The patient was seen by Dr. Ali Al-Bayyati 20-July-2015 complaining of painful swelling at midthird left foreleg for one year. The swelling is increasing with time, not associated with pareasthesia. MRI done 15-February-2015 showing the mass at the trajectory of the left posterior tibial nerve, FNB under US guidance was done in Saudia with histologic result of schwannoma.

On examination: the patient is neurologically free. Tinel sign over the swelling was positive.

New investigations were performed and MRI done 22-July-2015 showing big mass in the left posterior tibial nerve pushing the main nerve aside. There is also at the same level another schwannoma at the left deep peroneal nerve.

Projectional incision over the trajectory of the left posterior tibial nerve, which was exposed to see the proximal and distal ends around the mass. The nerve segment containing the tumor was studies and the major fibers were anterior to the mass, but the twigs of the nerve were forming complete cover over the tumor. Longitudinal incision was done to minimize the number of fibers was created and the mass was separated and removed in one piece. All the stages of resection were performed under continuous DNS stimulation of the nerve using Inomed IOM with current 2 mA After total resection of the tumor the nerve continued to show response to stimulation. The proximal end of the nerve was slightly widened and edematous, but no tumor inside it.  Through another incision, the deep peroneal nerve was exposed and the stimulation confirmed that it give supply to the dorsiflexion of the big toe left foot. The schwannoma was resected and the nerve continued to function after resection with the same parameters. Routine closure of the wounds.

Smooth postoperative recovery. The power of the left foot normalized  and was sent to the ward.

The patient patient has a growing mass mostly schwannoma. This change of size alert the malignant transformation and resection must be performed.

It was thought that the lesser tumor was of no clinical significance, but stimulation of the nerve after exposure showed its great importance, for what resection was limited to the tumor with preservation of the nerve.