Christopher R. Tench

Pyramidal tract mapping by diffusion tensor magnetic resonance imaging in multiple sclerosis: improving correlations with disability

Background: Current magnetic resonance imaging (MRI) outcome measures such as T2 lesion load correlate poorly with disability in multiple sclerosis. Diffusion tensor imaging (DTI) of the brain can provide unique information regarding the orientation and integrity of white matter tracts in vivo. Objective: To use this information to map the pyramidal tracts of patients with multiple sclerosis, investigate the relation between burden of disease in the tracts and disability, and compare this with more global magnetic resonance estimates of disease burden. Methods: 25 patients with relapsing-remitting multiple sclerosis and 17 healthy volunteers were studied with DTI. An algorithm was used that automatically produced anatomically plausible maps of white matter tracts. The integrity of the pyramidal tracts was assessed using relative anisotropy and a novel measure (Lt) derived from the compounded relative anisotropy along the tracts. The methods were compared with both traditional and more recent techniques for measuring disease burden in multiple sclerosis (T2 lesion load and “whole brain” diffusion histograms). Results: Relative anisotropy and Lt were significantly lower in patients than controls (p < 0.05). Pyramidal tract Lt in the patients correlated significantly with both expanded disability status scale (r = −0.48, p < 0.05), and to a greater degree, the pyramidal Kurtzke functional system score (KFS-p) (r = −0.75, p < 0.0001). T2 lesion load and diffusion histogram parameters did not correlate with disability. Conclusions: Tract mapping using DTI is feasible and may increase the specificity of MRI in multiple sclerosis by matching appropriate tracts with specific clinical scoring systems. These techniques may be applicable to a wide range of neurological conditions.

Spinal cord atrophy and disability in multiple sclerosis over four years: application of a reproducible automated technique in monitoring disease progression in a cohort of the interferon β-1a (Rebif) treatment trial

Background: Pathology in the cervical spinal cord is considered an important cause of disability in multiple sclerosis. However, the majority of serial studies have failed to find a correlation between spinal cord atrophy and disability. Objectives: To use a highly reproducible and accurate method to quantify spinal cord area change on three dimensional magnetic resonance imaging and relate this to disability change in patients with multiple sclerosis. Methods: 38 patients with multiple sclerosis (20 with the relapsing–remitting (RRMS) form and 18 with the secondary progressive (SPMS) form) were imaged at baseline and at months 6, 12, 18, and 48 during two treatment trials of the high dose subcutaneous thrice weekly interferon β-1a (IFNβ, Rebif). Thirty one healthy subjects were also imaged at baseline. Upper cervical cord area (UCCA) was measured using Sobel edge detection. Results: The intraobserver coefficient of variation of the method was 0.42%. A significant reduction in UCCA was detected at month 6 in the placebo group (p = 0.04) and at month 12 for INFβ (p = 0.03). The mean reduction of UCCA at month 48 was 5.7% for patients initially on placebo who received treatment at 24 months (RRMS) or at 36 months (SPMS), and 4.5% for those on IFNβ throughout the study (p = 0.35). The change in UCCA was significantly correlated with change in the expanded disability status scale at month 12 (r = 0.4, p = 0.016), month 18 (r = 0.32, p = 0.05), and month 48 (r = 0.4, p = 0.016) in the total cohort. Conclusions: Despite the small number of patients studied and the possible confounding effects of interferon treatment, this study showed that edge detection is reproducible and sensitive to changes in spinal cord area, and that this change is related to changes in clinical disability. This suggests a role for measurement of spinal cord atrophy in monitoring disease progression and possible treatment effects in clinical trails.

Tobacco smoking and disability progression in multiple sclerosis: United Kingdom cohort study

Tobacco smoking has been linked to an increased risk of multiple sclerosis. However, to date, results from the few studies on the impact of smoking on the progression of disability are conflicting. The aim of this study was to investigate the effects of smoking on disability progression and disease severity in a cohort of patients with clinically definite multiple sclerosis. We analysed data from 895 patients (270 male, 625 female), mean age 49 years with mean disease duration 17 years. Forty-nine per cent of the patients were regular smokers at the time of disease onset or at diagnosis (ever-smokers). Average disease severity as measured by multiple sclerosis severity score was greater in ever-smokers, by 0.68 (95% confidence interval: 0.36–1.01). The risk of reaching Expanded Disability Status Scale score milestones of 4 and 6 in ever-smokers compared to never-smokers was 1.34 (95% confidence interval: 1.12–1.60) and 1.25 (95% confidence interval: 1.02–1.51) respectively. Current smokers showed 1.64 (95% confidence interval: 1.33–2.02) and 1.49 (95% confidence interval: 1.18–1.86) times higher risk of reaching Expanded Disability Status Scale scores 4 and 6 compared with non-smokers. Ex-smokers who stopped smoking either before or after the onset of the disease had a significantly lower risk of reaching Expanded Disability Status Scale scores 4 (hazard ratio: 0.65, confidence interval: 0.50–0.83) and 6 (hazard ratio: 0.69, confidence interval: 0.53–0.90) than current smokers, and there was no significant difference between ex-smokers and non-smokers in terms of time to Expanded Disability Status Scale scores 4 or 6. Our data suggest that regular smoking is associated with more severe disease and faster disability progression. In addition, smoking cessation, whether before or after onset of the disease, is associated with a slower progression of disability.

Use of combined conventional and quantitative MRI to quantify pathology related to cognitive impairment in multiple sclerosis

Background: Cognitive impairment is one of the frequent and early findings in multiple sclerosis (MS). Objective: To determine the relation between cognitive abnormalities and the extent of macroscopic and microscopic tissue damage in the corpus callosum (CC), revealed by conventional magnetic resonance imaging (MRI), magnetisation transfer imaging (MTI) and diffusion tensor imaging (DTI). Methods: Conventional dual-echo, DTI and MTI of the brain were obtained from 36 patients with relapsing remitting (RR) MS, and 13 age and gender matched normal controls. Voxels from CC were identified using a tractography based algorithm. Mean apparent diffusion coefficient (ADCav) and MT ratio were measured for the CC as defined by tractography. Corpus callosum area (CCA) was measured using edge detection on the mid-sagittal slice on high resolution MRI images. The Expanded Disability Status Scale (EDSS) and Paced Auditory Serial Addition Test (PASAT) were scored. Results: Nine patients (25%) were found to be cognitively impaired. The CCA was not significantly different in the whole cohort of patients from controls (608.2 (428.6–713.0) mm2 vs 674.2 (585.8–754.4) mm2, p = 0.1), but was smaller in cognitively impaired than unimpaired group (417 (290–634) mm2 vs 652 (511–718) mm2, p = 0.04). The mean MT ratio of CC in patients was lower than in controls (0.41 (0.39–0.042) vs 0.43 (0.42–0.43), p<0.001). The ADCav in the CC in patients was higher than in controls (0.94 (0.89–0.99) vs 0.87 (0.85–0.89), p<0.001). PASAT was correlated with mean MT ratio (r = 0.47, p = 0.0046), ADCav (r = −0.53, p = 0.0012), CCA (r = 0.42, p = 0.01) and total T2 lesion load (r = −0.4, p = 0.017), but not with T2 lesion load within the CC (r = −0.24, p = 0.16), disease duration (r = −0.2, p = 0.24) or EDSS (r = −0.27, p = 0.12). Conclusions: ADCav, MTR and atrophy measures in the CC may offer a sensitive method detecting subtle macroscopic and microscopic changes associated with cognitive impairment in MS.

White matter mapping using diffusion tensor MRI.

Diffusion tensor MRI is used to define trajectories that reflect the long‐range order of in vivo white matter (WM) fiber tracts. Fiber tracking is particularly prone to cumulative error from noise and partial volume along the length of the trajectory paths, but the overall shape of each path is anatomically meaningful. By considering only the long‐range similarity of path shapes, a method of constructing 3D maps of specific WM structures has been developed. A trajectory is first computed from an operator‐selected seed voxel, located within the anatomical structure of interest (SOI). Voxels from the same structure are then automatically identified based on the similarity of trajectory path shapes, assessed using Pearsons correlation coefficient. The corpus callosum and pyramidal tracts in 14 patients with multiple sclerosis, and in 10 healthy controls were mapped by this method, and the apparent diffusion coefficient (ADC) was measured. The ADC was significantly higher in patients than in controls, and higher in the corpus callosum than in the pyramidal tracts for both groups. Using this method the different functional structures in the WM may be identified and mapped. Within these maps, MRI parameters can be measured for subsequent comparison with relevant clinical data. Magn Reson Med 47:967–972, 2002.

‘Importance sampling’ in MS: Use of diffusion tensor tractography to quantify pathology related to specific impairment

Specific neurological impairments in multiple sclerosis (MS) are dependent on the pathology in clinically eloquent areas of the central nervous system. We aimed to use diffusion tensor fiber tracking to identify the pyramidal tracts and corpus callosum in MS patients, measure the apparent diffusivity within the tracts, and evaluate whether this would correlate with relevant disability scores. Dual-echo and diffusion tensor magnetic resonance imaging (DT-MRI) brain scans were obtained from 29 patients with relapsing remitting MS, and 13 age and gender matched normal controls. Voxels from pyramidal tracts and corpus callosum were automatically identified using a tractography based algorithm. Mean apparent diffusion coefficient (ADC(av)) was measured for these tracts. Scores of Expanded Disability Status Scale (EDSS) and Paced Auditory Serial Addition Test (PASAT) were obtained. The median EDSS score was 2.5 (inter-quartile range 2-3.25). The ADC(av) in the pyramidal tracts (p=0.02) and corpus callosum (p=0.0004) in patients was significantly higher than in controls. Pyramidal tracts ADC(av) was correlated with pyramidal FSS (r=0.5, p=0.008). Corpus callosum ADC(av) was correlated with PASAT (r=-0.58, p=0.001). Global T2 lesion volume did not correlate with the EDSS, but correlated with ADC(av) of the pyramidal tracts (r=0.6, p=0.0007) and corpus callosum (r=0.8, p<0.0001). T2 lesion volume within the pyramidal tracts and corpus callosum correlated with ADC(av) in the pyramidal tracts (r=0.6, p=0.0009) and corpus callosum (r=0.65, p=0.0002) respectively, but not with pyramidal FSS or PASAT score. DT-MRI quantifies pathology in specific white matter tracts and may increase the specificity of MRI in monitoring progression of motor and cognitive deficits in MS.

Measurement of spinal cord atrophy in multiple sclerosis.

In multiple sclerosis (MS), the spinal cord is a common area of involvement, and its dysfunction is likely to be responsible for much of motor disability. It has been reported that atrophy in the cervical spinal cord occurs early and is detectable in patients presenting with a clinically isolated syndrome. This finding has important implications for the early treatment of patients with MS because atrophy is thought to reflect destructive, irreversible pathology and subclinical impairment. Recent clinical trials of disease‐modifying agents have included spinal cord imaging and, in particular, the measurement of atrophy as a secondary or exploratory measure of treatment efficacy. This review summarizes the underlying pathology responsible for spinal cord atrophy and the methods available to measure it. The relationships between spinal cord atrophy, other magnetic resonance imaging parameters, and clinical disability are also discussed.

Deep gray matter and fatigue in MS: a T1 relaxation time study.

Fatigue in multiple sclerosis (MS) occurs commonly, sometimes as the earliest symptom. Some MS patients consider fatigue to be their most troublesome complaint, and it has been shown to be an independent predictor of impaired quality of life. Several reports have demonstrated that subcortical gray matter pathology is related to fatigue. We hypothesized that MRI detectable changes in the deep gray matter of MS patients may correlate with fatigue severity.Our objective was: to assess the relationship between fatigue severity and detectable changes on magnetic resonance imaging (MRI), quantified using the mean T1 relaxation time (T1), in deep gray matter structures in relapsingremitting multiple sclerosis (RRMS). Using region of interest analysis, T1 values were measured for the thalamus, putamen and caudate nucleus in 52 RRMS patients and 19 healthy volunteers. Fatigue was assessed using the Fatigue Severity Scale. Results: The median T1 in the thalamus and the putamen were significantly higher in the patient cohort than in the healthy controls; the median T1 in the caudate was also higher in the MS patients but did not reach statistical significance. There was a significant correlation between fatigue severity and the T1 of the thalamus (rho = 0.418; p = 0.014). Furthermore, the median T1 in the thalamus was significantly higher in patients with fatigue compared with those without (p = 0.018). Our results provide further evidence for the role of subcortical gray matter structures in the pathogenesis of multiple sclerosis (MS)–related fatigue. This study also demonstrates that T1 relaxation time measurement is a suitable technique for detecting abnormalities of the deep gray matter in RRMS and presents further support of gray matter involvement in MS.

Increased iron accumulation occurs in the earliest stages of demyelinating disease: an ultra-high field susceptibility mapping study in Clinically Isolated Syndrome

Objective: To determine, using ultra-high field magnetic resonance imaging (MRI), whether changes in iron content occur in the earliest phases of demyelinating disease, by quantifying the magnetic susceptibility of deep grey matter structures in patients with Clinically Isolated Syndrome (CIS) that is suggestive of multiple sclerosis (MS), as compared with age-matched healthy subjects. Methods: We compared 19 CIS patients to 20 age-matched, healthy controls. Scanning of the study subjects was performed on a 7T Philips Achieva system, using a 3-dimensional, T2*-weighted gradient echo acquisition. Phase data were first high-pass filtered, using a dipole fitting method, and then inverted to produce magnetic susceptibility maps. Region of interest (ROI) analysis was used to estimate magnetic susceptibility values for deep grey matter structures (caudate nucleus, putamen, globus pallidus, the thalamus and its pulvinar). Results: Significantly increased relative susceptibilities were found in the CIS group, compared with controls, for the caudate nucleus (p = < 0.01), putamen (p < 0.01), globus pallidus (p < 0.01) and pulvinar (p < 0.05). We found no significant nor consistent trends in the relationship between susceptibility and age for either the study controls or CIS patients, in any ROI (r 2 < 0.5; p > 0.05). In CIS patients, the time elapsed since the clinical event and the Expanded Disability Status Scale (EDSS) scores were not correlated with iron levels in any ROI (r 2 < 0.5; p > 0.05); however, a moderate correlation (r 2 = 0.3; p < 0.01) was found between the T1 lesion load and the mean susceptibility of the caudate nucleus. Conclusion: CIS patients showed an increased iron accumulation, as measured using susceptibility mapping of the deep grey matter, suggesting that iron changes did occur at the earlier stages of CIS disease.

Plasma endocannabinoid levels in multiple sclerosis

BACKGROUND Multiple sclerosis (MS) is a chronic inflammatory disease of the CNS. Therapies that affect the endocannabinoid (EC) system may have immunomodulatory, symptomatic and neuroprotective effects. AIM The aim of this study was to determine how levels of EC and related compounds are altered in MS. METHODS Plasma and whole blood were collected from 24 MS patients (10 relapsing-remitting (RR); 8 secondary-progressive (SP); 6 primary-progressive (PP); 19 females; 25-66 years) and 17 controls (10 females; 22-62 years). Plasma EC and related compounds were quantified by liquid chromatography-tandem mass spectrometry. Fatty acid amide hydrolase (FAAH), cannabinoid receptors CB(1) and CB(2) mRNA were measured by quantitative reverse transcriptase-polymerase chain reaction. RESULTS Anandamide (AEA) and palmitoylethanolamide (PEA) were higher in RRMS compared to controls (p=0.001 and p=0.027). AEA, PEA and oleoylethanolamide were also increased in SPMS plasma (p=0.001, p=0.004, and p=0.005). PPMS patients had higher AEA plasma levels compared to controls (p=0.009). FAAH mRNA was decreased in SPMS (p=0.04) but not in RRMS or PPMS blood. CB(1) (p=0.012) and CB(2) mRNA (p=0.003) were increased in the PPMS. CONCLUSION The EC system is altered in MS. It may be dynamically modulated depending on the subtype of the disease, but further studies with larger subgroups are needed to confirm this.