Faculty Bibliography

Percutaneous retrogasserian glycerol rhizotomy (PRGR) was used during an 11-year interval in 53 patients with typical trigeminal neuralgia associated with multiple sclerosis. All patients had failed extensive medical trials prior to PRGR. Long-term (median follow-up, 36 months) complete pain relief (no further medication) was achieved in 29 (59%) of 49 evaluable patients. Eight patients (16%) had satisfactory pain control but required occasional medication. Twelve patients (25%) had initial unsatisfactory results with inadequate pain relief; nine underwent alternative surgical procedures. Sixteen patients (30%) subsequently required repeat glycerol rhizotomies to reachieve pain control. Twenty-seven patients (60% of 45 patients evaluated for this finding) retained normal trigeminal sensation after injection. Major trigeminal sensory loss developed in a single patient who had four glycerol rhizotomies over a 25-month interval. No patient developed deafferentation pain. We believe that PRGR is a low-morbidity, effective, and repeatable surgical procedure for the management of trigeminal neuralgia in the setting of multiple sclerosis.

PURPOSE: A multi-institutional experience in radiosurgery for solitary brain metastases was combined to identify factors associated with safety, efficacy, tumor control, and survival. MATERIALS AND METHODS: A review of 116 patients with solitary brain metastases who underwent gamma knife stereotactic radiosurgery at five institutions was performed. The median follow-up was 7 months following radiosurgery and 12 months following diagnosis. Minimum tumor doses varied from 8-30 Gy (mean, 17.5 Gy). Forty-five patients failed prior radiotherapy and 71 had no prior brain irradiation. Fifty-one patients had radiosurgery alone and 65 underwent combined radiosurgery with fractionated large-field radiotherapy (mean dose, 33.8 Gy). RESULTS: Median survival was 11 months after radiosurgery and 20 months after diagnosis. Follow-up documented local tumor control in 99 patients (85%), tumor recurrence in 17 (15%), and documented radiation necrosis in one (1%). The 2-year actuarial tumor control rate was 67 +/- 8%. Tumor histology affected survival (better for breast cancer, p = .004) and local control (better for melanoma and renal cell, p = .0003) in multivariate analyses. Combined fractionated radiotherapy and radiosurgery improved local control (p = 0.111), but not survival in multivariate testing. CONCLUSION: Radiosurgery is effective in controlling solitary brain metastases with low morbidity. Further study is needed to better define optimum treatment parameters for radiosurgery.

Swedish neurosurgeon Lars Leksell, frustrated by the invasiveness of existing surgical tools and the morbidity some neurosurgical patients endured, created the field of stereotactic radiosurgery in 1951. He subsequently pioneered the development of the dedicated multi-source Cobalt 60 Gamma Knife. During the 27 year interval from its first clinical use in 1967 to its latest application in 1994, single fraction, closed skull irradiation of deep intracranial targets has been performed in more than 20,000 patients worldwide. The goals of radiosurgery are obliteration or prevention of further growth of the target coupled with reduced patient risk in comparison to more invasive procedures.

To assess the long-term risk of facial nerve dysfunction after unilateral acoustic tumor stereotactic radiosurgery, we retrospectively analyzed our initial experience in 98 unilateral acoustic tumor patients who were evaluated at least 2 years after treatment. This observation interval permits an analysis of both the risk of onset and the potential for recovery of facial nerve function. The overall risk of developing any degree of delayed transient or permanent postoperative facial neuropathy was 21.4% (21 of 98 patients). Only one patient undergoing radiosurgery alone had poor residual facial nerve dysfunction worse than House-Brackmann grade III. Normal facial nerve function (House-Brackmann grade 1) was preserved in 95% of patients with small tumors (10 mm or less petrous-pons dimension) and in 90% of patients who had useful hearing and normal facial function preoperatively. Normal facial function was preserved in all patients with intracanalicular acoustic tumors. The risk of delayed facial neuropathy was reduced by performing radiosurgery when tumors were small (1000 mm(3) or less), by enclosing the tumor within the 50% isodose volume, by using multiple small radiation isocenters, and by detailed identification of the tumor volume using stereotactic magnetic resonance imaging.

The authors report the technique and results for stereotactic biopsy of intrinsic lesions of the medulla oblongata through the long-axis of the brainstem. Multi-planar stereotactic magnetic resonance imaging and/or reformatted computed tomography imaging is used for coordinate determination and trajectory selection and facilitates a completely intra-axial pathway through critical neural tissue. Two patients with small, solitary, enhancing lesions of the medulla had stereotactic sampling via this approach performed under local anesthesia. There was no morbidity and in both the patients a histologic diagnosis of lymphoma was obtained. We believe that with high-resolution, multi-planar stereotactic imaging, small lesions in the medulla can safely be biopsied, avoiding the need for either posterior fossa craniectomy and open biopsy, or for empiric management.

Successful clinical outcomes are not achieved in all patients who undergo image-guided stereotactic surgery as the initial procedure in the management of brain abscess. We sought to define those factors related to management failure, so that the initial surgical approach could be selected using preoperative clinical or imaging criteria. We reviewed our twelve-year experience in 29 consecutive patients. Twenty-two (76%) patients had drainage of abscesses with purulent centers. Seven (24%) underwent lesion biopsy for diagnosis. Twelve patients (with abscesses > 3 cm in average diameter) underwent stereotactic insertion of drainage catheters. Ten patients (34%) had adverse risk factors including immunologic suppression after prior organ transplantation, chronic steroid therapy, prior antineoplastic chemotherapy, or retained foreign body. Microbiological identification of the causative organism was obtained in 22 patients; 6 patients had positive Gram stains without growth in culture (bacteriological diagnosis = 97%). Long-term clinical evaluation (up to 8.5 years, median 3 years) confirmed disease resolution after initial single-procedure stereotactic management in 21 patients (72%). Eventual abscess resolution occurred in an additional 6 patients (21%), all of whom required multiple procedures. Five patients died of complications of their systemic disease during the follow-up period. Fifteen of the 18 (83%) surviving patients who had no associated risk factors returned to their premorbid functional capacity. Factors associated with initial treatment failure included inadequate aspiration, lack of catheter drainage of larger abscesses, chronic immunosuppression, and insufficient antibiotic therapy.