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Tomohiro Inoue, Nobutaka Kawahara, Junji Shibahara, Tomohiko Masumoto, Kenichi Usami and Takaaki Kirino

✓ Neurenteric cyst is a developmental malformation found mainly in the spinal canal. The authors report on a 47-year-old man with a neurenteric cyst of the cerebellopontine angle (CPA) who presented with progressive hearing disturbance and facial palsy. The tumor was located extradurally with marked destruction of the petrous bone around the internal auditory canal and demonstrated irregular and heterogeneous high-intensity signals on T1- and T2-weighted on MR images, which is atypical for neurenteric cysts. The pathological findings in samples obtained after resection disclosed a single epithelial layer (a feature of neurenteric cyst), which was accompanied by marked xanthogranulomatous changes. Although several neurenteric cysts have been reported in the CPA, extradural lesions with unusual imaging features and marked bone destruction have not been reported previously. This benign developmental lesion should be considered, although it is extremely rare, in patients harboring an extradural temporal bone tumor around the CPA.

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Satoru Osuka, Akira Matsushita, Eiichi Ishikawa, Kousaku Saotome, Tetsuya Yamamoto, Aiki Marushima, Naoaki Satou, Alexander Zaboronok, Tomohiko Masumoto and Akira Matsumura

Object

For several decades, clinicians have predicted intraparenchymal brain pressure or brain tissue compression indirectly based on the degree of distortion of the midline structures (midline shift) and ventricle wall (ventriculomegaly) observed on conventional MRI. However, this method has several limitations. Diffusion tensor imaging (DTI) is a novel MRI technique that can provide information about the microstructural properties of compressed tissue. In this study, the authors evaluated whether DTI can precisely define the degree of tissue compression in patients with chronic subdural hematoma (CSDH).

Methods

The study sample consisted of 18 patients (mean age 71 years, 10 men and 8 women) with unilateral CSDH and 12 age-matched volunteers. Diffusion tensor imaging results were acquired before and after the surgical irrigation in the CSDH group. Subdural pressure during the operation was also measured. Fractional anisotropy (FA) values were evaluated at several locations, including the gray matter.

Results

The FA values of the gray matter, especially in the caudate nucleus and putamen, were increased in the patients with CSDH compared with the control group. The change in FA data before and after surgery (ΔFA) correlated with the degree of tissue compression evaluated by measurement of the subdural pressure. Furthermore, the increased FA values in patients with CSDH decreased after surgery.

Conclusions

These findings indicate that FA values of the gray matter, especially in the caudate nucleus and putamen, may be important markers of tissue compression. The assessment of FA values of the gray matter will result in a new, less-invasive diagnostic technique to evaluate the degree of brain compression.

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Satoru Osuka, Akira Matsushita, Tetsuya Yamamoto, Kousaku Saotome, Tomonori Isobe, Yasushi Nagatomo, Tomohiko Masumoto, Yoji Komatsu, Eiichi Ishikawa and Akira Matsumura

Object

Ventriculomegaly is a common imaging finding in many types of conditions. It is difficult to determine whether it is related to true hydrocephalus or to an atrophic process by using only imaging procedures such as MR imaging after traumatic injury, stroke, or infectious disease. Diffusion tensor (DT) imaging can distinguish the compression characteristics of white matter, indicating that increased diffusion anisotropy may be related to white matter compression. In this preliminary study, the authors compared the DT imaging findings of ventriculomegaly with those of chronic hydrocephalus or atrophy to clarify the potential of diffusion anisotropy in the identification of hydrocephalus.

Methods

Ten patients with chronic hydrocephalus, 8 patients with atrophy (defined by conventional devices and surgical outcome), and 14 healthy volunteers underwent DT imaging. Images were acquired before and after shunting or once in cases without shunting. The fractional anisotropy (FA) values at many points around the lateral ventricle were evaluated.

Results

The FA patterns around the lateral ventricle in the chronic hydrocephalus and atrophy groups were different. Especially in the caudate nucleus, FA was increased in the chronic hydrocephalus group compared with the atrophy group. Furthermore, the FA values returned to normal levels after shunt placement.

Conclusions

Assessment of the FA value of the caudate nucleus may be an important, less invasive method for distinguishing true hydrocephalus from ventriculomegaly. Further research in a large number of patients is needed to verify the diagnostic ability of this method.

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Kanako Kunishima, Harushi Mori, Daisuke Itoh, Shigeki Aoki, Hiroyuki Kabasawa, Tomoyuki Koga, Keisuke Maruyama, Tomohiko Masumoto, Osamu Abe and Kuni Ohtomo

Object

Although conventional catheter angiography is commonly used in the evaluation of intracranial arteriovenous malformations (AVMs), less invasive tools are more suitable for screening or follow-up. Older MR angiography techniques cannot provide high enough temporal and spatial resolution for assessing AVMs. Threetesla time-resolved imaging of contrast kinetics (TRICKS)—a time-resolved, contrast-enhanced 3D MR angiography technique—achieves subsecond time resolution without sacrificing spatial resolution. The purpose of this study was to assess the accuracy of TRICKS at 3 T in the evaluation of AVMs.

Methods

Between November 2006 and November 2007, 31 patients who were known to have AVMs underwent evaluation in a 3-T unit with the TRICKS technique. The TRICKS images were then evaluated independently by 2 radiologists for nidus detection, early venous filling detection, and Spetzler-Martin classification, and these results were compared with the results of catheter angiography.

Results

Time-resolved imaging of contrast kinetics achieved 96% sensitivity and 100% specificity both in nidus detection and early venous filling detection. The Spetzler-Martin grades also showed excellent correlation with catheter angiography findings (κ= 0.89).

Conclusions

Although this is a preliminary study, the authors' results indicate that time-resolved contrast-enhanced 3D MR angiography at 3 T is a good tool to assess AVMs, and has the potential to replace catheter angiography in screening or follow-up examinations of patients with AVMs.

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Hiroyoshi Kino, Hiroyoshi Akutsu, Shuho Tanaka, Takuma Hara, Hidetaka Miyamoto, Noriaki Sakamoto, Shingo Takano, Tomohiko Masumoto, Masanari Shiigai, Eiichi Ishikawa and Akira Matsumura

OBJECTIVE

Rathke’s cleft cyst (RCC) is a benign cystic lesion with a relatively high incidence of local recurrence that occasionally requires repeat surgery. To prevent recurrence, simple cyst fenestration and drainage of the cyst contents to the sphenoid sinus is recommended, but it occasionally recurs. The authors postulated that obstruction of fenestration is a main cause of recurrence, and they developed a method, named the “mucosa coupling method (MC method),” that maintains persistent drainage. In this method, the RCC epithelium and the mucosa of the sphenoid sinus are connected, which promotes re-epithelialization between the two epithelia, maintaining persistent drainage. The outcome of this method was compared with that of conventional cyst fenestration.

METHODS

In a consecutive series of 40 patients with RCC, the surgical strategy was changed during the study period: from December 2009 to September 2014 (the conventional period), 24 patients were scheduled to be treated using the conventional fenestration method, whereas from September 2014 to September 2017 (the MC period), 16 patients were scheduled to be treated using the MC method. However, because of an intraoperative CSF leak, the fenestration was closed during surgery in 3 patients in the conventional period and 2 in the MC period; therefore, these 5 patients were excluded from the analysis. Twenty-one patients treated with the conventional fenestration method (conventional group) and 14 patients treated with the MC method (MC group) were analyzed. All patients regularly underwent MRI after surgery to detect reaccumulation of cyst contents. The rate of reaccumulation with and without reoperation, visual outcomes, endocrinological outcomes, and postoperative complications were compared between these two groups.

RESULTS

The median follow-up period in all 35 patients was 48.0 months (range 1–96 months), 54.0 months (range 1–96 months) in the conventional group and 35.5 months (range 12–51 months) in the MC group. No reaccumulation was detected on MRI in the 14 patients in the MC group, whereas it was noted in 9 (42.9%) of 21 patients in the conventional group, and 2 of these 9 patients required repeat surgery. There were no significant differences in visual and endocrinological outcomes and complications between these two groups.

CONCLUSIONS

The MC method for RCC is effective for preventing obstruction of cyst fenestration, which contributes to preventing cyst reaccumulation. Furthermore, this method is equivalent to the conventional fenestration method in terms of visual and endocrinological outcomes and the complication rate.

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Yosuke Masuda, Hiroyoshi Akutsu, Eiichi Ishikawa, Masahide Matsuda, Tomohiko Masumoto, Takashi Hiyama, Tetsuya Yamamoto, Hidehiro Kohzuki, Shingo Takano and Akira Matsumura

OBJECTIVE

MRI scans obtained within 48–72 hours (early postoperative MRI [epMRI]), prior to any postoperative reactive changes, are recommended for the accurate assessment of the extent of resection (EOR) after glioma surgery. Diffusion-weighted imaging (DWI) enables ischemic lesions to be detected and distinguished from the residual tumor. Prior studies, however, revealed that postoperative reactive changes were often present, even in epMRI. Although intraoperative MRI (iMRI) is widely used to maximize safe resection during glioma surgery, it is unclear whether iMRI is superior to epMRI when evaluating the EOR, because it theoretically shows fewer postoperative reactive changes. In addition, the ability to detect ischemic lesions using iMRI has not been investigated.

METHODS

The authors retrospectively analyzed prospectively collected data in 30 patients with glioma (22 and 8 patients with enhancing and nonenhancing lesions, respectively) who underwent tumor resection. These patients had received preoperative MRI within 24 hours prior to surgery, postresection radiological evaluation with iMRI during surgery, and epMRI within 24 hours after surgery, with all neuroimaging performed using identical 1.5T MRI scanners. The authors compared iMRI or epMRI with preoperative MRI, and defined a postoperative reactive change as a new postoperative enhancement or T2 high-intensity area (HIA), if this lesion was outside of the preoperative original tumor location. In addition, postoperative ischemia was evaluated on DWI. The iMRI and epMRI findings were compared in terms of 1) postoperative reactive changes, 2) evaluation of the EOR, and 3) presence of ischemic lesion on DWI.

RESULTS

In patients with enhancing lesions, a new enhancement was seen in 8 of 22 patients (36.4%) on iMRI and in 12 of 22 patients (54.5%) on epMRI. In patients with nonenhancing lesions, a new T2 HIA was seen in 4 of 8 patients (50.0%) on iMRI and in 7 of 8 patients (87.5%) on epMRI. A discrepancy between the EOR measured on iMRI and epMRI was noted in 5 of the 22 patients (22.7%) with enhancing lesions, and in 3 of the 8 patients (37.5%) with nonenhancing lesions. The occurrence of ischemic lesions on DWI was found in 5 of 30 patients (16.7%) on iMRI, whereas it was found in 16 of 30 patients (53.3%) on epMRI (p = 0.003); ischemic lesions were underestimated on iMRI in 11 patients.

CONCLUSIONS

Overall, given the lower incidence of postoperative reactive changes on iMRI, it was superior to epMRI in evaluating the EOR in patients with glioma, both with enhancing and nonenhancing lesions. However, because ischemic lesions can be overlooked on iMRI, the authors recommend only the additional DWI scan during the early postoperative period. Clinicians need to be mindful about not overestimating the presence of residual tumor on epMRI due to the high incidence of postoperative reactive changes.

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Takuma Hara, Hiroyoshi Akutsu, Shingo Takano, Hiroyoshi Kino, Eiichi Ishikawa, Shuho Tanaka, Hidetaka Miyamoto, Noriaki Sakamoto, Keiichiro Hattori, Mamiko Sakata-Yanagimoto, Shigeru Chiba, Takashi Hiyama, Tomohiko Masumoto and Akira Matsumura

OBJECTIVE

The Wnt/β-catenin signaling pathway is strongly implicated in the pathogenesis of adamantinomatous craniopharyngioma (adaCP). However, there is no evidence that the CTNNB1 mutation activates the target gene of Wnt/β-catenin signaling, and it is unknown whether it affects the tumorigenesis of adaCP. To assess the effect of the CTNNB1 mutation of adaCP, the authors analyzed the correlation between the mutation and clinical, radiological, pathological, and biological findings.

METHODS

Between 2003 and 2015, 42 patients (24 male and 18 female, median age 42 years) with either papillary craniopharyngioma (papCP) or adaCP underwent tumor resection at the authors’ institution. BRAF V600E and CTNNB1 in papCP and adaCP samples were sequenced by next-generation sequencing and the Sanger method, and mRNA expression levels of Axin2 and BMP4 were evaluated by RT-PCR. Axin2, BMP4, β-catenin, and BRAF expression were evaluated by immunohistochemistry. Other data were collected from clinical reports.

RESULTS

The BRAF V600E mutation was detected in all 10 cases of papCP (100%). CTNNB1 exon 3 mutations were detected in 21 of 31 (68%) cases of adaCP, excluding 1 case for which there were no available sequence data. The mRNA expression level of Axin2 was significantly higher in adaCPs with a CTNNB1 mutation than in those without (p < 0.05). The immunohistochemical findings of Axin2 and BMP4 did not correlate with CTNNB1 mutation positivity. When patients who received adjuvant radiation therapy were excluded, progression-free survival was shorter in the mutation-positive group than in the mutation-negative group (log-rank test, p = 0.031). Examination of clinical characteristics and immunohistochemical findings of adaCPs showed that there was no significant correlation between CTNNB1 mutation positivity and age, sex, tumor volume, gross-total resection, optic tract edema, calcification, or T1 signal intensity of cyst fluid on MRI, β-catenin, and MIB-1 index.

CONCLUSIONS

These results raise the possibility that the CTNNB1 mutation in adaCP may be associated with disease recurrence, and genes related to the Wnt/β-catenin signaling pathway might represent a therapeutic target.