6. Trigeminal neuralgia typical and atypical. A disease or two?

Abstract

Trigeminal Neuralgia (TN) is a clinical condition characterized by a sudden, usually unilateral, brief, stabbing, recurrent pain with a distribution consistent with one or more divisions of the fifth cranial nerve. In the classical form, the genesis of paroxysmal pain has been attributed to areas of focal demyelination due to vascular compression on the nerve. The 20–50% of patients with TN have an atypical form characterized by the presence of constant pain, often described as burning continuous or sub-continuous, as well as paroxysmal pain. We hypothesize an axonal damage underlying the constant pain component. We enrolled 55 patients with typical (n = 36) and atypical (n = 19) TN according to the criteria of the 3rd edition of the International Classification of Headache Disorders (ICHD-3). Each patient underwent magnetic resonance imaging (MRI), laser evoked potentials (LEPs) and trigeminal reflexes. The comparison between the duration of disease between the two groups showed no significant differences. We found a greater asymmetry of amplitude (healthy side vs affected side) of N2-P2 component from thermal stimulation in the group with atypical TN (p The atypical form has an axonal damage and is not a time-bound phenomenon. The involvement of C-fibers could be the mechanism behind continuous pain.