Differentiation between Tuberculous and Pyogenic Spondylodiscitis: The Role of the Anterior Meningovertebral Ligament in Patients with Anterior Epidural Abscess

Abstract

Background and purpose: Differentiation between tuberculous and pyogenic spondylodiscitis is a diagnostic challenge because imaging often does not reliably distinguish the 2 entities and percutaneous biopsies are often culture-negative. The purpose of this study was to determine whether violation of the anterior meningovertebral ligament in the setting of anterior epidural abscess discriminates between these entities.

Materials and methods: This was a retrospective cohort study of all patients with acid-fast bacillus testing and anterior epidural abscess diagnosed on spinal MR imaging between May 2014 and September 2019, with a final diagnosis of tuberculous or pyogenic spondylodiscitis. Six cases of tuberculous spondylodiscitis (mean age, 45.5 years; 80% male) and 35 cases of pyogenic spondylodiscitis were evaluated (mean age, 56.6 years; 49% male). Demographic characteristics were recorded. Cases were assessed for anterior meningovertebral ligament destruction on MR imaging, as demonstrated by the shape of the epidural collection. Segmental location of the infection was also assessed. Independent 2-sample t tests and χ² tests of independence were performed to evaluate the significance of the difference between the groups.

Results: Five of 6 (83.3%) cases of tuberculous epidural abscess had an intact anterior meningovertebral ligament, and 0/35 cases of pyogenic epidural abscess demonstrated an intact ligament (P < .001). The presence of an intact anterior meningovertebral ligament had 83.3% sensitivity and 100% specificity for tuberculous spondylodiscitis, a 100% positive predictive value, and a 97.2% negative predictive value.

Conclusions: The presence of an intact anterior meningovertebral ligament has high sensitivity and specificity for tuberculous spondylodiscitis-associated epidural abscess, though these results should be validated in a larger sample.

FIG 1.

Graphic representation of normal anatomy. The anterior meningovertebral ligament anchors the periosteum to the posterior longitudinal ligament, effectively creating 2 distinct compartments.

FIG 2.

Preserved anterior meningovertebral ligament with a unilobed anterior epidural abscess. Graphic representation of a unilobed anterior epidural space abscess (A). Axial T2WI (B) and contrast-enhanced T1WI (C) show a unilobed appearance of the epidural abscess.

FIG 3.

Preserved anterior meningovertebral ligament in 2 patients with bilobed anterior epidural abscess. Graphic representation of a bilobed anterior epidural space abscess (A). Axial T2WI (B) and contrast-enhanced T1WI (C) show a bilobed appearance of the epidural abscess in the setting of a preserved anterior meningovertebral ligament (arrow).

FIG 4.

Destruction of the anterior meningovertebral ligament in 2 patients. Graphic representation of destruction of the anterior meningovertebal ligament (A). Axial T2WI (B) demonstrates destruction of the anterior meningovertebral ligament (arrow). Axial contrast-enhanced T1WI (C) in a different patient similarly demonstrates destruction of the anterior meningovertebral ligament (arrow). The apices of the collections are midline and convex and do not respect left-right boundaries.