[Mechanism of vascular compression of cranial nerves - - role of changes of vertebro-basilar vasculatures (author's transl)]

Supine No-Retractor Method in Microvascular Decompression for Hemifacial Spasm: Results of 100 Consecutive Operations

Objectives In microvascular decompression (MVD) for hemifacial spasm (HFS), the patient is placed in the lateral or park-bench position that is complicated and uncomfortable for anesthesiologists, nurses, and even the patient. Careless retraction of the cerebellum by a spatula could be the major cause of surgical complications. In our method, a patient is laid supine avoiding the complicated positioning. The subfloccular approach from a small cranial window sited on the more lateral and basal side of the occipital cranium enables the surgeon to reach all the segments of the facial nerve root without a spatula. We introduce our surgical procedures in detail along with our excellent results. Methods A total of 100 consecutive patients experiencing primary HFS were operated on with MVD by a single surgeon in our institution from August 2012 to April 2014. Results Overall, 94 patients showed the complete disappearance or a satisfactory alleviation of HFS. De novo neurologic deficits were not encountered after surgery including hearing impairment. In 47 cases, multiple offending vessels were observed in multiple possible affected sites in addition to the root entry/exit zone. Conclusions We believe this approach is superior for the safe and precise decompression of any part of the facial nerve root.

Hemifacial spasm developed after contralateral vertebral artery ligation

Although the mechanism of hemifacial spasm (HFS) is not yet well established, vascular compression of the facial nerve root exit zone and hyperexcitability of the facial nucleus have been suggested. We report a case of HFS in the setting of coinciding intracranial hemorrhage (ICH) of the pons and proximal ligation of the contralateral vertebral artery (VA) for the treatment of a fusiform aneurysm of the distal VA and discuss the possible etiologies of HFS in this patient. A 51-year-old male with an ICH of the pons was admitted to our hospital. Neuroimaging studies revealed an incidental fusiform aneurysm of the right VA distal to the origin of the posterior inferior cerebellar artery. Eight months after proximal ligation of the VA the patient presented with intermittent spasm of the left side of his face. Pre- and post-ligation magnetic resonance angiography revealed an enlarged diameter of the VA. The spasm completely disappeared after microvascular decompression.

Microscopic measurement of the facial nerve root exit zone from central glial myelin to peripheral Schwann cell myelin

OBJECT

The authors have attempted to define the exact borders of the root exit zone (RExZ) of the facial nerve, measure the distribution of myelin histologically, and examine the relationship between contact vessels and the RExZ.

METHODS

Seventy-five facial nerves were obtained from brainstems excised from 44 adult patients at autopsy. The arteries and veins associated with the facial nerve were counted and measured. The facial nerves, associated vasculature, and adjoining portions of the brainstem were then removed en bloc. These tissues were serially sectioned and stained, and a photomicrograph of each section was obtained. The distribution of myelin on each section was measured from the upper edge of the supraolivary fossette, and the relationship between contact vessels and the RExZ examined. The lateral transitional zone of the facial nerve began 8 mm distal to the upper edge of the supraolivary fossette (root exit point [RExP]) and had a mean length of 1.9 mm. The root detachment point (RDP) of the facial nerve at the medial side was located very close to the beginning of the medial transitional zone. In more than 80% of the nerves that were examined, vascular structures compressed the central glial myelin of the nerve.

CONCLUSIONS

The authors propose the use of the terms "RExP," "RDP," and "transitional zone," instead of RExZ, which cannot be well defined. The RDP appears to be a good landmark for use during microvascular decompression.

Recurrent trigeminal neuralgia attributable to veins after microvascular decompression

OBJECTIVE

To demonstrate the cause of and optimal treatment for recurrent trigeminal neuralgia (TN) in cases where veins were observed to be the offending vessels during the initial microvascular decompression (MVD) procedure.

METHODS

An electronic search of patient records from 1988 to 1998 revealed that 393 patients were treated with MVD for TN caused by veins. The pain recurred in 122 patients (31.0%). Thirty-two (26.2%) of these patients underwent reoperations. Clinical presentations, recurrence intervals, surgical findings, and clinical outcomes were analyzed.

RESULTS

Analysis of 32 consecutive cases of recurrent TN initially attributable to veins revealed a female predominance (female/male = 26:5), with one female patient exhibiting bilateral TN caused by venous compression. Patient ages ranged from 15 to 80 years, with a prevalence in the seventh decade. The V2 distribution of the face was involved more frequently than other divisions. For 24 patients (75%), recurrence occurred within 1 year after the initial operation. At the time of the second MVD procedure, development of new veins around the nerve root was observed in 28 cases (87.5%). After successful subsequent MVD procedures, the pain was improved in 81.3% of the cases.

CONCLUSION

The recurrence rate for TN attributable to veins is high. If pain recurs, it is likely to recur within 1 year after the initial operation. The most common cause of recurrence is the development and regrowth of new veins. Even fine new veins may cause pain recurrence; these veins may be located beneath the felt near the root entry zone or distally, near Meckel's cave. Because of the variable locations of vein recurrence, every effort must be made to identify recollateralized veins. Given the high rate of pain relief after a second operation, MVD remains the optimal treatment for the recurrence of TN attributable to vein regrowth.

Follow-up results of microvascular decompression in trigeminal neuralgia and hemifacial spasm

OBJECTIVE

We evaluated the follow-up results of microvascular decompression in 1032 patients with trigeminal neuralgia (TN) and hemifacial spasm (HFS), who underwent operations between 1976 and 1991 and were followed for more than 5 years.

METHOD

Patients were divided into two groups, and their follow-up results were compared and studied. The early series, Group A (1976-1986), comprised 588 patients (127 with TN and 461 with HFS) followed from 10 to 20 years (mean, 12.6 +/- 2.1 yr), and the recent series, Group B (1987-1991), comprised 444 patients (154 with TN and 290 with HFS) followed from 5 to 9 years (mean, 7.0 +/- 1.4 yr).

RESULTS

The immediate postoperative cure rates were 92.9% in Group A and 96.7% in Group B for TN and 97.4% in Group A and 98.3% in Group B for HFS. Satisfactory results obtained by the follow-up study were 80.3% in Group A and 82.5% in Group B for TN and 84.2% in Group A and 89.0% in Group B for HFS. Incomplete cure rates were 7.1% in Group A and 3.3% in Group B for TN and 2.6% in Group A and 1.7% in Group B for HFS. Recurrence rates were 10.2% in Group A and 6.5% in Group B for TN and 8.9% in Group A and 6.9% in Group B for HFS. Postoperative hearing dysfunction occurred in 7.1% of patients with TN in Group A and 4.5% in Group B and 9.1% of patients with HFS in Group A and 3.7% in Group B.

CONCLUSION

Improved methods of repositioning the affected vessels and of straightening the axis of the trigeminal nerve are important to obtain satisfactory follow-up results after microvascular decompression.

Hemifacial spasm caused by contralateral cerebellopontine angle meningioma: case report

A large meningioma in the cerebellopontine angle manifested itself as a contralateral hemifacial spasm. On computed tomographic and magnetic resonance imaging scans, the brain stem was markedly displaced and distorted by the tumor. After total removal of the meningioma, the hemifacial spasm completely disappeared.

Vertebral artery section for treating arterial compression of the medulla oblongata. Case report

A case of a 30-year-old man who showed progressive pyramidal tract signs caused by compression of the left vertebral artery is presented. Initial decompression of the vertebral artery by placing a piece of sponge between the artery and medulla had no long-term effect. The left vertebral artery distal to the origin of the posterior inferior cerebellar artery was then sectioned, decompressing the medulla oblongata. The patient's symptoms improved postoperatively. This is the first reported case of brain-stem compression by an elongated vertebral artery treated by sectioning of the artery.

Trigeminal neuralgia caused by compression from arteries transfixing the nerve. Report of three cases

The authors present three patients with trigeminal neuralgia due to compression by an artery that transfixed the sensory root of the fifth cranial nerve. These cases represented 0.8% of 384 patients with trigeminal neuralgia treated by microvascular decompression at the authors' clinic during the past 12 years. In the remaining 381 cases, the compressing vessels were successfully removed from the trigeminal nerve without much difficulty, for an initial cure rate of 94.3%. In the three cases reported, however, the compressing artery penetrating the nerve could not easily be maneuvered away from the nerve. In the first two cases, partial rhizotomy perpendicular to the axis of the nerve at the site of arterial transfixion made it possible to separate the artery from the nerve. However, these two patients developed postoperative facial sensory impairment. In the third case, rhizotomy was performed longitudinal to the axis of the nerve at the site of arterial transfixion, making it possible to reposition the artery peripherally beyond the root entry zone of the nerve without causing any postoperative sensory deficits of the face. No recurrent pain has developed in more than 2 1/2 years since surgery in any of these three cases. When performing microvascular decompression surgery on patients in whom the compressing artery penetrates the nerve, the technique used in our third patient is the procedure of choice.

Hemifacial spasm: a review

Hemifacial spasm can be diagnosed by observation and clinical history. It is thought to arise primarily from compression of the facial nerve at the pons, usually by an adjacent artery. Although many approaches to treatment have been tried, the most effective is microvascular decompression of the facial nerve at the pons. That operation has well-recognized risks, including ipsilateral deafness. The latter complication ordinarily can be avoided by the use of intraoperative monitoring of auditory evoked potentials.