Microvascular decompression of the facial nerve

Endoscope Assisted Microvascular Decompression: Are the Advantages Still Worthy Towards More?

Background

Microvascular decompression is the definitive treatment of various neuralgias affecting cranial nerves. The compression on a cranial nerve could be at the root entry zone, especially the trigeminal nerve. Endoscope-assisted microsurgery may help avoid missing a hidden vascular structure.

Study design

Retrospective clinical case series.

Patient and methods

Twenty-five patients with facial pain and five patients with hemifacial spasm constituted this study. FIESTA MRI was the pre-operative neuroimaging modality. Retrosegmoid craniectomy was done for all patients. Microscope was initially used for exploration and arachnoid dissection around the nerve. The endoscope was applied thereafter for exploration and confirmation of the proper insertion of the Teflon.

Results

Using the endoscope, cerebellar retraction was reduced by 0.5 to 0.8 cm in 90% of patients. Root entry zone and entry of the nerve through the corresponding skull base foramen was clearly visualized by the endoscope. Endoscope enabled a wider area of exploration and panoramic view, which could not be obtained by the microscope. Patients with trigeminal neuralgia had a median pre-operative VAS of 9, while it was only 1 in early post-operative and 0 in 6-month post-operatively. Patients with HFS were completely recovered.

Conclusion

The advantages of microvascular decompression are still worthy. Complications are minimal, and the view is much more panoramic. The different viewing angles and ability to directly reach corners is an absolute endoscopic advantage. Therefore, avoidance of missing vascular structures and incomplete recovery can be assured.

Hypertension of neurogenic origin: effect of microvascular decompression of the CN IX-X root entry/exit zone and ventrolateral medulla on blood pressure in a prospective series of 48 patients with hemifacial spasm associated with essential hypertension

OBJECT

In spite of solid anatomical and physiological arguments and the promising results of Jannetta in the 1970s, treating essential hypertension by microvascular decompression (MVD) of the brainstem has not gained acceptance as a mainstream technique. The main reason has been a lack of established selection criteria. Because of this, the authors' attempts have been limited to patients referred for MVD for hemifacial spasm (HFS) who also had hypertension likely to be related to neurovascular compression (NVC).

METHODS

Of 201 patients referred for HFS, 48 (23.8%) had associated hypertension. All had high-resolution MR images that demonstrated NVC. All underwent MVD of the root exit/entry zone (REZ) of the ninth and tenth cranial nerves (CN IX-X) and adjacent ventrolateral medulla in addition to the CN VII REZ. Effects on hypertension, graded using the WHO classification, were studied up to the latest follow-up, which was 2–16 years from the time of surgery, 7 years on average. Also, effects of MVD on blood pressure (BP) according to the side of vascular compression were evaluated.

RESULTS

Preoperatively, hypertension was severe in all but 1 of the patients; in spite of medical treatment, 47 patients still had WHO Grade 1 or 2 hypertension, and 18 still had unstable BP. After MVD, at latest follow-up, BP had returned to normal (i.e., systolic pressure < 140 mm Hg) in 28 patients; 14 of these patients (29.10% of the whole series) were able to maintain normal BP without any antihypertensive treatment; the other 14 still required some medication to maintain their BP below 140 mm Hg (p < 0.0001). Also, at latest follow-up, BP remained unstable in only 8 of the 18 patients with instability prior to MVD (p < 0.02). Analysis according to side of compression showed that of the 30 patients with left-sided compression, 17 had their BP normalized (without medication in 11 cases), and of the 18 patients with right-sided compression, 11 had their BP normalized (without medication in 3 cases). The difference between sides was not significant.

CONCLUSIONS

These results argue for considering MVD for the treatment of hypertension likely to be due to NVC at the CN IX-X REZ and adjacent ventrolateral medulla. Criteria for selecting patients with hypertension alone still need to be established and could include the following indications: apparently essential hypertension, likely to be neurogenic, in patients in whom high-resolution MRI shows clear-cut images of NVC at the CN IX-X REZ and adjacent ventrolateral medulla and in whom BP cannot be controlled by medical treatment.

Is there a place for microsurgical vascular decompression of the brainstem for apparent essential blood hypertension? a review

There are anatomical and physiological evidences that the ventrolateral (VL) region of the medulla plays an important role in blood pressure regulation and that dysfunction at this level may generate hypertension (HT). Vascular compression by a megadolicho-artery from the vertebrobasilar arterial system at the root entry/exit zone (REZ) of the glossopharyngeal (IXth) and vagal (Xth) cranial nerves (CNs) and the adjacent VL aspect of the medulla has been postulated as a causal factor for HT from neurogenic origin. The first attempts at microvascular decompression (MVD) of the IX-Xth CNs together with the neighbouring VL brainstem was revealed promising. These surgical attempts, as well as the numerous MRI studies, with the goal to detect and identify likely responsible neurovascular conflicts (NVC), are reviewed. Established criteria for indication of MVD as an aetiological treatment of apparent essential HT are still needed.

Is hemifacial spasm accompanied by hemodynamic changes detectable by ultrasound?

BACKGROUND

Arterial tortuosity of the posterior circulation compressing the facial nerve induces the ephaptic axono-axonal cross-talk that sparks hemifacial spasm. We sought if a noninvasive method such as color duplex of these arteries might detect hemodynamical changes in this condition.

METHODS

Nine patients with hemifacial spasm, successfully treated with botulinum toxin, were examined with color-coded duplex ultrasound. Mean blood flow velocities of the vertebral, basilar, posterior inferior cerebellar, and anterior inferior cerebellar arteries were measured and side-to-side comparison performed.

RESULTS

In all nine patients, the mean blood flow velocity, averaging across the two arteries, was higher on the side of the hemifacial spasm (Fisher's exact p < 0.008; two-tailed). The results of the repeated measures ANOVA show that the main effect of side of flow was statistically significant, F(1,8) = 17.354, p = .0032, with higher mean blood flow velocities observed on the side of the hemifacial spasm. There was no significant association between the mean flow velocity of the vertebral artery and the side of spasm (p = 0.523).

CONCLUSIONS

Hemifacial spasm also seems to relate to hemodynamic changes, which may be detectable by color duplex imaging.

Preoperative evaluation of neurovascular relationships for microvascular decompression in the cerebellopontine angle in a virtual reality environment

Object

In this paper the authors' goal was to evaluate the feasibility and efficacy of a virtual reality (VR) system in preoperative planning for microvascular decompression (MVD) procedures treating idiopathic trigeminal neuralgia and hemifacial spasm. The system's role in surgical simulation and training was also assessed.

Methods

Between May 2008 and April 2009, the authors used the Dextroscope system to visualize the neurovascular complex and simulate MVD in the cerebellopontine angle in a VR environment in 16 patients (6 patients had trigeminal neuralgia and 10 had hemifacial spasm). Reconstructions were carried out 2–3 days before MVD. Images were printed in a red-blue stereoscopic format for teaching and discussion and were brought into the operating room to be compared with real-time intraoperative findings.

Results

The VR environment was a powerful aid for spatial understanding of the neurovascular relationship in MVD for operating surgeons and trainees. Through an initial series of comparison/confirmation experiences, the senior neurosurgeon became accustomed to the system. He could predict intraoperative problems and simulate surgical maneuvering, which increased his confidence in performing the procedure.

Conclusions

The Dextroscope system is an easy and rapid method to create a stereoscopic neurovascular model for MVD that is highly concordant with intraoperative findings. It effectively shortens the learning curve and adds to the surgeon's confidence.

Hemifacial Spasms and Involuntary Facial Movements. Role of Magnetic Resonance in the Diagnostic Work-up. A Case Report

Caution is required when dealing with patients presenting hemifacial spasm as the symptom is common to many disorders (tumours, herpes zoster, a frigore paralysis, neurovascular conflict…). Often no reasonable cause of the spasm is found, but treatment must be attempted because hemifacial spasm can be highly debilitating. We describe a case of hemifacial spasm, initially deemed idiopathic, in which MRI demonstrated neurovascular conflict as the cause. It is not always easy to find a clear MRI pattern, but if the scan identifies the tortuousness of the arteries in the vicinity of the VII nerve root exit, it is highly probable that this is the true cause of hemifacial spasm. Even when it is not possible to identify this pattern, neurovascular compression cannot be ruled out. The good results of microvascular decompression in patients without a typical MRI pattern suggest that MRI is specific, but not always sensitive. There is no consensus in the literature on the sensitivity of MRI in the detection of neurovascular compression and values vary widely. It is generally believed that experience and different performance of the MR systems strongly influence the diagnosis of neurovascular conflict.

Microvascular decompression for primary hemifacial spasm. Importance of intraoperative neurophysiological monitoring

There is considerable evidence that primary Hemi-Facial Spasm (HFS) is in almost all cases related to a vascular compression of the facial nerve at its Root Exit Zone (REZ) from brainstem, and that Micro-Vascular Decompression (MVD) constitutes its curative treatment. Clinical as well as electrophysiological features plead for mechanisms of the disease in structural lesions at the neural fibers (putatively: focal demyelination at origin of ephapses) and functional changes in the nuclear cells (hyperactivity of the facial nucleus). Lateral Spread Responses (LSRs) elicited by stimulation of the facial nerve branches testify of these electrophysiological perturbations. Monitoring LSRs during surgery is feasible; however the practical value of their intraoperative disappearance as control-test of an effective decompression remains controversial.MVD allows cure of the disease in most cases. Because the VIIIth nerve is at risk during surgery, intraoperative monitoring of Brainstem Auditory Evoked Potentials (BEAPs) is of value to reduce occurrence of hearing loss. Increase in latency of Peak V and decrease in amplitude of Peak I are warning-signals of an excessive stretching of the the cochlear nerve and impairment of the cochlear vascular supply, respectively.