Stereotactic Radiosurgery May Not Raise Risk of Intracranial Malignancy


Patients who undergo stereotactic radiosurgery for benign indications do not appear to be at increased risk of malignant transformation, new findings show.

“Although prospective cohort studies with longer follow-up are warranted to support the results of this study, the available evidence suggests the long-term safety of stereotactic radiosurgery and could support physicians counselling patients on Gamma Knife stereotactic radiosurgery,” Dr. Amparo Wolf of the University of Western Ontario in London, Canada, and colleagues conclude in The Lancet Oncology, online November 22.

Cases of patients developing new tumors after intracranial radiosurgery have been published, but larger studies with longer-term follow-up have not been conducted, the authors note.

To investigate, they looked at 4,905 patients treated at five international radiosurgery centers in the U.S. and Europe for arteriovenous malformations, trigeminal neuralgia or benign intracranial tumors with Gamma Knife surgery. All had at least five years of follow-up data, and none had received radiotherapy previously.

During a median follow-up of 8.1 years, suspected malignant transformation occurred in two of 3,251 patients with benign tumors (0.0006%, incidence 6.87 per 100,000 patient years).

One patient developed a new intracranial malignancy (0.0002%, 2.26 per 100,000 patient years), which was considered treatment-related because it occurred within the radiation field.

Two patients developed intracranial malignancies that were not within the radiation field.

Overall, the incidence of radiosurgery-associated malignancy was 6.8 per 100,000 person years, similar to the risk of developing a malignant tumor in the central nervous system for the general population of the U.S. and parts of Europe, which ranges from 3.1 to 9.1 per 100,000 patient-years, the authors note.

“Based on the results of this study, for patients who are having either primary or salvage stereotactic radiosurgery for a histologically benign brain tumour, the risk of neoplastic transformation or the risk of having a new radiation-induced intracranial malignancy after radiosurgery is low and similar to that of the annual incidence of primary CNS tumours in the general population, even at long-term follow-up (more than 10 years),” they conclude.

“We agree with Wolf and colleagues that the overall risk of secondary cancers appears reassuringly low at 10 years, and this concern alone should not preclude stereotactic radiosurgery when warranted,” Dr. Alejandro Berlin and colleagues of the University Health Network in Toronto write in a comment accompanying the study.

“With an expected long survival of patients with benign conditions, it is prudent to advocate for properly quantified longer-term outcomes (>15-20 years) to guide judicious decision making and surveillance strategies,” they add.

Stereotactic Radiosurgery Benefit for Brain Mets: Case Closed?


The use of stereotactic radiosurgery (SRS) alone on patents with limited (one to three) brain metastases results in less cognitive deterioration than when combined with whole brain radiotherapy (WBRT), investigators have reported.

In a study led by Paul D. Brown, MD, director of the CNS stereotactic radiotherapy program at the University of Texas MD Anderson Cancer Center, researchers determined there was less cognitive deterioration in patients who underwent SRS alone after 3 months (64%), than in patients who underwent SRS plus WBRT (92%).

The results, published online in the Journal of the American Medical Association, showed a “significant difference” in the level of cognitive deterioration, particularly considering the controversy surrounding the role WBRT should play in the treatment of patients with brain metastases, the authors wrote.

The use of WBRT has been associated with cognitive decline, and while previous randomized clinical trials have demonstrated improved intracranial tumor control with the combined use of WBRT and SRS for brain metastases, none have showed any significant survival advantage with adjuvant WBRT.

“Central to this issue is whether tumor progression anywhere in the brain is more detrimental to a patient’s well-being than the potential deterioration of cognitive function and quality of life associated with WBRT,” Brown and his colleagues wrote. “Because more than 200,000 individuals in the United States alone are estimated to receive WBRT each year, it is important that the potential benefits and risk of adjuvant WBRT be clearly defined.”

The study involved 213 patients from 34 institutions in North American who had between one and three brain metastases (all less than 3 cm in diameter); participants were randomized to receive SRS or SRS plus WBRT.

After excluding patients who died, did not return for a 3-month or subsequent evaluation, or did not complete the required baseline tests, 111 patients were available for evaluation.

 There was less cognitive deterioration at 3 months after use of SRS alone (40 of 63 patients, 63.5%) than with the SRS-plus-WBRT group (44 of 48 patients, 91.7%). This was a difference of 28.2%; 90% CI, -41.9% to -14.4%).

In addition, quality of life was higher at 3 months with SRS alone (mean change from baseline, −0.1 versus −12.0 points; mean difference, 11.9; 95% CI, 4.8-19.0 points).

The time to intracranial failure was shorter for those in the SRS-alone group compared with those in the SRS-plus-WBRT group (hazard ratio [HR], 3.6; 95% CI, 2.2-5.9), and there was no significant difference in functional independence between the two groups at three months.

Median overall survival was 10.4 months for patients receiving SRS alone and 7.4 months for those given the combined treatments (HR, 1.02; 95% CI, 0.75-1.38).

“In the absence of overall survival, these findings suggest that for patients with one to three brain metastases amenable to radiosurgery, SRS alone may be a preferred strategy,” the team concluded.

 Limitations to the study included the fact that a majority of the participants had lung cancer and the trial did not attempt to include other types of primary cancers. However, Brown and his colleagues noted that lung cancer is the predominant primary cancer reported in most brain metastases trials and that “there is no obvious biological basis to believe that the quality-of-life and cognitive effects of WBRT would vary between different primary cancers.”

The authors also noted that there was significant patient dropout in their trial, mostly due to death, and that clinicians and trial participants were not blinded to treatment.

In an editorial accompanying the study, titled “Whole Brain Radiotherapy for Brain Metastases: Is the Debate Over?,” Orit Kaidar-Person, MD, Carey K. Anders, MD, and Timothy M. Zagar, MD, wrote that the trial “confirms previous recommendations that WBRT should not be routinely added to SRS for patients with brain metastases of limited number or size.”

But, while there may be little role for WBRT in the type of patient enrolled in the this particular study, the editorial argued that based on the findings, and “until proven otherwise,” WBRT could still have an important role to play in the treatment of patients not in that disease category.

“However, the study results cannot be extrapolated to infer that SRS is the standard for patients with four or more metastases or that WBRT no longer has a role in the treatment of brain metastases,” Kaidar-Person and his colleagues wrote.

Impact of the radiosurgery prescription dose on the local control of small (2 cm or smaller) brain metastases


Abstract

OBJECTIVE

The impact of the stereotactic radiosurgery (SRS) prescription dose (PD) on local progression and radiation necrosis for small (≤ 2 cm) brain metastases was evaluated.

METHODS

An institutional review board–approved retrospective review was performed on 896 patients with brain metastases ≤ 2 cm (3034 tumors) who were treated with 1229 SRS procedures between 2000 and 2012. Local progression and/or radiation necrosis were the primary end points. Each tumor was followed from the date of radiosurgery until one of the end points was reached or the last MRI follow-up. Various criteria were used to differentiate tumor progression and radiation necrosis, including the evaluation of serial MRIs, cerebral blood volume on perfusion MR, FDG-PET scans, and, in some cases, surgical pathology. The median radiographic follow-up per lesion was 6.2 months.

RESULTS

The median patient age was 56 years, and 56% of the patients were female. The most common primary pathology was non–small cell lung cancer (44%), followed by breast cancer (19%), renal cell carcinoma (14%), melanoma (11%), and small cell lung cancer (5%). The median tumor volume and median largest diameter were 0.16 cm3 and 0.8 cm, respectively. In total, 1018 lesions (34%) were larger than 1 cm in maximum diameter. The PD for 2410 tumors (80%) was 24 Gy, for 408 tumors (13%) it was 19 to 23 Gy, and for 216 tumors (7%) it was 15 to 18 Gy. In total, 87 patients (10%) had local progression of 104 tumors (3%), and 148 patients (17%) had at least radiographic evidence of radiation necrosis involving 199 tumors (7%; 4% were symptomatic). Univariate and multivariate analyses were performed for local progression and radiation necrosis. For local progression, tumors less than 1 cm (subhazard ratio [SHR] 2.32; p < 0.001), PD of 24 Gy (SHR 1.84; p = 0.01), and additional whole-brain radiation therapy (SHR 2.53; p = 0.001) were independently associated with better outcome. For the development of radiographic radiation necrosis, independent prognostic factors included size greater than 1 cm (SHR 2.13; p < 0.001), location in the corpus callosum (SHR 5.72; p < 0.001), and uncommon pathologies (SHR 1.65; p = 0.05). Size (SHR 4.78; p < 0.001) and location (SHR 7.62; p < 0.001)—but not uncommon pathologies—were independent prognostic factors for the subgroup with symptomatic radiation necrosis.

CONCLUSIONS

A PD of 24 Gy results in significantly better local control of metastases measuring < 2 cm than lower doses. In addition, tumor size is an independent prognostic factor for both local progression and radiation necrosis. Some tumor pathologies and locations may also contribute to an increased risk of radiation necrosis.

Gamma Knife surgery for incidental cerebral arteriovenous malformations


A relatively benign natural course of unruptured cerebral arteriovenous malformations (AVMs) has recently been recognized, and the decision to treat incidentally found AVMs has been questioned. This study aims to evaluate the long-term imaging and clinical outcomes of patients with asymptomatic, incidentally discovered AVMs treated with Gamma Knife surgery (GKS).

METHODS

Thirty-one patients, each with an incidentally diagnosed AVM, underwent GKS between 1989 and 2009. The nidus volumes ranged from 0.3 to 11.1 cm3 (median 3.2 cm3). A margin dose between 15 and 26 Gy (median 20 Gy) was used to treat the AVMs. Four patients underwent repeat GKS for still-patent AVM residuals after the initial GKS procedure. Clinical follow-up ranged from 24 to 196 months, with a mean of 78 months (median 51 months) after the initial GKS.

RESULTS

Following GKS, 19 patients (61.3%) had a total AVM obliteration on angiography. In 7 patients (22.6%), no flow voids were observed on MRI but angiographic confirmation was not available. In 5 patients (16.1%), the AVMs remained patent. A small nidus volume was significantly associated with increased AVM obliteration rate. Thirteen patients (41.9%) developed radiation-induced imaging changes: 11 were asymptomatic (35.5%), 1 had only headache (3.2%), and 1 developed seizure and neurological deficits (3.2%). Two patients each had 1 hemorrhage during the latency period (116.5 risk years), yielding an annual hemorrhage rate of 1.7% before AVM obliteration.

CONCLUSIONS

The decision to treat asymptomatic AVMs, and if so, which treatment approach to use, remain the subject of debate. GKS as a minimally invasive procedure appears to achieve a reasonable outcome with low procedure-related morbidity. In those patients with incidental AVMs, the benefits as well as the risks of radiosurgical intervention will only be fully defined with long-term follow-up.

CyberKnife


Advertisements for a radiation delivery system called CyberKnife® have prompted a large number of questions from patients inquiring whether it employs a unique new technology.

CyberKnife is used in a type of radiation therapy called stereotactic radiosurgery (also known as stereotactic radiotherapy). This treatment destroys tumors with extremely precise, very intense doses of radiation while minimizing damage to healthy tissue, offering accuracy akin to the sharpness of a surgeon’s scalpel.

Memorial Sloan Kettering radiation oncologist Abraham J. Wu employs stereotactic radiosurgery to treat lung and gastrointestinal cancers. He explains that CyberKnife is a brand name for one of several available stereotactic radiosurgery devices that deliver radiation with linear accelerators, or devices that form beams of fast-moving subatomic particles. The beams are precisely directed through the use of advanced imaging technologies combined with a sophisticated computer guidance system.

“There are a lot of different machines and a lot of different marketing terms thrown around, but they all achieve the same goal, which has two critical components,” Dr. Wu says. “One is delivering a more intense dose of radiation in just a few sessions. The other is targeting the radiation very accurately by pinpointing the precise location of the tumor during treatment.”

The Importance of Image Guidance

Memorial Sloan Kettering radiation oncologists use linear accelerators made by a company called Varian. The Varian machine Dr. Wu most often uses — primarily to treat lung tumors — employs a system called TrueBeamTM, which incorporates computed tomography (CT) imaging into the same device that delivers the radiation. This allows the radiation therapists to make sure patients remain in the proper position during radiation therapy and to adjust the radiation beams as needed.

“Really, the big breakthrough in recent years has been the advent of CT imagers on the treatment machine itself — as we have with the TrueBeam — which allows us to ensure the accuracy of radiotherapy treatments with the highest precision,” he says. “Interestingly, CyberKnife does not incorporate a CT imaging machine into the device — it uses a different system of image guidance.”

The main distinguishing feature of CyberKnife is that the linear accelerator is mounted on a robotic arm. While this offers more flexibility and freedom of movement in how the radiation beam is delivered, Dr. Wu says that “in practice this is rarely something that is going to make a difference in how precisely we treat someone. We can still deliver the radiation to a given target.”

What is important, he explains, is the skill and experience of the radiation oncologists and medical physicists who define the radiation target.

“There are a lot of different technical solutions to achieve the kind of accuracy that you need to deliver very high doses of radiation — it’s a variety of different means to the same end,” Dr. Wu says. “We’re convinced that our Varian machines enable us to perform stereotactic radiosurgery at the highest level.”

Stereotactic radiosurgery yielded favorable remission of acromegaly.


Stereotactic radiosurgery may yield favorable remission response rates in patients with acromegaly with a low rate of adverse events, according to data published in the Journal of Clinical Endocrinology and Metabolism.

  • Surgical resection is currently the primary treatment for patients with acromegaly, according to researchers. The rates of endocrine remission relate to tumor size, degree of invasiveness and surgical expertise, the researchers wrote.

They conducted a retrospective review of 136 patients (mean age, 44 years) withacromegaly treated with stereotactic radiosurgery at the University of Virginia. Gamma Knife radiosurgery data were collected from 1989 to 2012.

Follow-up data at 61.5 months indicated that 65.4% of the patients reached remission of acromegaly, with a mean time to remission of 27.5 months.

Specifically, there was a 31.7% remission rate at 2 years, 64.5% at 4 years, 73.4% at 6 years and 82.6% at 8 years after radiosurgery, according to data.

After the withdrawal of growth hormone or insulin-like growth factor I medications, patients with an oral glucose tolerance test GH level <1 ng/mL or normal IGF-I were considered to be in remission, researchers wrote.

Favorable prognostic factors for remission included higher radiation combined with maximum dose and lower initial IGF-I levels, according to data.

Hypothalamic-pituitary dysfunction is the most common intermediate to late complication of [stereotactic radiosurgery] of pituitary adenomas. In our series, 31.6% patients developed new hormone deficiency at a median of 50.5 months following radiosurgery,” researchers wrote.

Two patients (1.5%) developed panhypopituitarism. Other risk factors for pituitary hormone deficiencies included a margin dose >25 G and tumor volume >2.5 mL. An adverse radiation effect was observed in one patient, visual deterioration in four, and new oculomotor nerve palsy in one. Seven patients who reached remission after surgery developed a recurrence of the disease at 42 months.

 

 
 

PERSPECTIVE

John D. Carmichael

  • Acromegaly is a difficult disease to treat in many cases. The patients’ clinical experiences range from those which are mild and straight-forward to those with aggressive tumors, very challenging biochemistry, and disease attributes that require multimodal therapy. It’s good to see a large study like this reporting on radiotherapy outcomes and safety, which is one part of our treatment armamentarium.

    The response rates that they report are encouraging in terms of the biochemistry because there are patients who do require more aggressive treatment than just surgery or medication.

    I think the difficulties of such a study are that long-term follow-up is challenged with treatment performed through a tertiary referral center, and as they acknowledge in their paper, they rely on other endocrinologists’ data in some cases and are unable to obtain complete data sets. This might be one of the shortcomings of the study: that sometimes, the tests that you want to complete don’t always get done in terms of both safety assessments and assessments of recurrence.

    In general, they compare their findings to both prior radiosurgery techniques and to prior conventional radiotherapy. I think that many people are hoping that the gamma knife radiosurgery will have significantly improved response rates and a better safety profile in terms of hypopituitarism and damage to adjacent structures.

    The authors have shown that their response rates are satisfactory enough to consider radiosurgery as a viable treatment. Unfortunately, the hypopituitarism demonstrated in these patients is comparable to prior reports of radiotherapy-induced hypopituitarism and practitioners are concerned about this adverse effect. These data are not going to make gamma knife radiosurgery more appealing to those who are concerned about the effects of hypopituitarism. The use of radiotherapy is a divisive topic in the treatment of patients with acromegaly and physicians have very strong opinions about the use and the timing of this mode of therapy. Some may utilize it earlier on in the care of patients, so that a patient will directly be treated with radiosurgery after failed transsphenoidal surgery, as many of the patients were in this study. Alternatively, one may use radiosurgery only in those resistant to medical therapy and unable to gain biochemical or tumor control.

    The follow-up for patients treated with radiosurgery does require longer duration of observation and while this group has some of the longest follow-up compared to other studies, nevertheless more time is required for safety assessments such as development of secondary tumors and hypopituitarism.

    • John D. Carmichael, MD
    • Assistant Professor of Medicine in the Division of Endocrinology, Diabetes and Metabolism at the David Geffen School of Medicine at the University of California, Los Angeles; and
      Staff Physician of Endocrinology/Metabolism at Cedars-Sinai Medical Center

Longitudinal analysis of hearing before and after radiosurgery for vestibular schwannoma.


The aim of this study was to perform an accurate analysis of changes in hearing in patients with vestibular schwannoma (VS) who have undergone Gamma Knife surgery (GKS) and distinguish the impact of radiosurgery from the natural course of hearing deterioration due to the tumor itself.

Methods

This study was a retrospective review of prospectively collected patient data. A group of 154 patients with unilateral nonsurgically treated VS was conservatively monitored for more than 6 months and then treated with GKS between July 1997 and September 2005. They were followed up with serial clinical examination, MRI, and audiometry. The annual hearing decrease rate (AHDR) was measured before and after radiosurgery, and the possible prognostic factors for hearing preservation were investigated.

Results

The mean dose prescribed to the tumor margins was 12.1 Gy. The mean radiological follow-up period after GKS was 60 months (range 7–123 months). The tumor control rate was 94.8%, and 8 patients underwent subsequent intervention due to tumor progression. The mean audiological follow-up times before and after GKS were 22 and 52 months, respectively. The mean AHDRs before and after GKS were 5.39 dB/year (95% CI 3.31–7.47 dB/year) and 3.77 dB/year (95% CI 3.13–4.40 dB/year), respectively (p > 0.05). The mean pre- and post-GKS AHDRs in patients who initially had Gardner-Robertson (GR) Class I hearing were −0.57 dB/year (95% CI −2.95 to 1.81 dB/year) and 3.59 dB/year (95% CI 2.52–4.65 dB/year), respectively (p = 0.007). The mean pre- and post-GKS AHDRs in patients who initially had GR Class II hearing were 5.09 dB/year (95% CI 1.36–8.82 dB/year) and 4.98 dB/year (95% CI 3.86–6.10 dB/year), respectively (p > 0.05). A subgroup of 80 patients had both early and late post-intervention AHDR assessment (with early referring to the period from GKS to the assessment closest to the 2-year follow-up point and late referring to the period from that assessment to the most recent one); in these patients, the mean early post-GKS AHDR was 5.86 dB/year (95% CI 4.25–7.50 dB/year) and the mean late post-GKS AHDR was 1.86 dB/year (95% CI 0.77–2.96 dB/year) (p < 0.001). A maximum cochlear dose of less than 4 Gy was found to be the sole prognostic factor for hearing preservation.

Conclusions

The present study demonstrated the absence of an increase in AHDR after radiosurgery as compared with the preoperative AHDR. There was even a trend indicating a reduction in the annual hearing loss after radiosurgery over the long term. To fully elucidate a possible protective effect of radiosurgery, longer-term follow-up with a larger group of patients will be required.

Source: Journal Of Neurosurgery.

 

 

Long-term radiosurgery effects in the treatment of temporal lobe epilepsy.


Epilepsy surgery is an effective treatment for medically resistant temporal lobe epilepsy (TLE). To minimize complication rates and potentially improve neuropsychology outcomes, stereotactic radiosurgery (SRS) has been explored as an alternative. Two pilot trials have demonstrated the effectiveness of SRS for the treatment of medically resistant TLE, with seizure-free outcomes for approximately 65% of patients at last follow-up. Despite encouraging results, no conclusive long-term outcomes are available for SRS. This article discusses a single patient who presented with recurrent seizures, worsening headaches, and persistent abnormal MRI findings 7 years and 8 months after SRS.

This 29-year-old woman with a history of medically refractory complex partial seizures since childhood was referred for evaluation. Medical management had failed in this patient. The workup was compatible with left mesial temporal lobe onset, with MRI findings suggestive of mesial temporal sclerosis. In 2003, at the age of 23 years, she underwent Gamma Knife surgery (GKS) targeting the left temporal mesial area with a dose of 24 Gy at the 50% marginal isodose line. After GKS, the patient’s seizures decreased in frequency over several months, but auras were persistent. Nine months after treatment, she developed worsening headaches. A follow-up MRI study demonstrated a thick, irregular, enhancing lesion in the medial part of the temporal lobe. She was placed on corticosteroids, with resolution of her headaches.

Her seizures and headaches recurred in March 2010. An MRI study showed a 2.2-cm, ill-defined, enhancing cystic lesion in the left mesial temporal lobe with T2 and FLAIR hyperintensity, which was presumably radiation induced. At that time, the patient opted for left temporal lobe resection to control her seizures. Histological examination showed moderately severe, remote, longstanding sclerosis at the level of the hippocampus. A vascular lesion was identified, and it was most consistent with radiation-induced capillary hemangioma. The entorhinal region was severely damaged, with hemorrhage, necrosis, neuronal loss, astrogliosis, and hemosiderin deposition. There was evidence of radiation vasculopathy.

Radiation-induced lesions after SRS for the treatment of epilepsy are not well documented. Although GKS is a promising technique for the treatment of medically resistant TLE, the ideal candidate is not yet well defined. The selection of the appropriate technical parameters to obtain a desirable functional effect without histological damage to the surrounding neural tissue remains a challenge. This case illustrates the need for long-term follow-up when radiosurgery is used for epilepsy.

Source: Journal of Neurosurgery.

 

 

Gamma Knife surgery for basal ganglia and thalamic arteriovenous malformations.


Gamma Knife surgery (GKS) has emerged as the treatment of choice for small- to medium-sized cerebral arteriovenous malformations (AVMs) in deep locations. The present study aims to investigate the outcomes of GKS for AVMs in the basal ganglia and thalamus.

Methods

Between 1989 and 2007, 85 patients with AVMs in the basal ganglia and 97 in the thalamus underwent GKS and were followed up for more than 2 years. The nidus volumes ranged from 0.1 to 29.4 cm3 (mean 3.4 cm3). The mean margin dose at the initial GKS was 21.3 Gy (range 10–28 Gy). Thirty-six patients underwent repeat GKS for residual AVMs at a median 4 years after initial GKS. The mean margin dose at repeat GKS was 21.1 Gy (range 7.5–27 Gy).

Results

Following a single GKS, total obliteration of the nidus was confirmed on angiograms in 91 patients (50%). In 12 patients (6.6%) a subtotal obliteration was achieved. No flow voids were observed on MR imaging in 14 patients (7.7%). Following single or repeat GKS, total obliteration was angiographically confirmed in 106 patients (58.2%) and subtotal obliteration in 8 patients (4.4%). No flow voids on MR imaging were observed in 18 patients (9.9%). The overall obliteration rates following one or multiple GKSs based on MR imaging or angiography was 68%. A small nidus volume, high margin dose, low number of isocenters, and no history of embolization were significantly associated with an increased rate of obliteration. Twenty-one patients experienced 25 episodes of hemorrhage in 850 risk-years following GKS, yielding an annual hemorrhage rate of 2.9%. Four patients died in this series: 2 due to complications of hemorrhage and 2 due to unrelated diseases. Permanent neurological deficits caused by radiation were noted in 9 patients (4.9%).

Conclusions

Gamma Knife surgery offers a reasonable chance of obliterating basal ganglia and thalamic AVMs and does so with a low risk of complications. It is an optimal treatment option in patients for whom the anticipated risk of microsurgery is too high.

Source: Journal of Neurosurgery

 

 

Outcomes of Gamma Knife surgery for trigeminal neuralgia secondary to vertebrobasilar ectasia.


Vertebrobasilar ectasia (VBE) is an unusual cause of trigeminal neuralgia (TN). The surgical options for patients with medically refractory pain include percutaneous or microsurgical rhizotomy and microvascular decompression (MVD). All such procedures can be technically challenging. This report evaluates the response to a minimally invasive procedure, Gamma Knife surgery (GKS), in patients with TN associated with severe vascular compression caused by VBE.

Methods

Twenty patients underwent GKS for medically refractory TN associated with VBE. The median patient age was 74 years (range 48–95 years). Prior surgical procedures had failed in 11 patients (55%). In 9 patients (45%), GKS was the first procedure they had undergone. The median target dose for GKS was 80 Gy (range 75–85 Gy). The median follow-up was 29 months (range 8–123 months) after GKS. The treatment outcomes were compared with 80 case-matched controls who underwent GKS for TN not associated with VBE.

Results

Intraoperative MR imaging or CT scanning revealed VBE that deformed the brainstem in 50% of patients. The trigeminal nerve was displaced in cephalad or lateral planes in 60%. In 4 patients (20%), the authors could identify only the distal cisternal component of the trigeminal nerve as it entered into the Meckel cave.

After GKS, 15 patients (75%) achieved initial pain relief that was adequate or better, with or without medication (Barrow Neurological Institute [BNI] pain scale, Grades I–IIIb). The median time until pain relief was 5 weeks (range 1 day–6 months). Twelve patients (60%) with initial pain relief reported recurrent pain between 3 and 43 months after GKS (median 12 months). Pain relief was maintained in 53% at 1 year, 38% at 2 years, and 10% at 5 years. Some degree of facial sensory dysfunction occurred in 10% of patients. Eventually, 14 (70%) of the 20 patients underwent an additional surgical procedure including repeat GKS, percutaneous procedure, or MVD at a median of 14 months (range 5–50 months) after the initial GKS. At the last follow-up, 15 patients (75%) had satisfactory pain control (BNI Grades I–IIIb), but 5 patients (25%) continued to have unsatisfactory pain control (BNI Grade IV or V). Compared with patients without VBE, patients with VBE were much less likely to have initial (p = 0.025) or lasting (p = 0.006) pain relief.

Conclusions

Pain control rates of GKS in patients with TN associated with VBE were inferior to those of patients without VBE. Multimodality surgical or medical management strategies were required in most patients with VBE.

Source: Journal of Neurosurgery