Faculty Bibliography

BACKGROUND AND PURPOSE: This study was designed to determine whether neuropsychological function in HIV-infected persons is correlated with loss of brain volume (as measured by percentage of brain parenchymal volume [PBV]). We hypothesized that whole-brain parenchymal volume might correlate with neuropsychologic performance, even before overt clinical dysfunction is apparent. METHODS: A computer-assisted segmentation technique with thin section MR imaging was used for 15 patients with HIV infection (seven symptomatic, eight asymptomatic) and for five HIV-negative control participants to quantify whole brain and CSF volumes. To determine the degree of brain atrophy, the PBV relative to that of intracranial content was calculated. Neuropsychological performance was assessed by using a standard battery of eight tests (NPZ-8 test battery). RESULTS: HIV-infected patients had significantly lower NPZ-8 scores (t[18] = 2.26, P <.05) and lower PBV (t[18] = 1.79, P <.01) than those of healthy control participants. With the Spearman rank order correlation coefficients, data analyzed for all 20 study participants (15 HIV-infected patients and five noninfected control participants) showed a significant (r = -0.50, P <.05) negative correlation between PBV and NPZ-8 test battery score. In addition, there was a significant negative correlation between subtest score of motor impairment and PBV (r = -0.69, P <.01) and between AIDS dementia complex score (r = -0.64) and PBV (P <.01). CONCLUSION: These correlations suggest that quantitation of PBV may offer an objective, easily acquired surrogate predictor of neuropsychological impairment and clinically apparent cognitive/motor dysfunction among HIV-infected persons

BACKGROUND AND PURPOSE: The T2-weighted MR imaging total lesion volume and Expanded Disability Status Scale (EDSS) score are two common measures of relapsing-remitting multiple sclerosis disability and pathologic abnormality. Because the whole-brain N-acetylaspartate concentration is considered to be a new marker of the disease burden, the purpose of this study was to evaluate the relationship among these three measures. METHODS: The whole-brain N-acetylaspartate concentration and T2-weighted lesion volume were quantified by using MR imaging and proton MR spectroscopy in 49 patients with relapsing-remitting multiple sclerosis (36 female and 13 male patients; average age, 39 years; age range, 24-55 years; average EDSS score, 2; range of EDSS scores, 0-6). Correlations among whole-brain N-acetylaspartate concentrations, T2-weighted lesion volumes, and EDSS scores were obtained. RESULTS: No correlation was found between whole-brain N-acetylaspartate levels and either T2-weighted lesion volumes or EDSS scores. A weak correlation was found between the EDSS scores and T2-weighted lesion volumes (P =.043, r(s) = 0.292). CONCLUSION: Despite the lack of correlation between whole-brain N-acetylaspartate concentration and the clinical disability reflected in the EDSS score, only the former evaluates the global neuronal cell disease in the entire brain, including those lesions that are occult to conventional imaging techniques

PURPOSE: The purpose of this work was to determine the extent of disease and disease severity in the conventional MR normal-appearing gray matter (NAGM) and white matter (NAWM) in patients with relapsing-remitting (RR) and secondary progressive (SP) multiple sclerosis (MS) utilizing quantitative magnetization transfer ratio (MTR) histogram analysis. METHOD: Twenty-seven patients with MS (16 RR, 11 SP) and 16 healthy control subjects were studied. MTR was calculated in the totally segmented GM and WM without T2 lesions in each group. RESULTS: Each of the RR and SP MS patient groups had significantly smaller MTR histogram mean values in NAGM and NAWM than the healthy subjects (p </= 0.0015). SP MS patients had a significantly lower first quartile and MTR histogram peak height for NAGM only (p </= 0.004) when compared with both RR MS patients and healthy subjects. The T2 lesion load had a modest negative correlation with MTR values in both RR and SP MS, but only in NAGM. CONCLUSION: Separate analysis of GM and WM MTR histograms may allow better detection of subtle damage and better understanding of the natural history of MS disease and ultimately the response to therapeutics

RATIONALE AND OBJECTIVES: Multiple sclerosis (MS) is an acquired disease of the central nervous system. Several clinical measures are commonly used to express the severity of the disease, including the Expanded Disability Status Scale and the ambulation index. These measures are subjective and may be difficult to reproduce. The aim of this research is to investigate the possibility of developing more objective measures derived from MR imaging. MATERIALS AND METHODS: Various magnetic resonance (MR) imaging protocols are being investigated for the study of MS. Seeking to replace the Expanded Disability Status Scale and ambulation index with an objective means to assess the natural course of the disease and its response to therapy, the authors have developed multiprotocol MR image segmentation methods based on fuzzy connectedness to quantify both macrosopic features of the disease (lesions, gray matter, white matter, cerebrospinal fluid, and brain parenchyma) and the microscopic appearance of diseased white matter. Over 1,000 studies have been processed to date. RESULTS: By far the strongest correlations with the clinical measures were demonstrated by the magnetization transfer ratio histogram parameters obtained for the various segmented tissue regions. These findings emphasize the importance of considering the microscopic and diffuse nature of the disease in the individual tissue regions. Brain parenchymal volume also demonstrated a strong correlation with clinical measures, which suggests that brain atrophy is an important disease indicator. CONCLUSION: Fuzzy connectedness is a viable, highly reproducible segmentation method for studying MS

PURPOSE: To determine the fractional brain tissue volume changes in the gray matter and white matter of patients with relapsing-remitting multiple sclerosis (MS) and to correlate these measurements with clinical disability and total lesion load. MATERIALS AND METHODS: Thirty patients with relapsing-remitting MS and 25 healthy control subjects underwent magnetic resonance imaging. Fractional brain tissue volumes (tissue volume relative to total intracranial volume) were obtained from the total segmented gray matter and white matter in each group and were analyzed. RESULTS: The fractional volume of white matter versus that of gray matter was significantly lower (-6.4%) in patients with MS (P <.0001) than in control subjects. Neither gray matter nor white matter fractional volume measurements correlated with clinical disability in the patients with MS. CONCLUSION: Loss of brain parenchymal volume in patients with relapsing-remitting MS is predominantly confined to white matter. Analysis of fractional brain tissue volumes provides additional information useful in characterizing MS and may have potential in evaluating treatment strategies

Diffusion imaging is a noninvasive technique for measuring the movement of water molecules. Although it has had its greatest impact thus far in the area of stroke imaging, the information garnered from diffusion experiments can provide an indication of myelin injury and perhaps axonal integrity. In this paper, we describe some current and potential future applications of diffusion imaging in multiple sclerosis. These include the use of global indices such as diffusion trace and anisotropy, as well as implementation of axonal fiber tracking methodologies for assessment of axonal integrity and connectivity between cortical regions

BACKGROUND AND PURPOSE: Contrast enhancement on MR images of patients with multiple sclerosis (MS) is known to be associated with abnormalities of the blood-brain barrier (BBB). However, little is known about diagnostic patterns and common features of enhanced MS lesions. This study was designed to evaluate initial enhancement patterns, changes in these enhancing patterns, and duration of enhancement in a cohort of patients with MS. METHODS: Twenty-five patients with clinically definite MS were studied retrospectively. The appearance of enhancing lesions and sequential changes in the appearance on axial contrast-enhanced spin-echo images were evaluated. The enhancing lesions were classified as nodular, ringlike, or 'other' (eg, arclike). RESULTS: Of 301 new enhancing lesions, 205 (68%) showed nodular enhancement, 70 (23%) a ring pattern, and 26 (9%) a pattern neither nodular nor ringlike (eg, arclike). Two hundred eighty (93%) of 301 enhancing lesions disappeared within 6 months, and seven (2%) lesions showed persistent enhancement longer than 6 months. The other 14 (5%) lesions, which disappeared by the time of the next scan, were excluded, because the course between two examinations was longer than 6 months. Of nine persisting nodular enhancing lesions on the follow-up images, seven were decreased in size, whereas all of two persisting ringlike enhancing lesions on the follow-up images were larger than before. CONCLUSION: Nodular enhancement is the predominant enhancement pattern for new MS lesions, and the temporal course of enhancement is usually shorter than 6 months. The appreciation of the evolution of MS-enhanced lesions aids in both identifying new MS lesions and distinguishing these lesions from other pathologic entities. This may be helpful in clinically evaluating the stage of MS lesions

BACKGROUND AND PURPOSE: Gray matter may be affected by multiple sclerosis (MS), a white matter disease. Magnetization transfer ratio (MTR) is a sensitive and quantitative marker for structural abnormalities, and has been used frequently in the imaging of MS. In this study, we evaluated the amount of MTR of gray matter among patients with relapsing-remitting MS and healthy control subjects as well as the correlation between gray matter MTR abnormality and neurologic disability associated with relapsing-remitting MS. METHODS: We obtained fast spin-echo dual-echo and magnetization transfer (with and without MT saturation pulses) images from eighteen patients with relapsing-remitting MS and 18 age-matched healthy control subjects. Gray matter was segmented using a semiautomated system. Gray matter MTR histogram parameters, Kurtzke Expanded Disability Status Scale (EDSS), total T2 lesion volume, and gray matter volumes were obtained for statistical analysis. RESULTS: A significant difference was found in gray matter MTR between patients with relapsing-remitting MS and healthy subjects (mean and median). Gray matter MTR histogram normalized peak heights in patients inversely correlated with EDSS (r = -0.65, P =.01). There was also an inverse correlation between mean MTR of gray matter and total T2 lesion volume. CONCLUSION: The MTR of gray matter significantly differed between patients with relapsing-remitting MS and healthy control subjects, suggesting that MS is a more diffuse disease affecting the whole brain, and neuronal damage accumulates in step with T2 lesion volume. Our finding of the relationship between gray matter MTR and EDSS indicates that measurement of gray matter abnormality may be a potentially useful tool for assessing clinical disability in MS