Faculty Bibliography

BACKGROUND: Gamma knife stereotactic radiosurgery (GKSR) is an effective minimally invasive option for the treatment of medically refractory trigeminal neuralgia (TN). Optimal targeting of the retrogasserian trigeminal nerve target requires thin-slice, high-definition stereotactic magnetic resonance imaging (MRI). The purpose of this study was to evaluate management outcomes in TN patients ineligible for MRI and who instead underwent GKSR using computed tomography (CT). METHODS: The authors reviewed their experience with CT-guided GKSR in 21 patients (median age: 75 years) with idiopathic TN. Contraindications to MRI included implanted pacemakers (n = 16), aneurysm clips (n = 2), cochlea implants (n = 1), metallic vascular stents (n = 1) or severe obesity (weight of 163 kg, n = 1). Contrast-enhanced CT at 1- or 1.25-mm intervals was acquired in all patients. One patient also underwent CT cisternography. The median target dose for GKSR was 80 Gy. The median follow-up was 35 months after GKSR. Treatment outcomes were compared to 459 patients who underwent MRI-guided GKSR for TN at our institute in the same time interval. RESULTS: Targeting of the trigeminal nerve guided by CT scan was feasible in all patients. Stereotactic frame titanium pin-related artifacts that interfered with full visualization of the trigeminal nerve were found in one patient who had the ipsilateral posterior pin placed near the inion. After GKSR, 90% of patients achieved initial pain relief that was adequate or better, with or without medication (Barrow Neurological Institute pain scores I-IIIb). Median time to pain relief was 2.6 weeks. Pain relief was maintained in 81% at 1 year, 66% at 2 years, and 46% at 5 years. Eight (42%) of 19 patients who achieved initial pain relief reported some recurrent pain at a median of 18 months after GKSR. Some degree of facial sensory dysfunction occurred in 19% of patients within 24 months of GKSR. These results are comparable to those of patients who had MRI-guided GKSR. CONCLUSIONS: CT-guided GKSR provides a similar rate of pain relief as MRI-guided radiosurgery. The posterior pins should be placed at least 1 cm away from the inion to reduce pin and frame-related artifacts on the targeting CT scan. This study indicates that GKSR using CT targeting is appropriate for patients with medically refractory TN who are unsuitable for MRI.

To evaluate the role of gamma knife stereotactic radiosurgery (SRS) in the management of newly diagnosed (early) or progressive (delayed) WHO grade II astrocytomas, the authors reviewed 25 patients who underwent SRS for pathologically proven WHO grade II astrocytomas between 1987 and 2009 at the University of Pittsburgh. The median patient age was 30 years (range 8-68 years). Sixteen patients had early SRS after stereotactic biopsy (n = 14), resection (n = 1) or radiation therapy (n = 1), and 9 underwent delayed SRS for progression after surgical resection (n = 3), radiation therapy (n = 4) or both (n = 2). The median tumor volume was 3.7 cm(3) (range 0.6-17.0 cm(3)) and the median margin dose was 14 Gy (range 11-20 Gy). At a median of 65 months of follow-up (range 6-208 months), tumor control was observed in 13 patients (52%). The progression-free survival rates after SRS at 1, 5 and 10 years were 91.3, 54.1 and 37.1%, respectively. On both univariate and multivariate analysis smaller tumor volume (<6 cm(3)), higher marginal dose (>/=15 Gy) and absence of contrast enhancement on imaging studies were associated with better progression free-survival. Gamma knife SRS is an additional option for patients with small volume, deep seated, non-enhancing and well-demarcated WHO grade II astrocytomas and does not preclude later conventional fractionated radiation therapy, cyst aspiration, or cautious debulking if feasible. It may also benefit patients with residual or recurrent tumors that have progressed after surgery, radiation therapy or both.

OBJECT: The aim of this study was to evaluate the outcomes of Gamma Knife surgery (GKS) when used for patients with intractable cluster headache (CH). METHODS: Four participating centers of the North American Gamma Knife Consortium identified 17 patients who underwent GKS for intractable CH between 1996 and 2008. The median patient age was 47 years (range 26-83 years). The median duration of pain before GKS was 10 years (range 1.3-40 years). Seven patients underwent unsuccessful prior surgical procedures, including microvascular decompression (2 patients), microvascular decompression with glycerol rhizotomy (2 patients), deep brain stimulation (1 patient), trigeminal ganglion stimulation (1 patient), and prior GKS (1 patient). Fourteen patients had associated autonomic symptoms. The radiosurgical target was the trigeminal nerve (TN) root and the sphenopalatine ganglion (SPG) in 8 patients, only the TN in 8 patients, and only the SPG in 1 patient. The median maximum TN and SPG dose was 80 Gy. RESULTS: Favorable pain relief (Barrow Neurological Institute Grades I-IIIb) was achieved and maintained in 10 (59%) of 17 patients at a median follow-up of 34 months. Three patients required additional procedures (repeat GKS in 2 patients, hypothalamic deep brain stimulation in 1 patient). Eight (50%) of 16 patients who had their TN irradiated developed facial sensory dysfunction after GKS. CONCLUSIONS: Gamma Knife surgery for intractable, medically refractory CH provided lasting pain reduction in approximately 60% of patients, but was associated with a significantly greater chance of facial sensory disturbances than GKS used for trigeminal neuralgia.

Tyrosine hydroxylase (TH) deficiency is a rare autosomal recessive metabolic disease that results in the decreased production of catecholamines. Standard treatment relies on combinations of levodopa and carbidopa, anticholinergic agents, serotonergic agonists, and monamine oxidase B inhibitors. Unfortunately, severely affected children often require escalating doses of medication and suffer from dyskinesias as well as significant on/off symptomatology. The authors present a case of medically intractable dopa-responsive dystonia in a 6-year-old boy whose condition significantly improved with bilateral subthalamic nucleus deep brain stimulation. This case is unique in its novel approach to tyrosine hydroxylase deficiency and the young age of the patient.

Gamma knife stereotactic radiosurgery (SRS) has proven to be an effective management approach for trigeminal neuralgia and as a minimally invasive alternative management option for cluster headache (CH). In CH, patients undergo single-session focused irradiation of the trigeminal nerve root (TN), sometimes coupled with irradiation of the sphenopalatine ganglion (SPG) as well. SRS provides early pain relief in most patients, but is associated with trigeminal sensory dysfunction in some patients. In the future, a prospective trial that compares a single target of TN to dual targets of both the TN and SPG may provide further understanding of the value of SRS for CH.

OBJECT: The optimal age and disease duration for consideration of deep brain stimulation (DBS) surgery are not well characterized in patients with Parkinson disease. The aim of this study was to assess variation in motor response to surgery among subgroups stratified by age and disease duration. METHODS: A total of 46 patients referred for DBS were recruited for the study. Preoperative dyskinesia and rigidity scores were recorded, and then patients received bilateral subthalamic nucleus stimulation. Preoperative motor scores were then compared with postoperative scores over 1 year. RESULTS: At 1 year postoperatively, patients with 10 years disease also showed a significant (70%) reduction in dyskinesia at 1 year postoperatively, but failed to show significant improvement in rigidity (31% reduction). Patients < 70 years old showed a significant (58%) improvement in rigidity and a significant (53%) improvement in dyskinesia. Finally, patients >/= 70 years old showed a significant (90%) improvement in dyskinesia, but failed to show any significant change in rigidity at 1 year postoperatively. CONCLUSIONS: The postoperative improvement in rigidity for younger patients with shorter disease duration may indicate that performing early surgery maximizes the benefit of DBS. However, older patients with primarily dyskinesia symptoms also appear to have significant clinical improvement, and DBS can offer relief from this common consequence of long-term levodopa use.

PURPOSE: The Pittsburgh radiosurgery-based arteriovenous malformation (AVM) grading scale was developed to predict patient outcomes after radiosurgery and was later modified with location as a two-tiered variable (deep vs. other). The purpose of this study was to test the modified radiosurgery-based AVM score in a separate set of AVM patients managed with radiosurgery. METHODS AND MATERIALS: The AVM score is calculated as follows: AVM score = (0.1)(volume, cc) + (0.02)(age, years) + (0.5)(location; frontal/temporal/parietal/occipital/intraventricular/corpus callosum/cerebellar = 0, basal ganglia/thalamus/brainstem = 1). Testing of the modified system was performed on 293 patients having AVM radiosurgery from 1992 to 2004 at the University of Pittsburgh with dose planning based on a combination of stereotactic angiography and MRI. The median patient age was 38 years, the median AVM volume was 3.3 cc, and 57 patients (19%) had deep AVMs. The median modified AVM score was 1.25. The median patient follow-up was 39 months. RESULTS: The modified AVM scale correlated with the percentage of patients with AVM obliteration without new deficits (2.00, 32%; F = 11.002, R(2) = 0.8117, p = 0.001). Linear regression also showed a statistically significant correlation between outcome and dose prescribed to the margin (F = 25.815, p <0.001). CONCLUSIONS: The modified radiosurgery-based AVM grading scale using location as a two-tiered variable correlated with outcomes when tested on a cohort of patients who underwent both angiography and MRI for dose planning. This system can be used to guide choices among observation, endovascular, surgical, and radiosurgical management strategies for individual AVM patients.