Management of musculoskeletal impairments Impairments that dominate the difficulties in neuro- rehabilitation of CNS mediated paralysis/paresis are muscle weakness/atrophy, limited passive and active joint range of motion, loss of motor control, spasticity, pain, and edema. A number of clinical 2 0 2 4 6 8 10 12 14 0 5 10 15 20 25 30 35 40 Perception Phase char ge Data Y 3.88481 2.31706 * ln(X)
Figure 9.2. Logarithmic relationship between phase charge and perception of stimulus discomfort in a single healthy volunteer. The perception of discomfort was determined by a visual-analog scale from 0% to 100%.
studies in chronic stroke have demonstrated that a daily or three times per week stimulation program over 3–6 weeks strengthens the stimulated muscles and restores some degree of active and passive range of motion of the mobilized joints (Smith, 1990; Hazlewood et al., 1994; Pandyan et al., 1997; Alon et al., 1998; Powell et al., 1999). More recent clinical trials have combined the NMES with task-specific training of the paretic upper limb (Alon, 2003; Cauraugh and Kim, 2002, 2003a, b, c). Significant improvement in motor control as documented by Fugl-Meyer score or EMG has been reported by a number of investigators (Faghri et al., 1994; Chae et al., 1998; Francisco et al., 1998; Powell et al., 1999; Cauraugh et al., 2000; Cauraugh and Kim, 2002, 2003a, b, c; Kimberley et al., 2004). Improved functional ability was limited to improvement in performance speed or increasing number of blocks transferred but not re-learning of hand function or ability lost due to paralysis, however.
Spasticity
Over 50 clinical studies are published on the appli- cation of stimulation for modification of spasticity. Three approaches have been used. The first approach uses sensory stimulation over the spastic muscle group. The second approach elicits muscle contrac- tion in the antagonist muscle group for strengthen- ing and simultaneous stretch of the spastic muscles. The third, most recent approach has been to stimu- late alternately both agonists and antagonists (Alon et al., 1998, 2003). All three approaches have been statistically equally beneficial. Many patients are likely to experience a long-term reduction in spastic- ity of about 0.7–1 notch on the 0–5 Ashworth scale, a rather modest effect that may not justify prescribing NMES for the sole purpose of spasticity management. For additional information on the mechanisms and management of spasticity, see Volume II, Chapter 17.
Stroke
Shoulder subluxation
Four clinical trials have been performed investigating whether early initiation of NMES could minimize
shoulder subluxation, a problem in 20–40% of stroke survivors (see Volume II, Chapter 36 on stroke reha- bilitation). (Faghri et al., 1994; Chantraine et al., 1999; Linn et al., 1999; Wang et al., 2000). The impairments of subluxation and shoulder pain can be minimized in the majority of patients while improving passive joint range and volitional deltoid activation after 4–6 weeks of training. This training is insufficient to yield meaningful reduction if the NMES is delayed for 6–12 months post-subluxation (Wang et al., 2000). It should be noted that these studies used reduction of subluxation as an out- come and not upper limb functional activities.
Upper limb function in hemiparesis
The value of NMES to the training of upper limb func- tion remains controversial. Recent studies have begun to test the contribution of NMES particularly to hand function (Cauraugh et al., 2000; Alon et al., 2002; Cauraugh and Kim, 2002, 2003a, b, c; Alon and Ring, 2003; Alon et al., 2003; Popovic et al., 2003). Outcome measures used in hand function evaluation vary considerably. Cauraugh and colleagues only use the box and blocks test while others also use the Jebsen-Taylor and the nine-hole peg (Alon and Ring, 2003; Alon et al., 2003; Kimberley et al., 2004). Popovic et al. (2003) recently used a comprehensive test bat- tery that included many ADLs that depend on the upper limb collectively termed upper extremity func- tioning test (UEFT) as well as hand drawing test and patients testimonial statements regarding reduced upper extremity motor activity long (MAL) tests.
Diversity of training programs and the delay of training initiation have contributed to the reluctance of the clinical community to accept FES as a valu- able intervention. Most studies that tested true upper limb function and not just impairments enrolled only patients with chronic stroke. Four clinical investigations synchronized clearly described task-specific activities with stimulation. Such syn- chronization resulted in upper limb functional improvement in 70–80% of participants (Alon and Ring, 2003; Alon et al., 2003; Berner et al., 2004; Ring et al., 2005). The authors added a cautionary note
that while the gains of hand functions were both statistically and clinically meaningful, the vast majority of patients improve the time of perform- ance but did not re-learn functional ability.
Ambulation in hemiparesis
Gait performance has been enhanced by FES during ambulation (Malezic et al., 1987). The most com- mon target muscle for stimulation has been the dorsiflexors of hemiparetic patients. The stimula- tion is typically synchronized with the gait cycle, so that the dorsiflexors are active during the swing phase. The main outcome measures that improve after 4–5 months of use are walking speed (20–27%) and physiological cost index (PCI). Walking speed after the training period without the stimulator only improves 10–14% if the stimulation was limited to the dorsiflexors, however (Burridge et al., 1997b; Taylor et al., 1999; Yan et al., 2005), multisegment stimulation of both plantar flexors and dorsiflexors has been used in stroke. Training involved increasing speed of ambulation as well as stair climbing and walking on different terrains. Using this paradigm, gait velocity improved 36% and cadence by 19% (Alon and Ring, 2003), which represents an improvement from the results with dorsiflexors stimulation alone.