Quantitative sensory testing in classical trigeminal neuralgia—a blinded study in patients with and without concomitant persistent pain

Abstract

The diagnostic criteria of the third International Classification of Headache Disorders state that there should be no neurological deficits in patients with classical trigeminal neuralgia (TN) at clinical examination. However, studies demonstrating sensory abnormalities at bedside examination in TN patients have questioned this. Our aim was to examine whether TN patients without sensory abnormalities at neurological examination have sensory abnormalities at quantitative sensory testing (QST) and whether there were any QST differences between TN with and without concomitant persistent pain. Thirty-six TN patients were investigated with the standardized QST protocol by the German Research Network on Neuropathic Pain. The investigators were blinded to presence of concomitant persistent pain and symptomatic side. Based on comparison to the German Research Network on Neuropathic Pain controls, z scores were calculated to process frequency analyses and Z-profiles. We found increased mechanical detection threshold on the symptomatic side (47.2% vs 0%, P = 0.008), asymptomatic side (33.3% vs 0%, P = 0.011), and hand (36% vs 0%, P < 0.001) in TN compared with controls. The Z-profiles demonstrated increased mechanical detection threshold on the symptomatic side compared with the asymptomatic side (-2.980 vs -2.166, P = 0.040). Thermal and mechanical hyperalgesia was detected bilaterally in the face and the hand. Trigeminal neuralgia patients with concomitant persistent pain tended to have higher mean z score values compared to TN with purely paroxysmal pain indicative of decreased detection thresholds. Trigeminal neuralgia patients with no sensory abnormalities at neurological examination had generalized subclinical hypoesthesia, which was more pronounced on the symptomatic side, and thermal and mechanical hyperalgesia. This could indicate pain-induced hypoesthesia and sensitization induced by central mechanisms.

Evaluating the impact of trigeminal neuralgia

“…Patients did report some altered sensation and this was highest in Group 2. This may be of importance as a recent study has suggested that classical TN (Group 1) may have sub-clinical hypoesthesia whereas those with concomitant pain (Group 2) were more likely to have more clinically detectable sensory changes but all had sensory changes not just on the side of pain but also on the opposite side and in other parts of the body suggesting central sensitisation 28 . What still needs to be established is whether patients move between the different groups during the course of disorder.…”

Quantitative Sensory Changes Following Gasserian Ganglion Radiofrequency Thermocoagulation in Patients with Medical Refractory Trigeminal Neuralgia: A Prospective Consecutive Case Series

“…Our finding of mechanical hypoesthesia measured at the affected side of the face before RFT corresponds to the results of previous studies. [30][31][32] Also, in other facial pain conditions such as persistent idiopathic facial pain and trigeminal traumatic neuropathic pain, tactile threshold increments were already demonstrated. 33,34 Our measurements also revealed pathologic vibration sensing in TN patients preoperatively that contradicts the findings of Flor et al, but this discrepancy may be explained by the heterogeneous characteristics of the study population.…”

Topical Ambroxol 20% for the Treatment of Classical Trigeminal Neuralgia – A New Option? Initial Clinical Case Observations

“…Sodium Channel Blockers and Trigeminal Na v 1.7 and Na v 1.8 Blockade.-In TGN, the trigeminal nociceptive system is sensitized 48 and sodium channel Potentially involved 9 TTX-r currents mediated by Na v 1.9 15 Medication with sodium channel blockade Carbamazepine Recommended; blocks only a very small extent of TTX-r-channels (Na v 1.7 and 1.8) 53,82 Na v 1.7 28,80,81 and Na v 1.8 blockade 13,14 Amitriptyline Recommended; blocks Na v 1.7 [83][84][85] and Na v 1.8 84 Na v 1.7 28,80,81 and Na v 1.8 blockade 13,14 Lamotrigine Recommended; blocks only a very small extent of TTX-r-channels (Na v 1.7 and 1.8) 53,82 Na v 1.7 28,80,81 and Na v 1.8 blockade 13,14 Phenytoin…”