The Role of Intraoperative Neuromonitoring in Surgery of Lumbosacral Schwannomas: Five Years of Experience in a Single Center

Abstract

Introduction Lumbosacral schwannomas are predominantly benign tumors arising from nerves within the spinal canal. Being one of the most common intradural extramedullary tumors, spinal schwannomas comprise up to 30% of such lesions. Surgery is the primary treatment modality and after total resection recurrence is rare. We present our experiences and results with patients operated on lumbosacral schwannomas with the use of intraoperative neuromonitoring with evoked potentials (SSEP, MEP, muscle EMG, cauda mapping). Materials and Methods A retrospective review of prospectively collected data from patients with a diagnosis of lumbosacral schwannomas operated at University Hospital Centre Zagreb, Croatia, from January 2009 to May 2014 was performed. We analyzed preoperative and postoperative medical records, pathological findings, radiographic studies, and clinical outcome of patients treated surgically for lumbosacral schwannomas. Surgical outcome was compared with evoked potential changes during surgery for lumbosacral schwannoma that significantly differed from baseline values. Results In the analyzed period, 26 patients were operated on for lumbosacral schwannomas at our institution. Of these were 11 male and 15 female patients. Mean age was 49.8 years. There were 4 giant and 22 nongiant schwannomas. Giant spinal schwannoma was defined as a tumor that extends over two or more vertebral levels, erodes vertebral bodies, and/or extends into the extraspinal space disrupting myofascial planes. Low back pain and radiculopathy were the most common presenting symptoms, rarely associated with urinary incontinence. Nongiant schwannomas were treated using minimal invasive unilateral approach, while giant schwannomas were treated using laminoplasty technique. In all patients, intraoperative neuromonitoring with SSEP, MEP, and spontaneous EMG was performed. Postoperatively, 21 patients fully recovered from preoperative neurological symptoms at 6-month follow-up. In 12 patients, SSEP changes occurred during surgery that differ from baseline values but had no impact on outcome. Four patients had transient neurological worsening which was in concordance with intraoperative SSEP and EMG disturbance findings. Out of 26 tumors excised, 2 were malignant schwannomas. One of the patients with the diagnosis of malignant schwannoma had to be reoperated for recurrence and died 2 years later. One patient with giant schwannoma developed an intracranial epidural hematoma postoperatively. Conclusion Intraoperative multimodality (SSEP, EMG) monitoring properly used and understood is a useful tool in lumbosacral schwannoma surgery. It assists the surgeon through the procedure as a means of intraoperative guidance allowing for completeness and safety of tumor removal and as such can influence the surgical outcome.