Navigated transoral approach to the cranial base and the craniocervical junction: technical note

OBJECTIVE: The transoral approach is an elegant reliable surgical procedure that provides anterior exposure of the cranial base and the craniocervical junction. Our objective was to demonstrate the advantages of neuronavigation in planning and performing the transoral approach. METHODS: Three patients with chordomas and one patient with rheumatoid atlantoaxial subluxation were considered for a neuronavigated transoral procedure. For image guidance, the Stryker navigation system (Stryker Instruments, Kalamazoo, MI) was used. Registration was performed with individually constructed occlusal splints with four markers. RESULTS: The transoral approach was successfully used for two patients with chordomas involving the cranial base and the upper spine and for one patient with dislocation of the dens and medullary compression. In one case, preoperative simulation of the approach and trajectory planning demonstrated that adequate resection could not be achieved via the transoral route, and a paracondylar suboccipital approach was used. The registration accuracy achieved with the occlusal splint was less than 1 mm. CONCLUSION: Neuronavigation is a useful tool for planning and performing a transoral approach. It optimizes preoperative planning, clarifies and secures resection limits, and reduces overall surgical morbidity. Registration with an occlusal splint with four markers proved to be an attractive alternative to conventional systems.     

Cosmetic considerations in cranial base surgery

Recent advances in the surgical techniques for the resection of cranial base tumors have allowed for improved degrees of tumor resection, functional outcomes, and esthetic results. If the resection and functional results are not compromised by procedures providing excellent cosmetic outcomes, there is no reason to ignore or compromise the esthetic aspect with regard to technical execution and planning. A thorough assessment of the patient's preoperative deficits and tumor anatomy and a working knowledge of the available cranial base approaches and their combinations permit the surgeon to design an approach that allows for optimal tumor resection with the best possible cosmetic result. In a time when alternative treatment options like radiosurgery exist for cranial base tumors, esthetic outcome is a significant quality-of-life issue that patients consider in their decision to choose surgery versus an alternative treatment.     

Antibiotic prophylaxis in cranial base surgery

The role of perioperative antibiotic prophylaxis was investigated in 95 patients undergoing 100 clean-contaminated cranial base surgeries. A variety of antibiotic regimens were employed. Potential risk factors for local infection were analyzed. Seven patients (7%) developed infections at the surgical site (meningitis, intracranial abscess, cellulitis/abscess, and osteomyelitis). Antibiotic prophylaxis for 24 hours or less was associated with a significantly increased risk of infection (p less than 0.04). Prolonged antibiotic prophylaxis (greater than 48 hours) was not more efficacious than prophylaxis for 48 hours. The surgical approach, type of reconstruction, duration of surgery, and use of drains were not significantly correlated with wound infection. The risk of intracranial infection following cranial base surgery is low despite the presence of bacterial contamination intraoperatively. Broad-spectrum coverage of gram-positive and gram-negative organisms for at least 48 hours is recommended. Attention to surgical technique is important in preventing infectious complications.     

Postoperative hydrocephalus in cranial base surgery

The incidence of postoperative hydrocephalus and factors relating to it were analyzed in 257 patients undergoing cranial base surgery for tumor resection. A total of 21 (8%) patients developed postoperative hydrocephalus, and all required shunting, Forty-two (17%) patients developed cerebrospinal fluid (CSF) leak that required placement of external drainage systems (ventriculostomy or lumbar drain, or both); 10 (23%) of these 42 patients eventually needed shunt placement to stop the leak because of hydrocephalus. Prior craniotomy, prior radiation therapy, and postoperative CSF infection were also associated with an increased risk of developing hydrocephalus (48% versus 6%, 19% versus 8%, and 14% versus 7%, respectively). Prior radiation and postoperative CSF infection increased the risk of CSF leak in patients with hydrocephalus (30% versus 18% and 30% versus 9%, respectively). CSF leak and hydrocephalus commonly occurred in patients who underwent resection of a glomus tumor. In conclusion, 8% of patients who underwent cranial base surgery for tumors developed de novo hydrocephalus; half of them also had CSF leak in addition to hydrocephalus; and all required shunt placement for CSF diversion.     

Gamma probe localization of cranial bone lesions: technical note

BACKGROUND: Intraoperative localization of cranial bone lesions may be challenging especially when the lesion is not well demonstrated on computed tomography (CT) scan but solely on a radio-isotope bone scan. We hereby demonstrate a technique for localizing such lesions using an intraoperative gamma probe reader and summarize the relevant literature. METHODS: A case report of a temporal osteoid osteoma causing local pain and unresponsive to conservative treatment is presented. The lesion was demonstrated preoperatively solely on a bone scan, and was intra-operatively localized by a gamma probe reader. RESULTS: The lesion was totally excised with normal background readings after lesion removal. Six months after total removal of the osteoid osteoma, the patient is asymptomatic. CONCLUSION: Intraoperative gamma probe reader is a simple, effective, and safe method for intra-operative localization of bone lesions, which are positive on bone scans. It is especially useful for skull lesions that are not demonstrated by other imaging methods.     

Avoidance of postoperative epistaxis and anosmia in endonasal endoscopic skull base surgery: a technical note

Background

Most endoscopic transsphenoidal approaches jeopardize the sphenopalatine artery and septal olfactory strip (SOS), increasing the risk of postoperative anosmia and epistaxis while precluding the ability to raise pedicled nasoseptal flaps (NSF). We describe a bilateral “rescue flap” technique that preserves the mucosa containing the nasal-septal vascular pedicles and the SOS. This approach can reduce the risk of postoperative complications, including epistaxis and anosmia.

Methods

A retrospective analysis was conducted of all patients who underwent endoscopic transsphenoidal surgery with preservation of both sphenopalatine vascular pedicles and SOS. In a recent subset of patients, olfactory assessment was performed.

Results

Of 174 consecutive operations performed in 161 patients, bilateral preservation of the sphenopalatine vascular pedicle and SOS was achieved in 139 (80 %) operations, including 31 (22 %) with prior transsphenoidal surgery. Of the remaining 35 operations, 18 had a planned formal NSF and 17 had prior surgery or extensive lesions precluding use of this technique. Of pituitary adenomas, RCCs or sellar arachnoid cysts, 118 (94 %) underwent this approach, including 91 % of patients who had prior surgery. Preoperative olfaction function was maintained in 97 % of patients that were tested. None of the patients had postoperative arterial epistaxis.

Conclusion

Preservation of bilateral sphenopalatine vascular pedicles and the SOS is feasible in over 90 % of patients undergoing endonasal endoscopic surgery for pituitary adenomas and RCCs. This approach, while not hindering exposure or limiting instrument maneuverability, preserves the nasoseptal vasculature for future NSF use if needed and appears to minimize the risks of postoperative arterial epistaxis and anosmia.     

Frameless stereotactic localization in cranial base surgery

Mastery of the three-dimensional anatomic relationships of the cranial base/paranasal sinuses is required to reduce the incidence of iatrogenic surgical complications, facilitate complete tumor extirpation, and enhance functional outcomes. Real-time intraoperative localization technology is one method available to assist the cranial base surgeon. We report our institutional experience with the StealthStationtrade mark treatment guidance platform. Eighty-eight consecutive patients with pathology of the cranial base/paranasal sinuses were operated on with the aid of real-time frameless stereotactic localization. Preoperative image data sets were acquired with either CT or MRI scans. Patient demographics, accuracy of the data sets, surgical approaches, pathology, complications, and further applications of this technology are presented. Procedures were performed on 47 women and 41 men ranging in age from 6 to 85 years. In these 88 procedures, 44 MRI and 44 CT scans with a mean accuracy of 1.57 and 1.23 mm, respectively, were used. Approaches to the cranial base included midface degloving (25), endoscopic (23), craniofacial (13), maxillectomy (12), rhinotomy without maxillectomy (5), transoral (5), pterional (2), transcondylar (1), and transcervical (2). Indications for surgery included severe inflammatory disease of the paranasal sinuses with epidural or subdoral abscess, or both (7), cerebrospinal fluid fistula or encephalocele, or both (11), and 40 benign and 30 malignant tumors. Complications occurred in 10 of 88 patients (11%). Real-time intraoperative localization can be applied to cranial base surgery in a variety of scenarios. The instantaneous transfer of imaging data to the surgical field is useful in localizing pathology, enhancing operative safety, and reducing morbidity, thereby improving outcomes. This technology will certainly play an integral role in minimizing complications and improving surgical outcomes as cranial base surgery moves into the next millennium.     

Scaled clips for aneurysm surgery: technical note

OBJECTIVE: The tips of clip blades are often invisible during operations on large, deep, or posteriorly projecting aneurysms. To overcome this problem, we sought to develop a series of scaled clips. METHODS: We made scaled clips modified from Ya?argil titanium clips. The blades of the new clips are scaled every 5 mm from the tips with alternating colors. We have added six new types of straight scaled clips. RESULTS: To date, we have performed approximately 40 aneurysm clippings using the new scaled clips and have confirmed their usefulness. CONCLUSION: Scaling on the blades helps confirm accurate placement of a clip, even during operations for large, deep, or posteriorly projecting aneurysms, in which blade tips are often invisible.     

Intraoperative monitoring of lower cranial nerves in skull base surgery: technical report and review of 123 monitored cases

The fundamental goal of skull base surgery is tumor removal with preservation of neurological function. Injury to the lower cranial nerves (LCN; CN 9–12) profoundly affects a patient’s quality of life. Although intraoperative cranial nerve monitoring (IOM) is widely practiced for other cranial nerves, literature addressing the LCN is scant. We examined the utility of IOM of the LCN in a large patient series. One hundred twelve patients underwent 123 skull base operations with IOM between January 1994 to December 1999. The vagus nerve (n = 37), spinal accessory nerve (n = 118), and the hypoglossal nerve (n = 83) were monitored intraoperatively. Electromyography (EMG) and compound muscle action potentials (CMAP) were recorded from the relevant muscles after electrical stimulation. This data was evaluated retrospectively. Patients who underwent IOM tended to have larger tumors with more intricate involvement of the lower cranial nerves. Worsening of preoperative lower cranial nerve function was seen in the monitored and unmonitored groups. With the use of IOM in the high risk group, LCN injury was reduced to a rate equivalent to that of the lower risk group (p > 0.05). The immediate feedback obtained with IOM may prevent injury to the LCN due to surgical manipulation. It can also help identify the course of a nerve in patients with severely distorted anatomy. These factors may facilitate gross total tumor resection with cranial nerve preservation. The incidence of high false positive and negative CMAP and the variability in CMAP amplitude and threshold can vary depending on individual and technical factors.     

Critical pathways in anterior cranial base surgery.

New advances in anterior cranial base surgery have dictated the need for a comprehensive, multidisciplinary approach in the treatment of lesions of this area, necessitating multiple modes of diagnostic and surgical techniques. Traditional consideration of the complex problems presented by neoplastic involvement of the anterior cranial base predicated on isolated syndrome analysis is no longer sufficient to adequately assess tumor pathology. To address these complex problems, we discuss a method of localization of pathology based on anatomic structure and function as well as the corresponding surgical approach to the anterior cranial base.     

A modified speculum for transsphenoidal surgery: technical note

This technical note presents the advantages of a modified nasal speculum for the translabial–endonasal transsphenoidal approach to the sphenoid sinus and sella for surgery on lesions of the pituitary. The width of the upper lateral wings of the speculum was reduced by half over approximately three fourths of their length. This increases interior clearance and makes it easier to introduce the instruments used during transsphenoidal operations. We performed 50 transsphenoidal procedures for pituitary adenomas using the remodeled speculum. Three experienced surgeons evaluated the visual field and instrument passage through it, and they found it superior to the conventional design. The modification resulted in marked reduction of the overall operation duration. In conclusion, the more open translabial–transnasal speculum described here definitely facilitates the transsphenoidal approach to the pituitary.     

Endoscopic surgery for thalamic hemorrhage: a technical note

BACKGROUND: Approximately 10% to 15% of cases of ICH involve the thalamus. Evacuation of a thalamic hematoma by craniotomy is associated with high rates of mortality and morbidity. Evacuation by endoscopic surgery is less invasive but is relatively inefficient because of limited visualization of the surgical field. Therefore, a procedure using a polypropylene endoscopic sheath was developed to improve endoscopic visualization and the efficiency of endoscopic evacuation of thalamic hematoma. METHODS: From September 2004 to September 2005, 7 patients underwent endoscopic evacuation of posterial-lateral type thalamic hemorrhage that had ruptured into the lateral ventricle of the trigum and caused acute hydrocephalus. The clinical evaluation included pre- and postoperative Glasgow Coma Scale (GCS) score, 30-day mortality rate, and Glasgow Outcome Scale score 6 months later. The surgical procedure was performed with the patient in the supine position while under general anesthesia. A 3-cm incision was made across the occipital-parietal scalp ipsilateral to the thalamic hematoma. A burr hole, 1 cm in diameter, was drilled on the Keen's point, which is located 3 cm posterior and 3 cm superior to the pinna. A transcortical intraventricular puncture was made with a rigid endoscopic tube. A 2.7-mm endoscope and the necessary surgical instruments were then inserted through this tube, permitting the simultaneous removal of hematoma in the intraventricular space and thalamus. A surgical demonstration of this technique to evacuate thalamic hemorrhage in a patient with acute hydrocephalus is provided herein. RESULTS: The preoperative mean GCS score was 8.4 and the postoperative mean GCS score was 9.4. The 30-day mortality rate was 15% and none of the patients developed shunt-dependent hydrocephalus. The average Glasgow Outcome Scale score was 3.7 six months later. CONCLUSION: Use of a rigid endoscopic sheath in combination with an endoscope and an approach from Keen's point to the collateral trigone of the lateral ventricle improves the efficiency of evacuating thalamic hematomas and prevents shunt-dependent hydrocephalus.     

Outcomes analysis in cranial base surgery — Preliminary results

Summary A system of analysis addressing predictors of management outcomes in Cranial Base Surgery has yet to be published. We therefore report data on seventy-nine consecutive patients undergoing surgery for tumors involving the cranial base, excluding patients with the diagnosis of pituitary microadenoma. Outcomes were defined prospectively in terms of completeness of tumor resection, complications of treatment with emphasis on neurological morbidity, and return to work or independent living. Also, preoperative features are analyzed as influencing cost of treatment, estimated in terms of the number of surgical procedures required, duration of hospital and Intensive Care Unit stay, and time taken to return to work. Preliminary analysis of data reveals that severe brainstem compression, large tumor size (average diameter > 3 cm), high cavernous sinus grade, and tumor encasement of major cerebral arteries are associated with incomplete tumor resection (p < 0.05). Patient age greater than 65, preoperative Karnofsky Performance Score (KPS) less than 80, and severe brainstem compression are associated with increased risk of stroke (p < 0.05). Age greater than 65 and preoperative KPS less than 80 are associated with an increased length of stay (p < 0.05). Other untoward events did not occur with sufficient frequency to reach statistical significance. A model of outcomes analysis in Cranial Base Surgery is proposed utilizing a database to incorporate a group of non-operated patients and include quality of life measurements in long-term patient follow-up.     

Outcome analysis of preoperative embolization in cranial base surgery

Summary  Objective: Management of cranial base tumors requires an interdisciplinary approach. Supraselective angiography and embolization is an important adjunct to cranial base surgery. Though successful embolization facilitates resection, the morbidity of this procedure remains poorly defined. Therefore, we set out to define the morbidity associated with embolization of skull base meningiomas, thus allowing for informed decision making when considering this adjunct to tumor resection.  Methods: A retrospective analysis was performed on our experience with embolization of 167 cranial base meningiomas. Cranial base meningiomas were defined as tumors originating from the olfactory groove, tuberculum sella, medial sphenoid wing, petro-clival region or foramen magnum.  Results: 280 feeding vessels were embolized with an average of 1.7 vessels per lesion. In 91% of patients embolized, good to excellent embolization was achieved without permanent neurological sequelae. In 20 patients no embolization was attempted due to the risk of new neurologic deficits or lack of an appropriate vessel for embolization. Twenty-one patients (12.6%) had transient worsening of their neurologic exam or a medical complication requiring hospitalization. Fifteen patients (9%) experienced permanent neurologic deficits or medical morbidity as a result of embolization. Four of the patients who experienced major complications had a decline in previously compromised cranial nerve function.  Conclusions: Embolization of cranial base tumors is an important part of the therapeutic armamentarium for the treatment of cranial base lesions. Recognition of the morbidity of this procedure will allow for the most appropriate use of this powerful adjunct to cranial base surgery. Published online October 31, 2002 Correspondence: Charles L. Rosen, M.D., Ph.D., Department of Neurological Surgery, West Virginia University School of Medicine, PO Box 9183, Morgantown, WV 26506.     

Use of modified pericranial flaps in anterior skull base reconstruction: technical note

Proper reconstruction of the cranial base is imperative in preventing cerebrospinal fluid leakage and in the protection of vascular elements. Living pericranial flaps are often key elements in such reconstruction; however, trauma, previous surgery, or pathologic involvement can result in the loss of important parts of the pericranium. Techniques for utilizing pericranial flaps despite defects in the pericranium are described and case examples are given to illustrate these techniques.     

Osteocutaneous radial forearm free flap for anterior cranial base reconstruction: Technical note

The reconstruction of anterior skull base defects after carcinologic surgery is challenging. Large defects can require the use of autologous free tissue transfer. Currently, most reconstructions use soft-tissue flaps. We describe the use of an osteocutaneous radial forearm free flap to reconstruct a large defect secondary to a malignant paraganglioma extending into the anterior cranial fossa and both orbits. The surgical resection required endonasal and transcranial approaches. We reconstructed the defect with a free osteocutaneous radial forearm flap. We laid the bone flap across the defect, resting on the orbital roof on each side, and sutured the soft component to the edge of the dura. The pedicle was funnelled from the craniotomy to a prepared cervicotomy and the micro-anastomoses were performed onto the facial artery and two satellite veins. Potential indications and major drawbacks of this technique are briefly discussed. Osteocutaneous radial forearm free flaps can be a valuable reconstructive option for patients with a large defect of the anterior skull base, needing both rigid support and a watertight closure.