MS Symptoms

Vision loss, especially in low light, may contribute to problems with walking in multiple sclerosis (MS) patients, a researcher said here.

Lower visual acuity in low-contrast situations among MS patients was significantly associated with poorer performance on a gait test in a controlled trial, said Rachel Tripoli, a medical student at Florida State University in Tallahassee, Fla.

Moreover, many of the MS patients showed improvements when they wore contrast-enhancing yellow lenses, she said -- a simple and practical solution to a problem that diminishes quality of life and can cause physical injury.

Tripoli reported the findings at the joint meeting of the Consortium of Multiple Sclerosis Centers and the Americas Committee for Treatment and Research in Multiple Sclerosis.

Previous studies had indicated that reduced vision in low light was common in MS with or without overt optical neuropathy, Tripoli said.

She and colleagues recruited 22 MS patients and 22 age-matched healthy controls for their study, in which participants underwent visual and gait testing under a variety of lighting conditions.

The vision testing involved low-contrast Sloan charts, which display letters that appear increasingly faded as one reads down.

Participants also underwent optic coherence tomography scans to evaluate optic nerve morphology.

Finally, walking ability was measured on a "gait pad," a 22-foot carpet embedded with sensors that capture footfall pressure and duration, as well as gait speed and total time to traverse the pad. The data were used to calculate a functional ambulation performance (FAP) score.

Walking was evaluated under low light (less than 4 candelas) and four brightly lit (more than 80 candelas) conditions. Participants were tested four times under each lighting condition -- with and without obstacles (cones placed on the pad) and with and without contrast-enhancing yellow lenses.

The optic coherence tomography testing showed that, as expected, the MS patients had significantly decreased optic nerve thickness relative to controls, Tripoli said.

Sloan chart scores also were lower in the MS patients than in controls, she reported.

Under three different contrast conditions, MS patients were able to read about five fewer letters than controls.

On the gait tests, MS patients' FAP scores were negatively associated with EDSS disability scores, indicating that increased disability was correlated with poorer walking performance.

Differences in gait measurements in MS patients versus controls were apparent only under low light. In bright light, no significant deficiency for patients was apparent, Tripoli said.

With obstacles, the mean FAP score for patients was about 75, compared with more than 90 in controls. The difference in the obstacle-free test was smaller, about 10 points, but still significant, Tripoli said.

Use of yellow lenses improved FAP scores in patients to the point that they no longer differed significantly from controls, both with and without obstacles.

She said it was reasonable to conclude that the lenses "increase obstacle discrimination" and could be useful for injury prevention.

The study had no commercial funding.

Tripoli and other investigators said they had no relevant financial interests.

Primary source: Consortium of Multiple Sclerosis Centers and the Americas Committee for Treatment and Research in Multiple Sclerosis
Source reference:
Tripoli R, et al "Deficient contrast visual acuity in patients with multiple sclerosis degrades gait performance under conditions of low illumination" CMSC-ACTRIMS 2012.

Source: Medpage Today © 2012 Everyday Health, Inc. (07/06/12)

Summary: This study from Italy comparing healthy controls to patients with MS with and without symptoms of fatigue found that there were significant quantitative MRI differences between the groups.

Although cord-normalized cross-sectional area did not differ significantly between groups, both groups of MS patients had significantly different cord average fractional anisotropy (FA). MS patients without fatigue had a lower brain normal-appearing white matter average FA and increased cord recruitment than patients with fatigue. In all patients, fMRI signal change of all activated voxels was significantly correlated with the severity of fatigue. The authors have therefore concluded that abnormalities of function, but not of structure, of the cervical cord are likely to contribute to the pathogenesis of fatigue in MS.

Abstract
Background/Objective We aimed to investigate whether cervical cord damage and dysfunction is associated with the presence and severity of fatigue in multiple sclerosis (MS) using a multiparametric magnetic resonance (MR) approach.

Methods: Cervical cord functional magnetic resonance imaging (fMRI) during a tactile stimulation of the right hand, and structural brain and cord MRI were acquired from 20 controls, 15 MS patients without fatigue (NF) and 20 MS patients with fatigue (F). Between-group differences in the extent of focal lesions and diffusivity abnormalities in the brain and cord, cord-normalized cross-sectional area (CSAn) and fMRI activity were assessed.

Results: All structural MRI measures differed significantly among groups, except for cord lesion number and CSAn. Compared with controls, NF-MS patients experienced higher cord recruitment (p=0.04). Compared with F-MS, NF-MS patients had a lower brain normal-appearing white matter average fractional anisotropy (p=0.001) and increased cord recruitment (p=0.02). In patients with MS, the extent of cord recruitment was correlated with the severity of fatigue (r=-0.34, p=0.04). Compared with the other two groups, F-MS patients had a more diffuse recruitment of cord quadrants on the axial and longitudinal planes.

Conclusions: Abnormalities of function, but not of structure, of the cervical cord are likely to contribute to the pathogenesis of fatigue in MS.

Rocca M, Absinta M, Valsasina P, Copetti M, Caputo D, Comi G, Filippi M.

Source: Mult Scler. 2012 Mar 2 & Pubmed PMID: 22389415 (07/03/12)

Abstract (provisional)
Background
Fatigue is a frequent and serious symptom in patients with Multiple Sclerosis (MS). However, to date there are only few methods for the objective assessment of fatigue.

The aim of this study was to develop a method for the objective assessment of motor fatigue using kinematic gait analysis based on treadmill walking and an infrared-guided system. Patients and Methods: Fourteen patients with clinically definite MS participated in this study.

Fatigue was defined according to the Fatigue Scale for Motor and Cognition (FSMC). Patients underwent a physical exertion test involving walking at their pre-determined patient-specific preferred walking speed until they reached complete exhaustion. Gait was recorded using a video camera, a three line-scanning camera system with 11 infrared sensors. Step length, width and height, maximum circumduction with the right and left leg, maximum knee flexion angle of the right and left leg, and trunk sway were measured and compared using paired t-tests (alpha=0.005).

In addition, variability in these parameters during one-minute intervals was examined. The fatigue index was defined as the number of significant mean and SD changes from the beginning to the end of the exertion test relative to the total number of gait kinematic parameters.

Results
Clearly, for some patients the mean gait parameters were more affected than the variability of their movements while other patients had smaller differences in mean gait parameters with greater increases in variability. Finally, for other patients gait changes with physical exertion manifested both in changes in mean gait parameters and in altered variability. The variability and fatigue indices correlated significantly with the motoric but not with the cognitive dimension of the FSMC score (R=-0.602 and R=-0.592, respectively; P<0.026).

Conclusions
Changes in gait patterns following a physical exertion test in patients with MS suffering from motor fatigue can be measured objectively. These changes in gait patterns can be described using the motor fatigue index and represent an objective measure to assess motor fatigue in MS patients. The results of this study have important implications for the assessments and treatment evaluations of fatigue in MS.

Full Article

Source: Journal of NeuroEngineering and Rehabilitation 2011, 8:59 doi:10.1186/1743-0003-8-59 © 2011 BioMed Central Ltd (01/11/11)