Faculty Bibliography

PURPOSE: To retrospectively determine whether relative cerebral blood volume (CBV) measurements can be used to predict clinical outcome in patients with high-grade gliomas (HGGs) and low-grade gliomas (LGGs) and specifically whether patients who have gliomas with a high initial relative CBV have more rapid progression than those who have gliomas with a low relative CBV. MATERIALS AND METHODS: Approval for this retrospective HIPAA-compliant study was obtained from the Institutional Board of Research Associates, with waiver of informed consent. One hundred eighty-nine patients (122 male and 67 female patients; median age, 43 years; range, 4-80 years) were examined with dynamic susceptibility-weighted contrast material-enhanced perfusion magnetic resonance (MR) imaging and were followed up clinically with MR imaging (median follow-up, 334 days). Log-rank tests were used to evaluate the association between relative CBV and time to progression by using Kaplan-Meier curves. Binary logistic regression was used to determine whether age, sex, and relative CBV were associated with an adverse event (progressive disease or death). RESULTS: Values for the mean relative CBV for patients according to each clinical response were as follows: 1.41 +/- 0.13 (standard deviation) for complete response (n = 4), 2.36 +/- 1.78 for stable disease (n = 41), 4.84 +/- 3.32 for progressive disease (n = 130), and 3.82 +/- 1.93 for death (n = 14). Kaplan-Meier estimates of median time to progression in days indicated that patients with a relative CBV of less than 1.75 had a median time to progression of 3585 days, whereas patients with a relative CBV of more than 1.75 had a time to progression of 265 days. Age and relative CBV were also independent predictors for clinical outcome. CONCLUSION: Dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging can be used to predict median time to progression in patients with gliomas, independent of pathologic findings. Patients who have HGGs and LGGs with a high relative CBV (>1.75) have a significantly more rapid time to progression than do patients who have gliomas with a low relative CBV

OBJECTIVE: To determine treatment outcome after surgical resection for progressive brain metastases after gamma knife radiosurgery (GKR) and to explore the role of dynamic contrast agent-enhanced perfusion magnetic resonance imaging (MRI) and proton spectroscopic MRI studies (MRS/P) in predicting pathological findings. METHODS: Between 1997 and 2002, 32 patients underwent surgical resection for suspected progression of brain metastases from a cohort of 245 patients with brain metastases treated with GKR. Postradiosurgery MRI surveillance was performed at 6 and 12 weeks, and then every 12 weeks after GKR. In some cases, additional MRI scanning with spectroscopy or perfusion (MRS/P) was used to aid differentiation of radiation change from tumor progression. The decision to perform neurosurgical resection was based on MRI or clinical evidence of lesion progression among patients with a Karnofsky performance score of 60 or more and absent or stable systemic disease. RESULTS: Thirteen percent (32 out of 245) of patients and 6% (38 out of 611) of lesions required surgical resection after GKR. The median time from GKR to surgical resection was 8.6 months (range, 1.7-27.1 mo). The 6-, 12-, and 24-month actuarial survival from time of GKR was 97, 78, and 47% for the resected patients and 65, 40, and 19% for the nonresected patients (P < 0.0001). The two-year survival rate of patients requiring two resections after GKR was 100% compared with 39% for patients undergoing one resection (P = 0.02). The median survival of resected patients was 27.2 months (range, 7.0-72.5 mo) from the diagnosis of brain metastases, 19.9 months (range, 5.0-60.7 mo) from GKR, and 8.9 months (range, 0.2-53.1 mo) from surgical resection. Tumor was found in 90% of resected specimens and necrosis alone in 10%. MRS/P studies were performed in 15 resected patients. Overall, MRS/P predicted tumor in 11 lesions, confirmed pathologically in nine lesions, and necrosis alone was found in two. The MRS/P predicted necrosis alone in three, whereas pathology revealed viable tumor in two and necrosis in one lesion. CONCLUSION: Surgical intervention of progressive brain metastases after GKR in selected patients leads to a meaningful improvement in survival rates. Further studies are necessary to determine the role of MRS/P in the postradiosurgery surveillance of brain metastases

OBJECTIVE:To determine whether relative cerebral blood volume (rCBV) can predict patient outcome, specifically tumor progression, in low-grade gliomas (LGGs) and thus provide a second reference standard in the surgical and postsurgical management of LGGs. METHODS:Thirty-five patients with histologically diagnosed LGGs (21 low-grade astrocytomas and 14 low-grade oligodendrogliomas and low-grade mixed oligoastrocytomas) were studied with dynamic susceptibility contrast-enhanced perfusion magnetic resonance imaging. Wilcoxon tests were used to compare patients in different response categories (complete response, stable, progressive, death) with respect to baseline rCBV. Log-rank tests were used to evaluate the association of rCBV with survival and time to progression. Kaplan-Meier time-to-progression curves were generated. Tumor volumes and CBV measurements were obtained at the initial examination and again at follow-up to determine the association of rCBV with tumor volume progression. RESULTS:Wilcoxon tests showed patients manifesting an adverse event (either death or progression) had significantly higher rCBV (P = 0.003) than did patients without adverse events (complete response or stable disease). Log-rank tests showed that rCBV exhibited a significant negative association with disease-free survival (P = 0.0015), such that low rCBV values were associated with longer time to progression. Kaplan-Meier curves demonstrated that lesions with rCBV less than 1.75 (n = 16) had a median time to progression of 4620 +/- 433 days, and lesions with rCBV more than 1.75 (n = 19) had a median time to progression of 245 +/- 62 days (P < 0.005). Lesions with low baseline rCBV (< 1.75) demonstrated stable tumor volumes when followed up over time, and lesions with high baseline rCBV (> 1.75) demonstrated progressively increasing tumor volumes over time. CONCLUSION/CONCLUSIONS:Dynamic susceptibility contrast-enhanced perfusion magnetic resonance imaging may be used to identify LGGs that are either high-grade gliomas, misdiagnosed because of sampling error at pathological examination or that have undergone angiogenesis in the progression toward malignant transformation. This suggests that rCBV measurements may be used as a second reference standard to determine the surgical management/risk-benefit equation and postsurgical adjuvant therapy for LGGs.

OBJECT: The goal of this study is to report the incidence and clinical evolution of neurological deficits in patients who underwent resection of gliomas confined to the parietal lobe. METHODS: Patient demographics, findings of serial neurological examinations, tumor location and neuroimaging characteristics, extent of resection, and surgical outcomes were tabulated by reviewing inpatient and office records, as well as all pre- and postoperative magnetic resonance (MR) images obtained in 28 consecutive patients who underwent resection of a glial neoplasm found on imaging studies to be confined to the parietal lobe. Neurological deficits were correlated with hemispheric dominance, location of the lesion within the superior or inferior parietal lobules, subcortical extension, and involvement of the postcentral gyrus. The tumors were located in the dominant hemisphere in 18 patients (64%); had a mean diameter of 39 mm (range 14-69 mm); were isolated to the superior parietal lobule in six patients (21%) and to the inferior parietal lobule in eight patients (29%); and involved both lobules in 14 patients (50%). Gross-total resection, documented by MR imaging, was achieved in 24 patients (86%). Postoperatively, nine patients (32%) experienced new neurological deficits, whereas seven (25%) had an improvement in their preoperative deficit. A correlation was noted between larger tumors and the presence of neurological deficits both before and after resection. Postoperatively higher-level (association) parietal deficits were noted only in patients with tumors involving both the superior and inferior parietal lobules in the dominant hemisphere. At the 3-month follow-up examination, five of nine new postoperative deficits had resolved. CONCLUSIONS: Neurological deterioration and improvement occur after resection of parietal lobe gliomas. Parietal lobe association deficits, specifically the components of Gerstmann syndrome, are mostly associated with large tumors that involve both the superior and inferior parietal lobules of the dominant hemisphere. New hemineglect or sensory extinction was not noted in any patient following resection of lesions located in the nondominant hemisphere. Nevertheless, primary parietal lobe deficits (for example, a visual field loss or cortical sensory syndrome) occurred in patients regardless of hemispheric dominance

OBJECTIVES: Multichannel auditory brainstem implants (ABI) are currently indicated for patients with neurofibromatosis type II (NF2) and schwannomas involving the internal auditory canal (IAC) or cerebellopontine angle (CPA), regardless of hearing loss (HL). The implant is usually placed in the lateral recess of the fourth ventricle at the time of tumor resection to stimulate the cochlear nucleus. This study aims to review the surgical and audiologic outcomes in 18 patients implanted by our Skull Base Surgery Team from 1994 through 2003. STUDY DESIGN: A retrospective chart review of 18 patients with ABIs. METHODS: We evaluated demographic data including age at implantation, number of tumor resections before implantation, tumor size, surgical approach, and postoperative surgical complications. The ABI auditory results at 1 year were then evaluated for number of functioning electrodes and channels, hours per day of use, nonauditory side effect profile and hearing results. Audiologic data including Monosyllable, Spondee, Trochee test (MTS) Word and Stress scores, Northwestern University Children's Perception of Speech (NU-CHIPS), and auditory sensitivity are reported. RESULTS: No surgical complications caused by ABI implantation were revealed. A probe for lateral recess and cochlear nucleus localization was helpful in several patients. A range of auditory performance is reported, and two patients had no auditory perceptions. Electrode paddle migration occurred in two patients. Patient education and encouragement is very important to obtain maximum benefit. CONCLUSIONS: ABIs are safe, do not increase surgical morbidity, and allow most patients to experience improved communication as well as access to environmental sounds. Nonauditory side effects can be minimized by selecting proper stimulation patterns. The ABI continues to be an emerging field for hearing rehabilitation in patients who are deafened by NF2

Advanced MRI techniques, such as MR spectroscopy, diffusion and perfusion MR imaging can give important in vivo physiological and metabolic information, complementing morphologic findings from conventional MRI in the clinical setting. Combining perfusion MRI and MR spectroscopy can help in patients with brain masses in who the pre-operative differential diagnosis is unclear. This review demonstrates the use of dynamic, susceptibility weighted, contrast-enhanced MR imaging (DSC MRI) and magnetic resonance spectroscopic imaging (MRSI) to distinguish surgical from non-surgical lesions in the brain. There is overlap in the MRI appearance of many enhancing and ring-enhancing lesions such as gliomas, metastases, inflammatory lesions, demyelinating lesions, subacute ischemia, abscess and some AIDS related lesions. We review examples of histopathologically confirmed high-grade glioma, a middle cerebral artery territory infarct, a tumefactive demyelinating lesion and a metastasis for which conventional MR imaging (MRI) was non-specific and potentially misleading and demonstrate how DSC MRI and MRSI features were used to increase the specificity of neurodiagnosis. At several institutions, many patients routinely undergo MRI as well as MRSI and DSC MRI. Cerebral blood flow (CBF), mean transit time (MTT), and relative cerebral blood volume (rCBV) measurements are obtained from regions of maximal perfusion as determined from perfusion color overlay maps. Metabolite levels and ratios are determined for Choline (Cho), N-Acetyl Aspartate (NAA), Lactate and Lipids (LL). Metabolite levels are obtained by measuring the peak heights of each metabolite and the ratios are obtained from these measurements for Cho/Cr, Cho/NAA and NAA/Cr. Neurosurgical intervention carries substantial morbidity, mortality, financial and potential emotional cost to the patient and family. Making a pre-operative diagnosis allows the neurosurgeon to be confident in the choice of treatment plan for the patient and allays considerable patient anxiety. The utility of combining clinical findings with multi-parametric information from perfusion and spectroscopic MR imaging in differentiating surgical lesions from those which do not require surgical intervention is discussed