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Redundant nerve roots of the cauda equina: Cauda equina; Spinal stenosis; Spine; Magnetic resonance imaging. In imaging diagnosis, redundant nerve roots of the cauda equina are characterized by the presence of elongated, enlarged and tortuous nerve roots in close relationship with a high-grade lumbar spinal canal stenosis.

This is not an independent entity, but it is believed to imagenollgia a consequence of the chronic compression at the level of the lumbar canal stenosis and thus may be part of the natural history of lumbar spinal stenosis. The present paper is aimed at reviewing the histopathological, electrophysiological and imaging findings, imagejologia at magnetic resonance imaging, as well as the clinical meaning of this entity.

As the current assessment of canal stenosis and root compression is preferably performed by means of magnetic resonance imaging, this is the imaging method by which the condition is identified. The recognition of redundant nerve roots at magnetic resonance imaging is important, particularly to avoid misdiagnosing other conditions such as intradural arteriovenous malformations.

The literature approaching the clinical relevance of the presence of redundant nerve roots is controversial. There are articles suggesting that the pathological eqiuna of the nerve roots are irreversible at the moment of diagnosis and therefore neurological symptoms are less likely to improve with surgical decompression, but such concept is not eqiuna consensus.

Initially, Rquina of the cauda equina was described as being identified at myelography as serpiginous filling defects associated with partial or total blockage preventing the transit of contrast material Most recently imaging findings of RNR of the cauda equina were also described for magnetic resonance imaging MRI The prevalence of this syndrome may reach Some studies attribute the first description of RNR of the cauda equina to Verbiest Such studies specifically mention an article where Verbiest has described a series of surgically confirmed cases of lumbar spinal stenosis 14 but, as the original text was evaluated, the authors of the present review concluded that Verbiest described elongated nerve roots in another series of cases about rare presentations of cauda equina compression The literature is controversial on the clinical relevance of the presence of redundant roots of the cauda equina.

There are articles suggesting that the degenerative pathological changes in the affected nerve roots are irreversible and, therefore, the neurological symptoms would be less likely to improve with surgical decompression, but consensus is still to be reached on such concept.

Redundancy of the nerve roots is probably the pathological result of a chronic compressive force at the level of the site of spinal canal constriction 9. The present article is aimed at reviewing the findings described on publications related to RNR of the cauda equina, with emphasis on imaging findings, and particularly at Imagenologa.

Additionally, studies on the clinical significance of this entity were reviewed. The main pathological findings in patients with RNR of the cauda equina were derangement and reduction in the number imagenologja nervous fibers, demyelination, besides endoneural fibrosis and Schwann cells proliferation 8,9.

In their investigation, those authors have not demonstrated any significant change in the anterior ikagenologia and in the anterolateral columns of the spinal cord. Low degree of nerve cells loss and spinal ganglion fibrosis were observed, but such changes were equally present in non-redundant roots and were, therefore, considered as changes related to aging.

The topographic distribution in observed in cases of redundant nerve roots was The anatomical study developed by Suzuki et al. No redundancy was observed in roots which did not pass by the site of canal constriction 8.

Demyelination and axonal loss was considered as being a consequence of the continuous mechanical compression of nerve roots confined to the stenosed spinal canal 8.

The study authors have suggested that such results reflected the reduction and degeneration of the nerve fibers 8. They also have not found any significant difference in the electrophysiological manifestation between ventral and dorsal redundant nerve roots. Measurements of the redundant and non-redundant nerve roots conduction velocity were performed during surgery In that study, the velocity of conduction of redundant nerve roots was approximately one half the normal value and, in general, the redundant nerve roots presented multiphase action potentials temporarily dispersed as compared with the normal roots.


Only one case report approached the evaluation of electromyographic changes related to RNR of the cauda equina in the postoperative period Such report has documented preoperative partial denervation of the left medial segment of the gastrocnemius muscle and, in spite of the significant pain relief experienced by the patient after laminectomy, electromyographic changes in the gastrocnemius muscle were still present over the three-month and sixmonth follow-up.

Spontaneous extrusion of elongated roots usually occurs during the surgical opening of the dura mater 2,6,7,11, The opening of the dura mater may be performed to rule out the hypothesis of arteriovenous malformation 7 or simply because surgeons have decided that such a procedure should be a part of the decompression 6, Also, there are reports on the indication of duroplasty in association with decompressive laminectomy was indicated for the relief of nerve root compression 11, At the time, myelography was the only imaging method available to document the anatomy and pathology of nerve roots of the cauda equina in vivo.

Currently, myelography has been widely replaced by MRI and its utilization has remained restricted to the rare cases where MRI is contraindicated or for those cases where postoperative metal artifacts are enough to severely degrade MRI images.

The myelographic pattern described in redundant nerve roots of the cauda equina corresponds to serpiginous intradural filling defects associated with a partial or complete blockage of the transit of contrast material and, therefore, spinal canal stenosis Variations in the positioning of the patients may influence the presentation of RNR of the cauda equina at the images.

The orthostatic position yields a better visualization of redundant roots 1,7,8, Serpiginous filling defects may also be identified by myelography in the presence of dural or intradural arteriovenous malformations 17thus constituting an important differential diagnosis. Less frequently, a plexiform neurofibroma or a neurinoma may cause thickening and redundancy of nerve roots Other diseases can cause hypertrophic neuropathy such as arachnoiditis, chronic inflammatory demyelinat-ing polyneuropathy and some hereditary neuropathies; but association between such entities and serpiginous nerve roots of cauda equina was not reported.

Thickened, elongated and tortuous or serpiginous nerve roots adjacent to a site of lumbar vertebral canal stenosis represent typical findings.

In the literature, signal intensity abnormalities nerve roots have not been reported in association with RNR of the cauda equina.

Imagenologia en Equinos

Figures 1 and 2 illustrate the typical MRI findings in cases of redundant nerve roots. A year-old woman with neurogenic claudication. Preoperative MRI images obtained for planning of surgical decompression. Sagittal MRI T2-weighted image imagenolohia degenerative changes of the spine with disc herniation and vertebral canal stenosis at L and L levels arrowhead.

Elongated and tortuous nerve roots of the cauda equina can be identified arrow. Axial MRI T2-weighted image obtained at a level slightly above the L stenosis, also presenting tortuous nerve roots arrow.

A year-old man with clinical manifestations of neurogenic claudication. Sagittal MRI T2-weighted image demonstrates severe lumbar spinal canal stenosis arrow and redundant nerve roots of the cauda equina roots arrowheads.

Surgically confirmed spinal arteriovenous fistula. Sagittal MRI T2-weighted image showing dilated serpiginous vessels arrow. Presence of increased signal intensity in the spinal cord substance arrowhead associated with medullary ischemia secondary to steal phenomenon.

Coronal MRI T2-weighted image also demonstrating dilated serpiginous vessels in the venous plexus arrow. At MRI, the main differential diagnosis must be done with dural arteriovenous malformations or arteriovenous fistulas. In such conditions, MRI usually shows intradural serpiginous vessels and ectasia of the coronal venous plexus Figure 3. However, the clinical presentation of vascular malformations is different from that of canal stenosis, and there are MRI findings that help in the differentiation between these two conditions.

RNR are typically associated with vertebral canal stenosis, and clinically the patient presents neurogenic claudication.

Radiologia Brasileira – Raízes nervosas redundantes da cauda equina: revisão da literatura

At the images, arteriovenous malformations are frequently associated with great draining vessels, and may clinically present with signs of myelopathy, subarachnoid hemorrhage or medullary ischemia 7, Dural arteriovenous fistula is usually associated with abnormalities in signal intensity imagenologiq the spinal cord on MRI T2-weighted sequences All the patients in that study were imagenologiw submitted imafenologia myelography and MRI, and for the purpose of statistical analysis, the patients were divided into three groups, as follows: Statistically significant difference in relation to clinical symptoms was found between groups A and C.


The patients group where MRI imavenologia RNR of the cauda equina group A presented more severe clinical symptoms than group C, both pre- and postoperatively. Then, the same authors speculated that the redundancy would have been underestimated at MRI in the less severe cases, where the redundancy was only demonstrated at myelography, probably because of the fact that, at MRI, the lumbar spine image acquisition is routinely performed with the patient in a neutral positioning, while the myelography study was performed with dynamic evaluation in the orthostatic position.

In another study, the relative length of the redundant nerve roots was measured on sagittal MR images and presented statistical relationship with clinical improvement within the group of patients with RNR Imqgenologia authors standardized the measurement of the relative length of the nerve roots on the most central sagittal image of the lumbar column. The relative length was obtained by measuring the distance from the maximum kmagenologia level to the most distant point where the qeuina of redundant roots could be identified, and by dividing such obtained value by the height of the vertebral body located above the stenosis level.

The greater the relative length, the better the postoperative outcomes, a result that, at a first analysis, seems to be unexpected, leading the study authors to raise the hypothesis that such result was related to a greater accommodation capability of the longer redundant roots during flexion and extension of the spinal column, as related to effects of traction forces The present study authors did not find any other study investigating such type of imaging finding in relation to postsurgical outcomes.

Imagenlogia clinical condition of patients with RNR of the cauda equina is related to the natural history of the lumbar spinal canal stenosis.

One believes that chronic lumbar stenosis is the primary cause of symptoms. The results from the study developed by Suzuki et al. The literature is controversial about the implication of the imaagenologia of RNR in the indication for decompressive surgery for spinal canal stenosis. Some investigations suggest that such abnormalities of the nerve roots are irreversible, and, therefore, the eqiina symptoms are not susceptible to improvement after surgical decompression 8,9.

In two other studies, the postoperative improvement was not statistically different in patients with and without RNR of the cauda equina 12,13but in one of those studies a tendency towards worse results for patients with RNR of the cauda equina was identified, similarly to the results reported by Ono et al.

Anyway, the complete regression of stenosis symptoms after surgical decompression is rare in patients with typical RNR, and they frequently continue complaining of dysesthesia and paresthesia The clinical significance of such abnormality of the cauda equina in the progression of lumbar canal stenosis is still controversial, but there are indications in the literature suggesting that its identification at MRI may indicate a tendency towards worse postoperative results.

Therefore the authors of the present review suggest that radiologists should look for RNR of the cauda equina at MRI and, if applicable, describe such finding in their reports. Serpentine myelographic defect caused by a redundant nerve root.

Redundant nerve roots in the cauda equina. The “redundant” or “knotted” nerve root: Gulati DR, Rout D. Myelographic imwgenologia caused by redundant lumbar nerve root. Serpentine cauda equina nerve roots. Redundant nerve roots of the cauda equina. Redundant lumbar nerve root syndrome: Redundant nerve roots of imagenopogia cauda equina caused by lumbar spinal canal stenosis. Clinical significance of the redundant nerve roots of the cauda equina documented on magnetic resonance imaging.

The redundant nerve root syndrome of the equin equina. Clinical significance of redundant nerve roots of the cauda equina in lumbar spinal imwgenologia. Redundant nerve roots in patients with degenerative lumbar spinal stenosis. A radicular syndrome from developmental narrowing of the lumbar vertebral canal. J Bone Joint Surg Br. Sur certaines formes rares de imagfnologia de la queue de cheval.

Electromyographic abnormalities in redundant nerve root syndrome of the cauda equina. Arch Phys Med Rehabil.