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Therapeutic role of Trans-foraminal nerve root block in management of lumbar radiculopathy

Treatment of Acute Lumbar Radicular pain has many controversies. While pure mechanical compression was considered previously as a source of sciatica, there is increasing evidence that chemical irritation of the nerve root plays an essential and perhaps even more important role. Trans foraminal selective nerve root block is an approved method for management of radicular pain. The aim of our study was to conduct a prospective study, 1. To assess the adequacy of relief provided by trans-foraminal Nerve Root Block for Lumbar Radicular pain. 2. To determine the effectiveness of selective (trans-foraminal) nerve root injection in diagnosis and treatment of patients with Lumbar radiculopathy. 28 patients with radicular pain involving single nerve root were selected. Trans-foraminal selective nerveroot block was done as per standard technique. Results were analyzed using VAS Score & RMDQ Score. Analyzing results showed that 89.3% patients had improvement. RMDQ score were reduced by 61% by end of 6 months. 18 patients (85.7%) who are on more than 6 months of follow up are able to do their daily activities without difficulty. We conclude by our study that, the trans-foraminal nerve root block combined with careful history, physical examination and quality radiolographic studies, is an important tool in the diagnosis and treatment of patients with predominant Lumbar radicular symptoms.


Introduction
Treatment of Acute Lumbar Radicular pain has many controversies. Most authorities recommend bed rest, anti-inflammatory medication and physical therapy (Riew et al. JBJS 1982 andTulder et al. Spine 22-1997) Comparing the results of operative and conservative treatment in selected patients, many authors (Weber et al. Hakelius et al.) [1] , found not much significant difference after first year and no difference after 4 years. However many patients treated conservatively complains of persistent pain and seek further intervention. The pathophysiology underlying radicular pain is poorly understood and it is thought that nerve root compression is a key factor and from a surgical perspective, nerve root decompression is considered to be the key therapeutic step. However, in patients with severe lumbar canal stenosis, radicular pain is not a typical feature. Only those patients with intervertebral disc lesions affecting a single lumbar nerve root were selected for the study. Those patients with more of back pain, than radiating pain were excluded. Those with bilateral symptoms, multiple nerve root involvement and neurological weakness were excluded.

Materials and methods Technique
All trans-foraminal Nerve Root Blocks were performed as inpatient procedures without premedication. Informed consent was obtained. Under aseptic precautions, under X ray fluoroscopy guidance, the nerve root was identified (Safe Triangle). 1 ml of lignocaine and 1 ml of Depomedrol is injected at the nerve root. All patients underwent a standardized program of intensive physical therapy, which included procedures for local pain relief and reconditioning exercises for the spinal muscle, for at least 6 weeks after the procedure. Pain severity was assessed immediately after the procedure and after 6hrs. Then after 24hrs. Patient was discharged the next day. Follow up was done weekly for upto 1 month. Then monthly for 6 months. Pain severity was evaluated using various assessment scales (visual analogue scale, Rolland -Morris 2 scale,) and results are analyzed both pre procedure and post procedure. Various parameters like age, sex, nature of work, duration of symptom, amount of pain relief, ability to return back to their regular activities were assessed and the role of selective nerve root block in management of Lumbar Radicular syndrome was studied.

Results
Total no of patients 28 21 patients had L4-L5 disc prolapse which usually affects the L5 nerve root that traverses at this level and exits below the L5 pedicle. 7 patients had L5-S1 disc prolapse that usually affects the S1 nerve root which exits in the first sacral foramina.  All patients were reviewed after one week and were given the Roland Morris Disability questionnaire for back pain and their score was noted. Mean overall RMDQ score at 1 week was 9.96 (n= 25) which denoted improvement. They were on physical therapy. And were advised not to do heavy manual works.3 patients had RMDQ score more than 15. They were given reassurance. By 3 weeks 3 patients with RMDQ > 15 had symptoms similar to pre procedure. They were excluded from further follow up. Review at one month had mean RMDQ score of 9.8(n=25). Next follow up was by 3 months mean RMDQ score was 9.48 (n=25).
Mean RMDQ scores at further follow up in 6 months (n=18) was 9.1. Analyzing results showed that 89.3% patients had improvement. RMDQ score were reduced by 61% by end of 6 months. 18 patients (85.7%) who are on more than 6 months of follow up are able to do their daily activities without difficulty.

Discussion
Lumbar disc herniation is one of the few abnormalities in the lumbar spine, were a clear relationship between the morphological alteration and pain seems to exist [3] . Previously, pure mechanical compression was considered as a source of sciatica. But now there is increasing evidence that chemical irritation of the nerve root plays an essential and perhaps even more important role. Nucleus pulposus has inflammatory properties, which causes intraneural oedema, a very important factor found in the pathogenesis of sciatic pain [4][5][6][7] . The inflamatory effect of nucleus pulposus on the nerve root can be greatly reduced by the application of methylprednisolone [8] . The compression of nerve root by nucleus pulposus tissue seems to be selflimiting. Otani et al. [9] have shown in an animal model, that this effect is most significant after seven days and spontaneously reduces to normalise within a two month period. These experimental findings explain, why sciatica has a favourable natural history for spontaneous recovery [10] . Surgery in patients presenting with a radiculopathy with or without minor neurological sensory/motor deficit (discectomy/nerve root decompression) is only required, if the initial pain cannot be well controlled by non-operative means. Otherwise, surgery is not required because spontaneous recovery can be expected [10,11] . Macnab first described selective nerve root blocks in 1971 [12] . This infiltration was aimed to differentiate different sources of leg pain in an equivocal clinical situation. The selective nerve root injection allows the diagnosis of the affected nerve root with a sensitivity of 100% in cases with disc protrusions and with a positive predictive value of 75 to 95% in cases of a canal stenosis [13] . In a prospective study, Weiner and Fraser [14] investigated the effectiveness of nerve root blocks in 30 patients with foraminal and extraforaminal disc herniation. In total, 22 of 28 patients (79%) had a significant and permanent pain reduction during a 1-10 year follow-up. Another study by Martin Narozny, Marco Zanetti, Norbert Boos [15] shows "In 60% of the patients a rapid permanent pain resolution occurred, there was no need for surgery".
One prospective, randomized, controlled, double-blind study by Riew et al. was performed in patients who had surgical indications for nerve root decompression and who initially wished to undergo surgery to relieve radiculopathy (J Bone Joint Surg Am. Nov 2000; 82-A(11): 1589-93) [16] . Approximately 71% of those who underwent trans-foraminal injection (anaesthetic + steroids), elected not to have surgery (follow-up, 16 months), whereas only 33% of those injected with bupivacaine (anaesthetic) alone avoided surgery. A subsequent follow-up study [17] in this cohort found that most of the patients who avoided surgical decompession for at least 1 year after undergoing SNRB, continued to avoid operative intervention for a minimum of 5 years. Zennaro et al. [18] found the greatest efficacy of steroid injections in patients who had foraminal stenosis, when compared with those who had foraminal disc herniations. Devulder [19] found that trans foraminal injection with steroids was associated with decreased treatment scores in patients with failed back surgery syndrome also. The average time of pain relief, in various studies, was 1-3 months in those patients that have initial improvement. Although some studies [20] have documented longer relief in a high percentage of patients.

Conclusion
Nerve Root Block is an effective therapeutic tool for Lumbar Radicular pain and is recommended for the initial treatment of this condition. The trans-foraminal nerve root block combined with careful history, physical examination and quality radiolographic studies, is an important tool in the diagnosis and treatment of patients with predominant Lumbar radicular symptoms.