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Tetsuyoshi Horiuchi, Tetsuya Goto, Yuichiro Tanaka, Kunihiko Kodama, Keiji Tsutsumi, Kiyoshi Ito, and Kazuhiro Hongo

OBJECT

Although a number of studies have assessed the surgical treatment of paraclinoid-segment carotid artery aneurysms and resulting visual complications, less attention has been given to the results with respect to the superior hypophyseal artery (SHA). The authors evaluated the relationship between the aneurysm, the SHA itself, and postoperative visual function in patients with ruptured and unruptured SHA aneurysms.

METHODS

From January 1991 through December 2013, 181 patients with 190 paraclinoid carotid artery aneurysms received treatment at Shinshu University Hospital and its affiliated hospitals. The authors retrospectively analyzed charts, operative records, operative videos, and neuroimaging findings for these patients with or without postoperative visual complications.

RESULTS

The authors identified 72 SHA aneurysms in 70 patients (mean age 58 years). Of 69 patients (1 patient died) evaluated, postoperative visual complications occurred in 9 (13.0%). Although the aneurysm size and SHA sacrifice did not lead to postoperative visual impairment, simultaneous treatment of bilateral aneurysms was a risk factor for postoperative visual complications.

CONCLUSIONS

Unilateral SHA impairment may be safe (i.e., it may not induce ischemia of the optic pathway) for many, but not all, patients with SHA aneurysm.

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Tetsuya Goto, Yuichiro Tanaka, Kunihiko Kodama, Yoshikazu Kusano, Keiichi Sakai, and Kazuhiro Hongo

✓The authors report a case in which a 62-year-old woman with a history of subarachnoid hemorrhage due to a ruptured aneurysm was found to have a de novo paraclinoid aneurysm in the right internal carotid artery during a routine medical examination. Surgical clip placement was performed via a contralateral pterional approach under visual evoked potential (VEP) monitoring. The superior hypophyseal artery (SHA) was found to originate from the aneurysm body. The artery was temporarily occluded prior to application of the clip to the aneurysm neck. The VEP signal was lost 3 minutes after the SHA was occluded, and the potentials gradually recovered 10 minutes after the artery was released. The disappearance of VEP signal was reproducible with SHA occlusion. The clip was applied to the aneurysm body to preserve the origin of the SHA. The patient did not have any deterioration of vision after surgery.

Intraoperative VEP monitoring can be used to help determine whether the SHA can be sacrificed safely.

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Yukinari Kakizawa, Tatsuya Seguchi, Kunihiko Kodama, Toshihiro Ogiwara, Tetsuo Sasaki, Tetsuya Goto, and Kazuhiro Hongo

Object

Neuroimages often reveal that the trigeminal or facial nerve comes in contact with vessels but does not produce symptoms of trigeminal neuralgia (TN) or hemifacial spasm (HFS). The authors conducted this study to determine how often the trigeminal and facial nerves came in contact with vessels in individuals not suffering from TN or HFS. They also investigated the correlation between aging and the anatomical measurements of the trigeminal and facial nerves.

Methods

Between November 2005 and August 2006, 220 nerves in 110 individuals (60 women and 50 men; mean age 55.1 years, range 19–85 years) who had undergone brain magnetic resonance (MR) imaging for other reasons were studied. The lengths, angles, ratio, and contact points were measured in each individual. A correlation between each parameter and age was statistically analyzed.

Results

The mean (± standard deviation) length of the trigeminal nerve was 9.66 ± 1.71 mm, the mean distance between the bilateral trigeminal nerves was 31.97 ± 1.82 mm, and the mean angle between the trigeminal nerve and the midline was 9.71 ± 5.83°. The trigeminal nerve was significantly longer in older patients. Of 220 trigeminal nerves, 108 (49.0%; 51 women and 57 men) came in contact with vasculature. There was 1 contact point in 99 nerves (45%) and 2 contact points in 9 nerves (4.1%). Contact without deviation of the nerve was seen in 91 individuals (43 women and 48 men), and mild deviation was noted in 17 individuals (8 women and 9 men). There was no moderate or severe deviation in any individual in this series. The mean length of the facial nerve was 29.78 ± 2.31 mm, the mean distance between the bilateral facial nerves was 28.65 ± 2.22 mm, the angle between the nerve and midline was 69.68 ± 5.84°, and the vertical ratio at the porus acusticus was 0.467 ± 0.169. Of all facial nerves, 173 (78.6%; 101 in women and 72 in men) came in contact with some vasculature. Contact without deviation was seen on 64 sides (in 37 women and 27 men), mild deviation on 98 sides (in 57 women and 41 men), and moderate deviation on 11 sides (in 7 women and 4 men). There was no severe deviation of the facial nerve in this series. The proximal length of the facial nerve, interval, angle, and ratio against the age were significantly shorter or smaller in the older individuals.

Conclusions

The findings in asymptomatic individuals in this study will help in deciding which findings observed on MR images may cause symptoms. In addition, the authors describe the variations of normal anatomy in older individuals. Knowledge of the normal anatomy helps to hone the diagnostic practices for microvascular decompression, which may increase the feasible results on such surgery.

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Tetsuya Goto, Yuichiro Tanaka, Kunihiko Kodama, Shoji Yomo, Yosuke Hara, Atsushi Sato, and Kazuhiro Hongo

✓ Intraoperative electrophysiological monitoring is essential for minimally invasive neurosurgery. The authors developed an innovative recording method using a staple electrode, consisting of a surgical skin staple and an integrated circuit (IC) test clip with a cable. The staple is put on the patient's skin after the induction of general anesthesia. After head fixation, the IC test clip is simply hooked to the staple. The authors used this method for recording in 158 consecutive cases. It took only a few minutes to set up 4–18 staple electrodes in each case. None of the staple electrodes became disconnected unintentionally, and the initial impedance was kept throughout the procedures. The authors conclude that the staple electrode is superior to conventional disc or needle electrodes in speed of setup, electrical stability, and cost-effectiveness and recommend its routine use for intraoperative electrophysiological monitoring.

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Toshihiro Ogiwara, Tetsuya Goto, Yoshikazu Kusano, Masafumi Kuroiwa, Takafumi Kiuchi, Kunihiko Kodama, Toshiki Takemae, and Kazuhiro Hongo

Microvascular decompression (MVD) via lateral suboccipital craniotomy is the standard surgical intervention for trigeminal neuralgia (TN). For recurrent TN, difficulties are sometimes encountered when performing reoperation via the same approach because of adhesions and prosthetic materials used in the previous surgery. In the present case report the authors describe the efficacy of the subtemporal transtentorial approach for use in recurrent TN after MVD via the lateral suboccipital approach. An 86-year-old woman, in whom an MVD via a lateral suboccipital craniotomy had previously been performed for TN, underwent surgery for recurrent TN via the subtemporal transtentorial approach, which provided excellent visualization of the neurovascular relationships and the trigeminal nerve without adhesions due to the previous surgery. Her TN disappeared after the MVD. The present approach is ideal for visualizing the trigeminal root entry zone, and the neurovascular complex can be easily dissected using a new surgical trajectory. This approach could be another surgical option for reoperation when the previous MVD had been performed via the suboccipital approach.