Adding some separation from the superior cerebellar artery relieves trigeminal neuralgia

The patient

A 67-year-old woman presented to clinic with a four-year history of right-sided facial pain. After the onset of her trouble, the pain went into remission for six months. It then recurred, and she was prescribed carbamazepine. This led to significant pain relief but caused adverse changes to her mood and balance. She was then prescribed lamotrigine, which was helpful initially, but lost effectiveness despite increasing doses. She then had a long period of pain remission two years later.

When she first presented to Norton Neuroscience Institute Face Pain Clinic, her pain was daily and severe. It was located in the right upper and lower jaws, consisting of brief attacks of excruciating stabs of electric pain, triggered by talking, brushing the teeth or touching the right lower lip. Oxcarbazepine was tried, which led to significant pain relief. Over the next two years, increasing doses of oxcarbazepine were required for continued relief, and side effects of balance impairment and cognitive impairment again developed.

The challenge

This patient’s debilitating and severe pain was now occurring daily and proved refractory to multiple adequate trials of medications. She described this as “the worst pain of my life that I would not wish on my worst enemy.” Many medications were helpful initially, but over time they required increasing doses and came with increasing attendant side effects for limited pain relief. Her neurologist referred her to see a neurosurgeon, for consideration of surgical options.

High-resolution MRI and magnetic resonance angiography (MRA) are obtained on a 3 tesla scanner, specifically protocolled for visualizing the trigeminal nerve. T2-SPACE images show the right trigeminal nerve contacting an anatomic structure at its root entry zone (blue arrows).

Contrast-enhanced sequences (left) confirm that this structure is a vascular structure, as it contrast-enhances, and MRA (right) confirms this is an artery, rather than a vein. 

Specialized high-resolution MRI and MRA demonstrated a not-unexpected finding: The superior cerebellar artery was contacting, and actually distorting, the trigeminal nerve, on the right side. Surprising pathology, such as tumor or arteriovenous malformation, are also ruled out.

The physicians

The solution

The high-resolution MRI also is used for intraoperative neuronavigation. The transverse (green arrow) and sigmoid (red arrow) sinuses are outlined and mapped in 3D space onto the patient’s real-time anatomy. This allows the surgeon to plan a smaller incision and craniotomy, centered just inferior to the transverse sinus and posterior to the sigmoid sinus, for entry to the cerebellopontine angle and approach to the cisternal portion of the trigeminal nerve, just after it exits the brainstem. The craniotomy is about the size of a half-dollar. end caption

Posterior fossa craniotomy was performed to explore the right trigeminal nerve. As expected, the superior cerebellar artery, which was duplicated (a common variant and frequent finding in this condition) was distorting the trigeminal nerve. Using neuronavigation, which helps to minimize the size of the incision and craniotomy, and microneurosurgical technique, the superior cerebellar artery was gently moved a few millimeters away from the trigeminal nerve. The separation was maintained with a nonabsorbable Teflon pledget. Given the close proximity of the facial and vestibulocochlear nerves, as well as the brainstem, integrity of these structures was monitored intraoperatively by the neurophysiology team.

Intraoperative photomicrograph (left) demonstrates a duplicated superior cerebellar artery (blue arrow) contacting the trigeminal nerve just after the nerve exits the brainstem. The nerve is actually thinned and distorted (black asterisk), as noted from the color changes and curvature, due to the pulsatile activity of the artery against it. There was also a vein (green arrow) seen contacting the nerve. To perform the microvascular decompression (right), both the artery and the vein were moved, with microsurgical instruments, away from the nerve, and the separation was maintained by Teflon pledgets (black stars). 

The result

The patient was discharged home from the hospital two days after surgery. She experienced minimal incisional pain, and her trigeminal neuralgia pain was immediately gone. A few days after surgery, she was able to taper off the anticonvulsant medications previously used for this pain, and her medication-induced side effects resolved. Her quality of life and ability to participate in daily activities such as eating, drinking and conversing were greatly improved. She stated she no longer lived in fear of terrible pain attacks.

Treatment and results may not be representative of all similar cases.