One hundred and ten patients with trigeminal neuralgia were treated with the Gamma Knife using a single isocenter, the 4 mm secondary collimator helmet and a radiosurgical dose maximum of 70 or 80-Gy. The isocenter was placed at the trigeminal sensory root adjacent to the pons as identified on stereotactic MRI scans. Follow-up periods range from 4–49 months (mean 19.8 months). Initial pain relief was achieved in 95.5% of patients with typical trigeminal neuralgia symptoms, who had not had prior surgical intervention, and only 3.3% of these patients experienced recurrent pain during the follow-up period. Patients with atypical features to their pains or who had prior unsuccessful surgical attempts to relieve their pains achieved initial and long-term pain relief in 88 and 69%, respectively. Three patients (2.7%) developed delayed loss of facial sensation following treatment, but no other complications of any kind were noted. We believe that Gamma Knife radiosurgery is the safest and most effective form of treatment which is currently available for trigeminal neuralgia. We recommend early radiosurgical treatment of trigeminal neuralgia once the diagnosis is clearly established.

Sixty patients with trigeminal neuralgia who did not have a response to pharmacologic treatment (including 22 who had no response to conventional surgical treatment) underwent stereotactic radiosurgical treatment with the Leksell Gamma Knife. A radiosurgical maximum dose of 70 Gy was delivered to the trigeminal nerve root adjacent to the pons via a 4-mm collimator helmet in 51 patients who presented with trigeminal neuralgia unrelated to tumors. In these patients, the root was localized by stereotactic MRI. Follow-up assessment of pain relief was accomplished by a third party not involved in the patients' clinical care. Within a latency period of 1 day to 4 months following the treatment, 38 of 51 patients (74.5%) were completely free of pain and eventually all medications were tapered off. An additional seven patients (13.7%) experienced reductions in pain from 50 to 90% and utilized little or no medications. Patients who had no prior surgical intervention fared much better than those who had previous surgery to relieve their facial pains. At last follow-up, a mean of 16.3 months (range 6-36 months) after treatment, 41 patients (80.4%) remained pain-free or had marked pain reduction. There were four patients with recurrent pain. All 26 patients with classical symptoms of trigeminal neuralgia with no atypical features who had no prior surgery, had complete or nearly complete pain relief, and none of these patients had recurrent pain. Nine patients with trigeminal neuralgia due to tumors received standard radiosurgical treatment directed at their tumors, and eight of nine (88.8%) had pain relief. Of the total of 60 patients treated for trigeminal neuralgia, 49 (81.7%) experienced complete or nearly complete relief of pain at last follow-up. Only one patient with pre-existing facial sensory loss due to a tumor had a mild increase in facial numbness. No other patient experienced either loss of facial sensation or any other complication. Gamma Knife radiosurgery appears to be a minimally invasive, safe, and effective therapy of trigeminal neuralgia.

Object. The purpose of this study was to investigate the long-term effects of gamma knife thalamotomy for treatment of disabling tremor. Methods. One hundred fifty-eight patients underwent magnetic resonance imaging—guided radiosurgical nucleus ventralis intermedius (VIM) thalamotomy for the treatment of parkinsonian tremor (102 patients), essential tremor (52 patients), or tremor due to stroke, encephalitis, or cerebral trauma (four patients). Preoperative and postoperative blinded assessments were performed by a team of independent examiners skilled in the evolution of movement disorders. A single isocenter exposure with the 4-mm collimator helmet of the Leksell gamma knife unit was used to make the lesions. In patients with Parkinson's disease 88.3% became fully or nearly tremor free, with a mean follow up of 52.5 months. Statistically significant improvements were seen in Unified Parkinson's Disease Rating Scale tremor scores and rigidity scores, and these improvements were maintained in 74 patients followed 4 years or longer. In patients with essential tremor, 92.1% were fully or nearly tremor free postoperatively, but only 88.2% remained tremor free by 4 years or more post-GKS. Statistically significant improvements were seen in the Clinical Rating Scale for tremor in essential tremor patients and these improvements were well maintained in the 17 patients, followed 4 years or longer. Only 50% of patients with tremor of other origins improved significantly. One patient sustained a transient complication and two patients sustained mild permanent side effects from the treatments. Conclusions. Gamma knife VIM thalamotomy provides relief from tremor equivalent to that provided by radiofrequency thalamotomy or deep brain stimulation, but it is safer than either of these alternatives. Long-term follow up indicates that relief of tremor is well maintained. No long-term radiation-induced complications have been observed.

Fifty-five patients underwent radiosurgical placement of lesions either in the thalamus (27 patients) or globus pallidus (28 patients) for treatment of movement disorders. Patients were evaluated pre- and postoperatively by a team of observers skilled in the assessment of gait and movement disorders who were blinded to the procedure performed. They were not associated with the surgical team and concomitantly and blindly also assessed a group of 11 control patients with Parkinson's disease who did not undergo any surgical procedures. All stereotactic lesions were made with the Leksell gamma unit using the 4-mm secondary collimator helmet and a single isocenter with dose maximums from 120 to 160 Gy. Clinical follow-up evaluation indicated that 88% of patients who underwent thalamotomy became tremor free or nearly tremor free. Statistically significant improvements in performance were noted in the independent assessments of Unified Parkinson's Disease Rating Scale (UPDRS) scores in the patients undergoing thalamotomy. Eighty-five and seven-tenths percent of patients undergoing pallidotomy who had exhibited levodopa-induced dyskinesias had total or near-total relief of that symptom. Clinical assessment indicated improvement of bradykinesia and rigidity in 64.3% of patients who underwent pallidotomy. Independent blinded assessments did not reveal statistically significant improvements in Hoehn and Yahr scores or UPDRS scores. On the other hand, 64.7% of patients showed improvements in subscores of the UPDRS, including activities of daily living (58%), total contralateral score (58%), and contralateral motor scores (47%). Ipsilateral total UPDRS and ipsilateral motor scores were both improved in 59% of patients. One (1.8%) of 55 patients experienced a homonymous hemianopsia 9 months after pallidotomy due to an unexpectedly large lesion. No other complications of any kind were seen. Follow-up neuroimaging confirmed correct lesion location in all patients, with a mean maximum deviation from the planned target of 1 mm in the vertical axis. Measurements of lesions at regular interals on postoperative magnetic resonance images demonstrated considerable variability in lesion volumes. The safety and efficacy of functional lesions made with the gamma knife appear to be similar to those made with the assistance of electrophysiological guidance with open functional stereotactic procedures. Functional lesions may be made safely and accurately using gamma knife radiosurgical techniques. The efficacy is equivalent to that reported for open techniques that use radiofrequency lesioning methods with electrophysiological guidance. Complications are very infrequent with the radiosurgical method. The use of functional radiosurgical lesioning to treat movement disorders is particularly attractive in older patients and those with major systemic diseases or coagulopathies; its use in the general movement disorder population seems reasonable as well.

Nineteen patients underwent a total of 24 medial thalamic lesions made with the Leksell Gamma Knife for the treatment of chronic intractable pain after extensive prior medical and surgical intervention had failed to provide pain relief. The lesion locations were based on prior experience with open radiofrequency medial thalamotomies for the treatment of pain and were directed at the intralaminar, mediodorsal, centromedian, and parafascicular nuclei. All lesions were made with the 4 mm collimator helmet at radiosurgical doses from 140-180 Gray. Follow-up MRI scans indicated anatomically distinct lesions which developed 3-6 weeks after the procedure and were fully formed by 8-12 weeks. The lesion volumes averaged 300-400 mm3 for a single isocentre, 600-900 mm3 for two isocentres, and 900-1100 mm3 for three isocentres. One patient developed a lesion 5500 mm3 in volume after a two isocentre lesion at 160 Gray. Of 15 patients who have been followed for more than 3 months (average follow-up 12 months) four patients (27%) are virtually pain free and functioning normally, whereas five other patients (33%) achieved greater than 50% pain relief. Thus 9/15 patients (60%) have had worthwhile benefit from medial thalamotomy with the Gamma Knife. Medial thalamotomy with the Gamma Knife produces thalamic lesions which are reliable in size, shape and location with a low complication rate and offers a minimally invasive, cost effective treatment for certain selected patients with chronic intractable pain.