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Hiroshi Nakaguchi and Mario Miyamoto

✓ The authors present the case of a 68-year-old man who experienced acute obstructive hydrocephalus after having suffered an infarction in the occipital lobe. Histopathological and serial neuroimaging examinations revealed that portions of a large disintegrating occipital infarct had entered the lateral ventricle and obstructed the passage of cerebrospinal fluid (CSF). Ventricular drainage was performed for 2 weeks until the patient's hydrocephalus resolved. The CSF initially contained a high concentration of protein (1070 mg/dl), a high leukocyte count of 115 cells/mm3, and a rich fibrinous exudate.

Findings in the present case indicate that collapse of a periventricular ischemic lesion into the ventricles may sometimes occur not only after cerebral hemorrhage but also after cerebral infarction.

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Hiroshi Nakaguchi and Kazuo Tsutsumi

Object. To date, there has been no published study in which the focus was on the mechanisms of head injuries associated with snowboarding. The purpose of this study was to identify these mechanisms.

Methods. The patient population consisted of 38 consecutive patients with snowboarding-related major head injuries who were treated at two hospitals in Japan, where for years many winter sports injuries have been treated. The skill level of the snowboarder, the cause of the accident, the direction of the fall, the site of impact to the head, and the condition of the ski slope were examined. The injuries were classified as coup, contrecoup, or shear injuries.

The predominant features of snowboarding-related major head injuries included: falling backward (68% of cases), occipital impact (66% of cases), a gentle or moderate ski slope (76% of cases), and inertial injury (76% of cases [shear injury in 68% and contrecoup injury in 8% of the patients]). Acute subdural hematoma frequently occurred after a patient fell on the slope (p = 0.025), fell backward (p = 0.0014), or received an occipital impact (p = 0.0064). Subcortical hemorrhagic contusions frequently occurred after the patient fell during a jump (p = 0.0488), received a temporal impact (p = 0.0404), or fell on the jump platform (p = 0.0075). Shear injury frequently occurred after a fall that occurred during a jump or after simple falls on the ski slope, and contact injury was frequently seen after a collision (p = 0.0441).

Conclusions. The majority of severe head injuries associated with snowboarding that occur after a simple fall on the slope are believed to involve the opposite-edge phenomenon, which results from a fall backward on a gentle or moderate slope causing occipital impact. The use of a device to protect the occiput is proposed to reduce head injuries associated with snowboarding.

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Hiroshi Nakaguchi, Takeo Tanishima, and Norio Yoshimasu

Object. Factors affecting the postoperative recurrence of chronic subdural hematomas (CSDHs) have not been sufficiently investigated. The authors have attempted to determine features of CSDHs that are associated with a high or low recurrence rate on the basis of the natural history of these lesions and their intracranial extension.

Methods. One hundred six patients (82 men and 24 women) harboring 126 CSDHs who were treated at Tokyo Kosei Nenkin Hospital between January 1989 and April 1998 were studied. Types of CSDHs were classified according to hematoma density and internal architecture, and the intracranial extension of the hematomas were investigated. The postoperative recurrence rate was calculated for each factor.

Based on the internal architecture and density of each hematoma, the CSDHs were classified into four types, including homogeneous, laminar, separated, and trabecular types. The recurrence rate associated with the separated type was high, whereas that associated with the trabecular type was low.

Chronic subdural hematomas are believed to develop initially as the homogeneous type, after which they sometimes progress to the laminar type. A mature CSDH is represented by the separated stage and the hematoma eventually passes through the trabecular stage during absorption.

Based on the intracranial extension of each hematoma, CSDHs were classified into three types, including convexity, cranial base, and interhemispheric types. The recurrence rate of cranial base CSDHs was high and that of convexity CSDHs was low.

Conclusions. Classification of CSDHs according to the internal architecture and intracranial extension may be useful for predicting the risk of postoperative recurrence.

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Hiroshi Nakaguchi, Takeo Tanishima, and Norio Yoshimasu

Object. This study was conducted to determine the best position for the subdural drainage catheter to achieve a low recurrence rate after burr-hole irrigation and closed-system drainage of chronic subdural hematoma (CSDH).

Methods. The authors studied 63 patients with CSDH in whom the drainage catheter tip was randomly placed and precisely determined on postoperative computerized tomography (CT) scans and 104 patients with CSDH in whom CT scans were obtained 7 days postsurgery. The location of the subdural drainage catheter, the maximum postoperative width of the subdural space, and the percentage of the ipsilateral subdural space occupied by air postoperatively were determined and compared with the postoperative recurrence and reoperation rates.

Patients with parietal or occipital drainage had a higher rate of CSDH recurrence and much more subdural air than those with frontal drainage. In addition, patients with residual subdural air demonstrated on CT scans obtained 7 days postsurgery also had a higher recurrence rate than those without subdural air collections. Furthermore, patients with a subdural space wider than 10 mm on CT scans obtained 7 days postsurgery had a higher recurrence rate than those with a space measuring 10 mm or less.

Conclusions. The incidence of postoperative fluid reaccumulation seems to be reduced by placing the tip of the drainage catheter in the frontal convexity and by removing subdural air during or after surgery.

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Kenichi Amagasaki, Shoko Abe, Saiko Watanabe, Kazuaki Naemura, and Hiroshi Nakaguchi

This 31-year-old woman presented with typical right trigeminal neuralgia caused by a trigeminocerebellar artery, manifesting as pain uncontrollable with medical treatment. Preoperative neuroimaging studies demonstrated that the offending artery had almost encircled the right trigeminal nerve. This finding was confirmed intraoperatively, and decompression was completed. The neuralgia resolved after the surgery; the patient had slight transient hypesthesia, which fully resolved within the 1st month after surgery. The neuroimaging and intraoperative findings showed that the offending artery directly branched from the upper part of the basilar artery and, after encircling and supplying tiny branches to the nerve root, maintained its diameter and coursed toward the rostral direction of the cerebellum, which indicated that the artery supplied both the trigeminal nerve and the cerebellum. The offending artery was identified as the trigeminocerebellar artery. This case of trigeminal neuralgia caused by a trigeminocerebellar artery indicates that this variant is important for a better understanding of the vasculature of the trigeminal nerve root.

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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.