High-b-value diffusion-weighted MR imaging of suspected brain infarction.

BACKGROUND AND PURPOSE: Recent technological advances in MR instrumentation allow acquisition of whole-brain diffusion-weighted MR scans to be obtained with b values greater than 1,000. Our purpose was to determine whether high-b-value diffusion-weighted MR imaging improved contrast and detection of signal changes in acute and chronic brain infarction. METHODS: We prospectively evaluated the MR scans of 30 subjects with a history of possible brain infarction on a 1.5-T MR imager with 40 mT/meter gradients (slew rate 150 T/m/s) by use of the following single-shot echo-planar diffusion-weighted MR sequences: 1) 7,999/ 71.4/1 (TR/TE/excitations, b = 1,000; 2) 999/ 88.1/3, b = 2,500; and 3) 7,999/ 92.1/4, b = 3,000. Diffusion-weighted MR imaging was performed in three orthogonal directions during all sequences. All subjects were scanned with fast fluid-attenuated inversion recovery (FLAIR) (10,006/145/2,200/1 [TR/TE/TI/excitations]) and fast spin-echo T2-weighted (3,650/95/3 [TR/TE/excitations], echo train length, 8). The diagnosis of brain infarction was established by clinical criteria. RESULTS: Twenty women and 10 men with a mean age of 67.7 years were enrolled in the study. One subject was excluded owing to poor image quality. Twelve of 29 subjects had a clinical diagnosis of acute infarction. All 12 had lesions that were hyperintense on diffusion-weighted images at all three b values; five were cortical and seven subcortical. There was increased contrast of all lesions on high-b-value scans (b = 2,500 and 3,000). Lesions that were hypointense on diffusion-weighted images were identified and evaluated at the three different b values. At b = 1,000, there were 19 hypointense lesions, whereas at b = 2,500 and 3,000 there were 48 and 55 lesions, respectively. On FLAIR and T2-weighted images, these low-signal lesions were predominantly chronic, subcortical, ischemic lesions and lacunar infarcts, but four chronic cortical infarcts, one porencephalic cyst, and one primary brain tumor were also found. Low-signal lesions were also noted to have increased contrast on high-b-value diffusion-weighted scans. CONCLUSION: High-b-value diffusion-weighted MR imaging (b = 2,500 or b = 3,000) had no impact on diagnosis of acute infarction. High-b-value diffusion-weighted MR imaging (b = 2,500) combined with diffusion-weighted MR imaging at b = 1,000 improves tissue characterization by increasing the spectrum of observed imaging abnormalities in patients with suspected brain infarction.

Serial CT and MR imaging of carmustine wafers.

BACKGROUND AND PURPOSE: A new option in the treatment of recurrent malignant glioma is surgical placement of chemotherapy-laden biodegradable wafers. We describe the CT and MR appearance of chemotherapy wafers in patients after surgery for recurrent malignant glioma METHODS: Eighteen patients had carmustine (BCNU) wafers implanted during reoperation for malignant glioma; three patients had empty, placebo wafers placed. The 21 patients had a total of 22 CT and 57 MR imaging studies. Repeat CT studies were conducted for up to 6 months, the MR studies for up to 1 year. Examinations were evaluated for attenuation on CT scans, signal abnormalities on MR images, and changing appearance during the follow-up period. Enhancement characteristics were also assessed. RESULTS: On CT scans, 13 of 16 acute (<7 days) cases showed linear high-attenuation wafers, with three showing low attenuation. On MR images, all T1 and T2 studies performed in the acute stage showed decreased signal of the wafers. Eight of 15 studies showed a transient increase in T1 only at about 2 months. Wafers decreased in conspicuity on both CT and MR studies after 2 months. The wafers did not enhance. One postoperative tumor showed a transient increase in edema and increased enhancement at 5 weeks. The presence or absence of BCNU within the wafers did not change their appearance. CONCLUSION: BCNU wafers have a characteristic appearance: in the first 7 days after implantation they are linear, usually of increased attenuation on CT scans, and always show decreased signal on MR images; they do not enhance, and become less conspicuous after 2 months.

Joubert's syndrome and prenatal hydrocephalus.

Joubert's syndrome is an autosomal-recessive condition characterized by dysgenesis of the cerebellar vermis, hypotonia, developmental delay, a respiratory pattern of alternating tachypnea and apnea, and abnormal eye movements. Radiologic findings include a midline cerebellar cleft in place of the vermis and a characteristic shape of the fourth ventricle. Prenatal hydrocephalus has been proposed as a possible etiology for the cerebellar abnormalities but has not previously been described in association with this syndrome. The authors report a patient with clinical and radiographic features consistent with Joubert's syndrome who presented with congenital hydrocephalus.

The syndrome of acute near-total intrauterine asphyxia in the term infant.

Eleven term infants sustained an acute, near-total intrauterine asphyxia at the end of labor. Imaging studies documented a consistent pattern of injury in subcortical brain nuclei, including thalamus, basal ganglia, and brainstem; in contrast the cerebral cortex and white matter were completely or relatively spared. This pattern of injury correlated with the acute and long-term neurologic syndromes in these patients. Four patients had a severe neonatal encephalopathy that included prominent signs of brainstem dysfunction. The other seven patients had a moderate neonatal encephalopathy. Three of these patients had dystonia consistent with basal ganglia injury; all seven remained normocephalic and had good cognitive outcomes consistent with sparing of cerebral cortex and white matter. Finally, in all 11 patients, injury to organs other than the brain was usually subtle. The distribution of injury in these patients reflects the hierarchy of metabolic needs that are unmet after a severe, sudden disruption of substrate supply as occurs in an acute, severe asphyxia. Thus, the higher metabolic rate of the brain compared with other organs explains the significant neonatal encephalopathy with relative sparing of nonbrain organs. Similarly, the higher metabolic rate of subcortical nuclei compared with cerebral hemispheres explains the preponderance of subcortical damage. This clinical and imaging syndrome is in contrast with that seen in more prolonged but less severe intrauterine asphyxia, in which shunting of blood flow from nonbrain organs to the brain and from cerebral hemispheres to the thalamus and brainstem renders nonbrain organs and cerebral hemispheres most vulnerable.

Differential diagnosis of nontraumatic intracranial hemorrhage.

Intracranial hemorrhage is a common initial symptom of intracranial vascular malformations. Although CT remains important in the acute setting, MR imaging has proved invaluable for diagnosis and characterization of intracranial hemorrhage. MR imaging of hemorrhage and the differential diagnosis of nontraumatic intracranial hemorrhage is presented in this article.

Spinal headaches after myelograms: comparison of needle types.

OBJECTIVE: We compared traditional bevel-tip end-hole spinal needles and pencil-point-tip side-hole needles for the incidence, severity, and duration of spinal headaches in subjects who had myelograms. Age, sex, and myelographic findings were examined. SUBJECTS AND METHODS: We studied 138 subjects referred for myelograms. For 108 procedures, we randomly used 22-gauge Quinke bevel-tip end-hole needles or 22-gauge Sprotte pencil-point-tip needles. The 30 additional subjects were examined with Gertie Marx pencil-point-tip needles. All myelograms were performed by one of two neuroradiologists using recommended doses of iohexol. The myelograms were examined by an independent neuroradiologist for quality of image and presence of extraarachnoid contrast material. Five to 14 days after myelography, subjects were telephoned by an independent observer and asked about the presence, severity, duration, and positional quality of headache. Spinal headache is defined by positional quality and increases in severity when the subject moves from horizontal to sitting or standing. RESULTS: We found that four (8%) of 52 subjects who had myelograms with Sprotte needles had spinal headaches. Likewise, 14 (25%) of 56 subjects who had myelograms with Quinke needles had spinal headaches. We calculated a statistically significant difference in the incidence of spinal headaches using chi-square analysis (p = .02). The average grade and duration of the spinal headaches did not differ significantly, although they were less marked in the Sprotte group. Spinal headaches occurred more frequently in young and middle-aged subjects than in older subjects. We found one definite extraarachnoid injection in each group. For the Gertie Marx needles, two (7%) of 30 subjects had spinal headaches. The average grade of postmyelogram headache was 2.5, and the mean duration was 1 day. There were no mixed injections. CONCLUSION: We found a significant reduction in spinal headaches after myelograms when we used the pencil-point-tip side-hole needle. These results support the routine use of these needles for myelography in young and middle-aged patients.

Evaluation of the lumbar spine in patients with glycogen storage disease: CT demonstration of patterns of paraspinal muscle atrophy.

CT studies of the lumbar spine were performed in 19 patients with glycogen storage disease. Nine of 10 patients with McArdle's disease and seven of nine patients with acid maltase deficiency demonstrated posterior paraspinal muscle atrophy out of proportion to their ages. In addition, the psoas muscles were spared in all 10 patients with McArdle's disease and were involved with atrophy in seven of the nine patients with acid maltase deficiency. We conclude that when patients with low back pain-or asymptomatic patients-demonstrate otherwise unexplained atrophy of the paraspinal muscles the diagnosis of glycogen storage disease should be considered. Furthermore, when the psoas muscles are spared, the specific diagnosis of McArdle's disease is suggested.

Venous sinus thrombosis as a cause of parenchymal and intraventricular hemorrhage in the full-term neonate.

A case of parenchymal and intraventricular hemorrhage in a full-term neonate is reported. The underlying cause in our patient is thought to be related to cerebral sinovenous occlusive disease secondary to Protein C deficiency, a rare coagulopathy.

Congenital spondylolisthesis of the 6th cervical vertebra: CT findings.

The CT demonstration of a case of congenital spondylolisthesis of the C6 vertebral body is reported. This entity includes bilateral bony defects in the pars interarticularis regions, deranged facet joints, as well as a midline bony cleft in the spinous process. This congenital deformity should be recognized and not mistaken for traumatic spondylolisthesis.

Imaging strategies for MR of the brain.

MR has emerged as the imaging modality of choice for the brain in patients presenting with seizures, chronic headaches, progressive neurologic deficits, ataxia, vertigo, hearing loss, visual loss, congenital abnormalities, signs of increased intracranial pressure, dementia, suspected multiple sclerosis, and in the vast majority of other elective neurologic problems. CT should currently be considered the primary imaging modality in patients with acute neurologic deficits (stroke), acute onset of severe headaches, and when fine bone detail is required. Acutely injured patients are more readily studied with CT. The vast majority of patients in whom CT is preferred are seen in emergent situations, frequently in hospital emergency rooms. The effects of trauma beyond the acute stage are best evaluated with MR. In the future, MR is likely to become the procedure of choice in even more clinical situations than at present. A summary of currently recommended primary imaging modalities in various clinical situations is provided in Table 1.

Imaging strategies for MR of the spine.

Magnetic resonance (MR) imaging has rapidly evolved as a primary modality for evaluating the spine. Following routine radiographs, MR is currently the preferred examination in evaluating patients presenting with myelopathy, suspected congenital abnormalities, discitis/osteomyelitis, and myeloradiculopathy. It is becoming the examination of choice in evaluating patients with radiculopathy as well when fast-scan techniques are available. MR of the spine will prove increasingly important as the technology advances. It is likely that MR will replace myelography entirely for many indications.

Fat within the falx: MR demonstration of falcine bony metaplasia with marrow formation.

Falcine bony metaplasia frequently is incorrectly labeled "dense calcification" on brain CT and conventional radiography. Of 3,000 brain magnetic resonance (MR) scans reviewed, 12 demonstrated a central area of increased signal intensity on T1 and T2 weighted images with a smooth peripheral rim of diminished signal intensity within the region of the falx. The central area of increased signal intensity corresponded to fat in the medullary cavity and the peripheral area of low signal intensity corresponded to cortical bone. The CT scans, available in nine of 12 patients, were compared with the MR scans and revealed dense mineralization in the corresponding region of the falx. A postmortem specimen of densely "calcified" falx cerebri was examined that revealed cortical bone and a medullary cavity complete with bony trabeculae and marrow. The MR findings of falx ossification should not be confused with other entities of greater clinical significance.

Double discontinuous lipomyelomeningocele: CT findings.

A 3-year-old girl with repaired cloacal exstrophy and two skin-covered dorsal lumbosacral masses was documented to have two lipomyelomeningoceles at noncontiguous levels of a tethered spinal cord. The clinical, radiographic, myelographic, CT, and surgical appearances are presented to illustrate the features of this extremely rare anomaly.