Background & Aims
Diagnosis of neuropathic pain in patients with nerve root lesions is challenging (1). Magnetic resonance imaging (MRI), and clinical neurological examination are fundamental in the diagnostic process to establish involved nerve root segment. Knowledge of human dermatomes are widely used when assessing pain radiating to the limbs and areas of sensory disturbances. However, existing dermatomal maps are variable and largely based on works published in 1933 by Foerster (2), and Keegan and Garrett (3) in 1948. Clarified in a review by Lee et al. (4), dermatomal maps frequently reproduced in textbooks have not been substantiated. Conversely, later works report interindividual variation, large overlaps, and shifts up or down of the segmental innervation (5-8). We hypothesize that knowledge of pain and areas of sensory disturbances in patients with MRI verified nerve root lesions and radiculopathy may aid in establishing the diagnosis of neuropathic pain.
Methods
Patients with radiculopathy and MRI verified compression of one or two nerve root segments were included in a cross-sectional descriptive study. The examiner was blinded to affected nerve root segment(s). Medical history was obtained including pain drawing, and pain-related questionnaires. Clinical neurological examination was conducted to establish motor and reflex deficits. Sensory disturbances on the symptomatic extremity were examined using light touch, pinprick, pin scratch, warm roll (45 °C) and cold roll (20 °C). Based on patient report during examination, sensory changes were categorized as “reduced”, “absent”, “increased with pain”, “increased without pain” and “different”. Sensory changes were marked on the patient’s skin with pens and photographed. In a subgroup of patients, we will quantify mechanical and thermal detection- and pain thresholds. Additionally, in this subgroup, we will record contact heat evoked potentials and dermatomal somatosensory evoked potentials.
Results
Preliminary results from 17 patients show that the majority of patients with MRI verified compression of one or two nerve roots report sensory changes in painful areas, most commonly reduced sensation to warmth or pinprick. All patients reported sensory changes in the painful limb, supporting the notion that pain in this patient group is neuropathic in origin. The study is ongoing. Results related to dermatomal mapping and summary statistics of sensory disturbances and evoked potentials will be presented at the meeting.
Conclusions
Patients with nerve root compression report sensory disturbances in the affected limb when examined with pin prick, pin scratch, light touch, warm and cold rolls. This will aid in the establishment of probable or definite neuropathic pain, as sensory disturbances in the affected area support this diagnosis. Additionally, a sensory examination entailing different sensory modalities may be warranted in patients with a discrepancy between imaging findings and presenting symptomatology.
References
1.Schmid AB, Tampin B, Baron R, Finnerup NB, Hansson P, Hietaharju A, et al. Recommendations for terminology and the identification of neuropathic pain in people with spine-related leg pain. Outcomes from the NeuPSIG working group. Pain. 2023;164(8):1693-704.
2.Foerster O. The Dermatomes in Man 1. Brain. 1933;56(1):1-39.
3.Keegan JJ, Garrett FD. The segmental distribution of the cutaneous nerves in the limbs of man. Anat Rec. 1948;102(4):409-37.
4.Lee MW, McPhee RW, Stringer MD. An evidence-based approach to human dermatomes. Clin Anat. 2008;21(5):363-73.
5.Nitta H, Tajima T, Sugiyama H, Moriyama A. Study on dermatomes by means of selective lumbar spinal nerve block. Spine (Phila Pa 1976). 1993;18(13):1782-6.
6.Hong CG, Nam WD. Reliability and Diagnostic Accuracy of Standard Dermatomes and Myotomes for Determining the Pathologic Level in Surgically Verified Patients With Cervical Radiculopathy. Neurospine. 2022;19(4):1006-12.
7.McAnany SJ, Rhee JM, Baird EO, Shi W, Konopka J, Neustein TM, et al. Observed patterns of cervical radiculopathy: how often do they differ from a standard, “Netter diagram” distribution? Spine J. 2019;19(7):1137-42.
8.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;17:9.
Presenting Author
Peter Andreas Andersen
Poster Authors
Topics
- Specific Pain Conditions/Pain in Specific Populations: Neuropathic Pain - Peripheral