gms | German Medical Science

The concept of vascular compression as a cause of trigeminal neuralgia (TN) was first described by Dandy in 1934 [Ref. 4] and rediscovered by Gardner in 1963 [Ref. 5]. Jannetta perfected and popularized the technique of microvascular decompression (MVD) for hyperactive dysfunction of cranial nerves [Ref. 7], [Ref. 8]. Ever since and as a result of advances in microsurgical techniques, the MVD procedure has become a main stay in the treatment of TN with favourable outcome [Ref. 1], [Ref. 6], [Ref. 7], [Ref. 9]. Since 1982, we have carried out 420 MVDs for TN and have climbed the learning curve. We present the surgical technique of MVD with some surgical tips that we have developed over the last 23 years.

Four hundred and twenty patients underwent posterior fossa exploration for TN between 1982 and 2004. We retrospectively reviewed the prospectively collected data. All patients presented with typical TN affecting one or more of the branches of the trigeminal nerve. All were consented for MVD ± partial sensory rhizotomy (PSR) and underwent keyhole retro-sigmoid posterior fossa exploration by the senior author or a supervised trainee.

MRI/MRA demonstrates vascular compression with 100% specificity and 95% sensitivity [Ref. 10]. Also look for petrous endostosis (PE), which can obscure trigeminal sensory root [Ref. 11]. When PE is suspected, CT scan with bony windows is useful not only to confirm the endostosis but also to assess the pneumatization of the petrous air cells.

The entire sensory root should be exposed and visualised. All vessels that might be compressing must be removed regardless of their size. As previously emphasized one should aim to achieve a total decompression with no vessel or prosthesis touching the nerve should be left [Ref. 8]. In cases where no vascular compression is found (10–15%) [Ref. 2], a PSR should be performed.

The patient is placed on the operating table in the semi-prone park bench position with the head secured in the Mayfield 3 pin head rest (OMI, Inc., Cincinnati, OH). Anatomical surface landmarks – asterion and mastoid tip – are identified. The angle of transverse/sigmoid sinus is exposed via 2.5 cm craniotomy. Gently “turn the corner” of the cerebellum using fine tapered retractor and following petrosal sinus pathway. Lateral petrosal bridging veins could be divided if necessary but better preserve the medial ones. Divide the arachnoid around and avoid any tension on the facio-acoustic bundle (VII & VIII cranial nerves) before proceeding further with the cerebellar retraction.

Once the region of the Neurovascular conflict is identified, use suction tip and ball dissector to mobilise the blood vessel – commonly the superior cerebellar artery (SCA) – from neural contact. Place the offending blood vessel on tentorium and overlay with Teflon wool sling and fibrin glue (Tisseel, Baxter Healthcare Ltd, Norfolk, UK). Compressive veins can be diathermied and divided with safety. If petrous endostosis is present (3.3%), use endoscopy or drill reduction, this frequently reveals a compressing vein. Seal mastoid air cells with muscle and glue. Watertight dural closure is performed using 5/0 proline and use muscle or artificial dural patches if necessary. Replace and secure the bone flap and close the wound in layers.

Table 1 [Tab. 1] shows the surgical findings in 420 posterior fossa explorations for TN. Average hospital stay is 3.5 days. Mean duration of follow-up is 5.6 years. Long-term cure for MVD and PSR is 86% and 85%, improvement is 9% and 13%, and failure is 5% and 2%. Figure 1 [Fig. 1] shows The Kaplan-Meier curve of recurrence – free rate, stratified by type of surgery. Average patient satisfaction with the outcome of surgery is 92%. Table 2 [Tab. 2] shows postoperative mortality and morbidity [Ref. 3].

The first vascular decompression operation was performed by Gardner [Ref. 5]. Using the microsurgical techniques, Jannetta [Ref. 7] popularized and perfected the technique and called it Microvascular Decompression (MVD). Ever since, Neurosurgeons have been using the technique with favourable long-term outcome [Ref. 1], [Ref. 6], [Ref. 7], [Ref. 9]. In a literature review, Zakrzewska [Ref. 12] included patients who had MVD from studies using actuarial methodology (n=2241). The probability of being pain-free after MVD was 70% in 10 years. Our results compare well with the published literature. The incidence of complications in the current series is in keeping with the published literature (Table 2 [Tab. 2]). Perhaps the incidence of CSF leak is slightly higher as we had to drill petrous endostosis in 14 cases and 5 of them developed postoperative CSF leak. We had no mortality and the incidence of aseptic meningitis is considerably less (0.8 Vs 7.0%) possibly because of the routine use of steroids in the perioperative period.

In the treatment of TN, MVD is minimally invasive “Keyhole” procedure, highly effective and very safe, but there is a learning curve. Consent for surgery should involve PSR in case no vessel is found (15% no vessel). The use of steroids in the perioperative period is beneficial to reduce postoperative nausea and aseptic meningitis.