Generally, MVD is indicated for all the patients suffering from drug-resistant trigeminal neuralgia as long as their general conditions do not contraindicate general anesthesia. We would like to point out that old age is not an unconditional contraindication for MVD. Instead, it is relatively easier to operate on the aged for they have a wider subarachnoid space as a result of brain atrophy (Sekula et al. 2008, 2011). Only those with decompensated dysfunction of vital organs should be evaluated cautiously. Hence, we suggest performing the surgery in the early stage before the patient’s quality of life is awfully influenced. Especially, for those undernourished because of less eating to avoid an attack of severe pain induced by oral movement, a prompt surgery is encouraged (Lemos et al. 2011; El-Ghandour 2010). In addition, MVD is indicated in patients with coexistent trigeminal neuralgia and hemifacial spasm (Zhong et al. 2011; Cook and Jannetta 1984), glossopharyngeal neuralgia, (Wang et al. 2014) or Bell palsy (Jiao et al. 2013).

General anesthesia is used for the process. Besides imperceptions and relaxations, decrease of intracranial pressure (ICP) should not be neglected. The dura should not be opened until a satisfactory ICP is ready. Otherwise, the brain tissue might be squeezed out and lead to cerebellar contusions. Hyperventilation can be used temporarily to reduce brain volume and decrease ICP when necessary. Meanwhile, the brain pulsation should be well controlled as it may generate a terrible cerebrospinal fluid (CSF) tide. The microscopic imagings of the trigeminal root and offending artery as well as petrosal veins will be transferred ceaselessly due to the changing optic refraction arose by CSF fluctuation. Hence, it will be a challenge to dissect the trigeminal root in such an SCF rapid – not to mention the deep and narrow operation field. As brain pulsation is generated by the heartbeat via the transmission of the arterial pulse, ventricular tachyarrhythmia should be avoided. Therefore, β-adrenergic blockers will be helpful. Basically, small doses of esmolol can be used repeatedly to control the perioperative tachycardia or hypertension.

We place the patient in a park bench position (3/4 lateral prone decubitus). This position is superior to supine or full prone position because it obviates the need to turn the patient’s head into an uncomfortable position and therefore decreases the risk of postoperative neck pain, especially for obese patients with generous supraclavicular fat pads. It is necessary to point out that the contralateral shoulder should be close to the edge of the bed so that the surgeon can easily reach the surgical site. Meanwhile, the ipsilateral shoulder should be pulled away from the head by a shoulder belt so as to create a satisfactory working space, which facilitates the instruments getting in and out of the surgical field. A fixation frame is used to hold the patient’s head stable and make it possible to apply retractor system when necessary. However, we no longer use retractors even in cases of secondary trigeminal neuralgia resulting from CPA masses since we have chosen an oblique position of the patients’ head. This inclined position with the patient’s head turning back 15° from the level surface facilitates the cerebellum to fall away under its own gravity from the petrosal bone and obviates the need of retractors. Therefore, a good exposure is achieved by rational positioning of the patient’s head rather than retracting of cerebellum (Fig. 6.1) (Zhong et al. 2012, 2014).

Although transversal, arc, or reverse ‘U’ shape incisions have been reported (Cohen-Gadol 2011), we choose a vertical linear incision. It is laterally parallel to the hairline and crosses the inion-zygomatic line with 1/3 above and 2/3 below. Nowadays, we have adopted a mastoid retractor to hold the incision and no scalp clip is needed. Owing to the limitation of the retractor’s open angle, an incision longer than 7 cm is not really necessary. To save a good blood supply, undue coagulation should be avoided during the incision making and a quick retraction of the incision is recommended. As the operator is sitting behind the patient, a more medial peeling will provide a good sight (Fig. 6.2).

Basically, a craniectomy of <3 cm in diameter is enough for most cases. The edge of the sigmoidal sinus should be exposed to ensure an ideal surgical corridor. To avoid dural sinus injury, we prefer craniectomy with pneumatic drill and Kerrison rongeur to craniotomy with milling cutters. Bone dust and chips were preserved for the later cranioplasty. The bone over the sigmoid sinus should be removed in small pieces. Bone wax is effective for homeostasis at the edge of dural sinuses. To obtain a good working angle, the mastoid antrum could be opened if necessary, but it should be immediately waxed to prevent infection and CSF leak (Fig. 6.2).

Before dural opening, a thorough irrigation is necessary. It is not merely for bone scraps cleaning but mainly for double checks of bleeding. Even a little oozing of blood may flow in your surgical field continuously, which may interfere with your vision and mood terribly. In spite of a variety of dural tailoring, we now prefer an arc-shaped cutting with its chord paralleling to the lateral rim of the craniectomy. After the dural mater is sutured back with double knotting, the suture thread remains in place (without cutting off), which facilitates tightening when necessary during the procedure. This pattern of dural opening leaves the majority of the dura on the cerebellum, which avails the protection of the cerebellar hemisphere during the process (Fig. 6.3). To avoid shrinkage of the dura due to the heat generated by the operating microscope’s lamp aimed at the surgical field during the intradural portion of the operation, pieces of wet Gelfoams are placed over the dura.

In our series of 6000 MVDs, the main reason of a failed surgery was that the exact offending vessel(s) were not recognized or the neurovascular conflict site was inaccessible intraoperatively. So we believe a full exposure of the entire trigeminal nerve root course is the key to obtain a good result. Advancing toward the target starts with a Cottonoid placed over the cerebellum and draining CSF slowly. Usually, an unhurried suction drainage of CSF and an ample adhesiolysis are effective enough to achieve brain relaxation, and no mannitol or lumbar puncture is needed for most of the cases. We do not use retracting blades because a narrow suction tube allows more mobility and can actually afford more working space than a wider spatula does during the procedure at a moment when a specific area is dissected. As a matter of fact, with a good knowledge of the regional anatomy, one does not have to visualize the whole area of CPA while operating at a particular site (but those surrounding structures should always be in mind). Basically, a Fukushima teardrop suction tube, a pair of microscissors, a microdissector, and a pair of bipolar coagulation forceps are enough to complete all the intracranial manipulation. Instead of the ordinary gun-shape forceps, a self-irrigating bipolar forceps can keep the Cottonoid over the cerebellum moist all the time and avoid cerebellar contusion. The action of clamping an artery should be avoided, which may cause vasospasm (Fig. 6.4).

The protection and management of petrosal veins poses the main challenges and risks during the process. In early cases, we approached the trigeminal nerve from the superolateral aspect of the cerebellum, and petrosal veins were often obstructing the access path. We used to sacrifice these veins to prevent unintentionally tearing at its entry to the superior petrosal sinus, which was tough to manage. In that case, compression with Gelfoam was the only way for homeostasis, while coagulation could only make things worse. However, when a Gelfoam was used to cover the bleeding point, working space became much narrower and the following procedures could be very difficult. To detour off those petrosal veins, we now dissect the arachnoid membranes around the petrous and the superior cerebellopontine fissures. Basically, the REZ of the V nerve will be directly in your sight with the cerebellar fissures opened thoroughly (Fig. 6.5) (Zhu et al. 2014).