gms | German Medical Science

Objective: Microvascular decompression (MVD) represents the neurosurgical gold-standard for patients with refractory classical trigeminal neuralgia (TN). Although success rates of MVD are high, there is a percentage of patients that relapse or do not profit in spite of typical symptomology or intraoperative decompression of a neurovascular conflict. So far, there is no standard established to quantify changes in the nociceptive trigeminal pathway. Laser-evoked potentials allow assessment of latency and amplitude of nociceptive neural fibers and could be used to find pattern of nerve damage that favor or hinder therapeutic success of MVD.

Methods: Patients with the clinical symptomology of classical TN according to the International Headache Society’s (IHS) criteria were included in this study. Atypical pain or previous surgical interventions at the trigeminal nerve were deemed as exclusion criteria. Patients received pre- and postoperative measurement of LEP measurements. Patients received a train of 20 impulses (inter-pulse interval 5seconds) with a C02 Laser (Stimul 1340, Deka-Laser) in the painful trigeminal dermatome and the corresponding contralateral dermatome (control). LEPs were measured using a122 channel whole head magnetencephalogram (MEG). Patients were tested prior to and 4 weeks after microvascular decompression.

Results: N=5 patients (as of November 2017) were included in this study. In all cases pre- and postoperative MEG-assisted LEP measurements were performed. There was a difference regarding latency and amplitude of the trigeminal LEP between the healthy and affected side preoperatively. Increased latency and decreased amplitude of the trigeminal LEP was detected in the insular region and the primary sensory cortex for the affected trigeminal dermatome compared to the unaffected contralateral dermatome. A trend towards lower latency and higher amplitude was observed postoperatively.

Conclusion: Trigeminal LEPs may be an indicator for trigeminal nerve dysfunction in trigeminal neuralgia. LEPs are affected by neurosurgical procedures. More patients need to be evaluated to assess whether changes detected in LEPs correlate with therapy response after MVD.