Electrical Stimulation and Dysphagia

“Neuromuscular electrical stimulation (NMES) is a noninvasive modality that  directly stimulates the peripheral nervous system to evoke an action potential via surface electrodes “ (Biber et. al)

HISTORY

In past years E-stim has been used for:

·        Tremors in Parkinson’s (deep brain stimulation)

·        Wound healing

·        Pain management

·        Reduction of edema

·        Muscle enhancement, specifically:

·        Increasing ROM

·        Improving strength

·        Reeducating contraction patterns and timing

·        Correcting abnormal muscle tone

E-Stim for treatment of dysphagia was introduced:

·        1975-  Marcy Freed developed her protocol while at Hillcrest Hospital in Ohio.

·        1999-  Teresa Biber in collaboration with PT and Otolaryngology departments while

      at the Cleveland Clinic in Florida.

Current FDA approved uses for NMES include:

·        muscle reeducation

·        prevent/retard disuse atrophy

·        relax muscle spasm

·        increase local blood circulation

·        immediate post surgical stimulation of calf muscles to prevent DVT

·        maintain or increase ROM

WHY E-STIM?

·        Traditional Treatment: Compensatory vs. Rehabilitative

·        Compensatory Intervention = “strategies that provide an immediate but typically transient effect on the efficiency or safety of swallowing. As a rule, if the strategy is not consistently executed, swallowing will return to the prior dysfunctional status.  

1.      Posturing (chin tuck, head turn)

2.      Diet/texture modifications

3.      Tube feeding

4.      Airway protection techniques (supraglottic swallow)

5.      Thermal-tactile stimulation

·        Rehabilitative Intervention = “intervention that, when provided over the course of time, are thought to result in permanent changes in the substrates underlying deglutition: i.e., changing the physiology of the swallowing mechanism.”

1.      Oral motor exercises

2.      Shaker Exercise

3.      LSVT

4.      Swallowing Maneuvers in combination with EMG biofeedback

5.      E-Stim ???

 “To date, no controlled trial efficacy data are available for the compensatory and rehabilitative strategies clinicians employ to treat adults with dysphagia.” (McCullough, ASHA 2003)

HOW DOES E-STIM WORK?

·        Electrical impulses transmitted transcutaneously via 2 electrodes places on the submental area, away from carotid arteries and not directly on larynx.

·        Body tissue (muscle) conduct electricity, causing a depolarization of the nerve fibers, thus creating a muscle contraction by dispersing an action potential across the muscle fibers.

-Normal vs. Stimulated muscle contraction:

·        Normal muscle contraction occurs when action potential is transferred to the muscle by the nerve. Stimulated muscle contraction occurs as a result of muscle fibers being directly stimulated by the electrical current from the voltage source.

-Muscle Fiber Recruitment

·        Type I muscle fibers are recruited first during normal muscle contraction, followed by Type II muscle fibers (swallowing muscles are primarily composed of Type II fibers)

·        Recruitment patterns during e-stim are reversed; Type II fibers are recruited first.

-Firing pattern

·        Normal muscle contraction is an asynchronous contraction pattern (one fiber relays message to another). This protects against fatigue; when demand on muscle exceeds its capacity, more motor units are recruited... leading to rapid fatigue and the muscle responding by increasing its capacity.

·        Stimulated muscle contraction is a synchronous contraction pattern (all muscle fibers within the path of the electrical current are recruited). Fatigue occurs more rapidly, therefore muscle strengthening is promoted and achieved. (increase muscle contraction = increase muscle strength)

TREATMENT USES

·        Maintain/strengthen muscle mass during inactive periods

·        Maintain/gain ROM: Facilitates laryngeal elevation by strengthening the extrinsic laryngeal muscles (laryngeal muscles are like other skeletal muscles stimulated by PT or OT). Ultimately, airway protection is achieved.

·        Facilitate voluntary motor control (swallowing maneuvers)

·        Increase sensory awareness (laryngeal/pharyngeal)