128 The Sagittal Angle of the Trigeminal Nerve at the Porus Trigeminus is a Radiologic Predictor of Surgical Outcome in Microvascular Decompression for Classical Trigeminal Neuralgia

INTRODUCTION: Classical Trigeminal Neuralgia (cTN) is a facial pain syndrome with specific diagnostic criteria, including paroxysms that last 1-120 seconds, are sharp, stabbing, or electric in character, and are induced by innocuous stimuli. The most commonly accepted cause of cTN is neurovascular compression (NVC) of the proximal cisternal segment of the trigeminal nerve by an adjacent artery. Microvascular decompression surgery (MVD) provides immediate and durable relief in many patients. METHODS: Pre-operative MRIs from 300 patients with cTN who underwent MVD were analyzed to identify patients with a hyperacute SATNaPT (defined as less than 3 standard deviations below the mean). The rate of surgical success (pain-free after at least 12 months) was compared between patients with a hyperacute SATNaPT and all other patients. RESULTS: Patients without a hyperacute SATNaPT had an 82% likelihood of surgical success, whereas patients with a hyperacute SATNaPT had a 58% likelihood of surgical success (p < 0.05). Patients with a hyperacute SATNaPT who also had no evidence of vascular compression on preoperative MRI had an even lower likelihood of success (29%, p < 0.05). CONCLUSIONS: In patients with cTN being considered for MVD, a hyperacute SATNaPT is a negative prognostic biomarker that predicts a higher likelihood of surgical failure. Patients with a hyperacute SATNaPT, particularly those without MRI evidence of vascular compression, may benefit from other surgical treatments or a modification of MVD to adequately address the underlying cause of cTN.