Digital Subtraction Myelography for the Detection of Type 1 Spinal CSF Leaks: Evaluation of Temporal Characteristics and Diagnostic Value.

Abstract

Background and purpose: Ventral dural tears (type 1 leaks) are reported to be the most common cause of spontaneous intracranial hypotension (SIH) and may require high dynamic myelography for detection. The aim of this cross-sectional study was to evaluate the temporal characteristics and diagnostic value of digital subtraction myelography (DSM) in type 1 leaks.

Materials and methods: Between April 2022 and August 2024, 104 consecutive patients with type 1 leaks were retrospectively identified. Institutional diagnostic standard included DSM as first-line examination; where deviating, patients were excluded. A previously described positioning technique of patients was used, enabling examination even in the challenging cervicothoracic junction of the spine. We evaluated the time for the contrast agent to first appear in the epidural space after reaching the level of the leak intrathecally, and the overall diagnostic yield of DSM.

Results: 100/104 patients (49 women) were included. Mean age was 49 years (SD ± 11.9 years), mean BMI 24.8 (SD ± 4.29), and median Bern SIH score 4 (IQR 5). Type 1 leaks most commonly occurred at the T1/2 and T2/3 level (each 20/100), range C6/7-L1/2. The mean time for the contrast to be visible in the epidural space was on average 1.5 seconds (range 0-9 seconds) with 1 frame-persecond acquisition being sufficient for all but one patient. DSM as first-line investigation made the diagnosis in 76/100 patients, confirmed in all patients undergoing surgery (74/76). 24/100 patients required one or more subsequent dynamic CT-myelography (dCTM) for definite diagnosis another day, with 21/24 leaks confirmed at surgery. Bern SIH Score was significantly lower in dCTM compared to DSM group (3.25 vs 5; p=0.009), whereas age (p=0.548) and BMI (p=0.185) were not found to have an impact.

Conclusions: DSM demonstrated a high diagnostic yield for type 1 leaks when used as a first-line investigation. We have confirmed the high-flow characteristics of these leaks, suggesting that DSM's high temporal resolution is ideally suited for their detection, with 1 frame-per-second being overall sufficient. A lower Bern SIH score could favor patients for primary use of dCTM, however, further research may clarify why DSM occasionally misses diagnoses.

Abbreviations: SIH=spontaneous intracranial hypotension, DSM=digital subtraction myelography, dCTM=dynamic CT myelography.