The Changing Face of Trigeminal Neuralgia

A Narrative Review

Stine Maarbjerg MD, PhD; Rafael Benoliel BDS (Hons)

Disclosures

Headache. 2021;61(6):817-837. 

In This Article

Classification

"TN" as a diagnosis can be established clinically (Table 2), but to subclassify the diagnosis, imaging is needed (Figure 1).[1] Classical trigeminal neuralgia (CTN) is defined as occurring with "demonstration on MRI or during surgery of NVC (not a simple contact), with morphological changes in the trigeminal nerve root."[1] Compression is typically associated with nerve atrophy or displacement. CTN remains subdivided into purely paroxysmal or with concomitant continuous pain (Table 3). Secondary trigeminal neuralgia (STN) is reserved for a typical TN phenotype associated with a space-occupying lesion or MS usually associated with demyelination of the trigeminal nerve root (Table 4 and Figure 1). A striking change is the introduction of a new, evidence-based subcategory: idiopathic trigeminal neuralgia (ITN). ICHD-3 defines ITN as "trigeminal neuralgia with neither electrophysiological tests nor MRI showing significant abnormalities." The use of "neither/nor" implies that both must be absent. Although MRI is widely available, electrophysiology equipment and trained staff are not. Our opinion is that ITN definition needs rewording, possibly: "Trigeminal neuralgia without significant morphological abnormalities on MRI. The diagnosis is strengthened by electrophysiological and other tests similarly showing no causative reason" (Table 5 and Figure 1). ITN is also subdivided into purely paroxysmal and those with concomitant continuous pain.[1] ICHD has now made the triggering phenomenon a compulsory criterion for TN[4] bringing the structure of the TN diagnostic criteria in line with those for other neuropathic pains.[5–7]

Figure 1.

Flow diagram for the diagnosis of trigeminal neuralgia into subtypes (see also Table 1). MRI, magnetic resonance imaging; NVC, neurovascular contact

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