Faculty Bibliography

BACKGROUND AND PURPOSE: Despite the ubiquity of G(M2) gangliosides accumulation in patients with late-onset G(M2) gangliosidosis (G(M2)G), the only clinical MR imaging-apparent brain abnormality is profound cerebellar atrophy. The goal of this study was to detect the presence and assess the extent of neuroaxonal injury in the normal-appearing gray and white matter (NAGM and NAWM) of these patients. METHODS: During a single imaging session, 9 patients with late-onset G(M2)G and 8 age-matched normal volunteers underwent the following protocol: (1) T1- and T2-weighted and fluid-attenuated inversion recovery MR images, as well as (2) multivoxel proton MR spectroscopy (1H-MR spectroscopy) to quantify the distribution of the n-acetylaspartate (NAA), creatine (Cr), and choline (Cho), were obtained. RESULTS: The patients' NAA levels in the thalamus (6.5 +/- 1.9 mmol/L) and NAWM (5.8 +/- 2.1 mmol/L) were approximately 40% lower than the controls' (P = .003 and P = .005), whereas the Cr and Cho reductions ( approximately 30% and approximately 26%) did not reach significance (P values of .06-.1). All cerebellar metabolites, especially NAA and Cr, were much (30%-90%) lower in the patients, which reflects the atrophy. CONCLUSION: In late-onset G(M2)G, NAA decreases are detectable in NAGM and NAWM even absent morphologic (MR imaging) abnormalities. Because the accumulation of G(M2) gangliosides can be reduced pharmacologically, 1H-MR spectroscopy might be a sensitive and specific for detecting and quantifying neuroaxonal injury and monitoring response to emerging treatments

BACKGROUND AND PURPOSE: Patients with nonlesional temporal lobe epilepsy have long been known to have abnormalities of memory. Recently, these patients have been shown to have increased diffusivity in the hippocampus. We hypothesized that in these patients, a negative correlation would exist between diffusivity measures of the mesial temporal lobe and performance on neuropsychological tests. METHODS: Twenty presurgical patients with temporal lobe epilepsy and 20 age- and sex-matched healthy controls underwent MR imaging of the brain. Apparent diffusion coefficient region of interest measures were taken in both hippocampi and parahippocampal gyri by 2 independent observers. Mean whole brain diffusivity was calculated. All patients completed neuropsychological testing. Electroencephalogram and pathology results were collected. Patients and controls were compared with respect to each apparent diffusion coefficient measure. In patients, apparent diffusion coefficients ipsilateral and contralateral to the seizure focus were compared. Associations were assessed between diffusivity measures and neuropsychological scores. RESULTS: Eleven patients had right-sided seizure foci and 9 had left-sided seizure foci. Patients demonstrated higher apparent diffusion coefficient values than controls over the whole brain, in the hippocampi, and in the parahippocampal gyri (P < .05). Patients demonstrated higher apparent diffusion coefficient within the ipsilateral hippocampus (1.19 +/- 0.22 x 10(-3) s/mm2) and parahippocampal gyrus (1.02 +/- 0.12 x 10(-3) s/mm2) compared with the contralateral side (1.02 +/- 0.16 x 10(-3) s/mm2 and 0.96 +/- 0.09 x 10(-3) s/mm2, respectively) (P < .05). Negative correlations were seen between hippocampal apparent diffusion coefficients and multiple memory tests (P < .05). CONCLUSION: Quantitative diffusion measurements in the hippocampus correlate with memory dysfunction in patients with temporal lobe epilepsy

BACKGROUND AND PURPOSE: We used quantitative diffusion MR imaging to investigate the microstructural changes that occur in white matter during normal aging in order to identify regional changes in anisotropy and to quantify global microstructural changes by use of whole-brain diffusion histograms. METHODS: Full diffusion tensor MR imaging was performed in 20 healthy volunteers, 20 to 91 years old. Thirteen subjects also underwent high-resolution T1-weighted imaging, so that diffusion images could be coregistered and standardized to normal coordinates for statistical probability mapping. Relative anisotropy (RA) was calculated, as was linear regression of RA with age for each pixel; pixels with a significant correlation coefficient were displayed. For histographic analysis, the average apparent diffusion coefficient (ADC) histograms were calculated on a pixel-by-pixel basis. Subjects were divided into two equal groups by the median age (55 years) of the population and plotted for statistical comparison. RESULTS: Regional analysis showed statistically significant decreases in RA with increasing age in the periventricular white matter, frontal white matter, and genu and splenium of the corpus callosum, despite the absence of signal abnormalities on visual inspection of conventional images. Significant increases in RA were found in the internal capsules bilaterally. ADC histograms showed higher mean ADC and reduced peak height and skew in the older age group on group comparisons. CONCLUSION: Quantitative diffusion histograms correlate with normal aging and may provide a global assessment of normal age-related changes and serve as a standard for comparison with neurodegenerative diseases

This study used fMRI to examine the response of the amygdala in the evaluation and short-term recognition memory of unpleasant vs. neutral words in nine right-handed healthy adult women. To establish specificity of the amygdala response, we examined the fMRI BOLD signal in one control region (visual cortex). Alternating blocks of unpleasant and neutral trials were presented. During the emotional decision task, subjects viewed sets of three unpleasant or three neutral words while selecting the most unpleasant or neutral word, respectively. During the memory task, subjects identified words that were presented during the emotional decision task (0.50 probability). Images were detrended, filtered, and coregistered to standard brain coordinates. The Talairach coordinates for the center of the amygdala were chosen before analysis. The BOLD signal at this location in the right hemisphere revealed a greater amplitude signal for the unpleasant relative to the neutral words during the emotional decision but not the memory task, confirmed by Time Course x Word Condition ANOVAs. These results are consistent with the memory modulatory view of amygdala function, which suggests that the amygdala facilitates long-term, but not short-term, memory consolidation of emotionally significant material. The control area showed only an effect for Time Course for both the emotional decision and memory tasks, indicating the specificity of the amygdala response to the evaluation of unpleasant words. Moreover, the right-sided amygdala activation during the unpleasant word condition was strongly correlated with the BOLD response in the occipital cortex. These findings corroborate those by other researchers that the amygdala can modulate early processing of visual information in the occipital cortex. Finally, an increase in subject's state anxiety (evaluated by questionnaire) while in the scanner correlated with amygdala activation under some conditions

OBJECTIVE: Relative hypointensity on T1-weighted MR imaging has been suggested as a putative disability marker. The purpose of our study was to determine if there are quantifiable diffusion differences among focal multiple sclerosis lesions that appear differently on conventional T1-weighted MR images. We hypothesized that markedly hypointense lesions on unenhanced T1-weighted images would have significantly increased diffusion compared with other lesions, and enhancing portions of lesions would have different diffusion compared with nonenhancing lesions. SUBJECTS AND METHODS: Average apparent diffusion coefficient (ADC) was calculated for 107 lesions identified on T2-weighted images in 16 patients with multiple sclerosis and was compared with the ADC of normal white matter in 16 age- and sex-matched control subjects. Seventy-five nonenhancing lesions (29 isointense, 46 hypointense) and 32 enhancing lesions (6 isointense, 26 hypointense) were categorized on the basis of unenhanced T1-weighted MR imaging. RESULTS: Hypointense and isointense nonenhancing lesions both showed significantly higher ADC than normal white matter (p < 0.0001). Hypointense nonenhancing lesions showed higher ADC values than isointense nonenhancing lesions (p < 0.0001). Diffusion in enhancing portions of enhancing lesions was decreased when compared with nonenhancing portions. CONCLUSION: Quantitative diffusion data from MR imaging differ among multiple sclerosis lesions that appear different from each other on T1-weighted images. These quantitative diffusion differences imply microstructural differences, which may prove useful in documenting irreversible disease

OBJECTIVE: To determine whether quantitative whole-brain MR diffusion histograms in patients with MS differ from those of normal control subjects. BACKGROUND: MRI detects macroscopic cerebral lesions in MS, but the white matter lesion burden on MRI correlates imperfectly to clinical disability. Previous reports have further suggested abnormalities in white matter of MS patients with no visible lesions on conventional MRI. METHODS: A total of 25 subjects (13 with MS [9 relapsing-remitting, 4 secondary progressive] and 12 healthy control subjects) underwent diffusion-weighted echoplanar MRI encompassing the entire brain. The average apparent diffusion coefficient (ADCave, or diffusion trace) was calculated on a pixel-by-pixel basis after segmentation of intracranial space from calvarium and extracranial soft tissues. Whole-brain ADCave histograms were calculated and plotted for statistical comparison. RESULTS: Mean whole-brain MR ADCave in MS patients was elevated and histograms were shifted to higher values compared with normal control subjects. Mean whole-brain ADCave of secondary progressive patients was shifted to higher values compared with relapsing-remitting patients. Whole-brain ADCave histograms of relapsing-remitting patients showed no significant difference from normal control subjects. CONCLUSION: Whole-brain MR diffusion histograms may quantitate overall cerebral lesion load in patients with MS and may be able to discern differences between clinical subgroups

OBJECTIVE: To discuss the computed tomographic (CT) and clinical findings of those entities that may present as recurrent deep neck infections. PATIENTS AND METHODS: Twelve patients with recurrent deep neck infections and CT scans were retrospectively identified since 1990. Their CT scans and medical histories were reviewed. The diagnosis was pathologically confirmed in all cases. RESULTS: The CT scans revealed an abscess or a localized infected cyst in the deep soft tissues of the neck, with varying degrees of associated inflammatory change in the adjacent soft tissues. The diagnoses in these cases included 1 first branchial cleft cyst, 3 second branchial cleft cysts, 1 third branchial cleft cyst, 2 fourth branchial cleft cysts, 2 infected lymphangiomas, 2 thyroglossal duct cysts, and 1 cervical thymic cyst. CONCLUSIONS: Most deep neck infections are the result of suppurative adenitis. The location of the primary focus is usually from the mucosa of the upper aerodigestive tract or from an odontogenic source. Less common causes are perforations due to a foreign body, thrombophlebitis of the internal jugular vein, or osteomyelitis of the spine. Recurrences in these situations are unusual. Less commonly, congenital lesions can present as deep neck infections, and recurrences are common. Our cases suggest that the recurrence of a deep neck infection should alert the physician to the possibility of an underlying congenital lesion and that CT is helpful in the early recognition of these lesions

Involvement of the brain and meninges is rare in Wegener's granulomatosis (WG); it has been reported in 1.2-8 % of patients. Meningeal involvement in WG has been reported in imaging as being confined to the dura mater, and is thought to represent granulomatous infiltration. We present a case of WG with abnormal pial enhancement and involvement of the perivascular spaces on MRI, pathologically proven to represent granulomatous infiltration due to the primary disease rather than to infection

Peritumoral edema and contrast enhancement of brain tumors are both thought to be due to breakdown of the blood-brain barrier (BBB); however, the exact mechanism by which these two phenomena occur and whether there is a quantitative or etiological relationship is not known. Our purpose was to determine whether the relationship between the breakdown of the BBB, defined radiologically as the degree of contrast enhancement, and the volume of surrounding edema is different for high-grade gliomas and meningiomas. We analyzed 13 meningiomas and 23 gliomas. A direct linear relationship between the degree of contrast enhancement (dC) and volume of peritumoral edema (V) with a high correlation coefficient (R = 0.66, P = 0.0006) was established for gliomas. A mathematical relationship between dC and V could not be established for meningioma. The findings for gliomas offer indirect radiological evidence that the defect in the BBB which causes edema is quantitatively and etiologically related to the defect in the BBB responsible for contrast enhancement. For meningiomas, the lack of a relationship between dC and V implies either that the mechanisms responsible for formation of edema and contrast enhancement are fundamentally different or that a physical barrier in certain meningiomas limits propagation of edema into the adjacent white matter