Carl H. Snyderman

Somatosensory Evoked Potential Monitoring During Endoscopic Endonasal Approach to Skull Base Surgery: Analysis of Observed Changes

BACKGROUND: Intraoperative neurophysiological monitoring, including upper- and lower-extremity somatosensory evoked potentials (SSEPs), has been used to identify and prevent injury to neurovascular structures during conventional skull base surgery. The expanded endonasal approach (EEA) is a novel minimally invasive approach to skull base surgery. However, it carries the risk of injury to neurovascular structures, including the internal carotid artery, anterior cerebral artery, and cranial nerves. OBJECTIVE: To evaluate the value of SSEP monitoring to predict and/or prevent neurovascular deficits during EEA to skull base surgery. METHODS: We retrospectively identified 999 consecutive patients who had intraoperative neurophysiological monitoring during EEA skull base surgery at our institution. A total of 976 patients had SSEP monitoring and a documented postoperative neurological examination. RESULTS: The incidence of changes in SSEP during the procedure was 20 of 976 (2%). The incidence of new postoperative neurological deficits was 5 of 976 (0.5%). The positive and negative predictive values of SSEPs during EEA to predict neurovascular deficits were 80.00% and 99.79%, respectively. CONCLUSION: Intraoperative SSEP monitoring was able to identify impending risk to neurovascular structures to prevent permanent postoperative neurological deficits. We advocate a comprehensive approach to neurophysiological monitoring during EEAs, including SSEPs, spontaneous and triggered electromyography of the cranial nerves III through XII, brainstem auditory evoked potentials, and electroencephalogram, depending on the surgical approach and location of the neural structures at risk.

Endoscopic Endonasal and Transcranial Surgery for Microsurgical Resection of Ventral Foramen Magnum Meningiomas: A Preliminary Experience

BACKGROUND Purely ventral foramen magnum meningiomas are challenging tumors to treat given their location, and proximity and relationship to vital neurovascular structures. OBJECTIVE To present endoscopic endonasal surgery (EES) as a complementary approach to the far-lateral suboccipital approach (FLA) for ventral midline tumors. METHODS From May 2008 to October 2013, 5 patients underwent EES and 5 FLA for primary ventral foramen magnum meningiomas. We retrospectively reviewed their records to evaluate outcomes. RESULTS Nine of 10 patients presented with long-tract and lower cranial nerve deficits. All patients who presented with deficits preoperatively completely normalized after tumor resection regardless of approach. Gross total resection was achieved in 2 cases in the EES group and 4 cases in the FLA group (the rest were near total). Vascular encasement was a limitation to gross total resection with both approaches. Preoperative median Karnofsky Performance Scale score was 80 and improved to 100 in both groups. Following EES, 1 patient developed cerebrospinal fluid leak with resultant meningitis. Two patients developed hydrocephalus, one of which developed an epidural abscess following necrosis of the nasoseptal flap, requiring debridement. In the FLA group, 1 patient developed a pseudomeningocele associated with hydrocephalus. One patient developed an abdominal fat graft site hematoma. CONCLUSION Both approaches provide excellent results for resection of ventral foramen magnum meningiomas, with reconstruction and hydrocephalus as the main sources of complication. In our practice, EES is a preferred technique in ventral, purely midline tumors with limited inferior extension and reduced lower cranial nerve manipulation, whereas FLA is preferred in tumors with lateral and caudal extension below the tip of the dens.

Endoscopic Endonasal Approach for Olfactory Groove Meningiomas

Background: Endoscopic endonasal approaches (EEAs) have been applied for pathologies across the entire anterior skull base. Olfactory groove meningiomas are tumors of the anterior b

The Learning Curve for Endonasal Surgery of the Cranial Base: A Systematic Approach to Training

Proper training in endoscopic endonasal surgery of the cranial base is essential to avoid unnecessary morbidity and mortality. An incremental program for the training of skull base surgeons is describ

Management of complications of endonasal cranial base surgery

Endoscopic endonasal surgery of the cranial base is maximally invasive surgery and poses many of the same risks as traditional skull base approaches. Preliminary data demonstrates that serious complications can be avoided through a strong foundation in endoscopic skull base anatomy, adherence to principles of surgical dissection, and a dedicated surgical team with proper training and experience. Surgical complications may be categorized by severity, location, organ system or tissue type, and time period. Advances in reconstruction have decreased the incidence of CSF leaks to less than 5%. Major complications such as vascular injury are rare and can be managed using endoscopic techniques. Nasal morbidity is acceptable.

Endoscopic Endonasal Approach to the Odontoid and Craniocervical Junction

Background: Endoscopic endonasal approaches (EEAs) have been applied for skull base pathologies from the christa galli to the clivus. This approach also provides a natural corridor

Computer assisted endoscopic sinus surgery: Clinical applications

In patients with sinonasal disease, recognition of anatomic landmarks may be difficult. The ISG Viewing Wand is an intraoperative navigational device that allows the surgeon to correlate the anatomy of the patient with a computerized display of the reformatted image of preoperative computed tomographic or magnetic resonance scans. We have found the ISG Viewing Wand to be a valuable tool for surgery of the paranasal sinuses. Representative cases are presented that illustrate the application of this device. An intraoperative navigational device enhances the surgeons ability to safely identify anatomic structures.

Closure Methods Following Transsphenoidal Surgery

Cerebrospinal fluid (CSF) leak is one of the most common postoperative complications following endonasal surgery. The rate varies with defect location, tumor type, reconstruction technique, surgeon experience, and patient factors. CSF leak rates range from 1.5 to 5% for pituitary adenomas to 10 to 16% for craniopharyngiomas and meningiomas. The severity of intraoperative CSF leak also correlates with the risk of postoperative leak. While this relationship is intuitive, classifying the severity can be challenging.