Introduction: Enhancing Mobility in Multiple Sclerosis

摘要

Mobility limitations, which affect the majority of individuals living with multiple sclerosis (MS), are frequently addressed by clinicians and researchers, as they are at the heart of patients' (and families') concerns at the time of diagnosis and throughout the course of the disease. Ambulation, one of the key components of mobility, is routinely assessed through patient report, direct observation, and standardized tests and scales to monitor the progression of MS and the efficacy of disease-modifying therapies. Mobility-related issues can be a major source of frustration for patients, families, and health-care providers given the progressive nature of the disease, its heterogeneity, and its unpredictability. However, the recent growth in the body of evidence for the assessment and management of mobility restrictions, and in the spectrum of interventions available, brings renewed energy and hope.One of the main features of mobility limitations, besides their high prevalence, is their complexity, as illustrated in Figure 1. A key underlying factor in the complexity of mobility limitations is the neurologic impairments (eg, loss of motor control, spasticity, sensory loss, imbalance) resulting from disease activity. We are just starting to understand how multiple impairments compound one another to create a synergistic rather than an additive disabling effect. For example, studies have demonstrated how cognitive challenges during walking can worsen motor-induced gait deviations by limiting compensation strategies. In turn, decreased mobility can affect MS-related impairments and symptoms (eg, increased fatigue due to decreased activity, decreased range of motion due to reduced voluntary limb motion), and may even affect the disease process (eg, frequent urinary-tract infections may lead to increased frequency of MS exacerbations). Comorbidities also affect mobility, whether they are indirectly related to MS (eg, musculoskeletal problems due to abnormal gait pattern, decreased respiratory function due to respiratory muscle weakness and deconditioning) or are independent of MS (eg, cardiovascular conditions). In turn, decreased mobility can increase the risk of comorbidities (eg, obesity, osteoporosis).Assessing mobility, and the effect of interventions on mobility, is more complex than it seems. Walking, the activity most often assessed, has been monitored through the clinician's observation of walking a specific distance, calculating walking speed, and documenting the need for assistive devices. Detailed gait analysis usually requires too much time and equipment to be used in clinical care, and performance on tests administered at a given point in time in the clinic do not fully reflect a patient's success in safe and efficient ambulation in his or her own environment over the course of a day or week. The clinical trials of dalfampridine have reignited a debate regarding the use of walking speed as a proxy for ambulation, and what represents a clinically significant change in walking speed. Walking speed is increasingly valued as a predictor of overall function and health outcomes in other fields, particularly in the elderly and in stroke survivors. This has yet to be demonstrated in MS. At this time, it seems that a combination of simple walking tests and validated questionnaires (in addition to a complete history and examination) is the most efficient way of monitoring mobility in a clinical setting. Beyond walking, the assessment of transfers, wheelchair mobility, driving, and the impact of trunk control and upper-extremity function is traditionally handled by rehabilitation professionals, to whom patients do not always have easy and consistent access.Addressing mobility limitations is indeed a complex task. Comprehensive MS care offers a variety of interventions designed to reduce or circumvent mobility limitations. Disease-modifying therapies, even though they often do not produce an immediate improvement in neurologic stat