TN is the most frequent disorder to affect the fifth cranial nerve. It usually begins as a relapsing disease with pain-free intervals that may last months or years. These intervals, however, typically grow shorter and eventually disappear. As the disease progresses, patients can have difficulty talking, eating, and maintaining facial hygiene out of fear of triggering the pain. Current treatment usually begins with carbamazepine, which frequently provides relief from symptoms. Unfortunately, the relief provided by carbamazepine or other drugs may decrease over time, and side effects such as hyponatremia or difficulty with balance may necessitate discontinuation of the medication. About half of all patients eventually require an operation for pain relief [7].
The characteristics of the patients in this series, such as sex, affected side, and affected division, were consistent with those of the previous reports [8, 9]. In this study, patients were predominantly female (male to female ratio was 2–3), pain was mainly right sided (right to left ratio was 2.3:1) and the mandibular area was most affected. The mean age of symptom onset was 57 years in the patients with all types of TN.
MVD is the mainstay of treatment for refractory TN. Furthermore, after MVD, the trigeminal nerve is preserved, and denervation of the face, with facial dysesthesia and anesthesia dolorosa, is avoided. Large published studies have shown that the pain is completely relieved in 70–91% of patients and is reduced in another 6–7.6% after MVD [10, 11] and the annual recurrence rate at long-term follow-up is estimated to be 1–3.5%.
The current study showed that MVD is effective in classical trigeminal neuralgia (p value < 0.001). The comparison of the outcomes with those in large published series showed similar success and recurrence rates. Barker et al. [10] presented their long-term outcome results after MVD of 1185 patients. Eighty percent of their patients were completely pain free after MVD, and 7.6% obtained partial relief. At the 10-year follow-up evaluation, 70% of them still had pain relief and no extra medications were needed, whereas 4% had partial relief. In the series of Tyler-Kabara et al. [12], 98.2% had immediate pain relief and excellent long-term pain relief was achieved in 73.7% patients.
Careful inspection of the trigeminal nerve in a circumferential fashion allowed us to detect the various patterns of neuro-vascular conflicts. Barker et al. in his series of 1185 operated patients, found the superior cerebellar artery (SCA) as the main vessel in contact with the nerve (75.5%), the anterior-inferior cerebellar artery (AICA) was involved in 9.6%, the vertebral artery in 1.6%, the basilar and the posterior-inferior cerebellar artery (PICA) in 0.7% and the labyrinthine artery in 0.2%. A vein contributed to the compression in 68% of patients and was the only compressing vessel in 12%. However, the veins involved in this compression were not listed completely by name [10].
Various patterns of neuro-vascular conflicts are seen through posterior approach of right cerebello-pontine angle, superior cerebellar artery located supero-medial or superolateral to the trigeminal nerve or anterior inferior cerebellar artery inferiorly compressing the trigeminal root entry Zone at the pons [13].
Venous structures causing a neurovascular contact were more inconsistent. The normal anatomy of the veins in this region is quite variable and it includes, among other things, the superior petrous vein that arises after the junction of a transverse pontine vein, the vein of the medial cerebellar peduncle and the cerebellar-pontine scissure vein among others. The superior petrous vein goes up and laterally to find the superior petrous sinus [14].
Matsushima et al. found three kinds of veins to be the offending vein. The transverse pontine vein was the vein most frequently found in 67.2% of the cases. Both the ponto-trigeminal vein and the vein of the cerebellar-pontine fissure were found in 28.6% [15].
Depending on the anatomic situation, three different methods for decompression of the veins are used, including cutting, interposing, and transposing by the sling technique. The offending vein is coagulated and cut when the vein is one of several superior petrosal veins. However, the vein is not cut in cases in which it was a large main drainer, such as the single superior petrosal vein, because of fear of complications arising when sacrificing the superior petrosal vein. In our case, we used the cutting method followed by interposing pieces of Teflon between the nerve and the vessel stump.
The use of the endoscope after microscopic decompression was completed yielded no further benefit. It was performed in 4 patients to evaluate the quality of the initial decompression and/or defining any missed trigeminal nerve conflicts. Using a similar technique on a larger number of cases, Jarrahy et al. [16] found that 14 out of 51 (28%) compressive vessels were only visible on endoscopy and that MVDs were inadequate in 21 patients (25%) after endoscopic review. However, comparison of patient outcomes with those of larger series [10, 17] suggested that despite a subjectively better perspective and an objectively improved detection of pathology, overall surgical results are unchanged by the addition of endoscopy.
Low rates of severe postoperative facial numbness and dysesthesia in our study are additional advantages of microvascular decompression which are more likely with both radiofrequency thermal rhizotomy and glycerol rhizotomy [18]. The morbidity rates in the largest published series included: intracranial hemorrhage or stroke after MVD develops in 0.1–2%, hearing loss is noted in 3–8%, sensory loss occurs in 5–31%, and the mortality rate is 0–1% (42–53). In the series of Levi and Jannetta [17] that included 1336 consecutive MVD procedures, there were 2 deaths (0.15%), 5 vascular complications (0.37%), and 42 permanent cranial nerve deficits (3.1%). In another large series reported by Tyler-Kabara et al. [12], vascular complications were recorded in 0.2%, edema in 0.4%, hydrocephalus in 0.1%, facial nerve palsy in 1.7%, and hearing loss in 1.4%; other cranial nerves were affected in 4.6%, CSF leak occurred in 1.6%, and the mortality rate was 0.2%. There were no perioperative mortalities regarding our study.
