Gary J. Felsberg

Fast Spin-Echo, Magnetic Resonance Imaging-Measured Hippocampal Volume: Correlation with Neuronal Density in Anterior Temporal Lobectomy Patients

Summary: To assess the value of magnetic resonance imaging (MRI)‐measured hippocampal volume in the detection of hippocampal sclerosis, we studied 28 patients undergoing anterior temporal lobectomy for medically intractable mesial temporal lobe epilepsy. Hippocampal volumetry and visual analysis of T2 signal change were performed using fast spin‐echo T2‐weighted MRI. Quantitative neuronal density measurements were performed in the resected hippocampal specimens. There was a significant correlation between MRI‐measured absolute hippocampal volume (AHV) and neuronal density in CA1, CA2, and CA3 subfields (p<0. 0001, p < 0.01, and p < 0.05, respectively). Differential hippocampal volume (side‐to‐side volume difference) failed to detect bilateral atrophy in three patients, but the bilateral hippocampal atrophy was recognized by considering AHV in these patients. This study suggests that MRI‐measured AHV can be of value in evaluating patients with mesial temporal lobe epilepsy, especially when there is no side‐to‐side difference in hippocampal volumetry.

Successful treatment of childhood pilocytic astrocytomas metastatic to the leptomeninges with high‐dose Cyclophosphamide

Leptomeningeal dissemination of childhood pilocytic astrocytoma (PA) is a rare event with little information available regarding therapy. We report here four children with disseminated PA whom we treated with high doses of cyclophosphamide with clinical benefit. The patients were aged 2.5 to 8 years. Three patients presented with PA localized in the posterior fossa, initially treated with surgical resection (n = 3) and radiotherapy (n = 1). Leptomeningeal dissemination occurred at 32, 44, and 8 months from diagnosis, respectively. The fourth patient presented with an optic pathway tumor with leptomeningeal dissemination at diagnosis. At commencement of cyclophosphamide therapy, disease was present in the subarachnoid space (intracranial, n = 2; spinal, n = 4), cerebral ventricles (n = 2), and primary site (n = 3). Histology was identical at diagnosis and recurrence in the two biopsied cases and cerebrospinal fluid was negative in all cases. Treatment was with cyclophosphamide 4-5 g/m2/cycle given every 4 weeks for a total of two cycles (n = 1) and four cycles (n = 3). One patient achieved disease stabilization (duration 27 months at the time of publication) and three patients experienced significant reductions in tumor burden. Subsequent intrathecal therapy was administered to two patients. Two patients developed disease progression at 10 and 9 months from cessation of chemotherapy. The one re-treated patient responded to further, lower dose, cyclophosphamide. This is the first report of the use of high dose cyclophosphamide for disseminated PA. The recurrence of disease in two cases with a further response to lower dose cyclophosphamide has implications for the optimal duration of therapy for these low grade, aggressive tumors.

Spinal Dural Arteriovenous Fistula: Demonstration Using Phase Contrast MRA

Contrast angiography is the standard means of diagnosing spinal dural arteriovenous fistulas. We present a patient in whom a spinal dural arteriovenous fistula was demonstrated on phase contrast MR angiography.

Practical choices of fast spin echo pulse sequence parameters: clinically useful proton density and T2-weighted contrasts

SummaryWith the development of fast spin echo (FSE) MRI techniques, T2-weighted images of the brain may be obtained much more quickly than when using conventional spin echo techniques (CSE), because made the individual echoes on the FSE pulse sequence are phase encoded, allowing acquisition of the same spatial information as in CSE with less excitations. The pulse sequence parameters (echo train length, bandwidth echo spacing) are discussed. Images were obtained on four volunteers using both CSE and FSE while varying repetition time, echo time and matrix. Comparison for signal intensity gray-white differentiation, fat and CSE signal, arifacts and vascular resolution showed that FSE images comparable in quality to those of CSE can be obtained in less than half the time. A practical choice of FSE parameters is recommended for clinical use. However, artifacts, possibly related to CSF and vascular pulsation, of which the radiologist should be aware, were identified on the FSE images.

MRI of gangliocytoma of cerebellum and spinal cord.

Gangliocytomas are rare CNS tumors that occur in children and young adults. We present a case of a cerebellar gangliocytoma with invasion of the cervical spinal cord demonstrated on MR. Radiographic differentiation of gangliocytomas from other ganglion cell tumors--ganglioglioma, dysplastic gangliocytoma of Lhermitte-Duclos, and desmoplastic infantile ganglioglioma--is discussed.

Gliomatosis cerebri presenting with optic nerve involvement: MRI.

Abstract Gliomatosis cerebri is a rare form of astrocytoma characterized by extreme infiltration of the brain structure in conjunction with a relative paucity of clinical findings. We describe the MRI findings in a patient with gliomatosis cerebri widely infiltrating the brain who presented with symptoms related to involvement of the optic nerves and chiasm. Contrast-enhanced MRI showed enlargement of the optic nerves and chiasm with pathological enhancement; T2-weighted images showed extensive infiltration of the brain by tumor. Histopathologic examination of the biopsy specimen showed anaplastic astrocytoma with gemistocytic predominance and a diagnosis of gliomatosis cerebri was reached.

Utility of MR imaging in pediatric spinal cord injury

We evaluated the utility of MR imaging in pediatric patients with acute and subacute spinal cord injuries. MR imaging of 22 pediatric patients with suspected traumatic spinal cord injuries was reviewed. MR findings were correlated with physical examination and compared to available radiographs and CT examinations performed at time of presentation. Twelve patients had abnormalities on MR imaging. Seven had spinal cord contusions; five contusions were hemorrhagic. Five of seven patients with cord contusion had normal radiographs and CT exams. Six patients with normal radiographs and CT examinations had abnormal MR studies revealing cord contusion, ligamentous injury, disc herniation, and epidural hematoma. MR is useful in initial evaluation of pediatric patients with spinal cord injuries and in prognosis of future neurologic function. In the setting of spinal cord symptomatology and negative radiographic studies, MR imaging should be performed. Surgically correctable causes of cord compression demonstrated by MR imaging include disc herniation, epidural hematoma, and retropulsed fracture fragments. The entity of spinal cord injury without radiographic abnormality is a diagnosis of exclusion which should only be made after radiologic investigation with radiographs, high-resolution thin-section CT, and MR imaging.

Cystic brain masses: use of variable-bandwidth steady-state free-precession MRI

Our objective was to evaluate variable-bandwidth steady-state free-precession (VBSSFP) MRI in characterization of epidermoid tumors and arachnoid cysts. Axial conventional spin-echo and VBSSFP MR images were obtained in 12 patients with epidermoid tumors and 23 with arachnoid cysts and examined for ability to characterize these two lesions and to delineate lesion margin. On conventional spin-echo MRI, characterization of epidermoid tumor and arachnoid cyst was occasionally difficult, because of atypical cases. On VBSSFP MRI, lesion characterization was improved by recognition of two distinct patterns of internal texture and margins of the lesions could be separated from surrounding cerebrospinal fluid. The 25 operated cases confirmed the imaging impression. VBSSFP MRI complements conventional spin-echo imaging to help characterize epidermoid tumors and arachnoid cysts. The improved characterization of these cystic masses with VBSSFP MRI can help radiologists and surgeons establish more accurate preoperative diagnoses and more appropriate treatment plans.