Initital Presentation and History
Ms. D is a 41-year-old woman with relapse-remitting MS. She was diagnosed 6 years ago after experiencing initial symptoms of optic neuritis and some numbness in her right hand. Since then, she has developed greater weakness in both her legs and reports that her MS significantly impacts her ability to walk, both in terms of distance and the effort needed to ambulate.
Ms. D is independently ambulatory without the use of any assistive device. She reports that her balance is worse when walking on uneven surfaces, moving about in dimly lit environments, turning, or when walking in crowded spaces. Ms. D also shares that she has difficulty standing on one leg while pulling on socks. She states that she must concentrate and focus on her balance when in these challenging situations and that she has to consistently look where she is stepping.
Ms. D does not have any spasticity in muscles of the lower extremities, but on occasion does experience some numbness and tingling in her left foot. She experiences moderate fatigue that requires her to pace herself throughout her daily activities. She reports that her fatigue impacts her ability to concentrate or pay attention for long periods of time and impacts her motivation to engage in social activities. She states that she sleeps restlessly and is consequently tired when she wakes in the morning. Although she is sedentary, she has no history of cardiopulmonary issues or orthopedic problems.
Ms. D is 5’7” and weighs 175 pounds, with a BMI of 27.4. She presents with observable gait and balance impairment. On physical examination, she exhibits reduced bilateral strength of knee flexors and extensors as well as hip adductors, although the weakness is more evident on the left. On neurologic exam, she exhibits moderate disability in both sensory and cerebellar functioning (resulting in an Expanded Disability Status Scale score of 3.5) .
What is postural control?
What balance impairments are associated with MS?
Postural Equilibrium and Balance
For all individuals, postural orientation and equilibrium underlie the effective performance of life’s daily tasks. Postural orientation refers to the alignment of body segments to a reference (such as gravity, the support surface, or an object in the visual field), while postural equilibrium—often equated with balance—refers to maintaining or re-acquiring the body’s center of gravity (CoG) within the base of support (BoS) [17,18]. This paper will focus on postural equilibrium with MS across multiple contexts of balance tasks.
Horak  described contexts of balance tasks that affect the mechanisms of maintaining postural equilibrium. Some of these contextual variables include
- Biomechanical constraints (eg, strength)
- Limits of stability (functional reach, maximum lean)
- Anticipatory postural adjustments (voluntary postural transitions)
- Automatic postural responses (balance recovery from external perturbations)
- Sensory orientation (ability to reweight sensory information [somatosensory, visual, vestibular] depending on context
- Dynamic control during gait
- Cognitive-motor interaction (balance impairments when also performing a cognitive task)
Emotion represents another contextual variable of interest, because mood and fear can significantly modify postural control [19–23]. Knowing the contextual factors that modify balance control provides insight into underlying neuropathology associated with impairments of these postural control variables [24,25] as well as insight into what should be included during the examination of patients with MS based on patient descriptions of their symptoms and functional challenges.