MRI of basilar artery hypoplasia associated with persistent primitive trigeminal artery.

We report three patients with persistent trigeminal arteries, in all of whom the proximal basilar artery was hypoplastic. We draw attention to this common observation, which should not be mistaken for acquired narrowing.

Mamillary body enhancement on MR as the only sign of acute Wernicke encephalopathy.

We report a case of Wernicke encephalopathy in which the only sign of acute disease was enhancement of the mamillary bodies. This case demonstrates the utility of gadolinium enhancement at MR imaging as a means of diagnosing or confirming the syndrome of Wernicke encephalopathy even in the absence of atrophy or T2 abnormalities within the diencephalon and mesencephalon.

MR angiographic demonstration of an intracranial aneurysm not seen on conventional angiography.

A patient with documented subarachnoid hemorrhage underwent conventional angiography, which was negative. MR angiography performed immediately after the conventional angiogram demonstrated a 4-mm anterior communicating artery aneurysm. This finding was confirmed 1 week later with repeat angiography, and the aneurysm was clipped surgically.

Hamartomas of the tuber cinereum: CT, MR, and pathologic findings.

The neuroimaging studies, clinical evaluations, and surgical and pathologic findings in five children with biopsy-proved hamartomas of the tuber cinereum were reviewed. Surgical and/or MR findings showed that patients with precocious puberty had pedunculated lesions while those with seizures had tumors that were sessile with respect to the hypothalamus. The radiologic studies included six MR examinations in four patients and CT studies in all five patients. Three children presented with precocious puberty and two with seizures, one of which was a gelastic (spasmodic or hysteric laughter) type of epilepsy. MR studies were obtained both before and after surgery in two patients, only preoperatively in a third patient, and only postoperatively in the fourth child. MR was superior to CT in displaying the exact size and anatomic location of the hamartomas in all cases. The mass was isointense with gray matter on sagittal and coronal T1-weighted images, which best displayed the relationship of the hamartoma to the third ventricle, infundibulum, and mammillary bodies. Intermediate- or T2-weighted images showed signal characteristics of the hamartoma to be isointense (one case) or hyperintense (two cases) relative to gray matter. The difference in T2 signal intensity did not correlate with any obvious differences in histopathology. CT showed attenuation isodense with gray matter, and no calcium. There was no enhancement on CT. There was no enhancement on MR in the one case in which contrast medium was administered. Preservation of the posterior pituitary bright spot was noted on all pre- and postoperative T1-weighted MR scans.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical and pathological analysis of spinal cord astrocytomas in children.

Twelve children with pathologically confirmed, well-differentiated spinal cord astrocytomas were studied, and correlations among the degree of resection, pathological characteristics, and time of recurrence were examined. Eight tumors were sampled for biopsy or subtotally resected, and 4 were thought to have been totally removed. Clinical recurrence was seen in 4 of 12 patients, 2 of whom died of their disease. The time to recurrence was 1, 2, 2, and 35 years, respectively. The other 8 children remain free of symptoms, with follow-up ranging from 6 months to 35 years (mean, 8.8 years). In 3 of 8 patients who underwent biopsy or subtotal resection, the tumor recurred, and 2 patients died, whereas there was one recurrence in the patients in whom a "total" resection had been obtained. The histologically well-differentiated nature of the lesions correlated well with the relatively prolonged clinical course seen in this series during the period of observation. The relatively long clinical courses seen in our limited series should be considered before high-risk therapy for spinal cord astrocytomas in children is implemented. The presence of four pilocytic astrocytomas in this group was of special interest, and it seems likely that these discrete neoplasms can be distinguished from the more infiltrating fibrillary astrocytic neoplasms by magnetic resonance imaging with enhancement with gadopentetate dimeglumine.

MR imaging of hindbrain deformity in Chiari II patients with and without symptoms of brainstem compression.

We examined the MR appearance of the hindbrain deformity, including the upper cervical spinal canal and craniovertebral junction, in 33 patients with Chiari II malformation. In this disorder, there is impaction at birth of the medulla and cerebellar vermis into the upper cervical spine, resulting in obliteration of the subarachnoid space and scalloping of the dens. Spinal canal enlargement during the child's growth, combined with dorsal displacement of neural tissue, eventually causes marked widening of the precervical subarachnoid space. This enlargement may simulate an intradural mass. Our series documents the changes seen at birth and the progression of the widened precervical space through the first and second decades. Twelve (36%) of the 33 patients studied were symptomatic, with brainstem or longtract symptomatology, and 11 of these required surgery. This group was compared with the remaining 21 asymptomatic Chiari II patients to identify MR features associated with clinical deterioration. The level of descent of the hindbrain hernia was critical; eight of 12 symptomatic patients had a cervicomedullary kink at C4 or lower, while no asymptomatic patients had a fourth ventricle, medulla, or kink below C3-C4. The precervical cord subarachnoid space was slightly wider in asymptomatic patients, although there was great overlap. In five patients with follow-up scans, this space was seen to increase in width after laminectomy. A CSF flow void was present in the precervical space in about 25% of patients in both groups. In nine of 12 symptomatic patients, C1 arch indentation of the dura (causing significant compression) was confirmed surgically. However, seven (33%) of the 21 asymptomatic patients also had this appearance. Absolute measurement of the anteroposterior diameter of the canal at C1 ranged from 11 to 25 mm in both groups. Retrocollis, which persisted despite sedation for MR, was seen in two patients, both symptomatic. Recognition of the vermis, medullary kink, cervical cord, C1 arch, fourth ventricle, and precervical space in Chiari II patients is fundamental to the analysis of symptoms in

MR imaging of compact white matter pathways.

A prominent decreased signal intensity can be seen in many of the heavily myelinated, compact fiber pathways of the brain on T2-weighted spin-echo MR images (TR = 2500 msec, TE = 80 msec). These areas include the anterior commissure, internal capsule, optic tract and radiations, fornix, mammillothalamic tract, superior frontooccipital fasciculus, cingulum, corpus callosum, uncinate fasciculus, and superior longitudinal fasciculus. All these pathways could be identified in normal subjects 3 years old and older when 1.5-T axial and coronal images of 50 adults and 17 children were reviewed. Correlation of the in vivo and postmortem MR appearance of two human brains with Perls and Luxol fast blue stains indicates that the short T2 reflects heavy myelination and fiber density, not iron deposition. This is in contrast to the short T2 signal seen in the subcortical U fibers and deep nuclei of the brain that result from iron deposition. These pathways also differ from areas of brain iron accumulation in that (1) they may appear as areas of short T1 on partial-saturation or inversion-recovery pulse sequences and (2) they can be seen with regularity in all patients over 3 years of age. It is important to distinguish between the effect of the myelin sheath and the effect of brain iron on the T2 relaxation values seen in the normal brain since both result in shortened T2 relaxation. The importance of the role of these fiber tracts in disease processes and in modifying the spread of vasogenic edema and tumor needs further investigation.

Efficient pulse sequence for multisection dual-repetition time MR image acquisition.

A magnetic resonance imaging pulse sequence was developed in which multisection spin-echo image data are simultaneously acquired for two repetition time (TR) intervals (TR1 and TR2) in one imaging sequence. In a conventional multisection image at a single TR, the number of sections is limited to TR/TS, where TS is the readout time. With this new sequence, the number of sections that can be imaged at both TRs in one acquisition is equal to (TR1 + TR2)/(TS1 + TS2), where TS1 and TS2 may be different for the two TRs. Imaging time is equal to that for a single image at a TR of TR1 + TR2. Clinical images were obtained with the new sequence from 15 patients and compared with images acquired at the same TR/TE by means of standard multisection single-TR methods. Relative image quality was assessed by three radiologists in 37 comparisons. In general, the dual-TR results at the long TR were judged equivalent to those from a single-TR image. Dual-TR results at the short TR had a modest reduction in contrast, but in none of 15 cases were any pathologic features missed.

Parietal cephaloceles: radiographic and magnetic resonance imaging evaluation.

Three patients with parietal cephaloceles underwent evaluation and treatment at Duke University Medical Center between 1984 and 1987. All presented within the first 2 years of life with painful swelling near the vertex of the head. All patients had skull films and computed tomography, and two underwent magnetic resonance imaging (MRI). All 3 children had associated hindbrain deformities; two with Dandy-Walker malformation, the third with a Chiari II malformation. Each child eventually developed hydrocephalus. MRI is the procedure of choice to evaluate these patients, providing direct sagittal imaging of the posterior fossa and craniocervical junction, and displaying communication of the cephalocele with intracranial structures as well as associated venous vascular anomalies.

MR imaging of peripheral intracranial neoplasms: extraaxial vs intraaxial masses.

In an effort to determine magnetic resonance (MR) features of peripheral brain tumors that allow accurate localization. 11 extraaxial neoplasms were compared with 11 peripheral intraaxial tumors. The MR findings most often seen in extraaxial lesions include interruption of bone, white matter buckling, widening of adjacent subarachnoid space or cistern, and medial displacement of pial arteries or veins. Invasion of the cortex without white matter buckling, as well as flattening and lateral displacement of the surface veins, was most often seen in intraaxial lesions. Neither simple contiguity to a bony or dural surface nor vasogenic edema is a reliable predictor of intra- vs extraaxial masses.

Cranial computed tomography in the morbidly obese patient.

A method for positioning the obese patient for cranial CT without using the CT cradle is described. This method allows diagnostic images to be obtained in patients who exceed the table weight limit.

Recurrent vertebrobasilar embolism in an infant with Klippel-Feil anomaly.

The vertebral arteries have been hypothesized to be a source of recurrent emboli that obstruct the posterior circulation of the brain in children, but mechanisms for formation of such emboli have not been documented. An infant with Klippel-Feil anomaly experienced multiple embolic events in the posterior circulation, documented by serial computed tomography and cerebral angiography. Angiography identified a source for the emboli in the left vertebral artery. The value of lateral cervical spine radiographs in screening for bony abnormalities which may predispose to arterial anomalies is demonstrated.

MRI of corpus callosal syndromes.

Six patients, 6 to 13 years old, with corpus callosal abnormalities diagnosed by electroencephalography or CT were studied with a 0.15 T MR imager to determine the effectiveness of MRI in evaluating midline anomalies. Spin-echo images in the coronal, axial, and sagittal planes were obtained in two patients with Aicardi's syndrome and partial agenesis of the corpus callosum, in one patient with Dandy-Walker syndrome, and in two patients with septooptic dysplasia. Inversion recovery and spin-echo images were obtained in one patient with lipoma of the corpus callosum. Partial agenesis of the corpus callosum was seen in septooptic dysplasia, an association that has not been reported previously in the radiologic literature. Direct sagittal and coronal MRI provided better anatomic visualization of the brain and ventricles than did reformatted CT. T1-weighted images are sufficient to diagnose and delineate the extent of midline cerebral abnormalities. The unique capability of direct sagittal imaging makes MRI the best procedure for evaluating corpus callosal and other midline abnormalities.

MRI of radiation injury to the brain.

Nine patients with a history of radiation of 2400-6000 rad (24-60 Gy) to the brain were examined by magnetic resonance imaging (MRI) and computed tomography (CT). MRI demonstrated abnormalities in the periventricular white matter in all patients. The abnormal periventricular signal was characterized by a long T2 and was demonstrated best on coronal spin-echo (SE) 1000/80 images. A characteristic scalloped appearance at the junction of the gray-white matter was seen on MR images of seven patients, and represented extensive white-matter damage involving the more peripheral arcuate fiber systems. This differs from transependymal absorption, which is seen best on SE 3000/80 images and has a smooth peripheral margin. Cranial CT demonstrated white-matter lucencies in six cases but generally failed to display the extent of white-matter injury demonstrated by MRI. MRI is uniquely suited to detect radiation injury to the brain because of its extreme sensitivity to white-matter edema.

CSF rhinorrhea: detection and localization using overpressure cisternography with Tc-99m-DTPA.

We performed 32 overpressure radionuclide cisternography (ORNC) studies to examine 26 patients who were clinically suspected of having cerebrospinal fluid (CSF) fistula with rhinorrhea. Fifteen (47%) of these cisternography studies were positive, and the site of the leak was identified. No leak could be demonstrated in the other 17. Of 23 examinations performed in patients who had clinically documented CSF rhinorrhea, 15 (65%) were scintigraphically positive. The rapid cephalad transit of the radionuclide bolus allowed completion of the study within 30 to 45 minutes. Seven examinations were also performed with overpressure metrizamide CT cisternography (OMCTC), and five demonstrated concordant results with the radionuclide study. Patient discomfort and side effects were minimal. We conclude that radionuclide infusion cisternography is a safe, rapid, and accurate method of investigating a suspected or proven CSF rhinorrhea and that it is complementary to metrizamide cisternography.

Neonatal intestinal obstruction from omphalomesenteric duct remnants.

Three cases of omphalomesenteric band obstruction in early infancy with various radiographic presentations, including intermittent obstruction in one, are reported. Small-bowel volvulus was found in all three patients at surgery. One case progressed to bowel necrosis with portal venous gas. A survey of the mode of presentation, surgical findings, and pathology of 135 published cases of intestinal obstruction in children demonstrates that a closed loop, with or without volvulus, is the most common complication of remnant bands.