Inverted supinator reflex & its relevance to the manual therapist explained

Osteopaths like many other manual therapists such as chiropractors and physiotherapists have become known as specialists in back pain. For this reason, conditions such as spondylitis and spondylarthrosis are commonly seen by these practitioners, both of which can lead to compressive cervical myelopathy, compression of the spinal cord in the neck. Needless to say, osteopaths, physiotherapists and chiropractors must be familiar with the neurological tests that help differentially diagnose causes of neck and arm pain. In the upper limb it is less the sensory tests and more the motor tests and reflexes that help the osteopath to identify nerve root compression. The inverted supinator reflex is probably the the most important clinical sign that an osteopath, physiotherapist or chiropractor can illicit to decide whether there is spinal cord and spinal root compression. It is pathognomonic of cervical myelopathy at the level of C5/C6. In this article I will try and help the manual therapist; osteopath, physiotherapist and chiropractor the professions that use spinal manipulation, to understand the physiology of the inverted supinator reflex in order to appreciate its significance when treating patients.

One of the most common types of extra-dural cord compression (compression occurring outside of the dura matar) that an osteopath, physiotherapist or chiropractor is likely to come across is caused by spondylotic change, that is, spondylotic compressive myelopathy. Since the majority of movement in the cervical spine is focused between the levels of C5 and C6 vertebrae it is at this level that arthritic changes most frequently occur. At this level, On x-ray it is common to find a cervical bar due to disc degeneration, spondylosis, a posterior longitudinal ligament which is buckled, thickened and calcified and osteophytosis protruding into and narrowing the spinal canal. However, osteophytic changes narrowing the vertebral canal are unlikely to be limited to the spinal canal alone. It is likely that there will also be narrowing of the intervertebral foramen simultaneously due to thinning of the vertebral disc and thickening of the ligamentum flavum. The result of this is both compression of the spinal cord and compression of the nerve roots.

The osteopath must therefore be aware that any patient suffering with nerve root symptoms attributed to degeneration of the cervical spine, such as pain down the arm into the thumb, must be examined in order to exclude any long-track or spinal cord damage. It is for this reason that patients suffering with suspected cervical spine degeneration and nerve root symptoms in the upper limb must always be asked whether they also have leg symptoms such as heaviness, stiffness, difficulty climbing up stairs, tight band-like feelings (dorsal columns), a sensation of standing on a vibrating floor (dorsal columns), a sensation that water is running down the legs (spinothalamic tract) or pins and needles that don't conform to a nerve root pattern.

In addition to questioning the patient, the clearest indication of both nerve root and spinal cord compression in the cervical spine is displayed by the inverted supinator reflex. By tapping the brachioradialis tendon at the styloid process of the radius a force is sent down the bone, irritating the muscle spindles of all muscles at the front and back of the forearm, sending a message to the spinal cord, resulting in the reflex flexion of the forearm and fingers. The nerve roots responsible for elbow and finger flexion are C6 and C8 respectively. C7 however, responsible for elbow extension, is not activated despite its muscle spindles being irritated. This leads us to conclude that in a polysynaptic reflex, when a multitude of nerve roots are activated the reaction is for dominant nerve roots to react whilst others lie dormant.

Spondylosis, thinning of the disc between two vertebra causes compression of the nerve root between two vertebrae, deactivates its axons and gives other nerve roots, unaffected by compression, the opportunity to express themselves. In the event that there is also cord compression, an upper motor neuron lesion, above the level of the unaffected nerve roots, they will not only express themselves, they will be hyper-reactive. This explains the structural changes in the spine that result in an inverted supinator reflex. Bony changes of the intervertebral foramen between the vertebrae C5/C6 of the spinal column cause narrowing of the intervertebral foramen and compress the nerve root of C6 as it exits the spine causing a hypo-reflexive reaction from the nerve root C6. The bony changes in the form of a cervical bar, situated within the spinal canal at C5/C6 vertebrae, result in an upper motor lesion rendering everything below it hyper-reflexive. Therefore, C7, once dormant, now active, becomes hyper-reflexive as does C8. The result is an inverted supinator reflex, inverted because there is an absence of the C6 brachioradialis reflex and C7 is responsible for the elbow extension. One would also find a hyper-reflexive reaction at all reflexes on the same side of the body, that is, the knee jerk and ankle jerk reflex. One would also find clonus of the knee and ankle on the same side as well as an up-going planter response in-line with an upper motor neurons lesion.

This explains the pathophysiology of the the spinal column and the effect that altered structure can have on the nervous system. It should be clear why this sign is an important indicator for the osteopath, physiotherapist and chiropractor and GP as well as manual therapists using spinal manipulation Early identification of spondylotic compressive myelopathy can result in appropriate medical treatment being administered and avoids permanent neurological damage.

Danny Sher
Registered osteopath
Jerusalem: 14 Kaf Tet b'November Street
Modiin: Dimri Medical Center, 37 Yigal Yadin Street
02-561-1808
0522-606-774
Website: www.osteopath.co.il
Video: http://youtu.be/AxI2TfSatHE

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