Introduction

In school, you’ve surely learned about pain drawings for radicular pain. However, already in the first decade of the 21st century, it became clear that radicular pain does not necessarily follow a dermatomal distribution. This study wanted to take a closer look at the agreement between visual inspection of radicular pain drawings as noted by patients and MRI. In practice, often a patient expresses his complaints and this may be supplemented with a pain drawing. When radicular pain is suspected, often medical imaging is prescribed to determine the affected nerve root and the extent of the possible nerve root involvement. Although this makes in many cases part of routine practice, we do not know until we know the agreement between these pain drawings and the affected nerve root as determined using MRI. In this study, Marco et al. (2023)  compared radicular pain drawings and MRI findings.

Methods

To investigate the agreement between radicular pain drawings and MRI findings, this study included participants with a 2-month history of persistent pain, who were diagnosed with cervical radiculopathy on MRI. This diagnosis was made by a neurosurgeon based on clinical information and MRI findings as rated by a radiologist.

The pain drawings were made on body charts, both from an anterior and posterior view. These charts were then shown to 4 clinicians (2 surgeons, and 2 physiotherapists) who were unaware of the involved nerve root as defined by the MRI scan. They only received the information that all patients from which they were presented the pain drawings, were diagnosed with cervical radiculopathy at just one level between C4 and C7. Based on the pain drawing of the patient, they had to identify the spinal level that was involved. Agreement between the MRI-verified spinal level and the clinician’s pain drawing based-judgment was assessed with kappa. Furthermore, the inter-rater agreement was examined with the kappa statistic as well. Kappa values were interpreted as:

• no agreement when <0.00
• slight agreement 0.00-0.20
• fair agreement 0.21-0.40
• moderate agreement 0.41-0.60,
• substantial agreement 0.61-0.80
• almost perfect agreement >0.81

Results

In total, 98 patients presenting with single-level radiculopathy were included. They had a mean age of 48 years. Most of the participants had a C6 or C7 radiculopathy, and only 4 and 7 cases had the C4 and C5 roots affected, respectively.

Ninety-five valid responses were collected from the clinicians. The comparison of the radicular pain drawings and MRI findings revealed that overall agreement was poor. In only 35.7% of cases (mean), the MRI-verified spinal level was the same as the clinician-rated involved level based on the pain drawing. None of the raters attributed C4 as the involved level, while MRI did in 4 patients. Only 7% agreement was found between the clinician-determined and MRI-verified level when C5 was considered. For C6, agreement was 34.7% between MRI and the pain drawings and for C7 this was 47.7%. When we use those ciphers to get a better look, for C6 only 18 of 54 subjects were correctly identified and for C7 only 15 out of 33 were classified correctly. This revealed that there was no agreement between the clinicians based on pain drawings and MRI.

The inter-rater agreement was rated as fair to moderate as kappa ranged between 0.281 and 0.561. It appears that when clinicians base themselves on the pain drawings, they agree in a relatively similar way.

Questions and thoughts

This study confirms what we could have already imagined ourselves: radicular pain drawings and MRI findings do not correspond well. This is in fact logical, given that pain drawings of radicular pain, derived from surgical or nerve block studies for example, poorly reflect the pain diagrams we all learned at school. Important to consider was that C8 nerve root involvement was not taken into account, however, this level also makes up part of the cervical spinal nerves. When it would have been included, it would have been very likely that the slightly higher C7 scores would have been relatively similar to those of C6. In my opinion, C7 was better rated since C8 was not a possible option. This study talked about radiculopathy, which is a broader term that encompasses radicular pain and sensory, motor disturbances, and reflex abnormalities. Yet in this paper, only pain is considered, therefore the title could have also indicated radicular pain, rather than radiculopathy.

Radicular pain is often said to be worse in the arm than in the neck, yet Table 1 reveals that the VAS scores of the arm and neck pain are practically similar. This would mean that it doesn’t necessarily have to be that the arm hurts more than the neck to be confident that you have a possible radicular nerve root involvement in this patient.

This sample showed considerable disability, seen from the scores of the Neck Disability Index. Importantly, these patients were scheduled to receive surgery, which may mean that the more complex and/or severe cases have been analyzed by this paper. Also, several patients showed pain referrals beyond the expected referral patterns of the arm. Some even indicate leg and lower back pain. This may mean 3 things:

• The patients didn’t receive a good explanation about which pain they had to describe
• They had a central sensitization component
• In the absence of a provocative testing maneuver, the typical radicular pain was not augmented, and the subject had difficulties in separating radiating pain from the neck from other pains in the body.

This reflection is mine, and I do not know to what extent this accounts for the results. But I hope this gets you thinking about these results. If you are interested in the possibilities where pain drawings can in fact be useful, I recommend you read the following blog post: http://physiotutors.com/dermatome-maps-may-still-be-useful

Talk nerdy to me

Some of the limitations this study came across were the relatively small sample size and the fact that these results were obtained from collected data, but not from a real clinical encounter. The latter is an important thing in diagnostic reasoning as Bertilson and colleagues in 2007 showed that more than 60% of patients made additions to their initial pain drawing. This would have also permitted reporting of the pain severity in more detail, which could have improved the diagnostic accuracy between the pain drawings and MRI.

A positive point is that these findings were not based on p-values, rather, an insight into the results was discussed.

Take home messages

Clinicians’ judgments about the involved cervical nerve root level based on radicular pain drawings and MRI findings do not correspond. The pain drawings as collected here possibly posses room for improvement when patients could give additional clinical information as is the case in a real clinical encounter. Based on these results, we can conclude that based on a pain drawing, one cannot confidently say which cervical nerve root level is affected.

Learn more

Read: http://physiotutors.com/dermatome-maps-may-still-be-useful

Watch:

Reference

Marco B, Evans D, Symonds N, Peolsson A, Coppieters MW, Jull G, Löfgren H, Zsigmond P, Falla D. Determining the level of cervical radiculopathy: Agreement between visual inspection of pain drawings and magnetic resonance imaging. Pain Pract. 2022 Jun 28. doi: 10.1111/papr.13147. Epub ahead of print. PMID: 35765137.

Additional references

Murphy DR, Hurwitz EL, Gerrard JK, Clary R. Pain patterns and descriptions in patients with radicular pain: does the pain necessarily follow a specific dermatome? Chiropr Osteopat. 2009 Sep 21;17:9. doi: 10.1186/1746-1340-17-9. PMID: 19772560; PMCID: PMC2753622.