Application of short-segment nerve conduction studies in the entrapment of the peroneal nerve across the fibular head / 中华神经科杂志

ABSTRACT

Objective To evaluate the usefulness of the short-segment nerve conduction studies (SSCSs,inching test) of the peroneal nerve across the fibular head in order to diagnose and localize the site of entrapment of the nerve.Methods Fifty-four patients with suspected peroneal nerve palsy and 30 controls were studied.The symptoms all occurred in unilateral leg,involving 25 left legs and 29 right legs.Both long segment motor nerve conduction studies (LSMCs) and SSCSs were performed in all patients and controls.SSCSs were obtained at 2 cm intervals,starting 6 cm proximal (P6,P4 and P2) and 4 cm distal (D2 and D4) ending to the fibular head prominence (P).Results When nerve conduction of the entire 10 cm segment across the fibular head was tested by the conventional method,only 40 showed reduction in amplitude or slowing of motor conduction velocity or both.However,with SSCSs,54 peroneal nerves were all discovered abnormal.The results of comparison of conventional methods suggested that there were significant differences in conduction velocity between the fibular head-Ankle segment and the knee-fibular head segment in the case group,the latter ((33.63 ± 9.29) m/s) being slower than the former ((47.92 ± 4.04) m/s;t =9.776,P =0.000),while there was no obvious abnormality in the control group.The results of the control group detected by SSCSs showed that there was no significant difference between the left and right sides of the mean amplitude of the stimulation points and the mean time of segmental nerve conduction.Therefore,we set the exception criteria as the segmental nerve conduction time is longer than the corresponding control group (i + 2 s),and the CMAP amplitude of proximal stimulation point decreased by more than 20％ than the adjacent distal segment.In accordance with this standard,we found that the lesions were located in P6 to P4 in 2/54 (3.7％) legs,P4 to P2 in 4/54 (7.4％) legs,P2 to P in 43/54 (79.6％) legs,P to D2 in 12/54 (22.2％) legs,D2 to D4 in 3/54 (5.6％) legs,respectively.Consequently,the P2 to P segment was most vulnerable to damage.Conclusions SSCSs are more sensitive in detecting the entrapment of the peroneal nerve across the fibular head than the LSMCs.SSCSs could precisely localize the entrapment lesions,might be a useful tool especially for the detection of mild entrapment which has normal LSMCs findings of the peroneal nerve across the fibular head.