Amir A. Zamani

Clinical and neuroradiographic manifestations of eastern equine encephalitis.

BACKGROUND Eastern equine encephalitis occurs principally along the east and Gulf coasts of the United States. Recognition of the neuroradiographic manifestations of eastern equine encephalitis could hasten the diagnosis of the illness and speed the response to index cases. METHODS We reviewed all cases of eastern equine encephalitis reported in the United States between 1988 and 1994. The records of 36 patients were studied, along with 57 computed tomographic (CT) scans and 23 magnetic resonance imaging (MRI) scans from 33 patients. RESULTS The mortality rate was 36 percent, and 35 percent of the survivors were moderately or severely disabled. Neuroradiographic abnormalities were common and best visualized by MRI. Among the patients for whom MRI scans were available, the results were abnormal for all eight comatose patients as well as for all three noncomatose patients who subsequently became comatose. The CT results were abnormal in 21 of 32 patients with readable scans. The abnormal findings included focal lesions in the basal ganglia (found in 71 percent of patients on MRI, and in 56 percent on CT), thalami (found in 71 percent on MRI and in 25 percent on CT), and brain stem (found in 43 percent on MRI and in 9 percent on CT). Cortical lesions, meningeal enhancement, and periventricular white-matter changes were less common. The presence of large radiographic lesions did not predict a poor outcome, but either high cerebrospinal fluid white-cell counts or severe hyponatremia did. CONCLUSIONS Eastern equine encephalitis produces focal radiographic signs. The characteristic early involvement of the basal ganglia and thalami distinguish this illness from herpes simplex encephalitis. MRI is a sensitive technique to identify the characteristic early radiographic manifestations of this viral encephalitis.

Frequency and patterns of MRI abnormalities due to status epilepticus

BACKGROUND MRI changes due to status epilepticus (SE) often suggest a combination of cytotoxic and vasogenic edema, but it is unclear why only certain patients have MRI changes. OBJECTIVES To determine the frequency of MRI changes due to SE and the associated patient characteristics. METHODS We reviewed records for demographics, medical history, and MRI changes attributable to seizures of all patients admitted to Brigham and Womens Hospital or Massachusetts General Hospital for SE from 1/1999 to 7/2003 and who had MRI during admission. RESULTS Ten (11.6%) of the eighty-six patients identified had MRI abnormalities likely due to seizures. Four, two with pre-existing epilepsy and two with extratemporal structural lesions, had focally increased signal on T2 and diffusion-weighted imaging (DWI) in the hippocampus ipsilateral to the seizure focus. One, with elevated levels of clozapine, had increased signal on T2 weighted images and variably restricted diffusion in the splenium. Five had gyral distribution of restricted diffusion and increased signal on T2 weighted images; they had complex medical comorbidities and possible hypoperfusion or hypoxia associated with SE. CONCLUSIONS Among patients with SE who had MRI changes, those with previous epilepsy or extratemporal structural lesions showed increased diffusion in the hippocampus and may have selective hippocampal vulnerability to seizure-induced hyperexcitability. Patients with hyperintense signal in the cortical gray matter had episodes of possible hypoperfusion or hypoxia.

The clinical spectrum of hemorrhagic infarction.

The hospital records and head CT scans of 44 patients with hemorrhagic infarction were retrospectively analyzed. The majority of cases (73%) were embolic or possibly embolic in etiology, and 55% were not associated with anticoagulant therapy. Adverse prognosis was most clearly related to infarct size, underlying systemic illness, and symptomatic hemorrhage. Of the nineteen patients in whom serial CT scans documented conversion from bland to hemorrhagic infarction, 12 exhibited no clinical worsening at the time that hemorrhagic infarction was observed; the remaining seven, all of whom worsened, were receiving anticoagulant therapy at the time of documented conversion. Fourteen patients in whom anticoagulant therapy was used despite the findings of hemorrhagic infarction remained stable or improved during hospitalization.

Statistical assessment of perceptual CT scan ratings in patients with alzheimer type dementia

Three neuroradiologists perceptually evaluated CT of 24 patients with Alzheimer type dementia and 22 normal control subjects and made a dichotomous judgment for each case (i.e., normal control or Alzheimer type dementia). The mean percentage of patients correctly classified was 83.3%. The neuroradiologists also completed perceptual ratings on each scan. Thirteen regions were rated for atrophy on a scale of 0-4. Discriminant function analyses of several sets of perceptual atrophy ratings (optimized on an exploratory set and evaluated on a test set) showed that the perceptual ratings of temporal lobe regions produced an average accuracy of 88.57%. In contrast, only 74.26% of the cases were correctly classified when the discriminant functions were based on perceptual ratings of midventricular and supraventricular areas. Linear measures of atrophy correctly classified only 65.20% of the subjects. The results suggest that atrophy ratings of brain regions that show the characteristic macroscopic neuropathological changes of Alzheimer disease may be used by neuroradiologists to reach more accurate diagnostic decisions.

Initial experience with intraoperative magnetic resonance imaging in spine surgery.

Study Design A case series of 12 patients who underwent spine surgery in an intraoperative magnetic resonance imager (IMRI). Objectives To determine the advantages, limitations, and potential applications to spine surgery of the IMRI. Summary of Background Data Existing stereotactic navigational systems are limited because images are obtained before surgery and are not updated to reflect intraoperative changes. In addition, they necessitate manual registration of fiducial landmarks on the patient’s anatomy by the surgeon to the previously obtained image data set, which is a potential source of error. The IMRI eliminates these difficulties by using intraoperative acquisition of MRI images for surgical navigation with the capacity for both image update and image-guided frameless stereotaxy. The IMRI is a novel cryogenless superconducting magnet with an open configuration that allows the surgeon full access to the patient during surgery and intraoperative imaging. Methods T1- and T2-weighted fast spin echo images were obtained for localization, after surgical exposure and after decompression during the course of 12 spine surgeries performed in the IMRI. Results The authors performed a series of 12 procedures in the IMRI that included three lumbar discectomies, three anterior cervical discectomies with allograft fusion, three cervical vertebrectomies with allograft fusion, two cervical foraminotomies, and one decompressive cervical laminectomy. The system provided rapid and accurate localization in all cases. The adequacy of decompression by MRI during surgery was confirmed in 10 of 12 cases. Conclusions The IMRI provided accurate and rapid localization in all cases and confirmed the adequacy of decompression in the majority of cases. Future applications of the IMRI to spine surgery may include intraoperative guidance for resection of spine and spinal cord tumors and trajectory planning for spinal endoscopy or screw fixation.

Impaired Cerebral Autoregulation Is Associated With Vasospasm and Delayed Cerebral Ischemia in Subarachnoid Hemorrhage

Background and Purpose— Cerebral autoregulation may be impaired in the early days after subarachnoid hemorrhage (SAH). The purpose of this study was to examine the relationship between cerebral autoregulation and angiographic vasospasm (aVSP) and radiographic delayed cerebral ischemia (DCI) in patients with SAH. Methods— Sixty-eight patients (54±13 years) with a diagnosis of nontraumatic SAH were studied. Dynamic cerebral autoregulation was assessed using transfer function analysis (phase and gain) of the spontaneous blood pressure and blood flow velocity oscillations on days 2 to 4 post-SAH. aVSP was diagnosed using a 4-vessel conventional angiogram. DCI was diagnosed from CT. Decision tree models were used to identify optimal cut-off points for clinical and physiological predictors of aVSP and DCI. Multivariate logistic regression models were used to develop and validate a risk scoring tool for each outcome. Results— Sixty-two percent of patients developed aVSP, and 19% developed DCI. Patients with aVSP had higher transfer function gain (1.06±0.33 versus 0.89±0.30; P=0.04) and patients with DCI had lower transfer function phase (17.5±39.6 versus 38.3±18.2; P=0.03) compared with those who did not develop either. Multivariable scoring tools using transfer function gain >0.98 and phase <12.5 were strongly predictive of aVSP (92% positive predictive value; 77% negative predictive value; area under the receiver operating characteristic curve, 0.92) and DCI (80% positive predictive value; 91% negative predictive value; area under the curve, 0.94), respectively. Conclusions— Dynamic cerebral autoregulation is impaired in the early days after SAH. Including autoregulation as part of the initial clinical and radiographic assessment may enhance our ability to identify patients at a high risk for developing secondary complications after SAH.

Intra-operative MRI (iop-MR) for brain tumour surgery.

Image-guided neurosurgery is an important development in the management of brain tumours. Intra-operative imaging is an extension of this modality. It is important because it compensates for brain shift, allows accurate navigation, and gives verification of what has been done surgically before the patient leaves the operating room. It extends the capacity of image-guided surgery significantly. This paper describes the use intra-operative imaging using MR for brain tumour surgery, the devices presently available for doing this, and potential future applications of intra-operative imaging. It describes in some detail the specific indications for intra-operative imaging including biopsy, resection of intra-axial tumours, and identification and resection of some extra-axial tumours. The description includes the advantages and disadvantages of using intra-operative MRI in this setting.

Parasagittal Solitary Fibrous Tumor of the Meninges. Case Report and Review of the Literature

Summary The clinical, radiologic and pathologic features of a case of parasagittal solitary fibrous tumor of the meninges are reported. The patient was a 44 year-old male who presented with a complex partial seizure and a history of headaches and confusion. Radiological studies showed a large extra-axial dural-based mass in the right parietal region, predominantly isointense with gray matter and hypointense with respect to white matter on T1-weighted images, and hypointense with respect to gray matter on T2-weighted images. At surgery, the mass was very vascular, quite firm and very adherent to the convexity. Histologically the tumor was composed of spindle-shaped cells growing in fascicles within a collagenous matrix. Solitary fibrous tumor of the meninges is a newly described entity, which should be kept in mind in the clinical and radiological differential diagnosis of extra-axial brain tumors.

Methylmalonic acidemia: brain imaging findings in 52 children and a review of the literature

BackgroundMethylmalonic acidemia (MMA) is an autosomal-recessive inborn error of metabolism.ObjectiveTo recognize the CT and MR brain sectional imaging findings in children with MMA.Materials and methodsBrain imaging studies (47 MR and 5 CT studies) from 52 children were reviewed and reported by a neuroradiologist. The clinical data were collected for each patient.ResultsThe most common findings were ventricular dilation (17 studies), cortical atrophy (15), periventricular white matter abnormality (12), thinning of the corpus callosum (8), subcortical white matter abnormality (6), cerebellar atrophy (4), basal ganglionic calcification (3), and myelination delay (3). The brain images in 14 patients were normal.ConclusionRadiological findings of MMA are nonspecific. A constellation of common clinical and radiological findings should raise the suspicion of MMA.

Cerebellopontine angle tumors: role of magnetic resonance imaging.

The cerebellopontine (CP) angle is bound anterolaterally by the posterior aspect of the petrous temporal bone and posteromedially by the cerebellum and pons. It contains important vascular structures and cranial nerves and is subject to a certain gamut of lesions, notably tumors with interesting radiological manifestations. Radiological investigation of these lesions has seen significant improvement in recent decades. Magnetic resonance is the imaging modality of choice for lesions of the CP angle and internal auditory canal. Lesions of the CP angles usually are divided into those native to the angle (vestibular schwannoma, meningioma, epidermoid, arachnoid cyst, metastases, lipoma, etc.) and those extending to the angle from adjacent structures (gliomas, ependymomas, choroid plexus papillomas, vascular malformations). Vestibular schwannomas are by far the most important lesion of the CP angle.