein. We have characterized two vessels: the middle tibial artery to the posterior tibial nerve and the arteria comitas nervus peroneus to the peroneal nerve. Plastic monomer and Evans blue labeled albumin injections established the anatomic model. The graft was reliably perfused at the time of isolation and 24 hours post-transplantation. The model was used to evaluate regeneration across allogeneic (ACI to Lewis, n = 12) versus syngeneic (Lewis to Lewis, n = 6) nerve grafts. Electrophysiologic and histomorphometric assessments demonstrated that the vascularized immunosuppressed allograft was similar to the vascularized syngeneic graft. Both were suerior to the vascularized allograft without immunosuppression. (Plast. Reconstr. Surg. 92: 516, 1993.)