Dynamic dermatome mapping by electrically elicited paresthesias.

Streef, P.B. (2014) Dynamic dermatome mapping by electrically elicited paresthesias. thesis, Medicine.

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Abstract

Background: The origin of lumbosacral radicular syndrome (LRS) is generally ascribed to a herniated disc compressing the nerve root and to inflammatory irritation of the nerve root and the adjacent dura. The presumed level of the affected nerve root is particularly determined by the segmental pattern of radiating pain, which is compared to a dermatome map with ‘fixed’ dermatome patterns. Diagnostic segmental nerve root blocks (SNRBs) are performed to confirm the level of the affected nerve root. Surprisingly, there are no maps that take into account inter-individual variability and overlap in dermatome areas. The present study is carried out to try and close this gap in our knowledge and to produce novel, ‘dynamic’ maps the lumbosacral dermatomes, in which the inter-individual variability is represented by areas of high and low intensity. These may help to improve the diagnostic accuracy of the level of the affected nerve root in LRS before diagnostic SNRBs are performed. Methods: In patients with LRS undergoing either a diagnostic or therapeutic SNRB, areas of paresthesia elicited by electrical stimulation of the dorsal root ganglion were documented andprocessed into ‘intensity maps’. The intensity maps display the number of participants sharing a certain area. High intensity areas (‘hotspots’) thus represent areas that correspond most between participants. Also, the acquired paresthesia patterns from this study were compared to the collected pain patterns and also to the most often used traditional dermatome maps by Foerster15 and Keegan & Garrett16. Results: A total of 54 participants was included, in whom 58 segmental nerve root blocks were performed. The paresthesia areas showed hotspots with an intensity of up to 50%. For L5 the hotspot was mainly located on the dorso-lateral leg. For S1 it was located on the midlateral buttock. In the majority of cases the correlation between the elicited paresthesia patterns and pain patterns in individuals was ‘moderate’ to ‘weak’. The paresthesia areas coincided with the corresponding dermatome in the Keegan & Garrett map in 30-60% of cases, for Foerster this was true in 20-40% of cases. Conclusion: For each lumbar dermatome variability was expressed as an intensity map. Hotspots were identified for the L5 and S1 nerve roots. Paresthesia patterns coincided less than expected with the traditional maps of Foerster and Keegan & Garrett. In addition, overlap of pain and paresthesia was not as high as expected. This is, at least partly, related to suboptimal dermatome identification in patients referred for SNRB. In our opinion, this is due to variation between patients as well as between current dermatome maps. Up to now, the number of participants is still relatively low. By increasing the number of measurements, the interpretation of our ‘dynamic’ dermatome maps will become more reliable.

Item Type:	Thesis (Thesis)
Supervisor name:	Groen, Prof. dr. GJ and Bosma, drs. WJ
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 10:46
Last Modified:	25 Jun 2020 10:46
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/773

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