David F. Sobel

Potential contribution of bilateral magnetic source imaging to the evaluation of epilepsy surgery candidates.

The current procedures that are used to evaluate candidates for epilepsy surgery are time-consuming, costly, and often invasive. Magnetic source imaging (MSI), the combination of magnetoencephalography and anatomic imaging modalities, has shown promise as an efficient noninvasive means of localizing and characterizing seizure sources for possible resection. However, MSI has been limited by the inability to conduct simultaneous bilateral monitoring. In this study, a newly developed dual-magnetometer system was employed to record bilaterally the interictal activity in 30 candidates for epilepsy surgery. A standard monitoring protocol that included concurrent electroencephalographic recording and required a 2- to 3-hour examination period for each patient was developed. As a first step in a series of studies, the resultant MSI indications were compared with the information available from standard magnetic resonance imaging and concurrent electroencephalographic results. In 83% of the cases, this MSI protocol provided new information about the location of interictal epileptic activity that could be directive for subsequent patient care. Based on these results, it seems that MSI may become a cost-effective early step in epilepsy surgery evaluation. To continue the development on this basis, a study intended to validate the accuracy of MSI indicated by comparison with invasive electroencephalography has been initiated.

Magnetic Resonance Scanning in Orbital Tumor Diagnosis

We have compared the accuracy of magnetic resonance scanning (MRI) versus computed tomography (CT) in the differentiation of lateral orbital masses. The MRI results did not improve our ability to accurately diagnose malignant epithelial and lymphoid tumors.

Cerebral amyloid angiopathy associated with massive intracerebral hemorrhage

SummaryCharacteristic computed tomographic, clinical and pathologic features are discussed in two patients with cerebral amyloid angiopathy (CAA) associated with massive intracerebral hemorrhage. Amyloid angiopathy should be considered in any elderly patient in whom intracerebral hemorrhage occurs at an atypical site. Cortical involvement, multiplicity of hemorrhages, bilaterality, and repeated episodes should further arouse diagnostic suspicion. Clinical management is confined to prevention of systemic hypertension.

Hypointense and Hyperintense Lesions on Magnetic Resonance Imaging in Secondary-Progressive MS Patients

Cranial magnetic resonance imaging (MRI) is widely used to monitor disease activity in clinical trials in multiple sclerosis (MS). The purpose of this study is to examine lesion burden as determined from hypointense regions on postcontrast T1-weighted scans (or black holes), and lesion burden on conventional T2-weighted scans, from a cohort of secondary progressive MS patients who participated in a placebo-controlled, randomized, double-blind cross-over trial assessing the therapeutic efficacy of cladribine. T2 lesion volumes and black hole volumes are approximately normal distributed when log-transformed, and are highly correlated (adjusted R2 = 0.63). Changes in clinical scores could be predicted with a reasonable degree of precision from baseline scores and changes in T2 lesion volumes (adjusted R2 values 0.52–0.7). Stratification schemes for clinical trials should include the acute proportion of the disease (enhancing T1 lesions), degree of permanent damage (black holes), and T2 lesion volume.

Relative value of computed tomography and hypocycloidal tomography in the diagnosis of pituitary microadenoma. A radio-surgical correlative study.

SummaryThe relative value of a second generation CT scanner and complex motion polytomography are compared in 36 patients undergoing transsphenoidal surgery due to clinical and biological evidence of pituitary hypersecretion. CT findings of focal glandular hypodensity in 17 patients and upward convexity of the sellar contents in 15 patients suggested the presence of a pituitary microadenoma. Complex motion tomographic findings suggesting a microadenoma were found in 21 of 32 cases and included bulging of the sellar floor or localized thinning of the lamina dura. Selective transsphenoidal adenomectomy was performed on 34 of the 36 patients and the preoperative location based on CT scanning data was positively correlated with surgical results in 75% of the cases. When there is a strong clinical suspicion of pituitary hypersecretion both CT and polytomography may suggest the existence and location of a microadenoma. CT should be the radiographic technique of choice since it produces accurate information as to the size and density of the pituitary gland.

Magnetic Resonance Imaging (MRI) of the Eye and Orbit

The contents of the orbit and its osseous margins have been particularly well imaged since the development of x-ray computed tomographic (CT) imaging. The greatly differing x-ray attenuation characteristics of the constituent tissues allow their separation and segregation into discrete compartments (11). Magnetic resonance imaging (MRI) is a newly emerging technique that may supplant or supplement CT for diagnostic imaging. MRI also has the potential to provide fine structural detail and tissue characterization in this region, while avoiding ionizing radiation to the globe and providing some unique information. The present discussion reflects our initial experience in examination of the eye, orbit, and structures therein by using this evolving imaging technology.

New Hypointense Lesions on MRI in Relapsing-Remitting Multiple Sclerosis Patients

Background: Preliminary observational studies with multiple sclerosis (MS) patients have reported strong correlations between an increase in hypointense lesion load (black holes) on T1-weighted spin echo images, and an increase in disability. Objective: We assessed the relationship of hypointense lesions to the clinical course of disease among 50 relapsing-remitting MS patients in the controlled setting of a randomized clinical trial. Methods: Fifty patients with relapsing-remitting disease were enrolled in a randomized double-blind two-arm (cladribine vs. placebo) clinical trial of 1-year duration. All patients had monthly clinical evaluations and MRIs over the course of the trial. Multivariate techniques were used to identify predictors of clinical severity from information on exacerbations, MRIs, baseline clinical parameters, and demographics. Results: At baseline, clinical severity is weakly related to counts of black holes, with rank correlations between counts and clinical scores (EDSS and SNRS) of absolute magnitude 0.3. Rates of appearance of new black holes over the course of the trial are higher for patients with more severe disease at baseline (EDSS ≥ 4) than for the less severe patients. Changes in clinical severity over the course of the trial are best predicted by baseline neurologic scores and numbers of exacerbations, with black holes adding no further improvement in prediction. Conclusions: Numbers of exacerbations seem more critical to short-term clinical outcomes in relapsing-remitting MS, as reflected by patients’ clinical scores, rather than black holes. Various imaging methods and MRI indices capture complementary information relating to MS disease processes. The determination of which processes are affected by different drugs should lead to more effective treatment of MS patients.

Tolerability and efficacy of Hexabrix in cerebral angiography.

In a double-blind study of 62 patients, Hexabrix was compared with Conray 60% in cerebral angiography. Both agents were injected into the same patient, the patient serving as his own control, and volumes injected into a single vessel were identical. Considerably less pain was experienced with Hexabrix. Changes in pulse, respiration and blood pressure were not significantly different. The two contrast media provided images of comparable quality.