Use of Modalities in Upper Limb Management in Tetraplegia

Original Editor - User Name

Top Contributors - Ewa Jaraczewska, Jess Bell and Tarina van der Stockt  

Introduction

A wide range of therapeutic modalities addressing upper limb function in patients with tetraplegia is available in spinal cord injury rehabilitation.

Vibration

Muscle vibration is a technique that has potential to reduce muscle tone and spasticity in individuals with neurological disorders. Direct effect of muscle vibrations include an increase in corticospinal excitability and inhibition of neuronal activity in the antagonistic muscle. The use of focal vibration as a modality in spinal cord injury facilitates a contraction of the agonist muscle. Isometric contraction in triceps brachii were induced with the application of vibratory stimuli at 80 Hz on the muscle.

Three motor effects achieved through muscle vibration are as follow:

1. Sustained contraction of the vibrated muscle via tonic vibration reflex
2. Depression of the motor neurones innervating the antagonistic muscles via reciprocal inhibition or antagonistic inhibition
3. Suppression of the monosynaptic stretch reflexes of the vibrated muscle while being vibrated.

The sustained effect of vibration remains under investigation. According to Laessøe et al. , lower limb spasticity was reduced up to 3 hours following vibratory stimulation at 100 Hz. Questions still remain as to whether vibration has any sustained effect on the muscle. Muscle Vibration is generally applied to directly to the chosen muscle or tendon and may be applied in two ways: high frequency and low frequency vibration.Two different vibration frequencies can be chosen and applied directly to the muscle or tendon: high frequency

High Frequency Vibration

The high-frequency vibration is driven from a vibrator that optimally operates at a frequency of 100 - 200 Hz and at an amplitude of 1 – 2 mA. This type of vibration produce facilitation of muscle contraction through what is known as tonic vibration reflex. This facilitatory effect sustained for a brief time after application. Therefore it can be used for stimulating muscles whose primary function is one of tonic holding.

Low Frequency Vibration

The low-frequency stimulation occurring between 5 -50 Hz has an inhibitory effect on muscle through its activation of spindle secondary endings and the Golgi tendon organs.

While Vibration has the potential as a good treatment technique there is still limited evidence on its effectiveness the therapist must be aware of the precautions that must be considered when using it as a treatment option including heat generation at the point of application that has the potential for skin damage, particularly at high amplitude. Further studies are needed in the future well-designed trials with a bigger sample size to determine the most effective frequency, amplitude and duration of vibration application in the neurorehabilitation.

You can read more about self-applied vibration here.

Surface Stimulation

Two the most commonly used forms of surface stimulation are:

• Transcutaneous Electrical Nerve Stimulation (TENS)
• Functional Electrical Stimulation(FES).

TENS

This type of stimulation delivers high-frequency (50–150 Hz) and low-intensity (below motor threshold) surface electrical current decreased spasticity due to the use of this modality. For instance, TENS has recently reduced spasticity in SCI patients and the effects outlasted up to several hours after treatment [34]. This is because TENS activates sensory nerves that in turn may activate inhibitory interneurons that will inhibit the spastic muscle activity [34]. More specifically, these anti-spastic effects are due to the release of gamma-aminobutyric acid (GABA) that acts as inhibitory neurotransmitters, achieving similar anti-spastic effects to those of baclofen [32], which is a first-line treatment for spasticity, especially in adults who suffered a SCI [35]. Results of spasticity treatment using TENS seem to improve when combined with physical therapy [36]. Given its low cost, lack of adverse event effects, and ease to use, TENS seems to be a very good solution to treat spasticity after SCI. Moreover, since TENS alleviates pain and fatigue and can be used for periods of several hours, it seems to be appropriate for the beginning of the rehabilitation after SCI, when training is not very intensive.

FES

FES delivers trains of electrical stimulation above motor threshold to stimulate a muscle or the efferent nerve supplying a muscle in order to attain a muscle contraction [14]. The higher the amplitude of this stimulation, the bigger is the number of recruited efferent fibers and, therefore, the higher the muscle contraction. In the case of SCI, it is well known that artificially induced contraction of weak or paralyzed muscles brings several therapeutic benefits, such as prevention of lower limb muscle atrophy, increased muscle strength, endurance, and cardiovascular fitness [38, 39]. In addition to these benefits, the coordinated stimulation of efferent nerves (usually to stimulate agonist-antagonist muscles of a joint) can be paired with a functional activity to produce a given biomechanical task and, thus, restore motor function.Finally, FES has also been used to reduce spasticity in SCI patients, usually by stimulating the spastic muscle. This is hypothesized to modulate recurrent inhibition via Renshaw cells [34]. These inhibitory interneurons are excited by collaterals of the axons of motoneurons and make inhibitory synaptic connections with several populations of motoneurons, including those that excite them [40]. This reciprocal inhibition is important to prevent overshooting muscle contraction induced by FES. Despite all the benefits here described, FES presents several challenges for tasks that are executed for long periods of time. Limited muscle force generation, rapid onset of muscle fatigue, and nonlinear, time-dependent mechanical responses, as well as the redundancy of the musculoskeletal system are the main challenges of this technology that traditionally hamper generalized use for rehabilitation and/or motor compensation of walking. However, multi-electrode techniques are showing promising results [41] and should be explored.

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