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Fumitaka Yoshioka, Shoko Shimokawa, Jun Masuoka, Tomoko Izaki, Yukiko Nakahara, Masatou Kawashima, Shuji Sakata and Tatsuya Abe

Here, the authors present an extremely rare case of an extensive spinal epidural teratoma (SET) in an infant and provide a review of the cases in the literature. In this report, the authors focused on the clinical manifestation and management of extensive SET. A 64-day-old girl presented with severe dyspnea and paraparesis caused by a large thoracic mass. Imaging studies revealed that the mass originated from the epidural space of the thoracic spine and extended from C7 to L1. The tumor extended bilaterally through the intervertebral foramina and formed a large posterior mediastinal mass. The tumor was partially resected via laminotomy after an emergency thoracotomy. The remnant grade I immature teratoma grew rapidly. After a re-laminotomy and bilateral thoracotomy, the residual tumor stopped growing. However, the patient’s paraparesis improved very little, and her scoliosis progressed gradually. Therefore, SET should be included in the differential diagnosis when an infant patient with paraparesis of the lower extremities is encountered. Timely diagnosis, aggressive treatment, and close monitoring are of critical importance to successful recovery in such patients.

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Atsushi Ogata, Masatou Kawashima, Tomihiro Wakamiya, Masashi Nishihara, Jun Masuoka, Yukiko Nakahara, Ryo Ebashi, Kohei Inoue, Yukinori Takase, Hiroyuki Irie and Tatsuya Abe

OBJECTIVE

Hypoxia induces angiogenesis and plays a major role in the progression of carotid plaques. During carotid intervention, plaques with high-intensity signals on time-of-flight (TOF) magnetic resonance angiography (MRA) often cause ischemic stroke and embolic complications. However, the role of intraplaque hypoxia before carotid endarterectomy (CEA) and carotid artery stenting is not presently understood. In this study the authors aimed to investigate the relationship between intraplaque hypoxia and MRA findings.

METHODS

Nineteen consecutive patients with 20 carotid artery stenoses who underwent CEA at Saga University Hospital between August 2008 and December 2014 were enrolled in the study. The expressions of hypoxia-inducible transcription factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) were analyzed by immunohistochemical analysis. In addition, the relationship between the findings on TOF MRA and pathology for the carotid plaques was analyzed.

RESULTS

High-intensity plaques on TOF MRA showed higher expression levels of HIF-1α (p = 0.015) and VEGF (p = 0.007) compared with isointensity plaques. The rate of intraplaque hemorrhage (IPH) on TOF MRA was also significantly higher in the high-intensity plaques than in the isointensity plaques (p = 0.024). Finally, the mean number of neovessels was significantly higher in those without plaque hemorrhage than in those with plaque hemorrhage (p = 0.010).

CONCLUSIONS

Plaques with high-intensity signals on TOF MRA were associated with IPH and evidence of intraplaque hypoxia. This fact may represent an opportunity to establish novel therapeutic agents targeting intraplaque hypoxia.

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Yukiko Nakahara, Toshio Matsushima, Tetsuya Hiraishi, Tetsuro Takao, Takeshi Funaki, Jun Masuoka and Masatou Kawashima

Object

The authors adopted the infrafloccular approach for microvascular decompression (MVD) surgery to treat hemifacial spasm (HFS). The inferior portion of the flocculus is retracted to observe the root exit zone of cranial nerve (CN) VII between CN IX and the flocculus. During the procedure, the rhomboid lip, a sheetlike layer of neural tissue forming the lateral recess of the fourth ventricle, is sometimes encountered. The existence of the rhomboid lip in cases of HFS was reviewed to determine the importance of the structure during MVD surgery.

Methods

Preoperative imaging and intraoperative observations in 34 consecutive cases of HFS treated in the period from October 2008 through September 2011 were used to assess the frequency of encountering the rhomboid lip.

Results

The rhomboid lip was observed during MVD surgery in 9 (26.5%) of the 34 cases but had been demonstrated on preoperative MR images in only 3 cases (8.8%). On T2-weighted images, it appeared as a high-intensity nonstructural area on the ventral side of the flocculus and continued into the fourth ventricle via the foramen of Luschka.

Conclusions

A large rhomboid lip presents an impediment to MVD surgery in a significant minority of patients with HFS. It is seldom observed on preoperative MR images. Proper dissection of the rhomboid lip away from the arachnoid membrane and/or the lower CNs during MVD surgery provides good visualization of the root exit zone of CN VII and reduces injury of CNs IX and X, avoiding postoperative deficits like dysphagia.

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Masatou Kawashima, Yukinori Takase and Toshio Matsushima

Object

The cerebellomedullary fissure (CMF) is a space between the cerebellum and the medulla oblongata, which often adhere to each other. The purpose of the present study was to demonstrate the importance of the unilateral CMF dissection for clipping vertebral artery (VA)–posterior inferior cerebellar artery (PICA) aneurysms.

Methods

Five adult cadaveric specimens were studied after colored silicone was infused into the arteries and veins. The microsurgical anatomy of the CMF and the trans-CMF approach for VA-PICA aneurysm surgery were examined in stepwise dissections. In addition, 6 patients underwent surgery for VA-PICA saccular aneurysms (2 ruptured and 4 unruptured aneurysms) via posterolateral approaches, with wide opening of the unilateral CMF to obtain good visualization and a wide working space in the lateral part of the cerebellomedullary cistern. Clinical data including neurological and radiological findings and patient outcomes were analyzed in all 6 cases.

Results

In all cases, the aneurysm was successfully clipped and no permanent neurological deficits remained. The wide opening of the unilateral CMF on the lesion side made it possible to retract the inferolateral part of the cerebellum easily, provided a wide operative field in the cerebellomedullary cistern, and enabled successful clip placement without difficulty.

Conclusions

For safe and effective VA-PICA aneurysm surgery, it is very important to dissect the CMF on the lesion side as well as to remove the lateral part of the foramen magnum. Direct clip placement is very safe and useful in cases involving VA-PICA aneurysms.

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Necmettin Tanriover, Hiroshi Abe, Albert L. Rhoton Jr., Masatou Kawashima, Galip Z. Sanus and Ziya Akar

Object

The purpose of this study was to define the patterns of drainage of the superior petrosal venous complex (SPVC) along the petrous ridge in relation to the Meckel cave and internal acoustic meatus (IAM) and to delineate its effect on the surgical exposures obtained in subtemporal transtentorial and retrosigmoid suprameatal approaches.

Methods

The patterns of drainage of the SPVC along the petrous ridge were characterized according to their relation to the Meckel cave and the IAM based on an examination of 30 hemispheres. Subtemporal transtentorial and retro-sigmoid suprameatal approaches were performed in three additional cadavers to demonstrate the effect of the drainage pattern on the surgical exposures.

Conclusions

The SPVC emptied into the superior petrosal sinus (SPS) within a distance of 1 cm from the midpoint of the Meckel cave. The patterns of drainage of the SPVC were classified into three groups. Type I emptied into the SPS above and lateral to the boundaries of the IAM. The most common type, Type II, emptied between the lateral limit of the trigeminal nerve at the Meckel cave and the medial limit of the facial nerve at the IAM, within an area of approximately 13 mm. Type III emptied into the SPS above or medial to the Meckel cave. The ideal SPVC for a subtemporal transtentorial approach (with or without anterior extradural petrosectomy) seems to be a Type I. In SPVC Type III and those Type II cases in which the SPVC is located near the Meckel cave, the amount of working space is significantly limited in a subtemporal transtentorial approach. In contrast, the ideal type of SPVC for a retrosigmoid suprameatal approach would be a Type III, and the SPVC must be divided in the majority of Type I and II cases for a satisfactory surgical exposure along the Meckel cave and middle fossa dura. The proposed modified classification system and its effect on the surgical exposure may aid in planning the approach directed along the petrous apex and may reduce the probability of venous complications.

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Masatou Kawashima, Albert L. Rhoton Jr., Necmettin Tanriover, Arthur J. Ulm, Alexandre Yasuda and Kiyotaka Fujii

Object. Revascularization is an important component of treatment for complex aneurysms that require parent vessel occlusion, skull base tumors that involve major vessels, and certain ischemic diseases. In this study, the authors examined the microsurgical anatomy of cerebral revascularization in the anterior circulation by demonstrating various procedures for bypass surgery.

Methods. Twenty-five adult cadaveric specimens were studied, using 3 to 40 magnification, after the arteries and veins had been perfused with colored silicone. The microsurgical anatomy of cerebral revascularization in the anterior circulation was examined with the focus on the donor, recipient, and graft vessels. The techniques discussed in this paper include the superficial temporal artery (STA)—middle cerebral artery (MCA), middle meningeal artery (MMA)—MCA, and side-to-side anastomoses; short arterial and venous interposition grafting; and external carotid artery/internal carotid artery (ICA)—M2 and ICA—ICA bypasses. Bypass procedures for cerebral revascularization are divided into two categories depending on their flow volume: low-flow and high-flow bypasses. A low-flow bypass, such as the STA—MCA anastomosis, is used to cover a relatively small area, whereas a high-flow bypass, such as the ICA—ICA anastomosis, is used for larger areas. Cerebral revascularization techniques are also divided into two types depending on the graft materials: pedicled arterial grafts, such as STA and occipital artery grafts, and free venous or arterial grafts, which are usually saphenous vein and radial artery grafts. Pedicled arterial grafts are mainly used for low-flow bypasses, whereas venous or arterial grafts are used for high-flow bypasses.

Conclusions. It is important to understand the methods of bypass procedures and to consider indications in which cerebral revascularization is needed.

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Masatou Kawashima, Albert L. Rhoton Jr., Necmettin Tanriover, Arthur J. Ulm, Alexandre Yasuda and Kiyotaka Fujii

Object. Revascularization is an important component of treatment for complex aneurysms, skull base tumors, and vertebrobasilar ischemia in the posterior circulation. In this study, the authors examined the microsurgical anatomy related to cerebral revascularization in the posterior circulation and demonstrate various procedures for bypass surgery.

Methods. The microsurgical anatomy of cerebral and cerebellar vessels as they relate to revascularization procedure and techniques, including extracranial-to-intracranial bypass grafting, arterial interposition grafting, and side-to-side anastomosis, were examined by performing stepwise dissections in 22 adult cadaveric specimens. The arteries and veins in the specimens were perfused with colored silicone.

Dominant cerebral and cerebellar revascularization procedures in the posterior circulations include superficial temporal artery (STA)—posterior cerebral artery (PCA), STA—superior cerebellar artery (SCA), occipital artery (OA)—anterior inferior cerebellar artery, OA—posterior inferior cerebellar artery (PICA), and PICA—PICA anastomoses. These procedures are effective in relatively small but critical areas including the brainstem and cerebellum. For revascularization of larger areas a saphenous vein graft is used to create a bypass between the PCA and the external carotid artery. Surgical procedures are generally difficult to perform in deep and narrow operative spaces near critical vital structures.

Conclusions. Although a clear guideline for cerebral revascularization procedures has not yet been established, it is important to understand various microsurgical techniques and their related anatomical structures. This will help surgeons consider surgical indications for treatment of patients with vertebrobasilar ischemia caused by aneurysms, tumors, or atherosclerotic diseases in the posterior circulation.

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Necmettin Tanriover, Albert L. Rhoton Jr., Masatou Kawashima, Arthur J. Ulm and Alexandre Yasuda

Object. The purpose of this study was to define the topographic anatomy, arterial supply, and venous drainage of the insula and sylvian fissure.

Methods. The neural, arterial, and venous anatomy of the insula and sylvian fissure were examined in 43 cerebral hemispheres.

Conclusions. The majority of gyri and sulci of the frontoparietal and temporal opercula had a constant relationship to the insular gyri and sulci and provided landmarks for approaching different parts of the insula. The most lateral lenticulostriate artery, an important landmark in insular surgery, arose 14.6 mm from the apex of the insula and penetrated the anterior perforated substance 15.3 mm medial to the limen insulae. The superior trunk of the middle cerebral artery (MCA) and its branches supplied the anterior, middle, and posterior short gyri; the anterior limiting sulcus; the short sulci; and the insular apex. The inferior trunk supplied the posterior long gyrus, inferior limiting sulcus, and limen area in most hemispheres. Both of these trunks frequently contributed to the supply of the central insular sulcus and the anterior long gyrus. The areas of insular supply of the superior and inferior trunks did not overlap. The most constant insular area of supply by the cortical MCA branches was from the prefrontal and precentral arteries that supplied the anterior and middle short gyri, respectively. The largest insular perforating arteries usually arose from the central and angular arteries and most commonly entered the posterior half of the central insular sulcus and posterior long gyrus. Insular veins drained predominantly to the deep middle cerebral vein, although frequent connections to the superficial venous system were found. Of all the insular veins, the precentral insular vein was the one that most commonly connected to the superficial sylvian vein.

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Masatou Kawashima, Toshio Matsushima and Tomio Sasaki

Object. Most distal anterior cerebral artery (ACA) aneurysms arise at the pericallosal—callosomarginal artery (PerA—CMA) junction, which is usually located in the A3 segment of the ACA around the genu of the corpus callosum. Aneurysms in the PerA—CMA junction are divided into two types according to their location: supracallosal and infracallosal. Infracallosal distal ACA aneurysms are defined as those located in the lower half of the A3 segment, which makes it more difficult to gain proximal control. In this study, the authors examined the microsurgical anatomy of the distal ACA region, focusing especially on the relationship between the PerA and CMA located in the lower half of the A3 (infracallosal) segment, and present a surgical strategy for dealing with distal ACA aneurysms.

Methods. The microsurgical anatomy of the distal ACA region was examined in 22 adult cadaveric cerebral hemispheres after perfusion of the arteries and veins with colored silicone. The relationships of the infracallosal segment of the PerA to the CMA and the A2 segment of the PerA to the frontopolar artery were examined. The distance between the nasion and the site at which a parallel line directed along the long axis of the infracallosal PerA just proximal to the origin of the CMA artery crosses the forehead (which we have named the PC point) was also measured. Surgical approaches to distal ACA aneurysms were examined in stepwise dissections.

Conclusions. The PerA—CMA junctions were located in the supracallosal and infracallosal segments of A3 in 36 and 55% of cases, respectively. In the infracallosal region, it was difficult to identify the proximal PerA and to establish proximal control of the vessel. The infracallosal part of the proximal PerA coursed almost parallel to the frontal cranial base, and the PC point was 42.2 ± 15.9 mm (mean ± standard deviation) from the nasion. These findings indicate that there is only a limited space in which to access an infracallosal distal ACA aneurysm below the PC point and establish proximal control by the anterior interhemispheric approach. When the approach is made above the PC point, an anterior callosotomy may be necessary to establish proximal control before final aneurysm dissection and clip placement are completed. The PC point is an important surgical landmark in planning the surgical strategy for infracallosal distal ACA aneurysms.

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Necmettin Tanriover, Masatou Kawashima, Albert L. Rhoton Jr, Arthur J. Ulm and Robert A. Mericle

Object. The cortical arteries arising from the main trunk of the middle cerebral artery, proximal to its bifurcation or trifurcation, are called “early branches.” The purpose of this study was to characterize these early branches.

Methods. The early branches were characterized according to their sites and patterns of origin, diameters, and relative proximity to the internal carotid artery bifurcation, as well as the course and area of supply of their cortical branches based on an examination of 50 hemispheres. Special attention was directed to the perforating arteries that arose from the early branches and entered the anterior perforated substance. The anatomical findings were compared with data obtained from 109 angiograms.

Conclusions. Early branches directed to the temporal and frontal lobes were found in 90 and 32% of the hemispheres, respectively. The early branches that arose more proximally from the M1 segment were larger than those arising distally. Lenticulostriate arteries arose from 81% of the early frontal branches (EFBs) and from 48% of the early temporal branches (ETBs). An average of two cortical arteries arose from the EFBs and 1.3 from the ETBs, the most common of which supplied the temporopolar and orbitofrontal areas. Although the microsurgical anatomy of the early branches demonstrates abundant diversity, they can be classified into clearly defined patterns based on anatomical features. These patterns can prove helpful in evaluating angiographic data and in planning an operative procedure.