Faculty Bibliography

PURPOSE: To assess for the presence of microscopic abnormalities in otherwise normal-appearing white matter on T2-weighted images in patients with multiple sclerosis (MS) by using magnetization-transfer (MT) measurements. MATERIALS AND METHODS: Twenty-three patients with MS and nine healthy control subjects underwent magnetic resonance (MR) imaging with a 1.5-T system. MT ratios (MTRs) were measured in 16 areas of normal-appearing white matter identified on conventional T2-weighted images in patients with MS. MTRs in the same white-matter locations in control subjects were determined. The two groups were compared. RESULTS: The mean whole-brain MTR of normal-appearing white matter in patients was 40.13% +/- 1.37 (standard deviation; range, 36.31%-42.09%); in control subjects, 42.93% +/- 0.95 (range, 41.62%-44.50%). The difference was statistically significant (P < or = .001). Except for the internal capsules, the difference in mean MTRs in each sublocation of the brain between patients and control subjects was statistically significant (P < or = .05). CONCLUSION: MT measurements are more sensitive than conventional MR imaging in the detection of abnormalities beyond the resolution of T2-weighted imaging

PURPOSE: To investigate the relationship between the appearance of multiple sclerosis lesions identified on unenhanced T1-weighted images and their corresponding magnetization transfer ratios. METHODS: A total of 119 white matter lesions seen on T2-weighted images in 17 patients with multiple sclerosis were evaluated. Axial T1-weighted images were used to classify the lesions as isointense to white matter (10 lesions), hypointense to white matter but hyperintense to gray matter (44 lesions), hypointense to gray matter (59 lesions), and relatively isointense to cerebrospinal fluid (6 lesions). The magnetization transfer ratio of each lesion was calculated, and an average magnetization transfer ratio for each subcategory was determined. RESULTS: The magnetization transfer ratio values became progressively lower with increasing hypointensity of lesions on T1-weighted images. The average magnetization transfer ratio for lesions isointense to white matter, hypointense to white matter but hyperintense to gray matter, hypointense to gray matter, and relatively isointense to cerebrospinal fluid was 34.90 +/- 2.67 mean +/- SD), 30.93 +/- 3.57, 27.27 +/- 3.56, and 23.62 +/- 2.83, respectively. All groups were significantly different from each other. CONCLUSION: Lesions isointense to white matter exhibited higher magnetization transfer ratio values than lesions that were hypointense. These findings are consistent with relative preservation of the myelin structure in the former, perhaps indicating that these lesions are predominantly inflammatory (edematous) in nature. The proportionately lower magnetization transfer ratio values of lesions that appear progressively more hypointense on T1-weighted images may reflect varying degrees of demyelination, with increasing lesion hypointensity corresponding to more breakdown in the macromolecular structure. These results suggest that T1-weighted images may be useful in characterizing the underlying pathologic substrate in multiple sclerosis plaques

CAVERNOUS MALFORMATIONS ARE uncommon lesions that are usually present in the cerebral hemispheres. Less frequently, these malformations are seen in the brain stem, basal ganglia, or paraventricular regions. We report four cases of cavernous malformations of the third ventricle. Patients presented with symptoms of hydrocephalus, memory loss, and signs of hypothalamic dysfunction. Magnetic resonance imaging and computed tomography provided characteristic images of the three lesions preoperatively. All patients underwent direct surgical excision of the malformations. Two patients had a transcallosal, transventricular approach, the third underwent a transcortical, transventricular approach, and the fourth had an infratentorial supracerebellar approach. Postoperatively, the patient with hypothalamic dysfunction has not improved and underwent ventriculoperitoneal shunting. The second patient did well initially; however, 8 days postoperatively, she became comatose and later died. The presumed cause of her deterioration was a hypothalamic venous infarction. The third and fourth patients have returned to their normal neurological baseline. The presenting signs and symptoms, magnetic resonance imaging and computed tomography findings, and treatment options for this rare lesion are discussed and illustrated

OBJECTIVE: Cerebral vein thrombosis (CVT) is a potentially life-threatening entity with a protean clinical presentation that can lead to delays in diagnosis and treatment. Computed tomography of the brain is often the initial imaging tool in evaluation of these patients, but is frequently nondiagnostic. This study identifies subcortical hemorrhage (SCH) as an indicator of radiographically occult CVT on CT. MATERIALS AND METHODS: A retrospective analysis of all subjects (n = 24) with CVT proven by MRI over a 4 year period was performed. The CT examinations of all subjects were evaluated for the presence of SCH and signs of CVT. An evaluation of the correlation between findings on CT and MRI as well as the delay in diagnosis and treatment secondary to unrecognized CVT on CT was also performed. RESULTS: Subcortical hemorrhage was noted in 9 of 24 (38%) subjects with CVT by MRI. The CT antedated MRI in eight of these subjects as the initial evaluation for presenting neurological symptoms. Subcortical hemorrhage was noted in six of eight of these subjects as the sole CT finding. Subcortical hemorrhage as well as CVT was seen in one subject, and no abnormality was seen in the final subject. Cerebral vein thrombosis was not suggested as a diagnosis in any of the six subjects with SCH as the sole radiographic finding. In all six of these cases, a delay in diagnosis occurred pending MRI obtained subsequently secondary to clinical deterioration. CONCLUSION: Subcortical hemorrhage can be seen in association with acute CVT and can be the sole abnormality on head CT. SCH as an isolated finding on CT suggests the possibility of unrecognized CVT, warranting further investigation by MRI

PURPOSE: To evaluate penetrating neck trauma for (a) sensitivity of the clinical examination as an indicator of clinically significant vascular injury, and (b) cost-effectiveness of performing screening diagnostic angiography. METHODS: The medical records of all patients with penetrating neck trauma presenting at our institution over 4 years were retrospectively reviewed. Injuries were classified into one of three anatomic zones and classified into four mutually exclusive groups based on the extent of vascular injury; (a) no vascular injury; (b) minor vascular abnormality; (c) major vascular abnormality without a change in clinical management; or (d) any injury requiring a change in clinical management. Cost data were also obtained for each patient's hospitalization. RESULTS: There were 111 patients with penetrating neck trauma. No statistically significant difference between the sensitivities of the clinical examination or angiography for the detection of vascular injury were detected. Of the 48 patients who had vascular injuries, 45 had an abnormal clinical findings (93.7% sensitivity). None of the remaining 3 patients with vascular injury and normal clinical findings would have had their treatment altered by the results of angiography. The calculated cost of using angiography as a screening tool for vascular injury in patients with normal clinical findings was approximately $3.08 million per central nervous system event prevented. CONCLUSION: Our study suggests that in patients with zone II penetrating neck injuries the clinical examination is sufficient to detect significant vascular lesions and that screening angiography may not be indicated. Because our sample size was relatively small and the mean follow-up only 13.3 days, further investigation is needed to demonstrate definitively the lack of usefulness of screening angiography

PURPOSE: To characterize with magnetization transfer imaging the pathologic substrate of the nonspecific periventricular hyperintense white matter changes seen on T2-weighted images of elderly patients. METHODS: Twenty-one elderly patients with periventricular hyperintense white matter on T2-weighted MR images and eleven control subjects were studied using MT technique. Magnetization transfer ratios (MTRs) were calculated for the periventricular hyperintense white matter and normal-appearing white matter. These MTRs were correlated with histopathologic changes that have previously been reported as well as with established MTRs for other lesions. RESULTS: The MTRs (mean, 35.2; SD, 1.2) in the periventricular hyperintense white matter are lower than those in the normal white matter of the patient (mean, 40.8; SD, 1.4) and control (mean, 41.3; SD, 1.8) groups. These MTRs are much higher than those of demyelinating lesions but are similar to those of experimental lesions with just edema. CONCLUSION: Because MTR may reflect to some extent histopathologic changes and thus provide more specificity than conventional pulse sequences, the main pathologic substrate accounting for the lower MTR in periventricular hyperintense white matter is probably the increased water content in reactive astrocytes

OBJECTIVE. The purpose of this study was to determine whether the CT attenuation value of the lens is helpful in diagnosing acute traumatic cataracts in patients with complicated eye injuries that preclude evaluation by any other means. SUBJECTS AND METHODS. The CT attenuation values of the lenses of 69 patients with acute orbital trauma, including 24 patients with clinically and surgically diagnosed acute traumatic cataracts, were compared with attenuation values of their own contralateral lens and with the attenuation values of the lenses of 103 consecutive asymptomatic control subjects. The study group was composed of consecutive patients with unilateral orbital trauma who were clinically evaluated and referred for CT examination within 48 hr after their initial injury. In all patients, attenuation measurements of the injured lenses were obtained and compared with those of the contralateral lens as an internal control. All surgically diagnosed cataracts were histologically confirmed. RESULTS. The CT attenuation measurement of a lens in any asymptomatic control subject was identical (within the range of the standard deviation) to the measurement of the contralateral lens of that control patient. In patients with orbital injury, the CT attenuation of the patient's cataractous lens was markedly lower than in the contralateral lens (mean density difference, 30 H, p < .0001). This decreased attenuation corresponds to acute cataract formation with increased fluid within the lens. No patient with normal attenuation values of the lens in the traumatized globe (as compared with the contralateral lens) was found to have an acute traumatic cataract or have a cataract develop within a 1-year follow-up period. CONCLUSION. CT may be useful in the examination of patients with acute traumatic cataracts, unsuspected lens injury, opacification of the anterior chamber, or other injuries of the globe with complications that preclude lens evaluation by any other means. This prompt diagnosis may allow timely removal of the lens in appropriate clinical circumstances, preventing damage to the anterior chamber of the globe and other complications of delayed diagnosis and treatment. Further, normal CT findings at the time of trauma suggest that the lens will not undergo acute traumatic cataract formation

PURPOSE: To define the relationship between magnetization transfer and blood-brain-barrier breakdown in multiple sclerosis lesions using gadolinium enhancement as an index of the latter. METHODS: Two hundred twenty lesions (high-signal abnormalities on T2-weighted images) in 35 multiple sclerosis patients were studied with gadolinium-enhanced spin-echo imaging and magnetization transfer. Lesions were divided into groups having nodular or uniform enhancement, ring enhancement, or no enhancement after gadolinium administration. For 133 lesions, T1-weighted images without contrast enhancement were also analyzed. These lesions were categorized as isointense or hypointense based on their appearance on the unenhanced T1-weighted images. RESULTS: There was no difference between the magnetization transfer ratio (MTR) of lesions as a function of enhancement. MTR of hypointense lesions on unenhanced T1-weighted images was, however, lower than the MTR of isointense lesions. CONCLUSION: We speculate that diminished MTR may reflect diminished myelin content and that hypointensity on T1-weighted images corresponds to demyelination. Central regions of ring-enhancing lesions had a lower MTR than the periphery, suggesting that demyelination in multiple sclerosis lesions occurs centrifugally. In addition, the short-repetition-time pulse sequence seems useful in the evaluation of myelin loss in patients with multiple sclerosis

Evaluation of the patient with suspected vasculitis affecting the nervous system requires consideration of a broad range of differential diagnostic possibilities. Appreciating pertinent neuroradiologic findings as well as understanding the capabilities and limitations of the imaging methods employed is a prerequisite for proper evaluation. Most importantly, integration of the imaging features with clinical and laboratory findings is necessary to maximize the chance of a correct diagnosis

PURPOSE: To examine the sensitivity of proton MR spectroscopy for detecting early central nervous system abnormalities in neonates born to human immunodeficiency virus (HIV)-positive mothers. METHODS: Asleep, unsedated, and continuously monitored by electrocardiography, 10 newborns, 5 with HIV-positive and 5 with HIV-negative mothers, were studied within the first 10 days of life in a 1.5-T scanner. After T1- and T2-weighted images were obtained, proton spectra were performed using voxels of interest (3.4 cm3) in the deep parietooccipital white matter. Peaks were identified as N-acetyl-aspartate (2.0 ppm), creatine and phosphocreatine (3.0 ppm), choline (3.2 ppm), and inositol (3.5 ppm). Peak areas were used to calculate metabolic ratios: N-acetyl-aspartate to creatine, inositol to creatine, and creatine to choline. RESULTS: All newborns of HIV-positive mothers had abnormal proton spectra compared with control infants; a nonspecific amino acid peak in the 2.1- to 2.6-ppm area was elevated, broad, and overlapping the N-acetyl-aspartate peak in all the HIV-exposed newborns and in only 1 of the 5 control newborns. The choline-to-creatine ratio was higher in HIV-exposed newborns at 2.3 +/- 0.4 (normal term, 0.9 +/- 0.3), as was the N-acetyl-aspartate-to-creatine ratio at 2.6 +/- 0.9 (for control subjects, 1.2 +/- 0.4). MR images from these brain regions were all considered normal. Because acquired immunodeficiency syndrome develops in only a small fraction of neonates born to HIV-seropositive mothers, the above spectral abnormalities found in all our subjects may result from indirect effects of HIV, such as intrauterine growth retardation. CONCLUSIONS: These findings indicate that proton MR spectroscopy might play an important role in detecting early central nervous system complications in newborns of HIV-seropositive mothers