Article
Dorsal column mapping in resection of intramedullary tumours – a prospective comparison of two methods and neurological follow-up
Dorsal column mapping bei intramedullären Tumoren – ein prospektiver Vergleichzweier Methodenund neurologische Verlaufsbeobachtung
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Published: | June 26, 2020 |
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Objective: When performing surgery for intramedullary spinal cord tumours (imSCT) distortion of the regular anatomy makes visual identification of the dorsal columns (DC) and the midline for myelotomy challenging. For neurophysiological identification of the DC, dorsal column mapping (DCM) and spinal cord stimulation (SCS) are used. This study compares both methods in clinical use and describes their clinical impact.
Methods: In a single centre, prospective study patients with thoracic or cervical imSCT undergoing surgery from 04/2017 to 06/2019 were included. DMS was determined as follows:
- 1.
- visual identification and marking of the anatomical midline by the surgeon
- 2.
- recording of spinal SSEPs to follow tibial and/or median stimulation with an 8-channel DCM-electrode (AdTech Co., USA) and
- 3.
- SCS by bipolar concentric probe (Inomed Co., Germany) and recording of cortical SEP phase reversal at C3/C4 .
Time of measurement, handling, interpretation and reliability of both methods were analysed. Standardized neurological examinations were performed preoperatively and one week postoperatively.
Results: 13 patients (8 f; median age 43 years (15-79)) with a median McCormick Score (McS) of 1 (0-3) were studied.
The DCM electrode detected the midline in 9/13 patients, with handling limitations in the remaining patients. SCS was applicable in all patients with reliable results in 9/13. If both recordings could be acquired (5/13), concordance was 100%. If standard SSEPs were poor, both methods were unstable. The SCS method was significantly less time-consuming (9min. vs. 17min.; p=0,001).
The anatomical midline indicated by the surgeon diverged by a mean of 0.5 mm (± 0.8mm) compared to the neurophysiologically identified midline. In 9/13 patients with distorted anatomy, DCM and SCS were helpful to confirm optimal region of myelotomy.
In the surgeon’s perception implementation of the SCS probe was felt safer and easier compared to the DCM electrode. After myelotomy based on anatomical and neurophysiological findings, no losses of SSEPs occurred with worsening >50% in 3 patient. 3 patients deteriorated to a McS of >1 (med. 2 (1-3)).
Conclusion: DCM and SCS are helpful to identify the correct region for myelotomy in imSCT with a favourable clinical outcome in this cohort. Regarding reliability and interpretation of measurements both methods were comparable while the SCS method evolved to be superior to the DCM electrode concerning applicability and time expenditure.