Contrast-Enhanced CISS Imaging for Evaluation of Neurovascular Compression in Trigeminal Neuralgia: Improved Correlation with Symptoms and Prediction of Surgical Outcomes

Fellows’ Journal Club

Retrospective review of high-resolution MRIs was performed in patients without prior microvascular decompression. 3D-CISS imaging without and with contrast for 81 patients with trigeminal neuralgia and 15 controls was intermixed and independently reviewed in a blinded fashion. Cisternal segments of both trigeminal nerves were assessed for the grade of neurovascular conflict, cross-sectional area, and degree of flattening. Contrast-enhanced CISS more than doubled the prevalence of the highest grade of neurovascular conflict (14.8% versus 33.3%) and yielded significantly lower cross-sectional area and greater degree of flattening for advanced-grade neurovascular conflict on the symptomatic side compared with non-contrast-enhanced CISS.

Abstract

BACKGROUND AND PURPOSE

Trigeminal Neuralgia
Grade 2 neurovascular conflict. Coronal NE-CISS (A) and CE-CISS (B) and sagittal NE-CISS (C) and CE-CISS (D) images show neurovascular conflict of the cisternal segment of the patient’s right trigeminal nerve with a branch of the superior cerebellar artery from above (solid white arrow) and the superior petrosal vein from below (dashed white arrow), resulting in flattening of the nerve near the porus trigeminus. On the NE-CISS images (A and C), the nerve is not well-delineated from the adjacent vascular structures. On the CE-CISS images (B and D), the vessels enhance, outlining the compressed nerve between them. Zoomed-in images of the site of neurovascular conflict in the coronal plane (E and F) illustrate the poor contrast between vessels and nerve on the NE-CISS image (E) and the improved contrast after administration of gadolinium contrast material (F), allowing more confident delineation of the compressed nerve from the adjacent vessels (G). Both NE-CISS and CE-CISS images were interpreted as grade 2 compression. On the patient’s left, grade 0 was given for both the NE-CISS and CE-CISS images.

Thin-section MR imaging through the posterior fossa is frequently used for trigeminal neuralgia. Typical heavily T2-weighted imaging methods yield high anatomic detail and contrast between CSF and neurovascular structures, but poor contrast between vessels and nerves. We hypothesized that the addition of gadolinium-based contrast material to 3D-constructive interference in steady-state imaging would improve the characterization of trigeminal compression.

MATERIALS AND METHODS

Retrospective review of high-resolution MRIs was performed in patients without prior microvascular decompression. 3D-CISS imaging without contrast and with contrast for 81 patients with trigeminal neuralgia and 15 controls was intermixed and independently reviewed in a blinded fashion. Cisternal segments of both trigeminal nerves were assessed for the grade of neurovascular conflict, cross-sectional area, and degree of flattening. Data were correlated with symptom side and pain relief after microvascular decompression using the Fisher exact test, receiver operating curve analysis, and a paired t test.

RESULTS

Contrast-enhanced CISS more than doubled the prevalence of the highest grade of neurovascular conflict (14.8% versus 33.3%, P = .001) and yielded significantly lower cross-sectional area (P = 8.6 × 10−6) and greater degree of flattening (P = .02) for advanced-grade neurovascular conflict on the symptoms side compared with non-contrast-enhanced CISS. Patients with complete pain relief after microvascular decompression had significantly lower cross-sectional area on contrast-enhanced CISS compared with non-contrast-enhanced CISS on preoperative imaging (P = 2.0 × 10−7). Performance based on receiver operating curve analysis was significantly improved for contrast-enhanced CISS compared with non-contrast-enhanced CISS.

CONCLUSIONS

The addition of contrast material to 3D-CISS imaging improves the performance of identifying unilateral neurovascular compression for symptomatic trigeminal neuralgia and predicting outcomes after microvascular decompression.

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Contrast-Enhanced CISS Imaging for Evaluation of Neurovascular Compression in Trigeminal Neuralgia: Improved Correlation with Symptoms and Prediction of Surgical Outcomes
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Jeffrey Ross
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