Faculty Bibliography

OBJECT: 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.

Functional neurosurgery includes surgery conducted to ablate, augment, or modulate targets that lead to improvement in neurological function or behavior. Surgical approaches for this purpose include destructive lesioning with different mechanical or biologic agents or energy sources, non-destructive electrical modulation, and cellular or chemical augmentation. Our purpose was to review the role of stereotactic radiosurgery used for functional indications and to discuss future applications and potential techniques. Imaging and neurophysiological research will enable surgeons to consider new targets and circuits that may be clinically important. Radiosurgery is one minimal access approach to those targets.

Stereotactic radiosurgery (SRS) is a well-established tool in the armamentarium for the treatment of metastatic tumors to the brain. Although SRS has proven to be highly effective in the management of brain metastases, it is not without risk. Despite selective targeting of lesions and the sharp dose fall-off associated with radiosurgical treatments, adverse radiation effects (AREs) can and do occur, albeit at a low rate, just as has been reported after conventional fractionated radiation therapy. One of the most vexing clinical scenarios for SRS practitioners is the distinction between ARE and tumor recurrence or progression after radiosurgery. Differentiation of these two entities is critical, as further treatment options range from oral medications to invasive surgical resection. In this review, we define AREs and discuss the possible mechanisms that produce them. Efforts to distinguish between ARE and tumor progression also are explored. Finally, a management algorithm for AREs is proposed.

We evaluated the role of Gamma Knife stereotactic radiosurgery in the multidisciplinary management of brain metastases ovarian and endometrial, prostate, thyroid, sarcoma, or unknown primary cancers. From a series of over 3,000 patients who had Gamma Knife radiosurgery for brain metastases we reviewed indications and outcomes in patients with less common cancer types. All tumor types responded favorably to radiosurgery. Patients with male and female genitourinary primaries tended to develop brain metastases late in their course and did worse. Patients with thyroid metastases appear to live much longer with a more indolent course. Radiosurgery is an effective and safe minimally invasive option for patients with brain metastases from these less common primary origins.

We discuss the current literature on the role of stereotactic radiosurgery in the multidisciplinary management of brain metastases and focus on the level of evidence that addresses key management questions. We reviewed the literature on the different roles of radiosurgery, radiotherapy, and resection, and in particular the 2009 Guidelines project of the Joint Section on Tumors of the AANS/CNS. Retrospective case series, matched cohort studies, and randomized trials show specific survival and local tumor control benefits after radiosurgery. Radiosurgery is an effective and safe minimally invasive option for patients with brain metastases. Randomized trials include tumors of different histologies which can detract from their relevance to specific tumor types.

Histopathological investigations revealed acute-, subacute-, and chronic-type tissue responses, accompanied by inflammatory cell reaction in radiosurgery treated cerebral metastases originating from different primary cancers. Immunohistochemistry demonstrated that the preponderance of CD68-positive macrophages and CD3-positive T lymphocytes in the inflammatory infiltration developed in better controlled metastases ( > 5 months). In contrast, it was sparse or absent in poorly controlled neoplasms ( < 5 months) after radiosurgery. This inflammatory reaction may be stimulated by the ionizing energy, probably influenced by the general condition of the patients' immune system as well, and seems to play a role in local tumor control after focused radiation.