The main cause of trigeminal neuralgia is a blood vessel pressing against the trigeminal nerve near the brainstem. In 75 to 80% of cases, the specific vessel responsible is the superior cerebellar artery. This compression damages the nerve’s protective coating, leading to misfiring signals that the brain interprets as extreme facial pain.
How a Blood Vessel Creates Severe Pain
The trigeminal nerve exits the brainstem at the back of the skull in a region called the posterior fossa. It’s a tight space shared with several arteries, and the nerve is especially vulnerable right where it leaves the brainstem, at what’s known as the root entry zone. In most people with trigeminal neuralgia, an artery loops too close to the nerve and presses into it with each pulse of blood flow.
The superior cerebellar artery is the culprit in the vast majority of cases. Other arteries can also be responsible, including the anterior inferior cerebellar artery and the vertebral artery. Occasionally a vein, such as the petrosal vein, causes compression instead. Regardless of the vessel involved, the result is the same: sustained pressure gradually strips away the myelin sheath, the insulating layer that keeps electrical signals traveling along their intended path.
Once that insulation breaks down, the nerve becomes hyperexcitable. Normal signals reflecting from the damaged zone can trigger prolonged bursts of high-frequency firing. Electrical activity also “jumps” between neighboring nerve fibers in a process called ephaptic transmission, essentially a short circuit. That’s why something as light as a breeze on the cheek or brushing your teeth can set off an intense shock of pain. The nerve treats a harmless touch signal as a pain signal because the damaged wiring can no longer keep the two apart.
Where the Pain Typically Strikes
The trigeminal nerve splits into three branches that supply sensation to different parts of the face. The lower branch, covering the jaw and lower face, is affected most often, accounting for about 55% of cases. The middle branch, which covers the cheek and upper lip area, is involved in roughly 39% of cases. The upper branch, serving the forehead and eye region, is the least commonly affected at around 6%. Pain tends to favor the right side of the face, though the reason for this isn’t fully understood.
The pain itself is distinctive: brief, electric-shock-like jolts that can last from a fraction of a second to a couple of minutes. Attacks may come in clusters throughout the day, sometimes triggered by eating, talking, shaving, or even a gust of wind. Some people also develop a continuous background ache between the sharp jolts, which can make the condition harder to manage.
Secondary Causes Beyond Blood Vessels
When trigeminal neuralgia isn’t caused by a blood vessel, it’s classified as secondary. Up to 15% of cases fall into this category, and the most well-known secondary cause is multiple sclerosis (MS). People with MS have a 20-fold increased risk of developing trigeminal neuralgia because the disease creates patches of demyelination inside the brainstem itself, right along the path of the trigeminal nerve. Between 2% and 5% of people with MS will develop trigeminal neuralgia at some point, regardless of which form of MS they have.
Tumors growing near the trigeminal nerve can also compress it. Among tumor-related cases, epidermoid cysts are the most common, responsible for about 65% of tumor-caused trigeminal neuralgia. Meningiomas account for roughly 21%, with rarer causes including vestibular schwannomas and lipomas. In a small number of cases, no identifiable cause is found on imaging or during surgery. These are classified as idiopathic.
Why Hypertension May Play a Role
A population-based study found that people with high blood pressure have roughly a 50% greater risk of developing trigeminal neuralgia compared to those without hypertension. The connection likely relates to the primary cause itself. Chronically elevated blood pressure can cause arteries to elongate, stiffen, and loop more aggressively, increasing the chance that a vessel near the brainstem pushes into the trigeminal nerve. The condition also becomes more common with age, affecting an estimated 4.3 to 28.9 people per 100,000 each year, with rates climbing in older populations where both vascular changes and hypertension are more prevalent.
How the Cause Is Confirmed
Diagnosing the vascular cause of trigeminal neuralgia relies on specialized MRI sequences that can visualize both the nerve and surrounding blood vessels in fine detail. A technique called 3D FIESTA captures the nerve at a resolution of less than a millimeter, while a companion sequence (3D TOF MRA) maps the arteries. When these two images are fused together, radiologists can see the nerve and vessels in different colors on a single 3D image, making it possible to tell whether a vessel is simply touching the nerve or actively pressing into and deforming it. Studies using this approach have found a strong statistical association between an artery visibly indenting the trigeminal nerve and the side of the face where pain occurs.
Standard brain MRI sequences are also performed to rule out secondary causes like MS plaques or tumors. If imaging reveals a clear vascular compression, the diagnosis of classical trigeminal neuralgia is confirmed. If a structural lesion other than a blood vessel is found, it’s classified as secondary. If nothing shows up at all, it’s labeled idiopathic.
How Treating the Cause Affects Outcomes
Because a compressing blood vessel is the root cause in most cases, a surgical procedure called microvascular decompression directly addresses it. The surgeon places a small cushion between the offending artery and the nerve, relieving the pressure and allowing the myelin to recover over time. Among patients with a clear vascular cause, 73% are pain-free after one year, and 82% maintain good long-term results over follow-up periods extending beyond a decade. The durability of those results reflects the fact that removing the source of compression allows the nerve’s insulation to heal, stopping the misfiring signals that produce pain.
For people whose trigeminal neuralgia stems from MS or a tumor, treatment is different. Tumor removal can relieve compression directly, while MS-related cases typically require medications that calm nerve excitability, since the demyelination is driven by the immune system rather than external pressure. Outcomes in secondary cases are generally less predictable than in vascular compression cases.