Robbins J, Butler SG, Daniels SK, Gross RD, Langmore S, Lazarus CL, Martin-Harris B, McCabe D, Musson N, Rosenbek JC. (2008). Swallowing and Dysphagia Rehabilitation: Translating Principles of Neural Plasticity into Clinically Oriented Evidence. Journal of Speech, Language, and Hearing Research, 51: S276-S300.
This article breaks down the principles of neural plasticity. Neural plasticity is defined as “the ability of the brain to change.” Central Nervous System Plasticity refers to “the ability of neuronal systems to alter functino in response to changes in input, both physiological and pathophysiological.” One thing the authors warn is that just because neural plasticity may result in a behavioral change, not all behavioral change results in neural plasticity.
There are 10 basic principles of neural plasticity. They are:
1.) Use It or Lose It
2.) Use It and Improve It
3.) Plasticity is Experience Specific (Swallow to Improve Swallowing)
4.) Repetition Matters (How many times you repeat an exercise)
5.) Intensity Matters (Longer training does not necessarily imply more difficult training)
6.) Time Matters (Time after incident)
7.) Salience Matters (Purposeful movement related to the behavior being trained)
8.) Age Matters (Younger brains are more responsive, but plasticity occurs across the life span)
9.) Transference (“The ability of plasticity within one set of neural circuits to promote concurrent or subsequent plasticity” such as LSVT or EMST)
10.) Interference (“the ability of plasticity within a neural circuitry to impede the induction of new or expression of existing, plasticity within the same circuitry”)
Techniques, compensations, maneuvers and exercises we have our patients use were broken down into 4 groups. Sensory Methods, Compensatory Methods, Motor with Swallow and Motor without Swallow.
The following is adapted from charts the authors created demonstrating behavioral vs. neural change within each group.
Sensory Methods: (From the literature)
Bolus Effects Behavioral Neural
Volume Yes No
Viscosity Yes No
Temperature Yes No
Taste Enhancement Yes No
Thermal-Tactile Stimulation Yes Yes
E-Stim Yes Yes
DPNS No No
Occluding Trach Yes No
Visual Feedback Yes No
Compensatory Methods: (From the literature)
Chin Tuck Yes No
Head Rotation Yes No
Head Tilt Yes No
Head Back No No
Side Lying Yes No
Breath Hold Yes No
Bolus Consistency Yes No
Motor with Swallow: (From the Literature)
Mendelsohn* Yes No
Super Supraglottic Yes No
Supraglottic Yes No
Effortful Swallow * Yes No
Tongue Hold * Yes No
Swallow (Frequency) Yes No
(* has the potential for plasticity)
Motor without Swallow: (From the Literature)
ROM Yes No
Strengthening-Tongue* Yes No
Strengthening-Respiratory * Yes No
Tongue Control Yes No
Shaker * Yes No
LSVT * Yes No
Pharyngeal Exercises* No No
Gargling No No
Vocal Exercises No No
Velar Elevation No No
Airway Closure/Breath Hold Yes No
So, some of the techniques, compensations and exercises we use do create a behavioral change, including increased airway protection to reduce or eliminate penetration/aspiration, better control of the bolus, etc. Few cause an actual neural change.
Looking at each principle and each category the authors created a great table which I will summarize. Looking at 5 categories 1.) Sensory Methods Bolus Effects 2.) Sensory Methods Stimulation 3.) Compensatory 4.) Motor with Swallow 5.) Motor without Swallow:
1.) Meets all 10 principles, with a question on Time Matters
2.) Meets all 10 principles with a question on Time Matters
3.) Meets all 10 Principles, however questioning interference.
4.) Meets all 10 principles except interference
5.) Meets all 10 principles except Salience Matters
There are many areas that continue to warrant research in the field of dysphagia. One thing we need to keep in mind that the authors point out: “the primary role of swallowing rehabilitation is to effect change (i.e. improved strength, duration and timing of movement) in the physiologic components of swallowing, which will have a direct influence on bolus flow kinematics through the aerodigestive tract.” Also “The immediate lesson for the swallowing clinician, however, is that training-even the training of a patient who is aspirating and at high risk for pulmonary or other health consequences-appears preferable to merely observing and documenting.”
Whether we’re using dry swallows or bolus swallows with our patient, we need to keep them swallowing.
I absolutely think this article is a MUST read for any dysphagia therapist.
Of course, after writing this article, I realized, I already blogged about it! Talk about needing some plasticity for memory skills!!! So, I will also post the original blog here as well!
Neural plasticity refers to the ability of the brain to change.
The 10 principles of plasticity are 1.) Use it or lose it, 2.) Use it and improve it, 3.) Plasticity is experience specific, 4.) Repetition Matters, 5.) Intensity matters, 6.) Time matters, 7.) Salience matters, 8.) Age matters, 9.) Transference and 10.)Interference.
For principle 1, Use it or Lose it, the simple act of swallowing will not improve the swallow in a person with dysphagia. They need to use the function with increasing competence. The question remains what are the best treatment strategies for swallowing. It makes sense that those patients that are NPO and have not swallowed in years will “lose” their swallow function. Simple saliva swallowing drills can help a person return to oral feedings.
Principle 2, Use it and improve it, there are many different treatment techniques including expiratory muscle strength training, lingual strengthening, Shaker, Mendelsohn, Masako and effortful swallow. Keep your patients swallowing to strengthen those muscles, but as they swallow, challenge the patient and challenge the swallow system. To merely sit and observe as a patient eats a meal is by no means therapeutic. To feed a patient during a meal is by no means therapeutic. Building the competence of a system is imperative, not just allowing a patient to complete the simple act of swallowing.
Principle 3, Plasticity is experience specific, to focus and rehab the swallow may or may not affect other aspects, such as dysarthria or voice deficits and vice versa. Does simply completing OME with patients improve the swallow?? If we have the patient complete voice exercises, that do not involve the swallow, how will that improve the swallow function. It’s a different function to complete the exercises without a bolus than it is with a bolus.
Principle 4, Repetition matters, number of repetitions of an exercise will affect the neural changes made by that exercise. Many of the effective exercises involve systematic repetition such as LSVT, isometric lingual exercises and the Shaker. Simply completing a movement or an exercise 10 times 3 times a day may not cut it. The Shaker uses 90 repetitions and 3 repetitions of holding the head up and seems far more effective than simple OME alone.
Principle 5, Intensity matters, there is building evidence that intensity is critical for swallowing therapy. Evidence is still pending for particular dosage recommendations that are therapeutic for the swallow. If you are training for a fight, to run, to lift weights, etc, how can you improve without an intense workout. We’re working with a muscular system with swallowing and should apply the same exercise science rules to swallowing as we do to any other training.
Principle 6, time matters involves the length of your session. A person is going to benefit more from a longer session, 30-60 minutes then they will a 15 minute session.
Principle 7, Salience matters, therapy has to be purposeful for swallowing. You can’t have the person stick out their tongues 15 times and expect their swalow to improve. Simple, repetitive movements and strength training are likely not going to improve swallow function.
Principle 8, Age matters, although neural plasticity does occur throughout the lifespan, a younger system will be more responsive to the changes. This may imply that older adults need a more strenuous or a program with a greater length of time.
Principle 9, transference defined as “the ability of plasticity within one set of neural circuits to promote concurrent or subsequent plasticity.” Evidence from NMES (neuro muscular electrical stimulation) applies to this principle. This continues to be a principle that needs further investigation for implications to the swallowing system.
Principle 10, interference results from inappropriate use of E-stim. E-stim can either facilitate or inhibit the corticobulbar excitability. A simple change in Hz can change the excitability which is why there is extensive study out there now on NMES.
These principles can and should be incorporated into therapy. The more a therapist understands the swallowing system, exercise physiology and neural plasticity, the better prepared they are to treat a dysphagic patient.
Bonnie Martin-Harris and colleagues found 14 physiologic components in the swallowing system,
~hold position/tongue control
~bolus transport/lingual motion
~initiation of pharyngeal swallow
~soft palate elevation and retraction
~anterior hyoid excursion
~pharyngeal stripping wave
~pharyngoesophageal segment opening
~tongue base retraction
Our role as a therapist is to improve the strength, duration and timing of the swallowing movements, with regards to the above components.
We have different options with different interventions including bolus effects by altering volume, viscosity, thermal, taste, tactile or temperature. We can use e-stim. Compensatory strategies including the chin tuck, head rotation, head tilt, head back and side lying positions. We can use maneuvers such as the Mendelsohn, Supraglottic swallow, Super Supraglottic swallow, effortful swallow, double swallow or the Masako. We also use lingual exercises and the Shaker.
The Mendelsohn can alter the extent and duration UES opening as well as aiding in hyolaryngeal excursion.
The supraglottic and super supraglottic swallows facilitate the timing and extent of laryngeal closure at specific levels of the larynx.
The effortful swallow help to increase base-of-tongue retraction and results in increased tongue propulsive force, increased oral pressure, duration and extent of hyoid movement and laryngeal vestibule closure, longer duration of pharyngeal pressure and UES relaxation.
The tongue hold maneuver increases anterior motion of the posterior pharyngeal wall at the level of the tongue base.
You can find increased tongue base-pharyngeal wall pressure and contact duration when performing the effortful swallow, tongue-hold, Mendelsohn and super supraglottic swallow.
Robbins and her group demonstrated that lingual muscles have a propensity for increasing strength and mass and that as a result of non-swallowing exercises, improvement in swallowing pressures on liquid boluses occurred, penetraion Aspiration Scores were reduced and dysphagia-specific quality of life improved.
The Shaker exercise increases swallowing function through decreased aspiration following the swallow.
There is still a need for research from this article including looking at variables of repetition, intensity and time for rehabilitation and finding the appropriate site, stimulation frequency, amplitude, phase duration, optimal frequency and length of an individual stimulation treatment including potential effects.
When presented with a patient with dysphagia, research the disorder. If you are requesting an MBSS ask that the therapist look at muscle movement rather than just the absence or presence of aspiration/penetration. Treat the system as a whole and as a muscular system. We can actually learn much from our PT and OT friends on exercise physiology and use that to design our dysphagia therapy programs to better serve our patients.
Article and references can be found at: http://jslhr.asha.org/cgi/content/full/51/1/S276.