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IMF Therapy® (Intention triggered Myo-Feedback)

Study Results.

An innovative method in the treatment of peripheral nerve lesions

K. Hall¹, U. Schmidt², R. Schmidhammer³

¹ Reflex Therapeutics, UK - Shoreham-by-Sea
² IMF Reha GmbH, D- 07545 Gera
³ Millesi Center for Surgery of Peripheral Nerves, Wiener Privat Klinik, A- 1090 Wien

Problematic

“What do I have to do to be able to pick up a glass again?” That is the burning question for patients who suffer from motor and sensory defects in their arms and hands after brachial plexus lesion and have lost movement in those limbs. Despite the reconstruction of nerves there is often no recovery.

Physiotherapy is a well established part of the rehabilitation of peripheral nerve paralysis. The aim of this type of treatment is to re-establish arbitrary functions by improving the patients’ active and passive mobility as well as their strength and stamina. This is achieved through the activation of peripheral motor processes, such as proprioceptive neuromuscular facilitation (PNF) or passive muscle stimulation. Despite regular treatment sessions chronic patients exposed to IMF®-Therapy sometimes suffer not only from limited motor functionality but also severely impaired surface and depth sensitivity. Many chronic patients are also unable to imagine a movement learnt prior to becoming disabled. This phenomenon often only becomes apparent when patients are asked to simulate a specific arbitrary movement in their mind, for example pulling a folder from a shelf in their old office. As long as there is some remaining activity in the affected limb and the patients are encouraged to use physical strength to carry out the movement they will establish pathological movement patterns with every attempt. This leads to their positive learning experiences from the time before the illness being overshadowed by post-lesional, negative experiences.

Theories about channelling movement agree that planning and carrying out arbitrary movements is highly influenced by anticipating the specific aims of movements (Jeannerod, 1994; Prinz 1997; Rosenbaum & Krist, 1996). Not being able to imagine a movement means that the patient cannot remember the effects of previously carried out movements, resulting in an inability to reach similar desired results in the present situation. Planning and carrying out purposeful movements therefore becomes impossible. This poses two problems for the rehabilitation process. Finding solutions for these problems could significantly improve rehabilitation:

  • How do chronic patients acquire the ability to reactivate positive learning experiences despite not being able to remember previously learnt movements? Literature does not offer any answers.
  • How do patients acquire the ability to inhibit negative learning experiences? Literature does not offer any answers to this problem either.

IMF Therapy®’s approach goes beyond the purely neuro-scientific framework and also takes into account methods and concepts of the psychology of learning. The essential assumption is that things learnt in the past are firmly established in the long term motor memory and can be reactivated by the patient (Shadmehr, 1997).

Learning aims

The aim of IMF Therapy® is the re-learning of sensory-motor functions.

  • The therapy focuses on the ability to reactivate a positive learning experience whilst inhibiting the negative experience.
  • As soon as the patient is able to remember the old experiences, he or she shall learn to make use of these sensory-motor experiences and to re-establish an association of the imagined anticipated aim and the movement to be carried out with the affected limb. This is achieved through internal simulation of sensory consequences of individual actions.
  • The assumption is that these learning processes activate various mechanisms related to neuro-plasticity. Scientific research provides evidence for the theory that improvements to sensory-motor functions are based on neuro-plasticity and the ability of injured peripheral neural pathways to regenerate, which can be influenced by learning processes.
  • Therefore plastic changes could cause a reorganisation on the cortical level, which in turn could improve regeneration on the peripheral level.

Learning mechanisms

Sensory-motor experiences, anticipated aims, changes to the neural activity and amplification are based on learning mechanisms.

1. Reactivating previously learnt movements

To relearn sensory-motor functions means to be able to refer to cognitive concepts of movements acquired before the injury. These contain the positive learning experiences gained through putting arbitrary movements in relation to the aims of the movements. The lack of an expected effect of the movement caused by a lesion might reduce the ability to carry out the movement but it doesn’t eliminate it completely (Adams, 1971). Visual scientific results from cerebral research show that previously established neuronal structures are being transferred to other areas of the brain. This means there are still available and could be reactivated (Shadmehr R 1997,1999).

Apart from representations of positive learning experiences there are also those with negative experiences, which were acquired after the injury or illness. These include pathological patterns, a result of repeated active attempts of movements with unwanted effects. The basic prerequisite for relearning lost functions is to inhibit these representations and to reactivate old experiences.

IMF Therapy® suggests mental training as a solution to the problem of reactivating pre-lesional experiences. The method is based on the knowledge that actions can be carried out mentally (Hommel 1996). It is therefore possible to encourage the patient to imagine different situations from the time before falling ill and to search for movement patterns which used to lead to the anticipated effects in the affected limb. Memory is usually retrieved after a few repeated attempts.

We can assume that unwanted effects can be inhibited once the memory of the positive experience has been retrieved. The choice of specific movements depends on the power of the association and the relative importance of the movements (Hommel 1996, 1997, 1998, Hommel et al. 1999). Regular mental training reinforces the selection criteria in favour of the anticipated movement and against the unwanted effects.

2. Anticipation

Once the patient has succeeded in remembering movements learnt prior to the lesion the anticipation of a specific arbitrary movement becomes possible again. Anticipation is "a memory of consequences of actions experienced in the past" (Elsner, 2000). Simply "thinking of the intended effects of an action or imagining its effects is sufficient to trigger a movement which will result in exactly these effects" ("ideo-motoric principle", Lotze, 1852; James, 1890).

Hence movement is initiated through anticipation, or cognitive expectation, of its intended aims (Jeannerod 1994; Prinz 1997; Rosenbaum & Krist 1996; Elsner 2000). Neuro-scientific research backs the theory of anticipated aims. Brain research on monkeys showed that even before a movement is carried out certain neuronal areas in the brain are active, representing the anticipated aims of the action (Sakata et al., 1997). For example, when the intention is to grasp an object, the opening of the hand is being imagined and prepared on the cortical level, while the hand is still in the process of moving towards the object (Jeannerod 1981).

4. Amplification

Mental activity escapes conscious perception and control (Prinz, 1992). IMF®-Therapy assists in achieving perceptible effects with the help of an external mechanism, an EMG-driven muscle stimulating device called MfT Z². This technical innovation allows a mental connection of MfT Z² to arbitrary nerve impulses, provided an EMG rest activity is detectable in the paretic muscle. The EMG-activity, which correlates with the imagined movement, triggers a low-frequency muscle stimulation, which in return provides an intrinsic feedback. The patient may or may not be able to feel this, depending on his or her post-lesional sensory qualities. However, if the sensory stimulation triggers the anticipated aim in the patient’s mind through either proprioceptive or exteroceptive effects, then the same stimulation patterns of the cognitive representation are activated again, leading to the plastic mechanisms described above.

Muscle stimulation activates Type-II fibres. Just like with an arbitrary movement an activation of Type-I muscle fibres is followed by an activation of Type-II fibres, which has a positive effect on the intra-muscular co-ordination.

At the beginning of the treatment many patients are not quite sure whether the reaction and effect experienced close together means the reaction came first and was followed by the effect (amplification) or vice versa. After continued practice the patients learn that perceptible effects relate to the intention and the anticipated aims.

Method

IMF Therapy® contains mental, sensory and repetitive training, supported by the medical device MfT Z². An interface between the patient and MfT Z² allows the mental activation of the device via arbitrary nerve impulses.

1. Mental training

At the beginning of the therapy the therapist develops an individual "tailor-made" imaginary movement with the patient, which is directly aimed at the paralyzed muscles. Relevant electric activity in the form of EMG-potentials can be detected. The medical device MfT Z² picks up these potentials via sensors (surface-EMG-electrodes), amplifies them and feeds them back to the paralyzed muscles in the form of a two-channeled muscle stimulation.

With each imagined movement the arbitrary movement is channeled in order to trigger actual physical changes in the central nervous system, which enables and improves arbitrary movement.

The result of this channeling is the activation of the paralyzed muscle fibers (type I), which are most seriously affected by atrophy.

2. Sensory training

Imagining movements sensitizes the sensory system for feedback from peripheral structures. Contrary to actual movements imagined movement does not trigger a movement in the joints which will give relevant feedback noticeable to the patient. In IMF®-therapy artificial feedback is created with the help of the MfT Z².

Stimulation electrodes are placed on the paralyzed muscles and they are innervated through imagined movement (e.g. for the abduction and exterior rotation of the arm: M. supraspinatus, deltoideus, teres minor, infraspinatus). The stimulation activates the remaining muscle fibers (type II).

Every time the patient imagines a movement involving the affected limb he or she received feedback from the paralyzed muscles.

EMG graph

3. Repetitive training

The patients are inducted into the method at a therapy clinic to ensure that they have the necessary skills to use the device at home on their own. The frequency of the training sessions is vital for successful rehabilitation. Ideally the patient should practice several times a day with MfT Z².

Requirements for usage

The patient must have the mental ability to imagine a proper movement. A minimal nerve activity in the muscles has to be detectable in the affected muscle.

Indications

Peripheral nerve lesions.

Contraindications

Cardiac pacemaker, inflammation or thrombosis in the affected limb.

Myofeedback device MfT Z²

MfT Z² is a medical, wireless device, comprising one separate surface-EMG, one EMG-amplifier and two independent stimulation generators. The surface-EMG provides information on the patient’s channeling characteristics, the two-channeled stimulation gives immediate feedback on the results.

Value:

  • 0 – 2000 mV
  • 2-channelled
  • duration of 200 ms
  • 25-100 HZ
  • 1-12 s

Parameter

  • EMG-sensitivity:
  • Muscle stimulation:
  • Modified square pulse:
  • Frequency:
  • Duration of stimulation:
MfT Z2 device

Results

Can plasticity be induced?
The answer: Yes, by modifying the level of activity (Ebner 1997)

Treatment with IMF

Patient No. Interval (yrs) between accident and IMF treatment Patient No. Interval (yrs)between accident and IMF treatment
1 25 6 1.5
2 2 7 2.5
3 5 8 17
4 1 9 13
5 5 10 1.5
  Average 7.3
Duration of IMF® treatment:
Bullet Sensibility - 5 days: 1 patient
  2 weeks: 2 patients
 
Bullet Extended Treatment: 4 weeks: 2 patients
  6 weeks: 3 patients
  9 weeks: 2 patients
Assessments:
Bullet Sensibility - 2-Point Discrimination (2PD)
  Perception of Vibration (25 Hz)
Bullet Pain - Visual Analog Scale
Bullet Muscle Power and Resisting Range of Motion according to Lovett:
Grade Description Motor Deficit %
5 Complete active range of motion against gravity with full resistance (normal) 0
4a Complete active range of motion against gravity with moderate resistance (good) 5-10
4b Complete active range of motion against gravity with some mild resistance (moderate) 15-25
3 Complete active range of motion against gravity only, without resistance (fair) 30-50
2 Complete active range of motion with gravity eliminated (poor) 60-80
1 Evidence of slight contractility; no joint movement (trace) 90-95
0 No evidence of contractility (absent) 100

Results:

Short Treatment:
Improvement of Sensibility No. of Patients
Shoulder 2
Upper arm 2
Lower arm 0
2/3 patients got a better sensibility
Extended Treatment:
Improvement of Sensibility No. of Patients
Shoulder 7
Upper arm 7
Lower arm 6
7/7 patients got a better sensibility
Short Treatment:
Pre-treatment Pain VAS Post-treatment Pain VAS
0 0
8 5
8 5
2/2 patients had reduced pain
Extended Treatment:
Pre-treatment Pain VAS Post-treatment Pain VAS
2 0
2 0
6 3
6 5
5 0
2 0
0 0
4/6 patients had no pain at the end of treatment
2 patients had reduced pain
Improvement of muscle power max. 1 grade No. of Patients
Short treatment
1 unit of motion 2
Extended treatment
2 units of motion 1
3 units of motion 1
5 units of motion 1
5/10 patients with a re-innervation

Conclusion

IMF Therapy® may be a promising additional rehabilitation tool in peripheral nerve lesion.