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David Mathieu, Mathieu Beaudry, René Martin, Hans McLelland, Bruno Robert and Brendan Kenny

Object. The authors conducted a double-blind prospective randomized study to determine whether infiltration of Mayfield skull-pin sites with 0.5% bupivacaine, compared with placebo, would prevent hemodynamic stimulation, thus allowing for a reduction in the quantity of anesthetic agents required.

Methods. Thirty patients were randomized into two groups. There was a significant increase in blood pressure (mean systolic blood pressure 10 mm Hg, p = 0.003) in patients in the placebo group compared with that in patients in the bupivacaine group 1 minute after securing the head holder.

Conclusions. The local administration of bupivacaine for anesthetic purposes before skull-pin application may prevent potentially hazardous hemodynamic stimulation.

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Nicolas Dea, Martin Borduas, Brendan Kenny, David Fortin and David Mathieu

Object

Brain metastases are the most frequently occurring cerebral tumors. Tumors that are located in eloquent cerebral parenchyma can cause considerable morbidity and may pose a significant challenge during surgery. Gamma Knife surgery (GKS) is a recognized treatment modality for brain metastases. This study was undertaken to assess the safety and efficacy of GKS, specifically for brain metastases in eloquent locations.

Methods

Charts of patients harboring brain metastases that were treated by GKS at the Centre Hospitalier Universitaire de Sherbrooke between August 2004 and April 2008 were reviewed. Planning images were assessed by an independent neurosurgeon to assess tumor location. Eloquent locations included the primary motor, somatosensory, speech, and visual cortices; the basal ganglia; the thalamus; and the brainstem. Data on survival, tumor response, and complications were analyzed and compared with data published on surgical treatment of these lesions.

Results

During the study period, 650 metastases in 295 patients were treated with GKS; of these, 164 metastases in 95 patients were located in eloquent areas. In this subgroup, the median age of patients was 59 years and women constituted 57.9% of the population. The median Karnofsky Performance Scale score was 80% (range 50%–100%). Patients were categorized according to their recursive partitioning analysis class: Class 1, 22.1%; Class 2, 70.5%; and Class 3, 7.4% of patients. Non–small cell lung cancer was the most common primary tumor (63.2% of metastases), followed by small cell lung (8.4%), breast (7.4%), colorectal (5.3%), and renal cell (4.2%) cancers, as well as melanoma (4.2%). The median dose to the tumor margin was 18 Gy (range 14–24 Gy). The median duration of survival after GKS was 8.2 months. The recursive partitioning analysis class was the most significant variable affecting survival (p < 0.0001). Immediate control was achieved in 92.9% of tumors, and 68.6% of tumors were still controlled at the last follow-up. The median time to tumor progression was 16 months. Higher margin dose (p = 0.002), the absence of edema (p = 0.009), and the non–small cell lung cancer tissue type (p = 0.035) positively affected response rates. Steroid medications were no longer used in 46% of patients after GKS. New neurological deficits occurred in 5.7% of patients and seizures in 5.7%. All these deficits were transient and patients completely recovered in response to a temporary course of steroids. Imaging studies showed that new edema occurred in 8.6% of treated metastases and biopsy-proven radiation necrosis in 1.4%.

Conclusions

Gamma Knife surgery is safe and effective for brain metastases located in eloquent areas.

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Azad Sait, Nadipi Reddy Prabhav, Vijay Sekharappa, Reshma Rajan, N. Arunai Nambi Raj and Kenny Samuel David

OBJECTIVE

There has been a transition from long- to short-segment instrumentation for unstable burst fractures to preserve motion segments. Circumferential fixation allows a stable short-segment construct, but the associated morbidity and complications are high. Posterior short-segment fixation spanning one level above and below the fractured vertebra has led to clinical failures. Augmentation of this method by including the fractured level in the posterior instrumentation has given promising clinical results. The purpose of this study is to compare the biomechanical stability of short-segment posterior fixation including the fractured level (SSPI) to circumferential fixation in thoracolumbar burst fractures.

METHODS

An unstable burst fracture was created in 10 fresh-frozen bovine thoracolumbar spine specimens, which were grouped into a Group A and a Group B. Group A specimens were instrumented with SSPI and Group B with circumferential fixation. Biomechanical characteristics including range of motion (ROM) and load-displacement curves were recorded for the intact and instrumented specimens using Universal Testing Device and stereophotogrammetry.

RESULTS

In Group A, ROM in flexion, extension, lateral flexion, and axial rotation was reduced by 46.9%, 52%, 49.3%, and 45.5%, respectively, compared with 58.1%, 46.5%, 66.6%, and 32.6% in Group B. Stiffness of the construct was increased by 77.8%, 59.8%, 67.8%, and 258.9% in flexion, extension, lateral flexion, and axial rotation, respectively, in Group A compared with 80.6%, 56.1%, 82.6%, and 121.2% in Group B; no statistical difference between the two groups was observed.

CONCLUSIONS

SSPI has comparable stiffness to that of circumferential fixation.

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David Mathieu, Charles Deacon, Catherine-Andrée Pinard, Brendan Kenny and Julie Duval

Object

Hypothalamic hamartomas (HHs) are congenital lesions typically presenting with medically refractory epilepsy. Open or endoscopic surgical procedures to remove or disconnect the hamartoma have been reported to be effective but are associated with significant morbidity. The authors of studies on Gamma Knife surgery for HHs have reported an encouraging rate of epilepsy resolution with minimal side effects. At the Centre Hospitalier Universitaire de Sherbrooke, the authors have undertaken a prospective observational study of the outcomes of patients who underwent radiosurgery for HHs.

Methods

Patients were included in the study if they had an HH, refractory epilepsy, and no other suspected seizure focus. After radiosurgery, seizure status was assessed every 3 months and reported using the Engel Classification. Quality of life evaluation was performed annually using a standardized questionnaire, and neuropsychological evaluation was performed after 2 years.

Results

Nine patients were included in the study. They ranged in age from 12 to 57 years. Epilepsy began in infancy in all cases and was refractory to standard antiepileptic drugs. The patients received an average of 2 antiepileptic drugs before undergoing radiosurgery. Using the Régis Classification, 6 patients had smaller hamartomas (Grade I–III) and underwent treatment of the entire lesion, using a margin dose of 14–20 Gy. Treatment volume ranged from 0.3 to 1.0 ml. Three patients had larger lesions (Grade IV–VI) for which a radiosurgical disconnection was attempted, targeting the area of attachment to the hypothalamus. For those patients, the margin dose was 15 or 16 Gy, with treatment volume ranging from 0.8 to 1.8 ml. In all patients, the radiation dose received by the optic pathways was kept below 10 Gy. Disconnection led to no improvement in epilepsy (Engel Class IV). Four patients in whom the entire lesion was treated are now seizure free (Engel Class I), with another having only rare seizures (Engel Class II). Quality of life and verbal memory were improved in those patients with more than 3 years of follow-up. No adverse event occurred after radiosurgery.

Conclusions

Radiosurgery safely and effectively controlled the epileptic disorder in patients with HHs when the entire lesion could be targeted. Radiosurgical disconnection is ineffective and cannot be recommended.

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Shobhan Vachhrajani, Charbel Fawaz, David Mathieu, Cynthia Ménard, Michael D. Cusimano, Fred Gentili, Mojgan Hodaie, Brendan Kenny, Abhaya V. Kulkarni, Normand Laperriere, Michael Schwartz, May Tsao and Mark Bernstein

Object

Gamma Knife surgery (GKS) is used to treat benign and malignant brain tumors, arteriovenous malformations, trigeminal neuralgia, and other conditions. Patients experience reduced neurological morbidity from GKS compared with open microneurosurgery, but risks of radiation injury and technical limitations persist. The authors report treatment complications from the early experience of 2 Canadian GKS programs in Toronto and Sherbrooke.

Methods

In Toronto, a prospective administrative database was searched for adverse events and incomplete treatment administrations. In Sherbrooke, data were acquired by chart review. Patients were accrued until August 1, 2007, and a total of 973 patients were included in this report.

Results

During the radiosurgical procedure, 19 patients (2%) suffered anxiety or syncopal episodes, and 2 patients suffered acute coronary events. Treatments were incompletely administered in 12 patients (1.2%). Severe pain was a delayed complication: 8 patients suffered unexpected headaches, and 9 patients developed severe facial pain. New motor deficits developed in 11 patients, including edema-induced ataxia in 4 and one case of facial weakness after treatment of a vestibular schwannoma. Four patients required shunt placement for symptomatic hydrocephalus, and 16 patients suffered delayed seizures.

Conclusions

Gamma Knife surgery is a minimally invasive treatment modality for many intracranial diseases. Treatment is not risk free, and some patients will develop complications; these are likely to decrease as institutional experience matures. Expanding availability and indications necessitate discussion of these risks with patients considering treatment.