When a severe pain appears suddenly in the face, like an electric shock or a flash of lightning, trigeminal neuralgia is among the conditions that come to mind. Yet not every pain of the face, jaw or teeth arises from trigeminal neuralgia.
Findings That Suggest Trigeminal Neuralgia
Trigeminal neuralgia is a paroxysmal neuropathic pain arising from irritation of the fifth cranial nerve (the trigeminal nerve), which supplies sensation to the face. It is distinguished from ordinary facial and dental pain by the following features:
- Rhythmic, severe pain like an electric shock: unilateral attacks of stabbing pain.
- Pain-free intervals: between attacks patients are generally entirely free of pain.
- Provocation by light stimuli (allodynia): washing the face, shaving, brushing the teeth, eating, speaking, or even a light breeze against the face may set off an attack.
In the great majority of cases (classical trigeminal neuralgia), the underlying cause is a blood vessel that comes into contact with the fifth nerve and exerts pulsatile pressure upon it at the sensitive point where the nerve root leaves the brainstem (the root entry zone).
What Does Vascular Compression on MRI Mean?
Not every contact between a vessel and the nerve gives rise to trigeminal neuralgia. The clinical history and the neurological examination are fundamental to the diagnosis.
For imaging, thin-section three-dimensional MRI sequences (3D-CISS or FIESTA) are preferred over standard brain MRI. Besides demonstrating the anatomical detail of neurovascular compression, these sequences are critical in excluding secondary causes such as a tumor or multiple sclerosis.
When Are Further Assessment and Surgery Considered?
In trigeminal neuralgia, rather than ordinary analgesics, agents that reduce the hyperexcitability of the nerve — such as carbamazepine and oxcarbazepine — are used. Where these agents fail, other drug options may also be tried.
Further assessment is nonetheless required in the following circumstances:
- attacks of pain that cannot be brought under control despite drug treatment;
- the development of intolerable side effects attributable to the drugs;
- marked neurovascular compression on MRI.
At this stage the gold-standard surgical approach is microvascular decompression (MVD). Through an approach made behind the ear, a protective barrier is placed between the vessel and the nerve, and the compression is relieved permanently. In patients who are not suitable for surgery, or who are of advanced age, percutaneous procedures or Gamma Knife radiosurgery offer an alternative.
In short: not every facial pain is trigeminal neuralgia. A thorough examination and high-resolution MRI are essential to a correct diagnosis; and in cases that do not respond to medication, modern microsurgical methods achieve a high rate of success.
References
- European Academy of Neurology (EAN) — Guideline on Trigeminal Neuralgia (Bendtsen et al., 2019)
- The International Classification of Headache Disorders, 3rd edition (ICHD-3)
- Jannetta, P. J. — Neurovascular compression in cranial nerve disorders, Neurosurgery, 1980
- Maarbjerg, S. et al. — Trigeminal neuralgia – diagnosis and treatment, Nature Reviews Neurology, 2017