Allen D. Elster

Klippel-feil syndrome: Ct and mr of acquired and congenital abnormalities of cervical spine and cord

We reviewed MR and CT myelographic studies in patients with the Klippel-Feil syndrome (KFS) to determine the patterns of associated congenital and acquired abnormalities of the spine and spinal cord and to correlate these radiologic findings with the manner of clinical presentation. Twenty-four consecutive patients with radiologically definite KFS were evaluated by a cross-sectional imaging technique (CT or MR) over a 6 year period. Radiologic images were blindly interpreted by a panel of three experienced neuroradiologists and then correlated with clinical history. Cervical spondylosis or disk herniations were the most common radiologic abnormalities encountered, seen in 10 (42%) of the 24 patients. While some clustering of these secondary degenerative changes occurred at levels immediately adjacent to the fused vertebrae, in most patients spondylotic changes were seen widely distributed throughout the lower cervical region. Coexisting congenital defects of the spinal cord or brain were encountered in seven patients, six of whom were female, consisting of cervical cord dysraphism or diastematomyelia (n = 5) and Chiari I malformations (n = 2). In only eight patients (33%) had the diagnosis of KFS been suspected clinically prior to imaging by the presence of short neck, limited cervical mobility, or low occipital hairline. In the remaining 16 patients, mostly adolescents or adults being evaluated for cervical sensory or motor syndromes, the diagnosis of KFS was made radiologically at the time of the imaging referral.

Calculation of apparent diffusion coefficients (ADCs) in brain using two-point and six-point methods

We evaluated the relative accuracy of calculating apparent diffusion coefficients (ADCs) of intracranial tissues using a two-point versus a six-point regression technique. Echo planar diffusion-weighted MRI was performed at 1.5 T in three standard locations and in pathologic regions in 10 subjects using gradient strengths corresponding to b values of 1, 100, 200, 500, 800, and 1,000 s/mm2. Estimation of ADCs was made using two methods: a nonlinear regression model using measurements from the full set of b values (six-point technique) and linear estimation using b values of 1 and 1,000 only (two-point technique). A high correlation between the two methods was noted (R2 = 0.999), and the mean percentage difference was 0.84%. These results suggest there is little error in estimating brain ADCs using a two-point technique.

High b-value diffusion-weighted MRI of normal brain.

Purpose As MR scanner hardware has improved, allowing for increased gradient strengths, we are able to generate higher b values for diffusion-weighted (DW) imaging. Our purpose was to evaluate the appearance of the normal brain on DW MR images as the diffusion gradient strength (“b value”) is increased from 1,000 to 3,000 s/mm 2 . Method Three sets of echo planar images were acquired at 1.5 T in 25 normal subjects (mean age 61 years) using progressively increasing strengths of a diffusion-sensitizing gradient (corresponding to b values of 0, 1,000, and 3,000 s/mm 2 ). All other imaging parameters remained constant. Qualitative assessments of trace images were performed by two neuroradiologists, supplemented by quantitative measures of MR signal and noise in eight different anatomic regions. Results As gradient strength increased from b = 1,000 to 3,000, both gray and white matter structures diminished in signal as expected based on their relative diffusion coefficients [calculated average apparent diffusion coefficient (ADC) values: gray matter = 8.5 × 10 −4 mm 2 /s, white matter = 7.5 × 10 −4 mm 2 /s]. The signal-to-noise ratios for the b = 1,000 images were approximately 2.2 times higher than for the b = 3,000 images (p < 0.0001). As the strength of the diffusion-sensitizing gradient increased, white matter became progressively hyperintense to gray matter. Relative to the thalamus, for example, the average MR signal intensity of white matter structures increased by an average of 27.5%, with the densely packed white matter tracts (e.g., middle cerebellar peduncle, tegmentum, and internal capsule) increasing the most. Conclusion Brain DW images obtained at b = 3,000 appear significantly different from those obtained at b = 1,000, reflecting expected loss of signal from all areas of brain in proportion to their ADC values. Consequently, when all other imaging parameters are held constant, b = 3,000 DW images appear significantly noisier than b = 1,000 images, and white matter tracts are significantly more hyperintense than gray matter structures.

Angiotropic Intravascular Large-Cell Lymphoma (Malignant Angioendotheliomatosis): Report of a Case and Review of the Literature

We present a case of angiotropic large-cell lymphoma and review the literature in order to define the neurologic features of this rare disorder. This is the first report of gadolinium-DTPA imaging in angiotropic large-cell lymphoma that demonstrates infarcts of multiple ages, as well as striking meningeal enhancement. Angiotropic large-cell lymphoma should be suspected in patients with clinical evidence of small and large cerebral vessel disease and diagnosis requires skin, liver, renal, meningeal, or brain biopsy. Single modality treatment, using either radiation therapy or steroids, has been ineffective, and new findings of a lymphomatous origin of this neoplasm suggest that combination chemotherapy may be indicated.

Neurosarcoidosis: gadolinium-enhanced MR imaging.

Two cases of neurosarcoidosis studied by Gd-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging are reported. Both patients demonstrated multifocal white matter abnormalities that were clustered near regions of intense meningeal enhancement. Presumed spread of neurosarcoidosis along Virchow-Robin spaces was demonstrated, as evidenced by contrast enhancement along the course of vessels supplying some of the white matter abnormalities.

Gadolinium‐enhanced MRI: A superior technique for the diagnosis of intraspinal metastases

Intraspinal medullary metastases are difficult to demonstrate radiographically. We describe the value of gadolinium-DTPA-enhanced magnetic resonance imaging in the diagnosis of intraspinal medullary metastases. This safe, sensitive procedure should be a requisite study in myelogram-negative patients with symptomatology indicative of a cord lesion.

Sexual dimorphism of the human corpus callosum studied by magnetic resonance imaging: Fact, fallacy and statistical confidence

Magnetic resonance (MR) imaging was performed in 120 normal right-handed individuals (60 males, 60 females) to clarify existing contradictory data concerning possible sexual dimorphism of the human corpus callosum (CC). Five linear and three area measurements of the CC and brain were obtained directly at the MR scanner console from midline sagittal T1-weighted images. The anteroposterior length of the CC was significantly larger in males than in females (p = 0.0005). No other differences in absolute callosal measurements between the sexes could be demonstrated. However, several size ratios did achieve statistical significance (p less than 0.05), being consistently larger in females: splenial width/length CC, splenial width/brain length, and area of CC/area of brain. Where no statistically significant differences were obtained, precision, tolerance, and confidence interval calculations are presented. The data in this large series support a limited but definite sexual dimorphism of the CC in right-handed individuals.

Diffusion-weighted imaging of cerebral infarctions: are higher B values better?

Purpose The purpose of this work is to determine whether high b-value (b = 3,000 s/mm2) diffusion-weighted (DW) imaging is superior to low b-value (b = 1,000 s/mm2) DW imaging for the detection of cerebral infarctions older than 6 h. Method Echo planar DW imaging was performed at 1.5 T in 26 consecutive patients (mean age 66 years) referred for clinical diagnosis of definite acute/subacute cerebral infarction (6 h to 14 days old). The DW imaging sequences were performed using matched parameters (TR = 10,000 ms, TEeff = 97 ms, FOV = 24 cm, 128 × 192 matrix, slice = 5 mm, NEX = 2) with b values of 1,000 and 3,000 s/mm2. Areas of infarction were compared visually by two experienced neuroradiologists. Quantitative measures of MR signal and noise levels in the infarcted areas compared with contralateral normal brain were also obtained. Results The median time after infarction was 2.5 days (range 10 h to 14 days). By visual inspection, all infarctions were reliably identified on both the b = 1,000 and the b = 3,000 images. The gross signal ratio (infarct/normal brain) was approximately 33% higher in the b = 3,000 images, but the b = 3,000 images were rated as noticeably “noisier” by both observers in every case. This visual observation was confirmed quantitatively: The signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were 70% and 51% higher in the b = 1,000 than the b = 3,000 images (p < 0.0005 for both). Conclusion For the evaluation of late acute/subacute cerebral infarctions, high b-value (b = 3,000 s/mm2) DW imaging offers no apparent diagnostic advantages compared with b = 1,000 images and is significantly inferior in terms of SNR and CNR.

Cranial MR imaging in hypomelanosis of Ito.

Hypomelanosis of Ito (HI) is a rare neurocutaneous syndrome frequently associated with neurologic abnormalities. Approximately 95 cases have been reported in the literature. Intracranial findings demonstrated by magnetic resonance imaging in a patient with HI include hemimegalencephaly, abnormal white matter signal, and small discrete bilateral periventricular cysts. No gray matter heterotopias or other migrational abnormalities were identified. Periventricular cystic lesions have not been described previously in this condition.

Hypertensive Encephalopathy in Children: Neuroimaging and Treatment

nance imaging (MRI) scans of patients with hypertensive encephalopathy have indicated edema in the cortex and subcortical white matter of the occipital lobes. 6-8 However, the majority of these patients were either adults with nonobstetric problems or obstetric patients who had preeclampsia or eclampsia syndrome. Only a few cases were children. We report the findings of brain MRI and CT scans in two children who had hypertensive encephalopathy, discuss the similarities to adult cases, and relate these findings to pathogenesis and treatment.