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Bruce E. Pollock

Object. The goal of this study was to analyze prospectively factors associated with facial pain outcomes after percutaneous retrogasserian glycerol rhizotomy (PRGR) for patients with medically unresponsive idiopathic trigeminal neuralgia.

Methods. Between July 1999 and December 2003, 98 patients underwent PRGR in the manner described by Håkanson. The mean patient age was 72.1 years and the average pain duration prior to PRGR was 8.6 years. Fifty patients (51%) had previously undergone surgery. In six patients (6%), the trigeminal cistern could not be defined and the procedure was aborted; six patients were lost to follow-up review. An excellent facial pain outcome was defined as the absence of facial pain without medications.

Thirty-two (35%) of 92 patients either received no benefit (17 patients) or experienced recurrent pain (15 patients) and required additional surgery at a mean of 7.5 months after PRGR; the mean duration of follow-up review in the other 60 patients was 28.7 months (range 3–52 months). Including patients who did not receive a glycerol injection, the 1- and 3-year chances of an excellent facial pain outcome were 61 and 50%, respectively. A multivariate analysis of clinical and surgical factors showed that the facial pain exhibited on glycerol injection correlated with excellent facial pain outcomes (relative risk [RR] = 1.02; 95% confidence interval [CI] 0.26–1.77; p < 0.01), whereas patients who experienced any constant pain less frequently had excellent outcomes (RR = 1.13; 95% CI 0.06–2.20; p = 0.04). Forty-six patients (53%) experienced either mild numbness/parathesias (39 patients) or dysesthesias (seven patients). New trigeminal deficits after PRGR were associated with excellent facial pain outcomes (RR = 1.25; 95% CI 0.56–1.93; p < 0.001).

Conclusions. Percutaneous retrogasserian glycerol rhizotomy remains a good operation for patients with medically unresponsive trigeminal neuralgia who are considered poor candidates for posterior fossa exploration. Predictive factors for success include patients without any constant facial pain, patients with immediate facial pain during glycerol injection, and patients with new trigeminal deficits after PRGR.

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Bruce E. Pollock

Object

Stereotactic radiosurgery (SRS) is commonly performed in patients with trigeminal neuralgia, and numerous investigators have found that facial pain outcomes after this procedure are better for patients in whom prior surgery did not fail. Researchers in some centers claim that the results of SRS are equivalent to posterior fossa exploration (PFE). The goal in this study was to verify that claim.

Methods

Information was retrieved from a prospectively maintained database of patients less than 70 years old with idiopathic trigeminal neuralgia who underwent PFE (55 patients) or SRS (28 patients) as their initial surgery between 1999 and 2004. Of the two groups, patients who underwent radiosurgery were older (60.5 compared with 50.7 years, p < 0.001). Microvascular decompression was performed in 49 patients (89%) and partial nerve section was performed in six (11%) in the PFE group. The mean maximum dose for SRS was 89.1 Gy. At a mean follow-up duration of 25.5 months, patients who had undergone PFE were more commonly pain free without medications (75% at 1 year, 72% at 3 years) compared with the patients treated with SRS (59% at 1 and 3 years; p = 0.01). Additional surgery was performed in 10 patients (18%) after PFE, compared with eight patients (29%) after SRS (p = 0.4). Eight patients (15%) had either new facial numbness (six cases) or dysesthesias (two cases) after PFE, whereas 12 (43%) had either new facial numbness (eight cases) or dysesthesias (four cases) after SRS. No correlation was noted between the development of facial numbness and facial pain outcome after PFE (p = 0.37), whereas patients in whom trigeminal dysfunction developed after radiosurgery were more frequently free of pain (p = 0.02).

Conclusions

The results support PFE as a more effective primary surgery than SRS in patients with idiopathic trigeminal neuralgia. Moreover, injury to the trigeminal nerve during PFE is not required to achieve excellent facial pain outcomes.

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Bruce E. Pollock

Object

Over the past 15 years stereotactic radiosurgery has become an accepted surgical option for patients with medically unresponsive trigeminal neuralgia (TN). The mechanism whereby radiosurgery causes pain relief remains unclear.

Methods

A review of recent papers on the radiosurgical management of TN reveals a correlation between maximum prescription dose and facial pain outcomes (p = 0.03) and between maximum prescription dose and new-onset trigeminal dysfunction (p < 0.01). In five of six studies in which investigators specifically analyzed whether there is any relationship between postradiosurgical trigeminal dysfunction and facial pain outcomes, there was a statistically significant greater chance of patients being pain free without medications if new trigeminal dysfunction developed after radiosurgery. Likewise, combining the results of two small series on repeated radiosurgery for TN also showed a significant correlation between postradiosurgical trigeminal dysfunction and facial pain outcomes (p = 0.02).

Conclusions

Although the quality of data available does not permit a formal metaanalysis of radiosurgery for TN, the preponderance of information supports an association between the development of facial sensory loss and pain relief after radiosurgery. Consequently, radiosurgery should be considered a destructive technique in which the goal is similar to that in other percutaneous ablative techniques used to manage TN: create sufficient damage to the trigeminal system to achieve pain relief, but not so much injury that the patient is at risk for deafferentation pain syndromes.

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Bruce E. Pollock

Object

Microsurgical removal of glomus jugulare tumors is frequently associated with injury of the lower cranial nerves. To decrease the morbidity associated with tumor management in these patients, gamma knife surgery (GKS) was performed as an alternative to resection.

Methods

Between 1990 and 2003, 42 patients underwent GKS as the primary management (19 patients) or for recurrent glomus jugulare tumors (23 patients). Facial weakness and deafness were more common in patients with recurrent tumors than in those in whom primary GKS was performed (48% compared with 11%, p = 0.02). The mean tumor volume was 13.2 cm3; the mean tumor margin dose was 14.9 Gy. The mean follow-up period for the 39 patients in whom evaluation was possible was 44 months (range 6–149 months). After GKS, 12 tumors (31%) decreased in size, 26 (67%) were unchanged, and one (2%) grew. The patient whose tumor grew underwent repeated GKS. Progression-free survival after GKS was 100% at 3 and 7 years, and 75% at 10 years. Six patients (15%) experienced new deficits (hearing loss alone in three, facial numbness and hearing loss in one, vocal cord paralysis and hearing loss in one, and temporary imbalance and/or vertigo in one). In 26 patients in whom hearing could be tested before GKS, hearing preservation was achieved in 86 and 81% at 1 and 4 years posttreatment, respectively. No patient suffered a new lower cranial nerve deficit after one GKS session; the patient in whom repeated GKS was performed experienced a new vocal cord paralysis 1 year after his second procedure.

Conclusions

Gamma knife surgery provided tumor control with a low risk of new cranial nerve injury in early follow-up review. This procedure can be safely used as a primary management tool in patients with glomus jugulare tumors that do not have significant cervical extension, or in patients with recurrent tumors in this location.

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Bruce E. Pollock

Object

Stereotactic radiosurgery (SRS) has become an important treatment option for patients with intracranial meningiomas. The author reviews the 12-year experience at a single institution and discusses the relative strengths and weakness of this management approach.

Methods

Between January 1990 and December 2002, 330 patients (with 356 tumors) underwent radiosurgery for intracranial meningiomas. One hundred thirty-eight patients (42%) harbored recurrent/residual tumors after having already undergone resection; 192 patients (58%) underwent radiosurgery as primary treatment. The majority of patients (70%) harbored skull base tumors. The median tumor volume was 7.3 cm3 (range 0.5–50.5 cm3). The median tumor margin dose was 16 Gy (range 12–20 Gy). In 278 patients with 297 lesions the mean clinical and imaging follow-up period was 43 months (range 2–138 months). Two hundred seventy-eight tumors (94%) remained stable or decreased in size, and 19 tumors progressed in size. Factors associated with progression were tumor histological type and prior surgery. Treatment-related complications occurred in 8% of the patients and included cranial neuropathies, symptomatic edema, cyst formation, and stenosis of the internal carotid artery. In three patients (1%) tumor dedifferentiation was noted after SRS.

Conclusions

Radiosurgical treatment of meningioma is safe and it has become the primary treatment for patients with small skull base tumors. Further study is needed to determine the long-term tumor control rates after such treatment, especially for patients treated with doses of 14 Gy or less.

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Nicolas de Tribolet

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Bruce E. Pollock and John C. Flickinger

Object. Radiosurgery is an effective treatment strategy for properly selected patients harboring arteriovenous malformations (AVMs). Grading scales that are currently used to predict patient outcomes after AVM resection are unreliable tools for the prediction of the results of AVM radiosurgery.

Methods. A grading system was developed to predict outcomes following AVM radiosurgery, based on the multivariate analysis of data obtained in 220 patients treated between 1987 and 1991 (Group 1). The dependent variable in all analyses was excellent patient outcome (complete AVM obliteration without any new neurological deficit). The grading scale was tested on a separate set of 136 patients with AVMs treated between 1990 and 1996 at a different center (Group 2).

One hundred twenty-one (55%) of 220 Group 1 patients had excellent outcomes. Multivariate analysis identified five variables related to excellent patient outcomes: AVM volume (p = 0.001), patient age (p < 0.001), AVM location (p < 0.001), previous embolization (p = 0.02), and number of draining veins (p = 0.001). Regression analysis modeling permitted removal of two significant variables (previous embolization and number of draining veins) and resulted in the following equation to predict patient outcomes after AVM radiosurgery: AVM score = (0.1)(AVM volume in cm3) + (0.02)(patient age in years) + (0.3)(location of lesion: frontal or temporal) = 0; parietal, occipital, intraventricular, corpus callosum, cerebellar = 1; or basal ganglia, thalamic, or brainstem = 2). Seventy-nine (58%) of 136 Group 2 patients had excellent outcomes. All variables in the model remained significant for the Group 2 patients: AVM volume (p = 0.01), patient age (p = 0.01), and AVM location (p < 0.001). Testing of the entire model on the Group 2 patients demonstrated that the AVM score could be used to predict patient outcomes after radiosurgery (p < 0.0001). All patients with an AVM score of 1 or lower had an excellent outcome compared with only 39% of patients with an AVM score higher than 2. The Spetzler—Martin grade (p = 0.13), the K index (p = 0.26), and the obliteration prediction index (p = 0.21) did not correlate with excellent patient outcomes.

Conclusions. Despite significant differences in preoperative patient characteristics and dose prescription guidelines at the two centers, the proposed AVM grading system strongly correlated with patient outcomes after single-session radiosurgery for both patient groups. Although further testing of this model by independent centers using prospective methodology is still required, this system allows a more accurate prediction of outcomes from radiosurgery to guide choices between surgical and radiosurgical management for individual patients with AVMs.

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Bruce E. Pollock and Christopher J. Boes

Object

Glossopharyngeal neuralgia (GPN) is a rare pain disorder characterized by severe, stabbing pain of the ear, posterior tongue, and throat. The authors report their early experience of using stereotactic radiosurgery (SRS) as an alternative to posterior fossa surgery for patients with medically resistant GPN.

Methods

Five patients (3 men, 2 woman) with medically resistant GPN underwent Gamma Knife surgery. The radiosurgical target was the distal portion of the glossopharyngeal and vagus nerves at the jugular foramen (glossopharyngeal meatus). The maximum radiation dose in all cases was 80 Gy. The median follow-up after radiosurgery was 13 months (range 2–19 months).

Results

Three patients became pain-free at 2 days, 3 days, and 2 weeks, respectively, and were able to discontinue the medications taken preoperatively for their pain. None of these patients have suffered recurrent pain since becoming pain free. Two patients experienced no benefit from the procedure and underwent posterior fossa surgery 2 and 5 months after SRS. Both of these patients continued to have pain after posterior fossa surgery. One of these patients was later discovered to have a head and neck cancer as the cause of his pain. No patient developed hoarseness or dysphagia after radiosurgery.

Conclusions

This preliminary experience demonstrates that SRS is an option for patients with medically resistant GPN. Additional follow-up and a larger number of patients are needed to demonstrate the long-term safety and optimal radiation dosimetry for this indication.

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Bruce E. Pollock and John Huston III

Object. To determine the natural history of colloid cysts of the third ventricle in patients in whom the cysts were incidentally discovered, the authors retrospectively reviewed cases observed during the modern neuroimaging era (1974–1998).

Methods. During this 25-year interval, 162 patients with colloid cysts were examined and cared for at our center. Sixty-eight patients (42%) were thought to be asymptomatic with regard to their colloid cyst and observation with serial neuroimaging was recommended. The mean patient age was 57 years at the time of diagnosis (range 7–88 years) and the mean cyst size was 8 mm (range 4–18 mm). Computerized tomography scanning revealed a hyperdense cyst in 49 (84%) of 58 patients. Three patients were excluded from the study because they died of unrelated causes within 6 months of scanning and seven patients were lost to follow-up review. Clinical follow-up evaluation was available at a mean of 79 months (range 7–268 months) in the remaining 58 patients. The numbers of patients who participated in follow-up review at 2, 5, and 10 years after diagnosis were 40, 28, and 14, respectively. The incidences of symptomatic progression related to the cyst were 0%, 0%, and 8% at 2, 5, and 10 years, respectively. No patient died suddenly during the follow-up interval. Two (6%) of 34 patients in whom follow-up imaging was performed either exhibited cyst growth (one patient) or experienced hydrocephalus (one patient) at a mean of 41 months after diagnosis (range 4–160 months).

Conclusions. Patients in whom asymptomatic colloid cysts are diagnosed can be cared for safely with observation and serial neuroimaging. If a patient becomes symptomatic, the cyst enlarges, or hydrocephalus develops, prompt neurosurgical intervention is necessary to prevent the occurrence of neurological decline from these benign tumors.

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Bruce E. Pollock and Robert L. Foote