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Hiroshi Ryu, Seiji Yamamoto, Kenji Sugiyama, Kenichi Uemura and Tsunehiko Miyamoto

✓ It is generally accepted that hemifacial spasm (HFS) and trigeminal neuralgia are caused by compression of the facial nerve (seventh cranial nerve) or the trigeminal nerve (fifth cranial nerve) at the nerve's root exit (or entry) zone (REZ); thus, neurosurgeons generally perform neurovascular decompression at the REZ. Neurosurgeons tend to ignore vascular compression at distal portions of the seventh cranial nerve, even when found incidentally while performing neurovascular decompression at the REZ of that nerve, because compression of distal portions of the seventh cranial nerve has not been regarded as a cause of HFS. Recently the authors treated seven cases of HFS in which compression of the distal portion of the seventh cranial nerve produced symptoms. The anterior inferior cerebellar artery (AICA) was the offending vessel in five of these cases. Great care must be taken not to stretch the internal auditory arteries during manipulation of the AICA because these small arteries are quite vulnerable to surgical manipulation and the patient may experience hearing loss postoperatively.

It must be kept in mind that compression of distal portions of the seventh cranial nerve may be responsible for HFS in cases in which neurovascular compression at the REZ is not confirmed intraoperatively and in cases in which neurovascular decompression at the nerve's REZ does not cure HFS. Surgical procedures for decompression of the distal portion of the seventh cranial nerve as well as decompression at the REZ should be performed when a deep vascular groove is noticed at the distal site of compression of the nerve.

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Hiroshi Ryu, Seiji Yamamoto, Kenji Sugiyama and Kenichi Uemura

✓ Selective cochlear neurotomy for intractable tinnitus is quite difficult to perform because there is no way to approach the cochlear nerve without interfering with other neural structures. The authors successfully performed selective cochlear neurotomy in the cerebellopontine cistern in a patient with persistent intractable high-pitched tinnitus, but with normal hearing and vestibular functions, by monitoring cochlear nerve compound action potentials and auditory brainstem responses. The procedure is a very simple and safe technique for the treatment of intractable tinnitus. Although this destructive procedure is the last choice of treatment, it can be justified in patients who have poor hearing and severe tinnitus in spite of normal vestibular functions. The procedure may also be applied in some rare cases such as that of the present patient whose quality of life was markedly reduced because loud tinnitis prevented him from hearing anything with the affected ear even though his hearing and vestibular functions were normal.

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Seiji Yamamoto, Weiyu Teng, Shigeru Nishizawa, Takeharu Kakiuchi and Hideo Tsukada

Object. The hydroxyl radical scavenger (±)-N,N′-propylenedinicotinamide (AVS) has been shown to ameliorate the occurrence of vasospasm following experimental subarachnoid hemorrhage (SAH) and to reduce the incidence of delayed ischemic neurological deficits (DINDs) in patients with SAH. The authors investigated whether prophylactic administration of AVS could improve cerebral blood flow (CBF) and cerebral glucose utilization (CGU) following SAH in rats.

Methods. Anesthetized rats were subjected to intracisternal injection of blood (SAH group) or saline (control group). Either AVS (1 mg/kg/min) or saline (vehicle group) was continuously injected into the rat femoral vein. Forty-eight hours later, positron emission tomography scanning was used with the tracers 15O-H2O and 18F-2-fluoro-d-glucose to analyze quantitatively CBF and CGU, respectively, in the frontoparietal and occipital regions (12 regions of interest/group).

In SAH rats receiving only vehicle, CBF decreased significantly (p < 0.05, Tukey's test) and CGU tended to decrease, compared with values obtained in control (non-SAH) rats receiving vehicle. In rats that were subjected to SAH, administration of AVS significantly (p < 0.05, Tukey's test) improved CBF and CGU in both the frontoparietal and occipital regions compared with administration of vehicle alone.

Conclusions. Prophylactic administration of AVS improves CBF and CGU in the rat brain subjected to SAH, and can be a good pharmacological treatment for the prevention of DINDs following SAH.

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Tomohide Hayashi, Seiji Yamamoto, Takeru Hamashima, Hisashi Mori, Masakiyo Sasahara and Satoshi Kuroda

OBJECTIVE

This study aimed to clarify the underlying mechanism of pathognomonic angiogenesis between the temporal muscle and neocortex after indirect bypass for moyamoya disease by shedding light on the role of platelet-derived growth factor receptor–α (PDGFRα) in angiogenesis.

METHODS

The gene for PDGFRα was systemically inactivated in adult mice (α-KO mice). The Pdgfra-preserving mice (Flox mice) and α-KO mice were exposed to bilateral common carotid artery stenosis (BCAS) by using microcoils. One week later the animals underwent encephalomyosynangiosis (EMS) on the right side. Cerebral blood flow (CBF) was serially measured using a laser Doppler flowmeter. Histological analysis was performed on the distribution of CD31-positive vessels and collagen deposit at 28 days after BCAS. Reverse transcription polymerase chain reaction (RT-PCR) was performed to assess the expression of collagen mRNA in the skin fibroblasts derived from Flox and α-KO mice.

RESULTS

BCAS significantly reduced CBF up to approximately 70% of the control level at 28 days after the onset. There was no significant difference in CBF between Flox and α-KO mice. EMS significantly enhanced the improvement of CBF on the ipsilateral side of Flox mice, but not α-KO mice. EMS significantly induced the development of CD31-positive vessels in both the neocortex and temporal muscle on the ipsilateral side of Flox mice, but not α-KO mice. Deposition of collagen was distinctly observed between them in Flox mice, but not α-KO mice. Expression of mRNA of collagen type 1 alpha 1 (Col1a1) and collagen type 3 alpha 1 (Col3a1) was significantly downregulated in the skin fibroblasts from α-KO mice.

CONCLUSIONS

This is the first study that denotes the role of a specific growth factor in angiogenesis after EMS for moyamoya disease by inactivating its gene in mice. The findings strongly suggest that PDGFRα signal may play an important role in developing spontaneous angiogenesis between the temporal muscle and neocortex after EMS in moyamoya disease.

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Hiroshi Ryu, Tokutaro Tanaka, Seiji Yamamoto, Kenichi Uemura, Yasuo Takehara and Haruo Isoda

Object. The detailed anatomy of intracranial structures has been studied mainly in cadavers, but the absence of cerebrospinal fluid and blood pressure in these models distorts normal spatial relationships. The authors investigated the rotation of the facial nerve (FN), superior vestibular nerve (SVN), inferior vestibular nerve (IVN), and cochlear nerve (CN) in the internal auditory canal (IAC) and cerebellopontine cistern in human volunteers and compared their results with those reported in cadaver studies.

Methods. The IACs and cerebellopontine cisterns of 30 normal adults (34 sides) were examined using magnetic resonance (MR) cisternography with a heavily T2-weighted two-dimensional fast spin—echo technique. The positions of the four components were unaffected by the presence of the meatal loop of the anterior inferior cerebellar artery in the IAC. The spatial relationship between the FN and SVN was quite constant, but the spatial relationship between the CN and SVN was quite variable: the former changed position, mainly in the IAC, on nine (26.5%) of 34 sides, and in the cerebellopontine cistern on the other sides (73.5%), conflicting with findings in cadaver studies.

Conclusions. It is more accurate to describe the CN and IVN as coursing beneath the SVN in either the IAC or cerebellopontine cistern, rather than stating that the three components rotate, as reported in cadaver studies. The MR cisternography studies provided quite detailed information about the topography of the four components and the relationship between the blood vessels and cranial nerves in the IAC and the cerebellopontine cistern.

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Hiroshi Ryu, Seiji Yamamoto, Kenji Sugiyama, Kenichi Uemura and Michihiko Nozue

Object. The authors sought to clarify the clinical characteristics of tinnitus resulting from neurovascular compression (NVC) of the eighth cranial nerve.

Methods. The authors explored the eighth cranial nerve in the cerebellopontine cistern during neurovascular decompression (NVD) of the facial nerve in 10 patients with hemifacial spasm who suffered from incidental tinnitus on the same side. The diagnosis of NVC of the eighth cranial nerve was confirmed in all patients. This condition was found in only seven of 114 patients with hemifacial spasm alone, indicating that NVC of the eighth cranial nerve is one of the causes of tinnitus (p < 0.001, chi-square test). The tinnitus resolved or was markedly improved after NVD of the eighth cranial nerve in eight patients (80%). Both pulsatile and continuous tinnitus responded well to NVD. All patients experienced various degrees of sensorineural hearing disturbance, but other neurotological examinations provided poor diagnostic value.

Conclusions. It is the authors' opinion that sensorineural hearing loss and positive findings on magnetic resonance imaging are the most reliable evidence for the presence of tinnitus caused by NVC of the eighth cranial nerve.

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Masaaki Yamamoto, Yoshihisa Kida, Seiji Fukuoka, Yoshiyasu Iwai, Hidefumi Jokura, Atsuya Akabane and Toru Serizawa

Object

Gamma Knife radiosurgery (GKS) is currently used for primary or postoperative management of cavernous sinus (CS) hemangiomas. The authors describe their experience with 30 cases of CS hemangioma successfully managed with GKS.

Methods

Thirty patients with CS hemangiomas, including 19 female and 11 male patients with a mean age of 53 years (range 19–78 years) underwent GKS at 7 facilities in Japan. Pathological entity was confirmed using surgical specimens in 17 patients, and neuroimaging diagnosis only in 13. Eight patients were asymptomatic before GKS, while 22 had ocular movement disturbances and/or optic nerve impairments. The mean tumor volume was 11.5 cm3 (range 1.5–51.4 cm3). The mean dose to the tumor periphery was 13.8 Gy (range 10.0–17.0 Gy).

Results

The mean follow-up period was 53 months (range 12–138 months). Among the 22 patients with symptoms prior to GKS, complete remission was achieved in 2, improvement in 13, and no change in 7. Hemifacial sensory disturbance developed following GKS in 1 patient. The most recent MR images showed remarkable shrinkage in 18, shrinkage in 11, and no change in 1 patient.

Conclusions

Gamma Knife radiosurgery proved to be an effective treatment strategy for managing CS hemangiomas. Given the diagnostic accuracy of recently developed neuroimaging techniques and the potentially serious bleeding associated with biopsy sampling or attempted surgical removal, the authors recommend that GKS be the primary treatment in most patients who have a clear neuroimaging diagnosis of this condition.