Delayed pain relief in patients with trigeminal neuralgia following microvascular decompression: A single-central retrospective study

Abstract

Background: Compared to hemifacial spasm after microvascular decompression (MVD), delayed relief (DR) rarely occurs in patients with trigeminal neuralgia (TGN).

Objective: To analyze the characteristics of post-MVD DR in TGN patients to provide useful clues for the clinical differential diagnosis of postoperative DR.

Methods: The clinical data of all patients with TGN who underwent MVD in our center from January 1, 2016, to December 31, 2020, were reviewed retrospectively.

Results: In 272 TGN MVD patients, DR occurred in nine patients (3.3%) during the follow-up periods of 1-6 years. During surgery, all nine DR-TGN patients were identified as having neurovascular conflicts (NVCs), involving the offending artery (OA) in eight patients (two OAs in two patients) and both an artery and a vein in the other patient. The compression site was near the root entry zone (REZ) in most DR patients (7/9). Delayed relief was relieved in seven patients within 5 days after surgery and within 30 days in the other two patients. No recurrence or serious complications were observed within the mean 4 (1-6)-year follow-up duration.

Conclusion: Delayed relief rarely occurs in TGN patients after MVD. Neurovascular conflicts located at the REZ and NVC of grade III may be two important factors contributing to DR in TGN patients. Delayed relief may occur when the pain gradually improves after the operation and responds effectively to a small dose of carbamazepine. The recurrence rate of TGN seems even lower in such patients.

Keywords: delayed relief; microvascular decompression; neurovascular conflict; root entry zone; trigeminal neuralgia.

Figure 1

Intraoperative findings in a DR patient with compression from a single offending artery on the root entry/exit zone. (A) An AICA is identified; the NVC is located on the ventral side of the TN REZ; the color of the nerve root on the dorsal side becomes bright and is uplifted and distorted upon squeezing. (B) A schematical picture of (A). (C) After pushing away the AICA, a Teflon sponge is inserted, and the nerve root immediately becomes morphologically normal. AICA, anterior inferior cerebellar artery; TN, trigeminal nerve; TS, Teflon sponge.

Figure 2

Findings in a DR patient whose cisternal segment of TN is compressed by the offending artery. (A) A SCA is impacted into the cisternal segment of TN, and the color of the TN root becomes dark, seriously deformed and depressed. (B) A schematical picture of (A). (C) After pushing away the SCA, a Teflon sponge is placed between the artery and the TN root. SCA, superior cerebellar artery; TN, trigeminal nerve; TS, Teflon sponge.

Figure 3

Findings in a DR patient whose offending vessel is a single VA. (A) The cisternal segment of TN becomes a flat thin layer because of the serious compression by VA. (B) A schematical picture of (A). (C) After pushing away the VA from multiple points, a Teflon sponge is placed between the TN and the VA to achieve decompression. VA, vertebral artery; TN, trigeminal nerve; TS, Teflon sponge.

Figure 4

Findings in a DR patient with two offending vessels compressing the TN. (A) A SCA is seen compressing the superior aspect of the TN REZ, and the nerve root becomes dark and deformed. (B) A schematical picture of (A). (C) After pushing away the SCA, a Teflon sponge is inserted between the SCA and the TN. (D) Another AICA is seen compressing the dorsal side of the TN REZ, and the surface of the nerve is depressed and changes in color. (E) After pushing away the AICA, a Teflon sponge is inserted between the AICA and the TN to achieve decompression. AICA, anterior inferior cerebellar artery; SCA, superior cerebellar artery; TN, trigeminal nerve; TS, Teflon sponge.

Figure 5

Findings in a DR patient whose OA and vein simultaneously compress the TN REZ. (A) A branch of the petrosal vein and an SCA are seen compressing the superior aspect of the TN REZ. (B) A schematical picture of (A). (C) After pushing away the SCA, the Teflon sponge is inserted between the TN. (D) Decompression is implemented by inserting the Teflon sponge between the vein participating in NVC and the TN root. SCA, superior cerebellar artery; TN, trigeminal nerve; TS, Teflon sponge; VO, venous offending.