How is trigeminal neuralgia (TN) diagnosed?

Doctors can generally diagnose trigeminal neuralgia based on your symptoms. A description of your pain, along with the area where it occurs and what seems to trigger it, is probably all the information your doctor will need to make an accurate diagnosis. Sometimes it may also be necessary to rule out other possible causes through testing or further questioning. If you have multiple sclerosis and are experiencing facial pain, your doctor can use magnetic resonance imaging (MRI) to determine whether or not the disorder is causing your trigeminal neuralgia.

Trigeminal neuralgia is usually diagnosed by history and neurologic examination, which is usually normal. There are no laboratory tests for trigeminal neuralgia. The MRI of the brain may be done in order to exclude other neurologic disorders ( multiple sclerosis or brain tumor).Normal MRI findings and normal neurological exam confirm the diagnosis of trigeminal neuralgia.
Donna Hill Howes, RN
Family Medicine
There is no single test to diagnose trigeminal neuralgia (TN). Diagnosis is generally based on the patient's medical history and description of symptoms, a physical exam, and a thorough neurological examination by a physician. Other disorders, such as post-herpetic neuralgia, can cause similar facial pain, as do syndromes such as cluster headaches. Injury to the trigeminal nerve (perhaps the result of sinus surgery, oral surgery, stroke, or facial trauma) may produce neuropathic pain, which is characterized by dull, burning, and boring pain. Due to overlapping symptoms, and the large number of conditions that can cause facial pain, obtaining a correct diagnosis is difficult, but finding the cause of the pain is important as the treatments for different types of pain may differ.

Most TN patients undergo a standard MRI scan to rule out a tumor or multiple sclerosis as the cause of their pain. This scan may show a blood vessel on the nerve. Magnetic resonance angiography can more clearly show blood vessel problems and any compression of the trigeminal nerve close to the brainstem.

This answer is based on source information from the National Institute of Neurological Disorders and Stroke.
There's no laboratory test that definitively makes the diagnosis of trigeminal neuralgia. The diagnosis is usually made by the patient’s description of the pain, and that diagnosis can be reinforced by doing a brain MRI scan.

We do a brain MRI scan not so much to see that the patient has trigeminal neuralgia, although that diagnosis can be suggested if we see a hint of a blood vessel pressing on the nerve. The MRI scan is actually done more to rule out other disorders of the brain that can mimic trigeminal neuralgia. Those include multiple sclerosis, certain types of benign tumors, and even vascular malformation or aneurysms that are near the trigeminal nerve. Part of the evaluation, for anyone who comes in who’s going to be considered for treatment for trigeminal neuralgia, is to get a brain MRI scan with a high-resolution look at the trigeminal nerve coming out of the area called the brain stem.

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