Como diagnosticar Neuralgia do Trigêmeo?

HOW TO DIAGNOSE TRIGEMINAL NEURALGIA?
Diagnosing the various facial pain disorders can be very difficult, and misdiagnoses are therefore extremely prevalent with huge costs for the patients.
According to the criteria of the IHS, trigeminal neuralgia is characterized by paroxysms of pain on one side of the face restricted to the innervation areas of the trigeminal nerve. Duration of paroxysms should be less than 2 minutes, intensity should be severe, and the quality should be electric, stabbing, or similar. Finally, there should be factors that can trigger pain such as touching the face, talking etc., and the pain should not be caused by other factors.
The clinical picture may not always be as characteristic as described above. Pain may become bilateral with time in a few patients, and patients may report that very severe attacks may radiate beyond the territory of the trigeminal nerve, typically to the ear. This does not necessarily rule out the diagnosis of trigeminal neuralgia, but atypical symptoms are red flags that should prompt further investigations. Duration can be particularly difficult. Patients may report that attacks may last for longer than 2 minutes, e.g., for 10 minutes, but sometimes the patients experience the duration longer than it is, because the pain is so severe, other times the patients mainly remember the few atypical long attacks, while most attacks are short. Diagnosis should be made based on the typical attacks.
Up to 50% of the patients will have a less severe, more or less constant, background pain. Sometimes, this makes the physician doubt the diagnosis of trigeminal neuralgia. However, this is a normal finding, and these patients should be subclassified as having trigeminal neuralgia with concomitant continuous pain.
The neurological examination is usually unremarkable, but on thorough sensory testing subtle sensory abnormalities can be detected in approximately 30% of patients with idiopathic or paroxysmal trigeminal neuralgia. However, finding of clearcut sensory abnormalities is a red flag that should prompt further investigations, e.g., for multiple sclerosis or cancer.
If a dental cause has not been excluded, the patient should be examined by a dentist with specific interest in trigeminal neuralgia.
All patients should undergo MRI, with specific focus on the degree of a possible neurovascular contact, to be able to subdivide patients into idiopathic trigeminal neuralgia and classical trigeminal neuralgia (where neurovascular contact with morphological changes of the nerve has been demonstrated), because this has consequences for decision making on when to refer to surgery. Moreover, MRI is needed to exclude secondary causes such as tumors compressing the trigeminal nerve or multiple sclerosis.
There are numerous types of facial pain other than trigeminal neuralgia, but trigeminal neuralgia is the best known, and therefore most patients with facial pain are referred to the more experienced centers with a diagnosis of trigeminal neuralgia. This is particularly true for patients with facial pain, where MR imaging has demonstrated neurovascular contact between the trigeminal nerve root and a vessel. However, simple contact, i.e., contact without morphological changes of the nerve, is seen in 78% of healthy nerves. It is important to remember that trigeminal neuralgia is a diagnosis based on clinical features.
For patients with significant autonomic features, trigeminal autonomic cephalalgias, such as SUNCT, should be considered.
Some of the most common of the other facial pain disorders, apart from trigeminal neuralgia, are persistent idiopathic facial pain and posttraumatic trigeminal neuropathy. Here it is important to rely on pain history and results of physical examination.
In conclusion, diagnosis of facial pain is by no way simple. A thorough medical history and clinical examination and MRI are essential to reach the correct diagnosis for the benefit of the patient.
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