Michael Schulder

Translocation of Broca's area to the contralateral hemisphere as the result of the growth of a left inferior frontal glioma

We report a case of a patient with a left inferior frontal glioma in whom language functional magnetic resonance imaging (fMRI) paradigms produced activation of Brocas area on the right and Wernickes area on the left. We propose that tumor invasion of the left frontal operculum led to cortical reorganization and interhemispheric transfer of Brocas area. This case emphasizes the importance of preoperative fMRI in assessing the location of eloquent cortices adjacent to a tumor and in guiding neurosurgical decision-making.

Regression of multiple intracranial meningiomas after cessation of long-term progesterone agonist therapy

The authors present the case of a patient that demonstrates the long-standing use of megestrol acetate, a progesterone agonist, and its association with multiple intracranial meningioma presentation. Discontinuation of megestrol acetate led to shrinkage of multiple tumors and to the complete resolution of one tumor. Histological examination demonstrated that the largest tumor had high (by > 25% of tumor cell nuclei) progesterone-positive expression, including progesterone receptor (PR) isoform B, compared with low expression of PR isoform A; there was no evidence of estrogen receptor expression and only unaccentuated collagen expression. This is the first clinical report illustrating a causal relationship between exogenous hormones and modulation of meningioma biology in situ.

Standardization of Amygdalohippocampectomy with Intraoperative Magnetic Resonance Imaging : Preliminary Experience

Summary:  Purpose: Intraoperative magnetic resonance imaging (IMRI) is an extremely useful neurosurgical tool in surgeries in which the extent of resection is known to have a significant impact on outcome. Residual hippocampus is the most common cause of recurrent seizures after temporal lobectomy for medial temporal lobe epilepsy. Although the risk/benefit ratio of a policy of universal radical hippocampal resection is not known, we hypothesized that IMRI would aid in the intraoperative assessment of the extent of hippocampal resection and assist in accomplishing a complete hippocampectomy.

Permanent low-activity iodine-125 implants for cerebral metastases.

Beginning in 1987, selected patients with metastatic braintumors were treated with permanent implants of low-activityradioactive iodine-125 (125I) seeds. These patients underwent craniotomy,gross total resection of the metastatic lesion, andplacement of the seeds. In general, criteria fortreatment included the presence of a recurrent tumorwith a volume too large to permit radiosurgery,and a Karnofsky Performance Score of 70 orhigher. Thirteen patients underwent 14 implant procedures; allreceived external whole-brain radiotherapy. Implant dose ranged from43 Gy to 132 Gy, with a meanof 83 Gy. Survival after implantation ranged from2 weeks to almost 9 years, with amedian of 9 months. Clinical and radiographic localcontrol was obtained in 9 patients. Two patientsdied of acute, postoperative complications within a monthof implantation, so no information regarding tumor controlis available for them. Late complications included abone flap infection in one patient and aCSF leak in another; both were treated withoutfurther sequelae.These results demonstrate that permanent 125I implants canresult in good survival and quality of life,and occasionally can yield long-term survival. Potentially, itis a cost-effective treatment in that a separateprocedure for stereotactic implantation or radiosurgery is notneeded, as is the case with the useof temporary high-activity seeds. The permanent implantation itselfadds less than 10 minutes to the craniotomy,and the risk of symptomatic radiation necrosis islow. We recommend consideration of this procedure inpatients harboring large, recurrent metastatic tumors that requirefurther surgery.

Stereotactic brain biopsy with a low-field intraoperative magnetic resonance imager.

BACKGROUND: Techniques for stereotactic brain biopsy have evolved in parallel with the imaging modalities used to visualize the brain. OBJECTIVE: To describe our technique for performing stereotactic brain biopsy using a compact, low-field, intraoperative magnetic resonance imager (iMRI). METHODS: Thirty-three patients underwent stereotactic brain biopsies with the PoleStar N-20 iMRI system (Medtronic Navigation, Louisville, Colorado). Preoperative iMRI scans were obtained for biopsy target identification and trajectory planning. A skull-mounted device (Navigus, Medtronic Navigation) was used to guide an MRI-compatible cannula to the target. An intraoperative image was acquired to confirm accurate cannula placement within the lesion. Serial images were obtained to track cannula movement and to rule out hemorrhage. Frozen sections were obtained in all but 1 patient with a brain abscess. RESULTS: Diagnostic tissue was obtained in 32 of 33 patients. In all cases, imaging demonstrated cannula placement within the lesion. Histological diagnoses included 22 primary brain tumors and 10 nonneoplastic lesions. In 61% of the cases, initial trajectory was corrected on the basis of the intraoperative scans. In 1 patient, biopsy was nondiagnostic despite accurate cannula placement. No patient suffered a clinically or radiographically significant hemorrhage during or after surgery. There were no intraoperative complications. CONCLUSION: Stereotactic biopsy with a low-field iMRI is an accurate way to obtain specimens with a high diagnostic yield. This accuracy, combined with the acceptable additional procedural time, may obviate the need for frozen section. The ability to correct biopsy cannula placement during surgery eliminates the chance of misdiagnosis because of faulty targeting, as well as the risks associated with inconclusive frozen sections and “blind” replacement of the cannula.

Stereotactic accuracy of a compact intraoperative MRI system.

Objective: To analyze the stereotactic accuracy of the PoleStar N-20, a compact intraoperative magnetic resonance imaging (iMRI) system, based on a 0.15-Tesla (T) magnet. Methods: An MRI-compatible phantom was scanned after being positioned in both the center of the magnetic field (COF) and the periphery of the field (POF) of the PoleStar N-20 magnet. Scans were acquired at various slice thicknesses in 3 sequences: T1 weighted, T2 weighted and Esteady (reversed fast imaging with steady-state precession, also known as ‘PSIF’). The distance between the actual location of the probe tip in space and the location of the target on the image was measured on the axial, coronal, and sagittal planes for 9 points on each image. Each measurement was repeated 3 times. We also compared the structural features of the PoleStar N-20 to those of its predecessor. Results: T1-weighted scans yielded the most accurate measurements. There was no statistically significant difference between scans acquired at thicknesses of 2, 3, 4 and 8 mm; all were accurate for clinical purposes. Comparison of COF with POF measurements using T1-weighted scans did not demonstrate a statistically significant difference in accuracy. Conclusions: The PoleStar N-20 0.15-T iMRI system provides surgical navigation that is at least as accurate as the first generation model of this system, which employed a 0.12-T magnet. Further analysis of stereotactic accuracy on clinical cases using the PoleStar N-20 is needed to confirm that these results will bear out in surgical reality.

Radiosurgical Dose Selection for Brain Metastasis

Dose selection for brain metastasis radiosurgery is based largely upon clinical data obtained over a half century of radiosurgical treatments for various benign and malignant conditions. It is expected that within the entire radiosurgical process, the step of dose selection will occur within a framework of accurate calibration of dose delivery and accurate and detailed imaging for planning the radiosurgical treatment. Brain metastasis radiosurgery should seek lifelong, uncomplicated control. A low radiosurgery dose that will not control the tumor will not achieve this therapeutic goal, and neither will a radiosurgery dose that controls the tumor but causes symptomatic brain radiation necrosis. The volume of the metastasis being targeted and the volume of normal tissues receiving substantial radiosurgical doses are of paramount importance in dose selection. A high degree of conformality of the high-dose radiosurgical treatment volume to the metastasis has been shown to decrease complications, as does a steep dose gradient between the metastasis and adjacent normal brain tissue. A dose-escalation trial conducted by the Radiation Therapy Oncology Group that differentially dose-escalated radiosurgical doses for tumors of different sizes established that single-fraction doses between 15 and 24 Gy are relatively safe in patients who have received prior fractionated radiation therapy to the brain. Corresponding data do not exist for patients who are treated with primary radiosurgery and no whole brain radiation therapy. A dose-escalation trial for three-fraction radiosurgical treatment of brain metastases is being conducted at Stanford. Knowledge of prior whole brain radiation therapy treatment details, including the dose delivered and the time interval since that treatment was given may affect the choice of radiosurgical dose, as may recent administration of systemic, radiation-potentiating chemotherapy. Physician knowledge and careful judgment, together with careful treatment planning and delivery can minimize the risks associated with brain metastasis radiosurgery.

Normal or non-diagnostic neuroimaging studies prior to the detection of malignant primary brain tumors

We aimed to describe a single institution experience of neuroimaging failure to demonstrate malignant primary brain tumors. We retrospectively reviewed case histories for all newly diagnosed adult patients with malignant primary brain tumors treated at a single institution between 1 July 2006 and 30 June 2008. We specifically looked at patients in whom neuroimaging was normal or non-diagnostic at initial presentation. Among 193 patients with malignant primary brain tumors, there were 102 with World Health Organization (WHO) grade IV gliomas (glioblastoma multiforme, GBM), 54 with anaplastic gliomas, 18 with low grade gliomas, and 19 with primary central nervous system lymphomas (PCNSL). Initial imaging was normal in nine patients and abnormal but non-diagnostic in an additional eight patients with primary brain cancer. Normal or non-diagnostic neuroimaging was not uncommon among patients with GBM. Dramatic, rapid tumor growth is possible. Close interval clinical and radiographic follow-up can be important especially in the management of elderly patients presenting with seizures and non-diagnostic neuroimaging studies.

Outcomes in Patients with Vestibular Schwannoma after Subtotal Resection and Adjuvant Radiosurgery

Background: The debate continues with a limited number of publications describing outcomes in patients with vestibular schwannoma (VS) treated with planned subtotal resection (STR) plus stereotactic radiosurgery (SRS). Here we present our experience. Methods: This is a retrospective review of 22 patients with VS Koos grade III and IV who were treated with STR followed by SRS. Tumor volumes, facial nerve function, hearing preservation, and the presence of trigeminal neuropathy were noted. Spearmans rank test was used to correlate facial nerve grade with postoperative tumor residual tumor volume. Results: Tumor control was achieved in all patients with a mean follow-up of 28 months. No patient required other treatment beyond the original surgery and adjuvant SRS during this period. After a mean postoperative period of 28 months, 19/22 patients had excellent (House-Brackmann I or II) facial nerve function grading. Improved facial nerve function was positively correlated with larger residual tumor volume (rs = 0.63). Kaplan-Meier curve showed around 80% probability for regaining facial nerve function after initial deterioration. Four patients reported postoperative facial numbness at the side of surgery, with 3 cases showing improvement within a month. Temporary postoperative caudal cranial nerve dysfunction was observed in 2 patients. Conclusion: Hybrid strategy of STR and adjuvant SRS provides patients with large VS excellent tumor control and a good clinical outcome.

Supratentorial Neurenteric Cysts: Case Series and Review of Pathology, Imaging, and Clinical Management

BACKGROUND Neurenteric cysts are rare congenital lesions along the neuroaxis, typically found in the spine, and rarely intracranially. Here, we present 3 patients who presented to our institution during a 6-year period with supratentorial intracranial neurenteric cysts and conduct a comprehensive review of the literature to describe the salient pathology, radiologic features, and clinical issues regarding these lesions. CASE REPORTS Three patients were treated surgically for supratentorial neurenteric cysts. One patient presented in extremis, whereas the others were treated electively. Each patient presented with significantly different signs and symptoms and unique radiologic findings. All patients were neurologically intact after surgery. CONCLUSIONS Neurenteric cysts present with a variety of signs and symptoms. Given the increased use of neuroimaging, supratentorial neurenteric cysts may be encountered more frequently and are important to include on the differential diagnosis and managed accordingly. Postoperative seizures occur in more than 20%, even in patients who had no preoperative seizures. Surgery can be performed safely with good neurologic outcomes.