Introduction: The authors aimed to investigate the value of a preoperative MRI to identify vascular compression in patients with trigeminal neuralgia (TN) destined to undergo microvascular decompression (MVD).

Methods: The records of 40 patients with TN who underwent MVD between 02/2004 and 01/2015 with a preoperative MRI were reviewed. Based on review of the operative record and intraoperative photographs when available trigeminal nerve compression was categorized as arterial, venous, or none. Two independent and blinded radiologists reviewed the preoperative MRI and likewise categorized trigeminal nerve compression in each case.

Results: At the time of surgery, 6 patients were found to have trigeminal nerve compression by a vein, 3 revealed no offending vessel, and the remaining 31 had arterial vascular compression. Preoperative MRI review correlated with the operative findings in all cases except five. In three cases of arterial compression, MRI revealed none in two cases and was suggestive of a vein in the other. In one case of venous compression, MRI revealed none. In a final case, in which no evidence of compression was noted at surgery, the preoperative MRI review was interpreted as positive for arterial compression. Overall, there was a disagreement rate of 12% (5/40) between preoperative imaging review and intraoperative findings. There was agreement in 88% (35/40).

Conclusions: In cases of TN, when the decision to proceed with surgical intervention with MVD has been made, the value of MRI in identifying the presence or absence of an offending vessel is not infallible. Thus we conclude that the decision to proceed with MVD or not should be based on clinical criteria, not imaging findings.

Patient Care: This research demonstrates the need to continue to rely on clinical judgment when considering microvascular decompresison. We show that clinicians should not become reliant on imaging when decideing to proceed with surgical intervention.

Learning Objectives: At the end of this session, participants will be able to: 1. Understand the role of preoperative imaging in microvascular decompression for Trigeminal Neuralgia. 2. Know the concordance rates of preoperative imaging for microvascular decompression patients and findings noted at surgery. 3. Understand that there remains a group of people with compression noted at surgery that may not be noted on standard preoperative imaging.

References: 1. Burchiel KJ: Microvascular decompression for trigeminal neuralgia. J Neurosurg 114:171; discussion 171, 2011 2. Burchiel KJ, Clarke H, Haglund M, Loeser JD: Long-term efficacy of microvascular decompression in trigeminal neuralgia. J Neurosurg 69:35-38, 1988 3. Elias WJ, Burchiel KJ: Microvascular decompression. Clin J Pain 18:35-41, 2002