Do All Patients with Multiple Sclerosis Benefit from the Use of Contrast on Serial Follow-Up MR Imaging? A Retrospective Analysis.

BACKGROUND AND PURPOSE: Patients with multiple sclerosis routinely have MR imaging with contrast every 6-12 months to assess response to medication. Multiple recent studies provide evidence of tissue deposition of MR imaging contrast agents, questioning the long-term safety of these agents. The goal of this retrospective image-analysis study was to determine whether contrast could be reserved for only those patients who show new MS lesions on follow-up examinations. MATERIALS AND METHODS: We retrospectively reviewed brain MRIs of 138 patients. To increase our sensitivity, we used a previously described computerized image-comparison software to evaluate the stability or progression of multiple sclerosis white matter lesions in noncontrast FLAIR sequences. We correlated these findings with evidence of contrast-enhancing lesions on the enhanced T1 sequence from the same scan. RESULTS: Thirty-three scans showed an increase in white matter lesion burden. Among those 33 patients, 14 examinations also demonstrated enhancing new lesions. While we found a single example of enhancement of a pre-existing white matter lesion that appeared unchanged in size, that same examination showed an overall increase in lesion burden with enhancement of other, new lesions. Thus, we found that all patients with enhancing lesions had evidence of progression on their noncontrast imaging. CONCLUSIONS: Because all enhancing lesions were associated with new lesions on unenhanced imaging and progression was only evident in 24% of patients, in patients with relapsing-remitting MS, it is reasonable to consider reserving contrast for only those patients with evidence of progression on noncontrast MR images.

Imaging characteristics of the subdural evacuating port system, a new bedside therapy for subacute/chronic subdural hematoma.

The Subdural Evacuating Port System is a new device intended to simplify the treatment of subacute/chronic subdural hematomas. The appearance of the winged canula positioned with its tip in the diploic space overlying the subdural space should allow the radiologist to identify it correctly. Its radiographic features are described here to help the radiologist comment on appropriate placement, and avoid mistaking it for a misplaced subdural drain.

Delayed sequelae after acute overdoses or poisonings: cranial neuropathy related to ethylene glycol ingestion.

A 31-year-old woman came to the hospital with breathlessness, confusion, and a refractory anion gap metabolic acidosis; acute renal failure subsequently developed. Her blood ethylene glycol concentration was 390 mg/L, and she was treated with an intravenous ethanol infusion and hemodialysis. During the tenth and eleventh day after admission bilateral seventh cranial nerve paralysis developed, as well as bilateral dysfunction of cranial nerves II, V, VIII, IX, X and XII. Magnetic resonance imaging of her head showed gadolinium enhancement of the fifth cranial nerve bilaterally and a communicating hydrocephalus. Over the subsequent 11 months she recovered full function of her cranial nerves V, VII, IX, X, and XII, and she had subjective clinical improvement to baseline function in cranial nerves II and VIII. This case serves to introduce a discussion of agents that cause delayed complications after their acute toxic ingestion.

Isolated inferior oblique paresis from brain-stem infarction. Perspective on oculomotor fascicular organization in the ventral midbrain tegmentum.

We present the case of an isolated inferior oblique muscle paresis from ventral midbrain infarction involving the oculomotor fascicular fibers. Based on this case and a review of the literature, the anatomic organization of the oculomotor nerve fascicles and of the pupillary fibers in the ventral midbrain tegmentum is proposed.

Brain activation during working memory 1 month after mild traumatic brain injury: a functional MRI study.

OBJECTIVE: To assess patterns of regional brain activation in response to varying working memory loads shortly after mild traumatic brain injury (MTBI). BACKGROUND: Many individuals complain of memory difficulty shortly after MTBI. Memory performance in these individuals can be normal despite these complaints. METHODS: Brain activation patterns in response to a working memory task (auditory n-back) were assessed with functional MRI in 12 MTBI patients within 1 month of their injury and in 11 healthy control subjects. RESULTS: Brain activation patterns differed between MTBI patients and control subjects in response to increasing working memory processing loads. Maximum intensity projections of statistical parametric maps in control subjects showed bifrontal and biparietal activation in response to a low processing load, with little additional increase in activation associated with the high load task. MTBI patients showed some activation during the low processing load task but significantly increased activation during the high load condition, particularly in the right parietal and right dorsolateral frontal regions. Task performance did not differ significantly between groups. CONCLUSION: MTBI patients differed from control subjects in activation pattern of working memory circuitry in response to different processing loads, despite similar task performance. This suggests that injury-related changes in ability to activate or to modulate working memory processing resources may underlie some of the memory complaints after MTBI.

Paternally derived de novo interstitial duplication of proximal 15q in a patient with developmental delay.

Interstitial duplications of proximal 15q containing the Prader-Willi syndrome/Angelman syndrome (PWS/AS) region have been found in patients with autism or atypical autism. In these cases with an abnormal phenotype, the duplications were maternally derived. Paternal origin of the duplication has been associated with a normal phenotype. We report on a patient who presented with nonspecific developmental delay and partial agenesis of the rostral corpus callosum. Fluorescence in situ hybridization (FISH) studies using probes specific for the PWS/AS region demonstrated a double signal on one chromosome 15, indicating the presence of an interstitial duplication of proximal 15q involving the PWS/ AS region in the patient. Parental chromosomes were normal with FISH studies. Methylation analysis at exon alpha of the SNRPN locus showed a maternal band at 4.2 kb and a paternal band of apparent double intensity at 0.9 kb, suggestive of one copy of the maternal allele and two copies of the paternal allele in the patient. Microsatellite analysis was informative at the GABRB3 locus in the family, which showed the inheritance of two different paternal alleles and a maternal allele in the patient consistent with the origin of this duplication from an unequal crossing over between the two chromosome 15 homologs in the father. This is the first report of an abnormal phenotype associated with a paternally derived duplication of proximal 15q shown to contain the PWS/AS region by molecular techniques.

Cerebral glycogenosis, alpha particle type: morphologic and biochemical observations in an infant.

A 3-month-old infant with congenital hypotonia suffering from an unusual form of glycogenosis is reported. The most striking neuropathologic findings were vacuolation of neuropile and glycogen accumulation, especially in the cerebral cortex and cerebellar molecular layer. Ultrastructurally, glycogen accumulation was present mainly in neurites and astrocytic processes, and mostly appeared as rosettes (alpha glycogen particles). Biochemical analysis of glycogen in various regions of the central nervous system showed an increase of up to 100-fold. The cerebral cortex, deep nuclei, and cerebellar cortex had the highest glycogen elevations, while the cerebral white matter glycogen level was normal. Among other tissues, the heart showed a several-fold increase in glycogen content. Muscle, liver, and kidney glycogen levels were not elevated. Findings in this case and in three other reported patients with cerebral glycogenosis of alpha particle type are discussed.

Magnetic resonance imaging in pituitary apoplexy.

The diagnosis of pituitary apoplexy, an often-fatal disorder, is frequently delayed. Computed tomographic (CT) scanning has been shown to be useful in the detection of pituitary apoplexy; however, the value of magnetic resonance imaging (MRI) is yet to be determined. The MRI and CT scans of three consecutive and histopathologically proved cases of pituitary apoplexy were reviewed. The MRI scans obtained at least five days after the onset of symptoms suggested pituitary apoplexy (hemorrhage) in all three cases, while CT scanning indicated pituitary hemorrhage in only one case. Increased signal on the T1-weighted image was the hallmark on MRI scans in all three cases. These findings suggest that MRI scanning may be superior to CT scanning in identifying pituitary apoplexy, at least in the subacute phase.

Asymmetric mamillary bodies: MR identification.

We report three cases in which there was marked asymmetry of the mamillary bodies, noted on MR in two and at autopsy in the third. Based on its proposed pathogenesis, we suggest that this finding could have value in locating temporal lobe disease in patients with intractable epilepsy.

MR of giant arachnoid granulation, a normal variant presenting as a mass within the dural venous sinus.

We report three cases of masses within the cerebral dural venous sinuses shown with either MR or angiography. The dural venous sinuses of 10 patients without known venous disease were examined at autopsy. In two patients, three giant arachnoid granulations were identified. On the basis of the literature and our limited autopsy series, we suggest that these lesions identified at imaging are giant arachnoid granulations, normal variants of no known clinical significance.

Neonatal pontomedullary disconnection with aplasia or destruction of the lower brain stem: a case of pontoneocerebellar hypoplasia?

We report a neonate who presented with marked hypotonia and absent suck reflex. MR demonstrated complete absence of the pons as well as absence of a basilar artery flow void. Our case exhibits features similar to those described in previous reports of pontoneocerebellar hypoplasia, but with a more severe degree of pontine involvement. The associated vascular findings suggest a vascular insult to the brain stem as the cause.

Pineal cysts: MR imaging.

MR brain scans of 672 consecutive patients were examined prospectively to determine the incidence of high-signal pineal glands on T2-weighted images. The scans were obtained on either a 0.15-T or 0.5-T unit. This finding was present in 29 patients, none of whom had hydrocephalus or symptoms of a pineal mass. A CT scan was available in 17 of these cases and none of these demonstrated a solid pineal mass. Because of the frequency of this observation (4.3%) and the absence of associated findings, it was concluded that benign pineal cysts are the most likely explanation for this high signal. It is important for the radiologist to consider benign cysts in the differential diagnosis of a bright pineal gland on T2-weighted MR images.

Aqueduct compression from venous angioma: MR findings.

Vascular compression as the cause of aqueductal stenosis is rare. In a 16-year-old girl with hydrocephalus, MR imaging provided evidence of aqueductal stenosis caused by a venous angioma in the tectum and midbrain. This indicates the usefulness of MR imaging for the evaluation of obstructive hydrocephalus.

Venous hypertension associated with a posterior fossa dural arteriovenous fistula: another cause of bithalamic lesions on MR images.

We report a case of a posterior fossa arteriovenous fistula (AVF) with bithalamic hyperintensity of MR images. The thalamic abnormality improved after surgery, suggesting reversible venous hypertension as the pathogenesis of the finding, as opposed to infarction. This manifestation of a posterior fossa AVF should be considered in the differential diagnosis of bilateral thalamic disease.

The asymmetric mamillary body: association with medial temporal lobe disease demonstrated with MR.

PURPOSE: To determine whether mamillary body atrophy is caused by deafferentation of the mamillary body in patients with mesial temporal sclerosis. METHODS: We studied 36 patients with thin-section MR to assess mamillary body symmetry. These patients included 10 control subjects without seizures and 26 patients with a history of seizures. Thin-section T1 scans were available for all cases. The patients with epilepsy underwent axial and coronal T2 scans as well. RESULTS: In five of eight cases with prior medial temporal lobe resection for intractable epilepsy, there was evidence of unilateral mamillary body atrophy ipsilateral to the resection. Similar findings were evident in three of six patients with MR findings of mesial temporal sclerosis without surgery. Two patients with medial temporal stroke or tumor also had ipsilateral mamillary body atrophy. CONCLUSION: These findings provide support for the proposed mechanism of mamillary body atrophy caused by prior medial temporal lobe injury.

Intradural lumbar disk fragment with ring enhancement on MR.

Intradural extension of a herniated intervertebral disk, an unusual complication of a common disease, may mimic an intradural tumor on MR. A case of a pathologically proved subdural disk fragment is presented; MR findings that suggested the correct diagnosis were: proximity of intervertebral disk disease; whorl-like mixed intensity on T2-weighted images; poor visualization of the mass on unenhanced T1-weighted images; and marked ring enhancement following administration of gadolinium.

Colloid cyst of the third ventricle: sometimes more conspicuous on CT than MR.

We present two cases of surgically proved colloid cysts that were more apparent on CT scans than on MR images. These cysts, while hyperdense on CT scans, were nearly isointense with brain on multiple MR sequences. This relative lack of visibility represents a potential pitfall when imaging a patient with headache.

Visualization of intravenously administered contrast material in the CSF on fluid-attenuated inversion-recovery MR images: an in vitro and animal-model investigation.

BACKGROUND AND PURPOSE: The FLAIR (fluid-attenuated inversion-recovery) pulse sequence has been shown to be sensitive to abnormalities of the subarachnoid space. Our clinical experience led us to investigate whether intravenously injected contrast material can affect the appearance of the subarachnoid space on FLAIR MR images. METHODS: After noting unexplained high signal in the subarachnoid space on FLAIR images in a patient, we studied two dogs with sequential FLAIR MR imaging after i.v. administration of contrast material. A third dog was studied with a 6-hour delayed FLAIR sequence after triple-dose (0.3 mmol/kg) i.v. contrast administration. CSF was obtained from two animals for measurement of gadolinium concentration. A phantom was developed to determine the lowest concentration at which the effects of gadolinium were evident on FLAIR images in vitro. RESULTS: In all three animals, the appearance of the CSF in the ventricles or subarachnoid space was modified after administration of i.v. contrast. This was most evident on delayed images. The CSF samples showed a gadolinium concentration of 0.007 mmol/L in the dog who received the 0.1 mmol/kg dose and 0.02 mmol/L in the dog who received a triple dose. In our in vitro phantom experiments, gadolinium effects were evident on FLAIR images at a concentration four times lower than those on T1-weighted images. CONCLUSION: I.v. contrast material can cross into the CSF in sufficient concentration to alter the appearance of the subarachnoid space on FLAIR images in normal dogs. Although we encountered two patients with CNS disease in whom enhancement of the CSF was seen on postcontrast FLAIR images, additional investigation is needed in humans to determine whether enhancement may occur at triple dose in healthy subjects.

Classification of biopsy-confirmed brain tumors using single-voxel MR spectroscopy.

BACKGROUND AND PURPOSE: Our purpose was to develop a classification scheme and method of presentation of in vivo single-voxel proton spectroscopic data from astrocytomas that most closely match the classification scheme determined from biopsy specimens. Since in vivo proton spectroscopy is noninvasive, it may be an attractive alternative to intracranial biopsy. METHODS: Single-voxel spectra were acquired using the point-resolved spectroscopic pulse sequence as part of the Probe spectroscopy package on a G.E. 1.5-T Signa scanner. Subjects consisted of 27 patients with biopsy-confirmed brain tumors (13 with glioblastoma multiforme, six with anaplastic astrocytoma, and eight with low-grade astrocytoma). The patients were divided into groups based on the histologic subtype of their tumor for different treatment protocols. RESULTS: Metabolic peak areas were normalized for each metabolite (choline, creatine, N-acetylaspartate, lactate) to the area of the unsuppressed water peak and to the area of the creatine peak. Kruskal-Wallis nonparametric analysis of variance (ANOVA) tests showed statistically significant differences among the tumor groups for all the area ratios. The lactate/water ratio could be used to distinguished all three tumor groups, whereas the choline/water ratio distinguished low-grade astrocytomas from the two high-grade groups. Both the choline and lactate ratios could be used to separate the high-grade from the low-grade tumors. CONCLUSION: Specific relative metabolic peak area ratios acquired from regions of contrast-enhancing brain tumor can be used to classify astrocytomas as to histopathologic grade.