New Studies on Gamma Knife Radiosurgery: Decades of Follow-Up Define Long-Term Outcomes in Meningioma, dAVF, Essential Tremor
October 23, 2026
Four decades of Gamma Knife® stereotactic radiosurgery (SRS) in the UPMC Center for Image-Guided Neurosurgery (CIGNS) have generated the clinical experience and longitudinal data needed to assess long-term outcomes after treatment. Three studies published in 2026 draw on that experience to examine long-term outcomes in meningioma, dural arteriovenous fistulas, and medically refractory essential tremor.
The UPMC Gamma Knife program began in 1987, when L. Dade Lunsford, MD, brought the first Gamma Knife in North America to Pittsburgh. The program treated its 20,000th patient in 2026 and has prospectively collected patient data throughout its history. That record allows the team to examine outcomes over follow-up periods that few programs can match and to use those findings to refine patient selection, treatment planning, and subsequent care.
“The questions we can answer today are different from the ones we could answer early in the Gamma Knife experience. We now have patients who have been followed for decades, so we can look at durability and long-term effects rather than relying only on what happens in the first few years after treatment,” says Constantinos G. Hadjipanayis, MD, PhD, director of the UPMC Center for Image-Guided Neurosurgery.
A Broader Role in Meningioma Treatment
Gamma Knife’s role in meningioma care has changed from predominantly treating difficult skull base tumors and postoperative residual disease to primary treatment of selected unresected tumors. The evidence for that broader use includes tumor control beyond the first few years after radiosurgery.
In a study published in Neurosurgery, led by first author Chris Z. Wei, MD, and senior author Dr. Lunsford, reviewed data on 1,760 patients with 2,220 meningiomas treated over 35 years. Estimated local control was 92.1% at five years and 81.1% at 20 years. For unresected tumors, estimated 20-year control was 84.8%. These results help answer a question that could not be resolved early in the program: whether primary radiosurgery could control a meningioma for decades.
“Originally, we would observe meningiomas that were small or moderate in size if the patient didn’t have symptoms. Now we have data supporting early intervention with Gamma Knife. In long-term studies, patients whose meningiomas were observed could have growth and needed an intervention later, whereas patients treated with Gamma Knife could have a tumor that stayed asleep and didn’t require anything further. These are things we’ve learned through years of experience and interaction with other centers throughout the world,” Dr. Hadjipanayis says.
The patients receiving treatment changed as that experience grew. Cavernous sinus tumors made up almost 25% of patients in the program’s first five years and 6.3% in the final five years of the analysis. Convexity tumors increased from 2.5% to approximately 25% of patients.
Improvements in imaging also changed treatment planning. MRI and high-resolution sequences allowed better definition of tumor boundaries and nearby brain structures. The median prescribed margin dose decreased from 16 Gy in the 1990s to 13 Gy in later years, while tumor control did not differ significantly between the earliest and most recent five-year treatment periods.
The experience also identified risks associated with treating different anatomical locations. Symptomatic adverse radiation effects occurred in 3.3% of patients overall, with higher rates for convexity tumors than for cavernous sinus or petroclival tumors. Expanding primary radiosurgery therefore requires attention to location and treatment risk as well as the likelihood of lasting control.
Radiosurgery Within dAVF Treatment
For dural arteriovenous fistulas, Gamma Knife’s usefulness depends on the fistula’s anatomy, venous drainage, prior treatment, and how urgently shunting must be eliminated. Embolization or microsurgical disconnection may be needed for immediate treatment. Radiosurgery offers another approach when those interventions are incomplete or unsuitable.
More than three decades of experience include treatment of small, residual, or inaccessible fistulas and subsequent use in more complex lesions. MRI and angiographic image fusion improved targeting by showing the fistulous connection, venous anatomy, and surrounding structures more clearly than the earliest CT-based planning.
In a study published in the Journal of Clinical Neuroscience, outcomes in 67 patients illustrate both the benefit and the time required for a response. Complete obliteration confirmed by angiography occurred in 53.7%, with a median time to confirmation of 26 months among those whose fistulas closed. Symptoms improved in 88.1%, including reductions in pulsatile tinnitus, headache, and ocular symptoms.
That difference matters during follow-up. Symptomatic improvement does not establish complete closure, and patients may still need angiography to assess residual shunting. Further treatment can include repeat radiosurgery, embolization, or surgery, depending on the remaining fistula and its risk.
No dAVF-related hemorrhage occurred after radiosurgery in the cohort. Two patients developed symptomatic perilesional edema, with no reported radiation-induced necrosis or new cranial neuropathy attributable to treatment.
"Dural AV fistulas show where Gamma Knife fits alongside other treatments rather than replacing them," Dr. Hadjipanayis says. "When a fistula needs to be obliterated right away, embolization or surgery is still the answer. But when those options are incomplete or carry too much risk, radiosurgery gives us another way to close the fistula over time. With more than 30 years of follow-up, we can see that patients in this series did not go on to bleed after treatment."
Gamma Knife Radiosurgery Provides Durable Functional Benefit in Essential Tremor
For patients with medically refractory essential tremor, treatment can improve writing, drinking, and other activities without eliminating tremor completely. Long-term follow-up after Gamma Knife thalamotomy allows the team to assess whether those improvements persist and how often tremor returns.
Jheremy S. Reyes, MD, and colleagues, with Ajay Niranjan, MD, MBA, as senior author, published a study of long-term results in Neurological Sciences. In 163 procedures in 139 patients, clinical improvement was seen after 93.3% of procedures, while complete tremor arrest occurred after 23.9%. Writing, drawing, and drinking scores all improved significantly. The difference between complete arrest and clinical benefit shows that persistent tremor did not necessarily prevent functional improvement for the individual.
The response develops over months rather than immediately. Median time to improvement was four months, reflecting the development of the radiosurgical lesion in the ventral intermediate nucleus of the thalamus. That delay is part of the treatment discussion before patients undergo thalamotomy.
With median follow-up of approximately eight years, tremor recurrence occurred after 9.8% of procedures and adverse radiation effects after 3.7%. Some patients were followed for nearly 30 years.
"Many of our patients with essential tremor who need a lesioning procedure now have focused ultrasound in our CIGNS. Gamma Knife thalamotomy remains important for patients who are not candidates, including older patients with significant comorbidities and those who cannot stop anticoagulation. For them, this study shows that a noninvasive treatment can deliver meaningful benefit that holds up over years of follow-up,” Dr. Hadjipanayis says.
Three Different Questions from One Longitudinal Experience
The meningioma study demonstrates how long-term tumor control changed the timing and role of radiosurgery itself. The dAVF study defines where radiosurgery can contribute within a multimodal strategy for a complex vascular lesion. The essential tremor study establishes durable functional benefit for a treatment that now occupies a more selective position among multiple existing and emerging options, for example, focused ultrasound.
What links these studies is the length of the clinical record available at UPMC. Each asks questions that become meaningful only after treatment has been used long enough to show how well the result holds up over time, what late complications emerge, and how the treatment can be used relative to others for the same condition.
"Patients sometimes come to us having been told that radiosurgery will damage the brain or cause cancer years down the road, and the data simply do not support that concern,” Dr. Hadjipanayis says. “We now have 20 and 30 years of follow-up in large patient populations, and those results have been very reassuring. They give us something concrete to show patients and referring physicians when they are weighing their options."
Study References
Hoang AH, Wei CZ, Deng H, et al. Stereotactic Radiosurgery and Dural Arteriovenous Fistulas: Three Decades of Experience at the University of Pittsburgh. J Clin Neurosci. 2026. Online ahead of print.
Reyes JS, Bouras A, Hadjipanayis CG, Lunsford LD, Niranjan A. Gamma Knife Thalamotomy Provides Durable Long-Term Relief from Essential Tremor: A 30-Year Single Institution Experience. Neurologic Sci. 2026. 47: 543. Online ahead of print.
Wei CZ, Niranjan A, Deng H, Puccio D, Shanahan R, McKendrick L, Flickinger JC, Kondziolka D, Hadjipanayis CG, Lunsford LD, On Behalf of The Meningioma Task Force. The 35-Year Evolution of Stereotactic Radiosurgery for Meningiomas. Neurosurgery. 2026; 98(3): 543-551).
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