Nuances of Spinal Radiculopathy. James Mallows

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1 Nuances of Spinal Radiculopathy James Mallows

2 Spinal dermatomes A dermatome is an area of skin that is mainly supplied by a single spinal nerve

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4 History of dermatomes Pioneering work by Sherrington (late 19 th century), Foester (1933) and Keegan and Garrett (1948) Based on multiple animal experiments and clinical situations

5 History of dermatomes Sherrington Study in monkeys Severed multiple spinal nerves above and below a single spinal nerve and mapped the sensory supply of that nerve Found very predictable dermatomes

6 History of dermatomes Other clinical data Herpes zoster War injuries Spinal root injections with local anaesthetic Human dermatomal maps varied little from the animal models

7 Dermatomes Most areas of the skin are innervated by 2 or more spinal nerve roots Also get intrathecal intersegmental anastomoses of dorsal spinal rootlets, allowing sensory neurons at one dorsal root ganglion to enter the spinal cord at a different level

8 Dermatomes Thus a single spinal nerve lesion may not cause noticeable sensory loss, especially in the trunk However in the limbs, complete interruption of a single peripheral nerve produces changes in sensation that are often appreciated by a patient

9 Diagnosis of radiculopathy Clinical decisions are made by correlating a patient s symptoms and imaging with sensory dermatomal maps Assumption is that pain and paraesthesias will follow the same dermatomal distribution

10 Dynatomes We are now gaining an understanding of pain distribution in spinal radiculopathy Dynatomes vs dermatomes A dynatome is an area of skin that can experience pain in pathology of a particular nerve root

11 Dynatomes Slipman CW, Plastaras CT, Palmitier RA et al. Symptom Provocation of Fluoroscopically Guided Cervical Nerve Root Stimulation. Spine 1998;23:

12 Slipman et al To document the distribution of pain and paraesthesia that result from stimulation of specific cervical nerve roots and compare that to documented dermatomal maps

13 Slipman et al Consecutive patients undergoing fluoroscopically guided cervical nerve root blocks (C4-C8) Immediately preceding contrast injection, mechanical stimulation of the nerve root was performed The site of the pain experienced was recorded and mapped

14 Slipman et al 134 nerve root stimulations on 87 patients

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17 Slipman et al Distinct differences between dynatomal and dermatomal maps

18 Dynatomes Murphy DR, Hurwitz EL, Gerrard JK and Clary R. Pain patterns and descriptions in patients with radicular pain: Does the pain necessarily follow a specific dermatome? Chiropractic & Osteopathy 2009;17.

19 Murphy et al To describe the distribution of pain in patients with cervical and lumbar radicular pain All patients either had: disc protrusion or lateral canal stenosis demonstrated on complex imaging; or EMG documentation of nerve root dysfunction

20 Murphy et al Used a variety of manoeuvres to elicit spinal root pain Patient then mapped where they experienced their pain This map was compared to standard dermatomal charts and was classified as either dermatomal or nondermatomal

21 Murphy et al 226 nerve roots in 169 patients Pain was non-dermatomal in 69.7% in cervical radiculopathy and in 64.1% in lumbar radiculopathy However in S1 radiculopathy, 64.9% of pain was dermatomal

22 Murphy et al In most cases nerve root pain should not be expected to follow along a specific dermatome, and a dermatomal distribution of pain is not a useful historical factor in the diagnosis of radicular pain. The possible exception to this is the S1 nerve root, in which the pain does commonly follow the S1 dermatome

23 Dynatomes Possible reasons Referred pain from discs or other tissues Overlaps between dermatomes Intense and persistent nociceptive input can expand the size of the receptive fields of those dorsal horn cells

24 Dynatomes Therefore we must beware the classical teaching of being able to correlate a patient s pain distribution to the dermatomal nerve root of the site of the pain

25 Epidural steroid injections Do they work? Everyone seems to do them I don t know, I work in emergency I m booked in for one next week but I just can t wait for it

26 Epidural steroid injections Shamilyan TA, Staal JB, Goldman d, Sands-Lincoln M. Epidural steroid injections for radicular lumbosacral pain: a systematic review. Physical Medicine and Rehabilitation Clinics of North America. 2014;25:

27 Shamilyan et al Most guidelines do not recommend routine use of epidural steroid injections Small short term but not long term improvement in leg pain and function Evidence does not support routine use of off-label epidural steroid injections

28 Epidural steroid injections Quraishi NA. Transforaminal injection of corticosteroids for lumbar radiculopathy: a systematic review and meta-analysis. European Spine Journal. 2012;21:

29 Quraishi 126 papers: 5 RCTs with 3 following up patients for more than 3 months 187 patients in the treatment group and 181 in the control group

30 Quraishi Improvement of pain but not disability was observed in the treatment group but not statistically significant

31 Epidural steroid injection Carmel A, Argoff CE, Samuels J, Backonja M-M. Assessment: Use of epidural steroid injections to treat radicular lumbosacral pain. Neurology 2007;68:

32 Carmel et al Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology

33 Carmel et al Epidural steroid injections may result in some improvement in radicular lumbosacral pain when assessed between 2 and 6 weeks following the injection, compared to control treatments (Level C, Class I III evidence)

34 Carmel et al Epidural steroid injection for radicular lumbosacral pain does not impact average impairment of function, need for surgery, or provide long-term pain relief beyond 3 months. Their routine use for these indications is not recommended (Level B, Class I III evidence)

35 Carmel et al There is insufficient evidence to make any recommendation for the use of epidural steroid injections to treat radicular cervical pain

36 Epidural steroid injections Cohen SP, Hanling S, Bicket MC et al. Epidural steroid injections compared with gabapentin for lumbosacral radicular pain: multicentre randomized double blind comparative efficacy study. BMJ 2015;350:h1748.

37 Cohen et al 145 people with lumbosacral radicular pain secondary to herniated disc or spinal stenosis for less than four years in duration and in whom leg pain is as severe or more severe than back pain

38 Cohen et al Participants received either epidural steroid injection plus placebo pills or sham injection plus gabapentin A positive outcome was defined as a 2 point decrease in leg pain coupled with a positive global perceived effect

39 Cohen et al Average reduction in pain scores 1 month Steroids -2.2 (SD 2.4) gabapentin -1.7 (SD 2.6) (p=0.25) 3 months Steroids -2.0 (SD 2.6) gabapentin -1.7 (SD 2.7) (p=0.43)

40 Cohen et al Gabapentin and epidural steroid injections used to treat lumbosacral radicular pain both resulted in modest improvements in pain and function, which persisted through three months

41 Cohen et al Although some differences favoured epidural steroid injections, these tended to be small and transient (and not significant) Similar outcomes between treatment groups suggest a trial with neuropathic drugs might be a reasonable first line treatment option

42 Cohen et all Likely causes 1. The treatments are equally effective but the effect dissipates over time 2. Neither treatment is effective ie placebo response or natural course of the disease 3. Epidural steroid injections are superior to gabapentin but sample was too small

43 Cognitive error Commission bias Tendency toward action when the evidence supports inaction Illusory correlation When 2 actions coexist but are not directly related to each other I got a steroid injection and the pain got a lot better [but then it got worse and I had to have another one]

44 Thank you