[Recovery of facial nerve function using sural nerve transplantation after its injury in acoustic nerve surgery]

Statoacoustic n. neurinoma is a benign, slow-growing and usually unilateral tumor. During its growth the tumor exerts pressure on the surrounding anatomic forms within the pontocerebellar angle: cranial nerves, pons, cerebellum. Therefore the first clinical symptoms are ear buzzing and deafness, vision disorders, occipital headache or walking difficulties. The diagnosis of such conditions must be precise, whereas CT (computerized tomography) and MRI (magnetic resonance imaging) are the methods of choice. Surgical tumor removal is the only therapy, but during surgery facial nerve injury occurs. The objective of this paper is a case report of a facial nerve injury and sural nerve transplantation during acoustic neurinoma surgery and recovery of facial nerve function.

A 23-year-old male patient suffered from ear buzzing in the right ear for a year and a half with gradual development of deafness. Due to frequent headaches and after ophthalmologic examination, the patient was urgently hospitalized at the Neurology Clinic of the Faculty of Medicine in Novi Sad where MRI of the endocranium was performed revealing a tumor of the pontocerebellar right angle, 3 x 3.5 cm in size. The patient has undergone surgery at the Neurosurgery Clinic of the Faculty of Medicine in Pees in Hungary, with suboccipital craniotomy and tumor ablation. During surgery facial nerve injury occurred in the premeatal segment and intraoperative transplantation of sural nerve grafts from the left leg to the distal parts of the facial nerve was performed. The histopathologic finding revealed an acoustic neurinoma (Schwannoma). After surgery a control CT was performed revealing a complete tumor removal. The wound healed per primam intentionem and the patient was released from hospital two weeks later. During the postoperative period physical therapy was performed in the aim of rehabilitation of the facial nerve due to peripheral paralysis. After electrodiagnostic tests using GALVOMED 20 apparatus, massage was performed in the periorbital and perioral regions. Kinesitherapy was also done in front of a mirror several times a day. 6 months after surgery an EMG (electromyography) of m. frontalis dx., m. orbicularis oculi dx. and m. orbicularis oris dx. were performed. The EMG revealed evident reinnervation possibilities. A year after surgery the control MR finding of the endocranium was regular, as well as the control MR two years after surgery (postoperative cyst without signs of recurrence of the removed neurinoma). Control EMG of the m. frontalis dx., m. orbicularis oculi dx., m. orbicularis oris dx. showed signs of reinnervation.

Tumors of the pontocerebellar angle are usually acoustic nerve neurinomas. 8% of intracranial tumors are Schwannomas. They originate from neurilemmal cells, by rule they grow slowly and are benign tumors. Therefore, for years the only signs pointing to them are ear buzzing and gradual development of deafness. That is why these anamnestic data are important for diagnosis. Headaches, walking difficulties, vision disorders are the usual difficulties due to which patients seek doctor's help. Computerized tomography and magnetic resonance imaging represent the diagnostic methods of choice in establishing the diagnosis. In this case MRI was performed on time. Surgery is the only therapy, but during tumor ablation the facial nerve was injured in the premeatal region. Intraoperative transplantation of grafts taken from sural nerve to proximal and distal parts of the facial nerve provides possibilities for injured nerve regeneration. The process of regeneration of such a nerve is long-term and often permanent 40% axon loss occurs. This is the reason to perform a control EMG two years after surgery. During peripheral paralysis rehabilitation is performed in the aim of preventing contractures. It is achieved by passive exercises in front of a mirror a few times a day. (ABSTRACT TRUNCATED)