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Hiroki Kurita, Tomio Sasaki, Syunsuke Kawamoto, Makoto Taniguchi, Chifumi Kitanaka, Hiroshi Nakaguchi, and Takaaki Kirino

✓ The authors report a rare case of a patient with a chronic encapsulated expanding hematoma and progressive neurological deterioration who presented 2 years after gamma knife radiosurgery for a cerebral arteriovenous malformation (AVM). A tough capsule containing multiple layers of organized hematoma resulting from previous bleeding was confirmed surgically. Histological examination revealed that the capsule consisted of a dense collagenous outer layer and a granulomatous newly vascularized inner layer with marked fibrosis. Hemosiderin deposits were frequently observed in the inner layer, which suggested recurrent minor bleeding from fragile vessels in this layer. An AVM was found in the hematoma, which had degenerated as the result of radiosurgery. A cross-section of the abnormal vessels showed various stages of obliteration due to intimal hypertrophy. The clinical course, radiological features, and histological findings in this case were compatible with those of previously reported chronic encapsulated hematomas. A possible mechanism of hematoma formation and its expansion are discussed.

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Hideki Matsuura, Takashi Inoue, Hiromu Konno, Makoto Sasaki, Kuniaki Ogasawara, and Akira Ogawa

✓ Although various biomaterials such as ceramics or titanium alloy are widely used in neurosurgery, the susceptibility artifacts that appear around these materials cause problems when a magnetic resonance (MR) imager is used to assess lesions after surgery. The purpose of the present study was to quantify the susceptibility artifacts produced by various biomaterials used for neurosurgical implants.

Using a 3-tesla MR imaging unit, we obtained MR images of various biomaterials, including six types of ceramics, a cobalt-based alloy (Elgiloy), pure titanium, a titanium alloy, and stainless steel. All implants shared a uniform size and shape. In each image, a linear region of interest was defined across the center of the biomaterial in the transverse direction, and the diameter of the susceptibility artifact was calculated.

The ceramics produced a considerably smaller artifact diameter than those produced by other biomaterials. Among the types of ceramics, zirconia was found to produce the smallest artifact diameter. Among the remaining biomaterials, the diameters of the artifacts decreased in order from that associated with stainless steel to those associated with cobalt-based alloys, pure titanium, and titanium alloy. Little difference was observed between the artifact diameters associated with pure titanium and titanium alloy.

Ceramics are the most suitable biomaterials for minimizing artifacts in high-field MR imaging.

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Tomio Sasaki, Makoto Taniguchi, Ichiro Suzuki, and Takaaki Kirino

✓ The authors report a new technique for en bloc petrosectomy using a Gigli saw as an alternative to drilling the petrous bone in the combined supra- and infratentorial approach or the transpetrosal—transtentorial approach. It is simple and easy and avoids postoperative cosmetic deformity. This technique has been performed in 11 petroclival lesions without injuring the semicircular canals, the cochlea, or the facial nerve.

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Kenya Miyoshi, Tsukasa Wada, Ikuko Uwano, Makoto Sasaki, Hiroaki Saura, Shunrou Fujiwara, Fumiaki Takahashi, Eiki Tsushima, and Kuniaki Ogasawara

OBJECTIVE

The consistency of meningiomas is a critical factor affecting the difficulty of resection, operative complications, and operative time. The apparent diffusion coefficient (ADC) is derived from diffusion-weighted imaging (DWI) and is calculated using two optimized b values. While the results of comparisons between the standard ADC and the consistency of meningiomas vary, the shifted ADC has been reported to be strongly correlated with liver stiffness. The purpose of the present prospective cohort study was to determine whether preoperative standard and shifted ADC maps predict the consistency of intracranial meningiomas.

METHODS

Standard (b values 0 and 1000 sec/mm2) and shifted (b values 200 and 1500 sec/mm2) ADC maps were calculated using preoperative DWI in patients undergoing resection of intracranial meningiomas. Regions of interest (ROIs) were placed within the tumor on standard and shifted ADC maps and registered on the navigation system. Tumor tissue located at the registered ROI was resected through craniotomy, and its stiffness was measured using a durometer. The cutoff point lying closest to the upper left corner of a receiver operating characteristic (ROC) curve was determined for the detection of tumor stiffness such that an ultrasonic aspirator or scissors was always required for resection. Each tumor tissue sample with stiffness greater than or equal to or less than this cutoff point was defined as hard or soft tumor, respectively.

RESULTS

For 76 ROIs obtained from 25 patients studied, significant negative correlations were observed between stiffness and the standard ADC (ρ = −0.465, p < 0.01) and the shifted ADC (ρ = −0.490, p < 0.01). The area under the ROC curve for detecting hard tumor (stiffness ≥ 20.8 kPa) did not differ between the standard ADC (0.820) and the shifted ADC (0.847) (p = 0.39). The positive predictive value (PPV) for the combination of a low standard ADC and a low shifted ADC for detecting hard tumor was 89%. The PPV for the combination of a high standard ADC and a high shifted ADC for detecting soft tumor (stiffness < 20.8 kPa) was 81%.

CONCLUSIONS

A combination of standard and shifted ADC maps derived from preoperative DWI can be used to predict the consistency of intracranial meningiomas.

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Katsushige Watanabe, Nobuhito Saito, Makoto Taniguchi, Takaaki Kirino, and Tomio Sasaki

Object. The frequency, nature, and history of subjective taste disturbance before and after vestibular schwannoma (VS) surgery was investigated.

Methods. Personal interviews were conducted in 108 patients with unilateral VS. Abnormalities in taste perception, either a significant reduction or a change in character, were experienced by 31 patients (28.7%) before surgery and by 37 (34.3%) after tumor removal. Preoperative taste disturbance worsened after surgery in five (16.1%) of the 31 patients, remained unchanged in eight (25.8%), improved in two (6.5%), and became normal in 16 (51.6%). Taste disturbance occurred postoperatively in 22 (28.6%) of 77 patients who had experienced no preoperative taste disturbance. The mean onset of the abnormality after resection was 1.1 ± 1.7 months. Postoperative taste disturbance resolved in 24 of the 37 patients (64.9%) within 1 year after onset.

Conclusions. Subjective taste disturbance was common before and after VS removal, and the natural history of this condition was very variable in the pre- and postoperative periods. All patients who undergo surgery for VS should receive appropriate counseling about the likelihood and course of postoperative complications, including dysfunction of the sensory component of the facial nerve.

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Hiroaki Saura, Takaaki Beppu, Hideki Matsuura, Shigeki Asahi, Noriyuki Uesugi, Makoto Sasaki, and Kuniaki Ogasawara

Yawning occurs in various conditions such as hypoxia, epilepsy, and sleep disorders including sleep apnea. Intractable yawning associated with a brain tumor has been rarely reported. A 19-year-old woman presented with intractable yawning. Magnetic resonance imaging showed a tumor in the supramedial cerebellum that compressed the dorsal side of the midbrain and upper pons. After subtotal removal of the tumor, the yawning completely disappeared. Postoperative MRI showed resolution of compression of the brainstem. The tumor was histologically diagnosed as a mature teratoma. The present case suggested that the intractable yawning resulted from the tumor compressing the dorsal side of the junction between the midbrain and pons.

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Ryounoshin Hirooka, Kuniaki Ogasawara, Makoto Sasaki, Keiko Yamadate, Masakazu Kobayashi, Yasunori Suga, Kenji Yoshida, Yasunari Otawara, Takashi Inoue, and Akira Ogawa

Object

Cerebral hyperperfusion after carotid endarterectomy (CEA) impairs cognitive function and is often detected on cerebral blood flow (CBF) imaging. The purpose of the present study is to investigate structural brain damage seen on magnetic resonance (MR) images obtained in patients with cerebral hyperperfusion and cognitive impairment after CEA.

Methods

One hundred and fifty-eight patients with ipsilateral internal carotid artery stenosis (≥ 70%) underwent CEA. Neuropsychological testing was performed preoperatively and at the 1st postoperative month. Cerebral blood flow was measured using single-photon emission computed tomography before, immediately after, and 3 days after surgery. Magnetic resonance imaging was performed before and 1 day after surgery. In patients with post-CEA hyperper-fusion (defined as a CBF increase ≥ 100% compared with preoperative values) on CBF imaging, MR images were also obtained on the 3rd postoperative day, the day on which hyperperfusion syndrome developed, and 1 month after the operation.

Results

The incidence of postoperative cognitive impairment was significantly higher in patients with post-CEA hyperperfusion on CBF imaging (12 [75%] of 16 patients) than in those without (6 [4%] of 142 patients; p < 0.0001). Only 1 of 5 patients with cerebral hyperperfusion syndrome developed reversible brain edema in the cerebral hemisphere ipsilateral to the CEA on MR images obtained on the day hyperperfusion syndrome occurred. However, postoperative cognitive impairment developed in all 5 patients with cerebral hyperperfusion syndrome regardless of the presence or absence of new lesions on MR images. In addition, postoperative cognitive impairment developed in 5 (45%) of 11 patients with asymptomatic cerebral hyperperfusion on CBF imaging despite the absence of new lesions on any postoperative MR images.

Conclusions

Although cerebral hyperperfusion syndrome after CEA sometimes results in reversible brain edema visible on MR imaging, postoperative cerebral hyperperfusion—even when asymptomatic—often results in impaired cognitive function without structural brain damage on MR imaging.

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Manabu Sasaki, Makoto Abekura, Shayne Morris, Chihiro Akiyama, Kazuya Kaise, Takamichi Yuguchi, Shintaro Mori, Koichi Iwatsuki, and Toshiki Yoshimine

Object

Microscopic bilateral decompression through a unilateral laminotomy (MBDUL) is a minimally invasive technique used to treat lumbar canal stenosis (LCS). In the present study, MBDUL was performed to treat LCS in eight patients undergoing hemodialysis.

Methods

Surgical outcomes were evaluated using the Japanese Orthopaedic Association (JOA) scale (highest possible score 29). The JOA scale was administered preoperatively, at 1 month and 3 months postoperatively, and at the final follow-up examination. One patient refused to undergo the postoperative assessment after the 1-month examination; the mean follow-up duration of the remaining seven patients was 24 months (range 18–31 months). The mean age at the time of surgery was 62 years (range 48–76 years), and the mean duration of hemodialysis therapy was 21.4 years (range 3–28 years). All patients could walk within 2 days of surgery. The mean angle of the straight leg–raising (SLR) test was 53.8° preoperatively, and this increased to 69.4° postoperatively. Six patients felt enhancement of sciatica or leg pain when performing the SLR test preoperatively, a finding that was absent postoperatively at least until the final follow-up examination. The mean preoperative JOA score was 11.6 (range 4–22), and the score markedly improved to 19.8 (range 15–23) at 1 month and 20.6 (range 16–25) at 3 months. The mean JOA score decreased to 17.1 (range 12–25) at the final follow-up examination, but this decrease was attributed to other physical disorders.

Conclusions

The authors conclude that MBDUL is a safe and effective surgical treatment for patients undergoing hemodialysis who are suffering from LCS.

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Shunsuke Kakino, Kuniaki Ogasawara, Yoshitaka Kubo, Hiroshi Kashimura, Hiromu Konno, Atsushi Sugawara, Masakazu Kobayashi, Makoto Sasaki, and Akira Ogawa

Object

Although angioplasty and stent placement for vertebral artery (VA)–origin stenosis have been performed using endovascular techniques, a high likelihood of restenosis has been observed in the long term. Therefore, the authors assessed the long-term clinical and angiographic outcomes in patients after VA–subclavian artery (SA) transposition.

Methods

Thirty-six patients (31 men, 5 women; mean age 64.3 years, range 46–76 years) underwent clinical evaluation (modified Rankin Scale [mRS]) and cervical angiographic evaluation preoperatively and within 1 month of and 6 months after VA-SA transposition undertaken to treat symptomatic stenosis of VA origin.

Results

Postoperative neurological deficits due to intraoperative brain ischemia did not occur, and MR imaging demonstrated no new postoperative ischemic lesions in any of the patients. One patient died of acute myocardial infarction 2 months after surgery and another developed a left thalamic hemorrhage (mRS score of 5) at 42 months postsurgery. None of the remaining 34 patients experienced further ischemic events, and the mRS score in all of these patients remained unchanged during a mean follow-up period of 54 months. The degree of VA-origin stenosis (preoperative mean 84%) was reduced to ≤ 30% after surgery (mean 2%). Long-term follow-up angiography in 29 patients (81%) revealed the absence of restenosis, defined as > 50% luminal narrowing, in all of them.

Conclusions

The clinical and angiographic long-term outcomes demonstrated here suggest that VA-SA transposition will be useful in patients with symptomatic stenosis of VA origin.

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Taro Suzuki, Kuniaki Ogasawara, Ryonoshin Hirooka, Makoto Sasaki, Masakazu Kobayashi, Daiya Ishigaki, Shunro Fujiwara, Kenji Yoshida, Yasunari Otawara, and Akira Ogawa

Object

Preoperative impairment of cerebral hemodynamics predicts the development of new cerebral ischemic events after carotid endarterectomy (CEA), including neurological deficits and cerebral ischemic lesions on diffusion weighted MR imaging. Furthermore, the signal intensity of the middle cerebral artery (MCA) on single-slab 3D time-of-flight MR angiography (MRA) can assess hemodynamic impairment in the cerebral hemisphere. The purpose of the present study was to determine whether, on preoperative MR angiography, the signal intensity of the MCA can be used to identify patients at risk for development of cerebral ischemic events after CEA.

Methods

The signal intensity of the MCA ipsilateral to CEA on preoperative MR angiography was graded according to the ability to visualize the MCA in 106 patients with unilateral internal carotid artery stenosis (≥ 70%). Diffusion weighted MR imaging was performed within 3 days of and 24 hours after surgery. The presence or absence of new postoperative neurological deficits was also evaluated.

Results

Cerebral ischemic events after CEA were observed in 16 patients. Reduced signal intensity of the MCA on preoperative MR angiography was the only significant independent predictor of postoperative cerebral ischemic events. When the reduced MCA signal intensity on preoperative MR angiography was defined as an impairment in cerebral hemodynamics, MR angiography grading resulted in an 88% sensitivity and 63% specificity, with a 30% positive- and a 97% negative-predictive value for the development of postoperative cerebral ischemic events.

Conclusions

Signal intensity of the MCA on preoperative single-slab 3D time-of-flight MR angiography is useful for identifying patients at risk for cerebral ischemic events after CEA.