Clipping a vertebrobasilar union aneurysm is one of the most difficult surgical procedures, because it is deep and surrounded by many important structures, such as the brain stem, lower cranial nerves and cerebellum.
We have experienced a successful clipping of the aneurysm at this portion through a transpetrosal-anterosigmoidal approach. We report it and discuss the approaches to aneurysm at this portion.
This approach has many advantages: 1) A small scalp incision. 2) Drilling the posterior pyramis is easy, because the procedure is superficial. 3) Both side of parent artery of the aneurysm can be kept. 4) Little damage to the brain stem, cerebellum and cranial nerves by retractions. 5) Short cut to the aneurysm. 6) A subtemporal approach can be easily combined if it should be required.

抄録全体を表示

Object : For anterior cervical fusion, hydroxyapatite (HA) grafts have been used extensively among Japanese neurosurgeons. Many different types of HA grafts have been devised and are being marketed in Japan. However, there are still no ideal grafts. New graft : The author devised a new type of compound HA column graft which is composed of the anterior portion (40% porosity) and the posterior portion (50%). This graft is 12mm in diameter (10 and 14mm are also available), while the anterior portion is 5mm in length and the posterior portion is 15mm. The compound structure was designed to replicate the autograft's cortical bone and the cancelleus bone. The hard anterior portion is strong enough to bear stress to the intervertebral space, and the soft posterior portion is more easily unified vertebral bone. Method and results : With this new HA graft, 146 patients were operated on by following the modified Cloward's surgical method between 1994 and 2001. Post-operative follow-up observations were made by plain X-ray and CT films. Thirty patients were followed-up for more than 3 years. All of the grafts were fused firmly without pseudo-arthrosis. No destruction nor separation of the two portions of the graft were found, except for a few cracks which caused no problems. Conclusion : This operative procedure is simple and the operative results were satisfactory. The new HA graft has superior quality in strength and bone union ability. Furthermore, it can be shaped to fit the host site by cutting the posterior end. The 40%-porous HA grafts can be used safely for anterior cervical fusion.

抄録全体を表示

A retrolabyrinthine presigmoid approach was employed successfully in four patients with aneurysms around the vertebral union. This approach allows excellent access to the vertebral union without resection of the sigmoid sinus, with minimum retraction of the cerebellum and brain stem. This approach can be recommended for not only aneurysms of vertebral union and lower basilar trunk, but also VA-PICA aneurysms that are located close to the midline, in high position from the foramen magnum, and far from the clivus.

抄録全体を表示

The case of a 65-year-old man with a ruptured VA-PICA aneurysm located at the midline is reported in this paper. He was admitted complaining of severe headache.
CT scan demonstrated massive subarachnoid hemorrhage, especially around the brain stem. Vertebral angiography showed a right VA-PICA aneurysm, located 4mm to the left from the midline and at lower 1/3 of clivus in height. The dome of the aneurysm projected to the right anteriorly. The aneurysm was approached with a combined subtemporal-transtentorial and lateral suboccipital approach.
The parent artery was reserved through a lateral suboccipital approach and the neck was clipped through a subtemporal transtentorial approach between the petrosal vein and the 7th, 8th nerve.
The combined subtemporal transtentorial and lateral suboccipital approach was advantageous in treating this VA-PICA aneurysm located at the midline and lower 1/3 clivus.

抄録全体を表示

Paramedian vertebral aneurysms in the lower third clival region are one of the most difficult lesions to access surgically. Although several approaches with drilling of the skull base have been considered for aneurysms in this region, successful clipping in the acute stage without permanent neurological deficits is thought to be extremely rare. We experienced a case of VA-PICA aneurysm located 6 mm across the midline that was successfully clipped in the acute stage via the far-lateral suboccipital approach. The usefulness of this approach is reported in this paper.
A 52-year old female was admitted to our hospital suffering from severe headache. Right vertebral angiography revealed a right VA-PICA aneurysm located 6 mm across the midline towards the left. The pre-operative condition of this patient was classified as Hunt and Kosnik's grade 1. Direct clipping was completed on day 0 via the far-lateral suboccipital approach. The long straight clip (Sugita No. 18) was applied above the hypoglossal nerve by left hand, permiting microscopic visualization of the aneurysm below the hypoglossal nerve. Transient vagal and hypoglossal nerve palsy noted post-operatively were restored within a week. The post-operative vertebral angiography revealed complete clipping of this aneurysm.
The far-lateral suboccipital approach, in which the postero-medial third of the occipital condyle is drilled out, permits access to the midline, lower third clival region from the extreme infero-lateral direction. Excessive retraction against the brainstem and obstruction of the operative view by the lower cranial nerves are therefore minimal with this approach. The wide longitudinal operative field afforeded by this approach allows insertion of the clip from various directions and acute stage operation. An additional drilling of the jugular tubercle should also be considered depending on the height of the aneurysm.

抄録全体を表示

We have been observing geoelectric field in land using the facilities of NTT corporation and on the ocean-floor using the ocean bottom seismograph observation systems of JMA, in the cenral part of Japan. By these observations we obtain highly stable data compared with those by ordinary observations. Some anomalous changes preceding earthquakes and volcanic eruptions were detected by simple methods. However, we still do not have general concepts about the anomalous changes in the electric fields as precursors of tectonic activities, that is, when, how long, how much intense and what type.
In order to improve the detectability of anomalous changes and automatically detect the precursory signals generated by seismic or volcanic activities in real-time or in quasi-real-time, we need to eliminate the effects of external geomagnetic changes and the motion of sea water. I have proposed that the induced electric fields in land and on the ocean-floor are expressed by a stochastic difference equation using the associated data such as the magnetic fields and/or sea level. The parameters of the equation are determined so as to minimize the AIC (Akaike Information Criterion).
In this study, I apply above method to the various electrical records from January to September, 1989. In the case of the electric fields at Mito-group, induced electric fields such as daily variations and telluric storms can be calcurated using the magnetic variations, and are considerably eliminated from the observed field. Then the degree of improvement in detecting anomalous electrical variations at the Mito-group is 5-10 times using X, Y and Z components of magnetic field. One at the Numazu-group is about 5 times using X and Y, and one on the ocean-floor is about 10 times using X, Y and sea level. In these cases, practically, the determined parameters were applicable for few months.

抄録全体を表示