Tag: interposition

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Evaluation of 2 Surgical Techniques—Transposition Versus Interposition Microvascular Decompression for Hemifacial Spasm: A Systematic Review of 19 437 Patients

Neurosurgery 97:16–27, 2025

This systematic review of 19,437 patients compares transposition and interposition microvascular decompression techniques for hemifacial spasm. Both methods show similar efficacy and safety, with no conclusive evidence favoring one. Slightly higher facial nerve weakness was noted with transposition. Prospective trials are needed for definitive comparison.

Hemifacial spasm (HFS) is a rare disorder caused by compression of the facial nerve, leading to involuntary facial muscle contractions.

• Microvascular decompression (MVD) is an effective surgical treatment for HFS, with two main techniques: interposition (placing a prosthesis between nerve and vessel) and transposition (moving the vessel away without direct prosthesis contact).

• A systematic review of 62 studies (19,437 patients) compared outcomes of interposition (18,627 cases) and transposition (810 cases) in MVD for HFS.

• Spasm freedom rates were similar: 90.4% for transposition and 89.6% for interposition.

• Complication rates were similar, though temporary facial nerve weakness/palsy was higher with transposition (9.52% vs 6.03%).

• No conclusive evidence was found that one technique is superior in safety or efficacy; interposition may be preferred in certain clinical situations.

• A prospective trial is needed to determine true differences and optimal indications for each technique.

• The review highlights the need for future studies to stratify outcomes by technique and report prognostic factors.

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Transposition versus interposition method in microvascular decompression for trigeminal neuralgia

J Neurosurg 140:1777–1784, 2024

Operative interposition of material between the trigeminal nerve and offending artery for surgical treatment of drug-resistant trigeminal neuralgia (TGN), following the Jannetta method, has been proven to be the most successful invasive treatment. Reexplorations of patients with recurrence of TGN have revealed nerve root irritations and scarring due to interposed material. To prevent these complications, modifications of microvascular decompression (MVD) aim at transposing the vessel away from the trigeminal nerve, without attachment of additional material to the nerve root. Given that both techniques (interposition and transposition) have been performed in the authors’ institution, they decided to analyze them for the short- and midterm outcomes.

METHODS All patients who had undergone MVD for drug-resistant TGN in the authors’ institution between 2008 and 2022 were analyzed retrospectively. Outcome at discharge and follow-up was evaluated using the Barrow Neurological Institute pain intensity score. Additionally, complications and pain recurrence were assessed.

RESULTS A total of 114 patients were operated on using transposition and 110 patients were treated using interposition. For transposition 102 patients were followed up for a median of 31.5 months, and for interposition 100 patients were followed up for a median of 95 months. At discharge 92.1% versus 94.5% of patients in the transposition and interposition groups, respectively, experienced a good outcome (Barrow Neurological Institute pain intensity scores I–III). At followup, 83.3% versus 85% of patients in the transposition and interposition groups, respectively, continued to demonstrate a good outcome. In 4.9% of patients in the transposition group and in 6% of patients in the interposition group, recurrence of pain occurred. Complications occurred in 24.6% of patients in the transposition and in 27.3% of those in the interposition group. The most frequent complications were facial hypesthesia (10.5% vs 11.8%, transposition vs interposition), followed by CSF leaks (2.6% vs 8.2%).

CONCLUSIONS Transposition for MVD is an elegant way of solving vessel-nerve conflicts at the cerebellopontine angle. Similar to interposition, transposition shows positive short- and midterm outcomes for patients experiencing drugresistant TGN. However, the main objective of transposition, which is improved prevention of recurrence and reduction of complications at the trigeminal nerve, could not be confirmed in this study.

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