Clinical research of eight areas of trigeminal nerves with electrical stimulation

Objective To study the distribution rule of sense and motor fibers in the normal trigeminal nerve roots by electrophysiologic monitoring. Methods Twenty patients accepted microvascular decompression because of primary mimetic convulsion, collected in our hospital from January 2011 and December 2013, was studied their normal trigeminal nerve roots through electroneurophysiology; during the operation, the trigeminal nerve roots were divided into 8 areas: I area is the external lateral area, II area is the external upper area, III area is the middle upper area, IV area is the internal upper area, V area is the internal lateral area, VI area is the internal bottom area, VII area is the middle bottom area, and VIII area is the external bottom area; and then, one mm diameter bipolar stimulator was adopted to give 0.2 mA electrical stimulation on these areas, respectively; and the compound nerve action potential (CNAP) at the foramina supraorbitale (V1), foramina infraorbitale (V2) and foramina mentale (V3) was recorded as the CNAPV1, CNAPV2 and CNAPV3 respectively; the compound muscle action potential (CMAP) at the masseter muscle (MM) and temporal muscle (TM) was recorded as CMAPMM and CMAPTM respectively; and finally, the distribution rules of the sense and motor fibers inside the trigeminal nerve roots were judged according to the laws of CNAP and CMAP emergence. Results During the operation, all patients could get stable CNAP and CMAP wave patterns at periphery according to the electrical stimulation on trigeminal nerve roots; the CNAPV1, CNAPV2 and CNAPV3, CMAPMM and CMAPTM seldom appeared in the I, II and VIII areas of trigeminal nerve roots, but more often appeared in the IV, V and VI areas, enjoying significant differences (P< 0.05); motor fiber located in the internal lateral area of the nerve, and the sense fiber located in the middle and external lateral area. By stimulating the sense taproot fiber, CNAP could be recorded, and by stimulation the motor taproot fiber, CMAP and several CNAP from V1, V2 and V3 could be recorded. Conclusion Electrical stimulation on motor taproot implies that there are anastomosing fibers existting in both motor and sense fibers; according the 8 areas being divided, motor fiber locating in the internal lateral area of the nerve, and sense fibers locating in the middle and external lateral areas can be concluded. Key words: Trigeminal nerve; Eight area; Electrical stimulation