Impact of MR Neurography in Patients with Chronic Cauda Equina Syndrome Presenting as Chronic Pelvic Pain and Dysfunction

Discussion

This retrospective analysis of a series of subjects with clinically suspected chronic cauda equina syndrome presenting with chronic pelvic pain or dysfunction in a tertiary care setting confirms the ability of lumbosacral MRN to impact their diagnoses and therapeutic strategies. No longer considered “experimental,” this imaging technique has the potential of quick transition into the community setting. Although CES is a challenging diagnosis, our analysis suggests that this examination can add considerable value to the evaluation of these patients because the clinical presentation, findings, and examination are often confounded with vague chronic and stable neurologic dysfunction and/or pelvic pain symptoms.¹² Lumbar spinal and lumbosacral nerve root analysis on MRN is more consistently able to distinguish arachnoiditis or clumping of nerve roots and tethered cord in regard to the effect on the neural components within the spinal canal. MRN was also able to help determine whether cysts within the spinal cord were creating an objective pathologic effect on the nerve roots (edema, inflammation, and so forth) or were merely seen in association with the nerve roots. Some other specific peripheral nerve findings on MRN, as noted by a trained radiologist, included peripheral nerve size and signal intensity (and associated symmetry), nerve discontinuity, mechanical distortion, relations of nerves to masses, image features revealing distortion of nerves at entrapment points, fibrosis, inflammation, and edema.^13⇓–15 These findings should be clinically correlated.

When performed appropriately, this examination can provide an accurate and timely diagnosis for patients with an often confusing clinical picture and complex differential diagnosis. Notably, one of the patients who demonstrated a change was diagnosed with extensive lymphadenopathy on MRN (no prior MR imaging), prompting admission to the hospital for malignancy work-up, later revealing Hodgkin lymphoma, though a simple MR imaging with contrast, had it been ordered earlier, would have been enough to identify this condition. Subsequent management changes that may not have occurred without the information obtained from MRN included neurosurgical referral, peripheral nerve blocks, epidural steroid injections, and discontinuation of pelvic physical therapy (treatment for lower motor neuron dysfunction via referral to spinal cord injury clinic). One large retrospective case series that looked at the role of MRN in the diagnosis of spinal and peripheral nerve lesions also concluded that a significant indication for MRN is in patients in whom electromyography/nerve conduction study and MR imaging findings are inconclusive.¹⁴ More accurate and timely diagnosis helps prevent further expensive and potentially invasive work-ups, providing some clarity to an otherwise confusing clinical picture. Although there were no cost-effectiveness analyses performed, the results of our study suggest that a more resolute diagnosis helps the patient focus more on symptom treatment and management rather than continuing further work-ups and misdirected treatments.

One potential point of contention that should be addressed is the appropriateness of the term “chronic” CES. Although CES is an acutely presenting syndrome with a classic presentation of red flag symptoms, it may also be a chronic condition as a result of delayed treatment of the acute syndrome. The chronic and progressive form is more commonly seen in inflammatory or demyelinating conditions. Giving reference to these more indolent etiologies of their neurologic compromise also gives patients more clarity in understanding their diagnosis.

A search of the literature did not reveal any other reports of using MRN to look for lumbosacral intraspinal lesions, and in particular chronic CES. Additionally, lumbosacral plexus MR neurography studies not only help identify lesions within the spinal cord but also aid in finding peripheral neuropathies and plexopathies elsewhere in the pelvis.^8,13,14

There are several limitations in our study. The analysis, including the retrospective methodology and, to some degree, the categorization of “no” or “yes” with regard to change in management, is somewhat subjective, leaving it open to bias. A few patients were lost to follow-up; thus, we do not have complete imaging or clinical management data for these subjects. Due to the retrospective nature of this study, no interobserver performance in repeat readings of the MRN examinations was obtained (all studies were ultimately interpreted by one of the authors), stressing the need for an increase in the number of radiologists qualified to read these studies. Figure 2 illustrates the increased sensitivity of the radiologist reading the MRN examinations. However, we were attempting to uncover the impact of routine reads of these examinations in a tertiary care setting.

Future directions include performance of a larger, prospective randomized clinical trial looking at the clinical impact of MR neurography on this and other neurologic diseases. A multicenter trial would be ideal to decrease potential bias, given the relative paucity of specialized radiologists qualified to read these studies. Performing a cost-effectiveness analysis on the impact of MRN results would also be helpful in identifying how these studies impact standard practice economy.¹⁶