Are Nerve Root Dysfunctions Visible on Radiological Investigation?
Nerve root demonstrates a sharper curve around disc bulge as it contacts the disc during neck flexion © NDS 2007
L4-5 Nerve root relaxed without neck flexion
© NDS 2007 In his second book, Adverse Mechanical Tension in the Central Nervous System (1978), Dr Alf Breig, showed that, in patients with symptoms of lumbar radiculopathy, mechanical dysfunction in the nerves can be visible with myelography.
As an example, a patient's nerve root symptoms could be reproduced with neck flexion and, in this same patient, the nerve root could be seen to distort around a disc bulge.
This pressure distortion occurred as the nerve pressed against the bulge due to the increased tension generated by the neck flexion (see Figure).
The transverse movement of the nerve was impaired also.
This is a good example of mechanical impairment of the neural tissues linking to production of symptoms in patients.
This phenomenon relates to important contemporary research on lumbar nerve root movement, abnormal neurodynamic tests and nerve root blood flow.
Can Nerve Root Tissue move relative to its Meningeal Sheath?
However, Dr Alf Breig showed that this may be possible. In one of his detailed dissections of the nerve root complex in fresh cadavers, he showed that the axons in a nerve rootlet (intradural bundle of nerve fibres between the cord and nerve root) have the capacity to slide inside their arachnoid sheath.
In Breig's dissections of fresh unembalmed cadavers, the neural tissues were seen to slide inside the arachnoid sheath as the tissues move with spinal movements.
This raises the possibility of potential for impairment of movement between these two structures in the presence of inflammation, oedema and scarring of the nerve root, pathology that was described in detail by Frykholm as early as 1951 and has been observed at surgery on numerous occasions.
Incidentally, Alf Breig worked with Frykholm in the early days.
Figures on the right: The nerve rootlet filaments can be seen to behave independently of their arachnoid covering.
Notice that the thin arachnoid is transparent and the axons in the nerve rootlet are taught and have moved relative to the arachnoid lining. Notice also the blood vessel distortion in the arachnoid with elongation.
Cadaver Dissection - Musculocutaneous Nerve
© 2007 Diane Jacobs, with permission.Diane Jabobs, PT, in British Columbia, Canada, has just released these hot pictures of her recent dissections of the cutaneous branches of the musculocutaneous nerve.
The branches are coloured black and can be seen to terminate in a disseminated fashion throughout the skin over the radial aspect of the forearm.
© 2007 Diane Jacobs, with permission.The nerve leaves the lateral cord of the brachial plexus (C5, 6, 7) and innervates the coracobrachialis, biceps and brachialis muscles and the skin over the radial aspect of the forearm.
During the median neurodynamic test, it becomes tight, where it can sometimes be seen as it passes across the lateral aspect of the elbow into the forearm.
© 2007 Diane Jacobs, with permission.The cutaneous division can often be readily palpated next to brachioradialis and is sometimes mistaken for the posterior interosseous nerve (PIN), even though the PIN is deep to these structures.
Diane is a spearhead of the newly formed and fast growing Canadian Physiotherapy Pain Sciences Group and has a particular interest in the relationships between skin innvervation and clinical pain states.
We are grateful for the opportunity to present these illustrations and thank her very much.
Visit the Canadian Physiotherapy Pain Sciences Group:
Close Links Shown Between Mechanical and Physiological Function of the Nervous System in Patients with Sciatica
A key question in relation to the concept of neurodynamics as proposed by Shacklock in 1995 is whether close links between mechanics and physiology of the nervous system really do exist in patients with known pain syndromes. The following abstract shows a number of critical aspects that have powerful implications philosophically, scientifically and clinically. This study should be considered a classic in illustrating direct interdependence of these two aspects of neurodynamics.
The relevant implications are:
- Mechanical dysfunction produced impairment in physiology (reduced intraneural blood flow) in lumbar nerve roots in patients with sciatica.
- Improvement of the mechanical dysfunction produced rapid improvements in nerve root blood flow. The blood flow in the nerve roots returned toward normal levels after decompression. Improvements were also made in nerve root movement in the foramen through excision of foraminal scar tissue that impaired nerve root sliding.
- The range of motion of the SLR at surgery at which impairment in nerve root blood flow commenced was the same range at which patients' preoperative symptoms were reproduced with the clinical SLR test.
- The clinical SLR test and nerve root movement and blood flow improved after the surgery.
Changes in nerve root motion and intraradicular blood flow during an intraoperative straight-leg-raising test
Kobayashi S, Shizu N, Suzuki Y, Asai T, Yoshizawa H 2003 Changes in nerve root motion and intraradicular blood flow during an intraoperative straight-leg-raising test. Spine 28 (13):1427-1434
STUDY DESIGN: An intraoperative straight-leg-raising (SLR) test was conducted to investigate patients with lumbar disc herniation to observe the changes in intraradicular blood flow, which then were compared with the clinical features.
OBJECTIVE: The legs of each patient were hung down from the operating table as a reverse SLR test during surgery, and intraradicular blood flow was measured.
SUMMARY OF BACKGROUND DATA: It is not known whether intraradicular blood flow changes during the SLR test in patients with lumbar disc herniation.
METHODS: The subjects were 12 patients with lumbar disc herniation who underwent microdiscectomy. The patients were asked to adopt the prone position immediately before surgery, so that their legs hung down from the operating table. A reverse SLR test was performed to confirm the angle at which sciatica developed. During the operation, the nerve roots affected by the hernia were observed under a microscope. Then the needle sensor of a laser Doppler flow meter was inserted into each nerve root immediately above the hernia. The patient's legs were allowed to hang down to the angle at which sciatica had occurred, and the change in intraradicular blood flow was measured. After removal of the hernia, a similar procedure was repeated, and intraradicular blood flow was measured again.
RESULTS: Intraoperative microscopy showed that the hernia was adherent to the dura mater of the nerve roots in all patients. The intraoperative reverse SLR test showed that the hernia compressed the nerve roots, and that there was marked disturbance of gliding, which was reduced to only a few millimeters. During the test, intraradicular blood flow showed a sharp decrease at the angle that produced sciatica, which lasted for 1 minute. Intraradicular flow decreased by 40% to 98% (average, 70.6% +/- 20.5%) in the L5 nerve root, and by 41% to 96% (average, 72.0% +/- 22.9%) in the S1 nerve roots relative to the blood flow before the test. At 1 minute after completion of the test, intraradicular blood flow returned to the value obtained at baseline. After removal of the hernia, all thepatients showed smooth gliding of the nerve roots during the second intraoperative test, and there was no marked decrease in intraradicular blood flow.
CONCLUSIONS: This study demonstrated that the blood flow in the nerve root is reduced when the nerve root is compressed in vivo.