MR characteristics of iophendylate (Pantopaque)

Although iophendylate (Pantopaque) has been largely replaced by water soluble agents for myelography, retained intracranial or intraspinal Pantopaque remains a common occurrence. Pantopaque has signal characteristics similar to fat with both short T1 and T2 relaxation times. In vitro measurements revealed T1 = 170 ms and T2 = 27 ms. Spine radiography is recommended in patients with a history of previous myelography and magnetic resonance abnormalities similar to fat.     

Neurofibromatosis type 1: brain stem tumours

We describe the clinical and imaging findings of brain stem tumours in patients with neurofibromatosis type 1 (NF1). The NF1 patients imaged between January 1984 and January 1996 were reviewed and 25 patients were identified with a brain stem tumour. Clinical, radiographical and pathological results were obtained by review of records and images. Brain stem tumour identification occurred much later than the clinical diagnosis of NF1. Medullary enlargement was most frequent (68 %), followed by pontine (52 %) and midbrain enlargement (44 %). Patients were further subdivided into those with diffuse (12 patients) and those with focal (13 patients) tumours. Treatment for hydrocephalus was required in 67 % of the first group and only 15 % of the second group. Surgery was performed in four patients and revealed fibrillary astrocytomas, one of which progressed to an anaplastic astrocytoma. In 40 % of patients both brain stem and optic pathway tumours were present. The biological behaviour of brain stem tumours in NF1 is unknown. Diffuse tumours in the patients with NF1 appear to have a much more favourable prognosis than patients with similar tumours without neurofibromatosis type 1. Received: 21 November 1996 Accepted: 22 December 1996     

MR of the cerebral operculum: abnormal opercular formation in infants and children.

PURPOSETo evaluate abnormalities of the cerebral operculum in infants and children and to propose the embryogenic basis of abnormal opercular formation as determined from MR imaging findings.METHODSEighty-six infants and children who had abnormally wide interopercular distances and/or distorted opercular topography seen on MR images were studied retrospectively. Clinically, patients presented with tonal abnormalities, macrocephaly, microcephaly, seizures, developmental delay, cerebral palsy, or facial dysmorphism. The abnormal opercula were compared with developing opercula at different stages of gestation.RESULTSAmong the 86 infants and children, two categories of opercular abnormalities were identified: an underdeveloped operculum (n = 64) and a malformed operculum (n = 22). The malformed operculum was further classified into three subtypes: nonformation of the operculum with lissencephaly (n = 1, 1%), abnormal opercular formation with pachygyria (n = 11, 13%), and nonformation or abnormal formation of the operculum without pachygyria or lissencephaly (n = 10, 12%). Two subtypes of the underdeveloped operculum were identified: an open operculum without a normal insula (n = 6, 7%) and an open operculum with a normal insula (n = 58, 67%). The five subtypes of abnormal opercular configuration showed a range of maturity that was comparable to the developing operculum at different ages.CONCLUSIONOpercular anomalies appear to follow sequentially predetermined normal steps in development. Arrest in opercular development or malformation may occur after an initial insult. MR imaging is the method of choice by which to identify these abnormalities.     

Ultrafast MR imaging of the normal posterior fossa in fetuses

OBJECTIVE: The purpose of our study was to determine if a standard imaging protocol using ultrafast MR sequences could adequately reveal normal posterior fossa anatomy in fetuses and, if so, to document a template on MR imaging for normal posterior fossa development. MATERIALS AND METHODS: A retrospective review found 66 MR imaging studies of 63 fetuses, 16-39 weeks' gestation age (mean, 25 weeks' gestation), who were referred between June 1996 and May 1999 for evaluation of non-central nervous system anomalies revealed on prenatal sonography. All fetuses had normal brains and spines on prenatal sonography. The standard MR imaging protocol included axial, sagittal, and coronal half-Fourier acquisition single-shot turbo spin echo (HASTE); sagittal and coronal two-dimensional fast low-angle shot (FLASH); and axial turbo T1-weighted FLASH images through the fetal brain. Structures that we analyzed were the fourth ventricle, the cisterna magna, the vermis, the cerebellar hemispheres, and the brainstem. Using the HASTE sequences, we documented gestational age-specific signal intensity changes in the cerebellar hemispheres and the brainstem. RESULTS: The posterior fossa anatomy was sufficiently well defined to exclude abnormalities of the fourth ventricle and cerebellar vermis in all cases. Because of high T2-weighting, good contrast enhancement, and good signal-to-noise ratios, HASTE images provided the best anatomic definition of the posterior fossa. CONCLUSION: Normal posterior fossa anatomy can be adequately shown on ultrafast MR images, which can be helpful when prenatal sonography is equivocal.     

Magnetic resonance imaging diagnosis of disseminated necrotizing leukoencephalopathy

Disseminated necrotizing leukoencephalopathy is a rare syndrome of progressive neurologic deterioration seen most often in patients who have received central nervous system irradiation combined with intrathecal or systemic chemotherapy in the treatment or prophylaxis of various malignancies. Magnetic resonance imaging was more sensitive than computed tomography in detecting white matter abnormalities in the case of disseminated necrotizing leukoencephalopathy reported here. Magnetic resonance imaging may be useful in diagnosing incipient white matter changes in disseminated necrotizing leukoencephalopathy, thus permitting early, appropriate therapeutic modifications.     

Diffusion-weighted imaging and fluid attenuated inversion recovery imaging in the evaluation of primitive neuroectodermal tumors

The aim of our study was to determine whether fluid-attenuated inversion recovery (FLAIR) imaging and diffusion-weighted imaging (DWI) would be helpful in characterizing primitive neuroectodermal tumors (PNET) from other pediatric brain tumors. We expected that the compact cellular nature and the relatively small extracellular space of this tumor would affect the signal intensity on both pulse sequences relative to the more sparsely cellular glial tumors that have larger extracellular spaces. Eighteen pediatric patients with PNET were examined on a 1.5 T MRI with routine imaging plus FLAIR and compared with 28 patients with non-PNET. DWI was also performed in 7 PNET and 18 non-PNET. Seventy-eight percent of PNET were isointense to gray matter on FLAIR while 82 % of non-PNET were hyperintense and only one was isointense (3 %). Diffusion was abnormally restricted in all 7 PNET examined (100 %) but was restricted in non-PNET in only 1 out of 18 (6 %) patients who had DWI. The differences in the histologic architecture between PNET and non-PNET are reflected in both FLAIR imaging and in DWI. Received: 3 February 2001/Accepted: 13 February 2001     

Magnetic resonance imaging of spinal cord disease of childhood

Correct diagnosis of spinal cord disease in childhood is often delayed, resulting in irreversible neurologic deficits. A major reason for this delay is the lack of a reliable means to noninvasively visualize the spinal cord. Magnetic resonance imaging (MRI) should be useful in the evaluation of diseases of the spinal cord. A 1.5 Tesla MRI unit with a surface coil was used to study 41 children, including eight patients with intrinsic spinal cord lesions, eight patients with masses compressing the cord, 12 patients with congenital anomalies of the cord or surrounding bony structures, three patients with syrinxes, and three patients with vertebral body abnormalities. Intrinsic lesions of the cord were well seen in all cases as intrinsic irregularly widened, abnormally intense cord regions. MRI was helpful in following the course of disease in patients with primary spinal cord tumors. Areas of tumor were separable from syrinx cavities. Extrinsic lesions compressing the cord and vertebral body disease were also well visualized. Congenital anomalies of the spinal cord, including tethering and lipomatous tissue, were better seen on MRI than by any other radiographic technique. MRI is an excellent noninvasive "screening" technique for children with suspected spinal cord disease and may be the only study needed in many patients with congenital spinal cord anomalies. It is also an excellent means to diagnose and follow patients with other forms of intra- and extraspinal pathology.     

Management of carotid coils during routine carotid endarterectomy

BACKGROUND: A coil in the internal carotid artery (ICA), defined as a circular configuration or exaggerated S shape of the ICA, is occasionally encountered during endarterectomy for carotid bifurcation lesions. The significance of coils as an etiology for symptoms is difficult to determine. It is thought, however, that the failure to correct coils and kinks during routine carotid endarterectomy (CE) may lead to turbulence and failure of the CE. Various techniques have been discussed to repair coils. METHODS: Our technique consisted of complete dissection of the coil, routine use of a Javid shunt, standard endarterectomy, resection of the redundant ICA, re-approximation of the posterior wall of the ICA and patch angioplasty of the anterior wall. Three hundred and fifteen patients underwent CE between August, 1998 and February, 2000. Fifteen patients (4.7%) had a carotid coil that was repaired. There were ten men and five women. Mean age was 72.6+/-6.1 years. Ten patients had an asymptomatic stenosis. Four patients had lateralizing symptoms and one patient had dizziness. Fifteen patients underwent preoperative duplex scanning and 14 of these patients had MRA scans performed. All patients had a preoperative stenosis of 80-99% by duplex on the operated side. The right carotid artery was repaired in 12 patients. The left in three patients. The length of resected artery varied from 1.2-2.8 cm (1.93+/-0.49 cm). RESULTS: All patients survived surgery. One patient developed a cerebellar stroke on the third postoperative day. A postoperative carotid duplex scan demonstrated a widely patent repair. There were no cranial nerve injuries in this series. One patient died seven months after surgery from cardiac events with no follow-up duplex exam. There have been no long term strokes or anastomotic complications. Follow-up duplex scans demonstrated widely patent repairs (1-15% stenosis) in seven patients and low end 15-49% stenosis in five patients. CONCLUSIONS: Resection of redundant ICA with re-anastomosis of the posterior wall and patch reconstruction of the anterior wall gives acceptable perioperative and long term results.     

Wall of infundibular recess: a CT and MR study

A ring of enhancement immediately posterior to the optic chiasm has been observed on postcontrast, thin section, axial CT. This ring represents enhancement of the infundibular recess' wall and does not have any pathologic significance. Magnetic resonance confirmed this anatomic interpretation.     

Comparison of metrizamide computed tomography and magnetic resonance imaging in the evaluation of lesions at the cervicomedullary junction

We compared intrathecal metrizamide-enhanced CT (metrizamide-CT) and magnetic resonance imaging (MRI) in the evaluation of 17 patients with clinical suspicion of lesions at the cervicomedullary junction. MRI was superior in imaging the position of the cerebellar tonsils and the size and extent of mass lesions. MRI and metrizamide-CT were equal in detecting syringomyelia. CT with and without IV contrast enhancement was necessary to detect calcium or defects in the blood-brain barrier within neoplasms.