What Is Trigeminal Neuralgia ?
Trigeminal neuralgia has also been called tic douloureux, and is discussed in much greater detail here. Some have also called it "suicide pain" because it can be so severe and debilitating. The pain occurs in one or more of the three areas of the trigeminal nerve in the face (forehead, cheek, chin). It occurs most commonly in the 2nd (cheek area) or 3rd (chin, lower face area) distribution of the trigeminal nerve. According to ICHD3 criteria, the pain occurs in sudden random attacks lasting from a fraction of a second to 2 minutes, and is of severe intensity. It is described as electric shock-like, stabbing, shooting, or sharp, and is triggered by stimuli to the affected side of the face such as touching, talking, brushing teeth, chewing, or cold air. Trigeminal neuralgia affects women (60%) more than men (40%), with an average age of onset around 53-57.
What Are The Different Types Of Trigeminal Neuralgia?
There have been many changes over the years of trigeminal neuralgia classifications. The most current classifications include 2 types; classical or idiopathic trigeminal neuralgia, or secondary trigeminal neuralgia. Evaluations for trigeminal neuralgia and differentiating the type revolves around the results of a contrast brain MRI and MRA (MR angiography), as detailed below.
Classical or Idiopathic Trigeminal Neuralgia
If the pain attacks fit with the description and features above, and the trigeminal nerve is being compressed by a blood vessel (neurovascular contact) causing morphological changes of the trigeminal nerve on the side of pain seen on the MRI, this is called classical trigeminal neuralgia. If there is neurovascular contact without compression or no neurovascular contact, then it is called idiopathic trigeminal neuralgia.
Classical and idiopathic trigeminal neuralgia are subdivided into 2 groups. The 1st consists of intermittent pain attacks (which must still fit the criteria above) with pain freedom between attacks. The 2nd is the same intermittent pain attacks, but with a continuous or near-continuous pain in between those severe attacks in the same area of the trigeminal nerve. Studies have suggested that 14-50% of patients can have a continuous lower severity background pain in between the attacks.
Secondary Trigeminal Neuralgia
This refers to trigeminal neuralgia pain attacks which fit the description above, but are caused by something else (a "secondary" cause) such as a brain tumor, aneurysm, multiple sclerosis, or some other pathology.
What Type of MRI is Needed For Trigeminal Neuralgia?
The contrast MRI and MRA should be done with a "trigeminal neuralgia protocol" which consists of a three-dimensional (3D) Constructive Interference in Steady State (CISS) gradient-echo T2-weighted, 3D time of flight and MRA, and 3D T1-weighted gadolinium MRI sequences. The MRI should be done on a 3.0 Tesla (T) or 1.5 T machine, although a 3.0 T resolution will more clearly delineate neurovascular compression of the trigeminal nerve.
There is often confusion between CISS vs. FIESTA-C (Fast Imaging Employing Steady-state Acquisition) MRI sequences for trigeminal neuralgia evaluations, but these are equivocal. The CISS sequence correlates to Siemens MRI machines, whereas the FIESTA-C sequence correlates to GE MRI machines, but they are evaluating the same thing.
Diffusion tensor imaging (DTI) for trigeminal neuralgia is a newer type of imaging test which can evaluate the nerve structure and myelination alterations as a result of neurovascular compression. This may eventually help to better identify which patients are more likely to benefit from microvascular decompression surgery. However, it is not currently used routinely in clinical practice and is more often being used in research.
How Long Does Trigeminal Neuralgia Last?
Individual attacks of trigeminal neuralgia last anywhere from a fraction of a second up to 2 minutes. After the patient has had multiple attacks triggered close together, there is often a temporary refractory period when the pain can not be triggered. Trigeminal neuralgia flares can go into remission for months or years, but it is unpredictable. For some patients it is chronic and unrelenting. In either case, a good treatment strategy must be sought to minimize its negative impact on the patient mentally, socially, financially, and medically (including being able to eat without pain being triggered).
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