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Gamma Knife surgery–induced meningioma

Report of two cases and review of the literature

Jason Sheehan, Chun PO Yen and Ladislau Steiner

✓Gamma Knife surgery (GKS) is a minimally invasive neurosurgical technique. During the past 30 years, radiosurgery has been performed for a number of intracranial disorders with a generally low incidence of side effects. Although radiation-induced neoplasia following radiotherapy is well documented, there are few reports of this complication following radiosurgery.

The authors are engaged in an ongoing project in which they are studying the delayed adverse effects of radiosurgical changes in 2500 patients with arteriovenous malformations (AVMs) treated within a 30-year period. The cases of 1333 patients treated by the senior author (L.S.) have been reviewed thus far. A subset of 288 patients in this group underwent neuroimaging and participated in clinical follow up for at least 10 years.

The authors report two cases of radiosurgically induced neoplasia. In both cases the patient was treated with GKS for an AVM. Longer than 10 years after GKS, each of the patients was found to have an incidental, uniformly enhancing, dura-based mass lesion near the site of the AVM. These lesions displayed the imaging characteristics of a meningioma. Because in both cases the lesion has displayed no evidence of a mass effect, they continue to be followed using serial neuroimaging. These are the fifth and sixth cases meeting the criteria for radiation-induced neoplasms defined by Cahan, et al., in 1998.

Although radiosurgery is generally considered quite safe, the incidence of radiation-induced neoplasms is not known. These cases and the few others detailed in the literature emphasize the need for long-term neurosurgical follow-up review in patients after radiosurgery.

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Chun Po Yen, Jason Sheehan, Greg Patterson and Ladislau Steiner

Object

Although considered benign tumors, neurocytomas have various biological behaviors, histological patterns, and clinical courses. In the last 15 years, fractionated radiotherapy and radiosurgery in addition to microsurgery have been used in their management. In this study, the authors present their experience using Gamma Knife surgery (GKS) in the treatment of these tumors.

Methods

Between 1989 and 2004, the authors performed GKS in seven patients with a total of nine neurocytomas. Three patients harbored five recurrent tumors after a gross-total resection, three had progression of previous partially resected tumors, and one had undergone a tumor biopsy only. The mean tumor volume at the time of GKS ranged from 1.4 to 19.8 cm3 (mean 6.0 cm3). A mean peripheral dose of 16 Gy was prescribed to the tumor margin with the median isodose configuration of 32.5%.

Results

After a mean follow-up period of 60 months, four of the nine tumors treated disappeared and four shrank significantly. Because of secondary hemorrhage, an accurate tumor volume could not be determined in one. Four patients were asymptomatic during the follow-up period, and the condition of the patient who had residual hemiparesis from a previous transcortical resection of the tumor was stable. Additionally, the patient who experienced tumor hemorrhage required a shunt revision, and another patient died of sepsis due to a shunt infection.

Conclusions

Based on this limited experience, GKS seems to be an appropriate management alternative. It offers control over the tumor with the benefits of minimal invasiveness and low morbidity rates. Recurrence, however, is not unusual following both microsurgery and GKS. Open-ended follow-up imaging is required to detect early recurrence and determine the need for retreatment.

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Chun Po Yen, Jason Sheehan, Greg Patterson and Ladislau Steiner

Object

The authors review imaging and clinical outcomes in patients with metastatic brainstem tumors treated using Gamma Knife surgery (GKS).

Methods

Between March 1989 and March 2005, 53 patients (24 men and 29 women) with metastatic brainstem lesions underwent GKS. The metastatic deposits were located in the midbrain in eight patients, the pons in 42, and the medulla oblongata in three. Lung cancer was the most common primary malignancy, followed by breast cancer, melanoma, and renal cell carcinoma. The mean volume of the metastatic deposits at the time of treatment was 2.8 cm3 (range 0.05–21 cm3). The prescription doses varied from 9 to 25 Gy (mean 17.6 Gy).

Imaging follow-up studies were not completed in 16 patients, because of the short-term survival in 11 and patient refusal in five. Of the remaining 37 patients, who underwent an imaging follow-up evaluation at a mean of 9.8 months (range 1–25 months), the tumors disappeared in seven, shrank in 22, remained unchanged in three, and grew in five. All but one of 18 patients with asymptomatic brainstem deposits remained free of symptoms. In 35 patients with symptomatic brainstem deposits, neurological symptoms improved in 21, remained stable in 11, and worsened in three. At the time of this study, 10 patients were alive, and their survival ranged from 3 to 52 months after treatment. Thirty-four patients died of extracranial disease, three of the progressing metastatic brainstem lesion, and six of additional progressing intracranial deposits in other parts of the brain. The overall median survival period was 11 months after GKS. In terms of survival, the absence of active extracranial disease was the only favorable prognostic factor. Neither previous whole-brain radiation therapy nor a single brainstem metastasis was statistically related to the duration of survival.

Conclusions

Compared with allowing a metastatic brainstem lesion to take its natural course, GKS prolongs survival. The risks associated with such treatment are low. The severity of systemic diseases largely determines the prognosis of metastases to the brainstem.

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Douglas Kondziolka

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Bruce E. Pollock

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Claire Olson, Chun-Po Yen, David Schlesinger and Jason Sheehan

Object

Intracranial hemangiopericytoma is a rare CNS tumor that exhibits a high incidence of local recurrence and distant metastasis. The purpose of this study was to evaluate the role of Gamma Knife surgery (GKS) in the management of intracranial hemangiopericytomas.

Methods

In a review of the University of Virginia radiosurgery database between 1989 and 2008, the authors found recurrent or residual hemangiopericytomas after resection in 21 patients in whom radiosurgery was performed to treat 28 discrete tumors. The median age of this population was 47 years (range 31–61 years) at the time of the initial GKS. Prior treatments included embolization (6), transcranial resection (39), transsphenoidal resection (2), and fractionated radiotherapy (8). The mean prescription and maximum radiosurgical doses to the tumors were 17.0 and 40.3 Gy, respectively. Repeat radiosurgery was used to treat 13 tumors. The median follow-up period was 68 months (range 2–138 months).

Results

At last follow-up, local tumor control was demonstrated in 47.6% of the patients (10 of 21 patients) with hemangiopericytomas. Of the 28 tumors treated, 8 decreased in size on follow-up imaging (28.6%), 5 remained unchanged (17.9%), and 15 ultimately progressed (53.6%). The progression-free survival rates were 90, 60.3, and 28.7% at 1, 3, and 5 years after initial GKS. The progression-free survival rate improved to 95, 71.5, and 71.5% at 1, 3, and 5 years after multiple GKS treatments. The 5-year survival rate after radiosurgery was 81%. Prior fractionated irradiation or radiosurgical prescription dose did not correlate with tumor control. In 4 (19%) of 21 patients extracranial metastases developed.

Conclusions

Radiosurgery is a reasonable treatment option for recurrent hemangiopericytomas. Long-term close clinical and imaging follow-up is necessary because of the high probability of local recurrence and distant metastases. Repeat radiosurgery may be used to treat new or recurrent hemangiopericytomas over a long follow-up course.

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Ayhan Kanat

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Chun Po Yen, Jason Sheehan, Melita Steiner, Greg Patterson and Ladislau Steiner

Object

Focal tumors, a distinct subgroup of which is composed of brainstem gliomas, may have an indolent clinical course. In the past, their management involved monitoring of open-ended imaging studies and shunt placement if cerebrospinal fluid diversion was required. Nonetheless, their treatment remains a significant challenge for neurosurgeons. Gamma Knife surgery (GKS) has recently been tried as an alternative to surgical extirpation. In the present study the authors assess clinical and imaging results in 20 patients who harbored focal brainstem gliomas treated with GKS between 1990 and 2001.

Methods

There were 10 male and 10 female patients with a mean age of 19.1 years. Sixteen tumors were located in the midbrain, three in the pons, and one in the medulla oblongata. The mean tumor volume at the time of GKS was 2.5 cm3. In 10 cases a tumor specimen was obtained either by open surgery or stereotactic biopsy, securing the diagnosis of pilocytic astrocytoma in five patients and nonpilocytic astrocytoma in five others. In the remaining 10 cases, the diagnosis was based on clinical and neuroimaging findings. The prescription Gamma Knife dose varied between 10 and 18 Gy, except in three patients who were receiving a boost to a site in which external-beam radiation was previously delivered. An average of four isocenters were utilized per GKS.

Patients were followed up for a mean of 78.0 months. The tumors disappeared in four patients and shrank in 12 patients. Of these patients, one experienced transitory extrapyramidal symptoms and fluctuating impairment of consciousness (from somnolence to coma) for 6 months. Another patient whose tumor disappeared 3 years following GKS died of stroke 8 years postoperatively. The rest of the patients either remained stable or improved clinically. Tumor progression occurred in four patients; of these four, one patient developed hydrocephalus requiring a ventriculoperitoneal shunt, two showed neurological deterioration, and one 4-year-old boy died of tumor progression.

Conclusions

Gamma Knife surgery may be an effective primary treatment or adjunct to open surgery for focal brainstem gliomas.

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Peter Varady, Jason Sheehan, Melita Steiner and Ladislau Steiner

Heading : Chun Po Yen

Object

Subtotal obliteration of cerebral arteriovenous malformations (AVMs) after Gamma Knife surgery (GKS) implies a complete angiographic disappearance of the AVM nidus but persistence of an early filling draining vein, indicating that residual shunting is still present; hence, per definition there is still a patent AVM and the risk of bleeding is not eliminated. The aim of this study was to determine the risk of hemorrhage for patients with subtotal obliteration of AVMs.

Methods

After GKS for cerebral AVMs, follow-up angiography demonstrated a subtotally obliterated lesion in 159 patients. Of these, in 16 patients a subtotally obliterated AVM developed after a second GKS was performed for the partially obliterated lesion. The mean age of these patients was 35.2 years at the time of the diagnosis of subtotally obliterated AVMs. The lesion volumes at the time of initial GKS treatment ranged from 0.1 to 11.5 cm3 (mean 2.5 cm3). The mean peripheral dose used in the 175 GKS treatments was 22.5 Gy (median 23 Gy, range 15–31 Gy). To achieve total obliteration of the AVM, 23 patients underwent a new GKS targeting the proximal end of the early filling vein. The mean peripheral dose given in these cases was 23 Gy (median 24, range 18–25 Gy).

The incidence of subtotally obliterated AVMs was 7.6% from a total of 2093 AVMs treated and in which follow-up imaging was available. The diagnosis of subtotally obliterated AVMs was made a mean of 29.4 months (range 4–178 months) after GKS. The number of patient-years at risk (from the time of the diagnosis of subtotally obliterated AVMs until either the confirmation of a total obliteration of the lesion on angiography or the time of the latest follow-up angio-graphic study that still visualized the early filling vein) was a mean of 3.9 years, ranging from 0.5 to 13.5 years, and a total of 601 patient-years. There was no case of bleeding after the diagnosis of subtotally obliterated AVMs. Of 90 patients who did not undergo further treatment and in whom follow-up angiography studies were available, the same early filling veins still filled in 24 (26.7%), and the subtotally obliterated AVMs were subsequently obliterated in 66 patients (73.3%). In 19 patients who underwent repeated GKS for subtotally obliterated AVMs and in whom follow-up angiography studies were available, the AVMs were obliterated in 15 (78.9%) and remained patent in four (21.1%).

Conclusions

The fact that none of the patients with subtotally obliterated AVMs suffered a rupture is not compatible with the assumption of an unchanged risk of hemorrhage for these lesions, and implies that the protection from re-bleeding in patients with subtotal obliteration is significant. Subtotal obliteration does not necessarily seem to be a stage of an ongoing obliteration. At least in some cases it represents an end point of this process, with no subsequent obliteration occurring. This observation requires further confirmation by open-ended follow-up imaging.

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Robert G. Louis Jr., Chun Po Yen, Carrie A. Mohila, James W. Mandell and Jason Sheehan

The authors report the case of a patient with an intraosseous spinal arteriovenous malformation (AVM) presenting as an epidural mass lesion that was causing spinal cord compression. The 59-year-old woman had bilateral numbness, weakness, and hyperreflexia of both legs. Magnetic resonance imaging revealed intermediate T1 signal and hyperintense T2 signal involving the right transverse process, bilateral pedicles, and T-5 spinous process; the lesion's epidural extension was causing severe canal compromise and cord displacement. Coil embolization was performed, and the patient underwent resection, after which preoperative symptoms improved. Histopathological analysis revealed a benign vascular proliferation consistent with an intraosseous spinal AVM. On review of the literature, the authors found this case to be the second intraosseous spinal AVM, and the first in a patient whose clinical presentation was consistent with that of a mass lesion of the bone.