Introduction: Trigeminal neuralgia (TGN) causes severe unilateral facial pain. The etiology is hypothesized to be segmental demyelination of the trigeminal nerve root via compression by the superior cerebellar artery (SCA). Microvascular decompression (MVD) allows for immediate and long term pain relief. Preoperative evaluation includes MRI (magnetic resonance imaging) and/or MRA (magnetic resonance angiography) of the brain. Having a pacemaker is a contraindication for MRI and limits the preoperative evaluation. There have been isolated reports of using computed tomography (CT) cisternography scans for radiation planning for TGN. We present a case of a 75-year-old male with a permanent pacemaker who had refractory TGN in the V2 (maxillary) distribution of the trigeminal nerve and underwent CT cisternography to prepare for MVD.

Methods: Our interventional radiologist (MP) performed lumbar puncture, midline at the L2/3 level; 15 cc of Isovue™ 180 contrast was injected into the subarachnoid space. Cervical spine fluoroscopy was used to verify cephalad dissipation of contrast. CT angiography with Isovue™ 370 intravenous contrast injection and 0.625 mm axial images were obtained from the skull base across the posterior fossa. This demonstrated that the right SCA abutted the medial margin of the proximal right trigeminal nerve.

Results: In surgery (KD), a standard retrosigmoid suboccipital craniotomy was performed to access the cerebello-pontine angle. Under the operating microscope, the SCA was identified abutting the trigeminal nerve at its root entry zone. Ivalon™ was placed to separate the nerve and artery. The patient had immediate pain relief and at 3 months was off of all pain relief medications.

Conclusions: MRI offers excellent visualization of vasculature in relation to the trigeminal nerve when evaluating for TGN. For patients who have contraindications to MRI, CT cisternography is an effective method for visualizing the trigeminal root entry zone and nearby vasculature in preparation for MVD of the trigeminal nerve.

Patient Care: By making the neurosurgical community aware that CT cisternography is an alternative method for neurovascular imaging in patients suffering from refractory trigeminal neuralgia in whom MRI is contraindicated and microvascular decompression is the only way to pain relief.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Review the etiology of trigeminal neuralgia and what comprises the preoperative evaluation of this condition. 2) Learn how to diagnose trigeminal neuralgia by visualizing the superior cerebellar artery abutting the trigeminal nerve via CT cisternography. 3) Recognize the use of CT cisternography as an alternative method for preoperative evaluation of patients with trigeminal neuralgia in whom MRI is contraindicated.

References: 1. Chen G, Wang X, Wang L, Zheng J. Arterial compression of nerve is the primary cause of trigeminal neuralgia. Neurol Sci. 2013;35:61–66. doi:10.1007/s10072-013-1518-2. 2. Grainger, A. C.Rowe, J. G.Romanowski, C. A.Hunt, K.Walton, L.Kemeny AA. CT cisternography for localisation of the trigeminal nerve prior to gamma knife radiosurgery. J Radiosurgery SBRT. 2:154–154. 3. MacDonald BK, Cockerell OC, Sander JW, Shorvon SD. The incidence and lifetime prevalence of neurological disorders in a prospective community-based study in the UK. Brain. 2000;123 ( Pt 4(4):665–676. doi:10.1093/brain/123.4.665. 4. Obermann M. Treatment options in trigeminal neuralgia. Ther Adv Neurol Disord. 2010;3:107–115. doi:10.1177/1756285609359317. 5. Tanrikulu L, Hastreiter P, Richter G, Doerfler A, Naraghi R. Virtual neuroendoscopy?: MRI-based three-dimensional visualization of the cranial nerves in the posterior cranial fossa. 2008;22(August 2007):207–212. doi:10.1080/02688690701632807. 6. Torelli P, Jensen RH, Tavanaiepour D, et al. The International Classification of Headache Disorders, 3rd edition (beta version). Cephalalgia. 2013;53(9):137–46. doi:10.1177/0333102413485658. 7. Vergani F, Panaretos P, Penalosa A, English P, Nicholson C, Jenkins A. Preoperative MRI/MRA for microvascular decompression in trigeminal neuralgia: consecutive series of 67 patients. Acta Neurochir (Wien). 2011;153(12):2377–81; discussion 2382. doi:10.1007/s00701-011-1135-x. 8. Worthington C, Hutson K, Boulware R, et al. Computerized tomography cisternography of the trigeminal nerve for stereotactic radiosurgery. Case report. J Neurosurg. 2000;93 Suppl 3(Suppl 3):169–171. doi:10.3171/jns.2000.93.supplement 3.0169.