Use of the ZLR method in microvascular decompression of the trigeminal nerve root

The availability of an objective, instrumental intraoperative method for assessing the eff ectiveness of microvascular decompression (MVD) in classical trigeminal neuralgia (cTN) is undoubtedly indispensable in modern neurosurgery.

The aim. To study the applicability of the ZLR method for intraoperative identification of the causative vessel and assessment of the completeness of trigeminal nerve root decompression in classical trigeminal neuralgia.

Materials and methods. A prospective study was conducted involving 10 patients with cTN. During MVD, a ZLR monitoring protocol was used, including stimulation of vessels in the neurovascular confl ict zone with a bipolar concentric electrode in the range of 0.1–2.5 mA, as well as recording of the masseter muscle responses (ZLR, ZL-response) before and after MVD. Postoperative pain regression was clinically assessed.

Results. In 90 % of cases, the causative vessel was the superior cerebellar artery (SCA). The arterial stimulation threshold before MVD was 0.4 ± 0.22 mA, after MVD – 1.5 ± 0.49 mA (p < 0.05). After decompression, there was no response to arterial stimulation up to 2.5 mA in 54.5 % of cases. Venous stimulation required higher parameters (1.3 ± 0.61 mA before MVD), and in most cases, there was no response from the target muscle either before or after decompression. Postoperatively, pain completely regressed in 90 % of cases; however, in one case, partial persistence of facial pain was noted, which completely regressed with conservative therapy.

Conclusion. Given the obtained stimulation threshold parameters, the ZL response method allows for intraoperative verifi cation of the causative arterial vessel and assessment of the effectiveness of microvascular decompression, as evidenced by favorable clinical outcomes. The role of venous compression requires further study. Further research is needed to evaluate the prognostic signifi cance of this method, as well as the role of venous compression.

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