Chronic subdural hematoma (CSDH) is one of the most common clinical entities in daily neurosurgical practice. The diagnosis and treatment are well established, but recurrence, complications, and factors related to these problems, especially in the elderly, are not completely understood. This study evaluated the clinical features, radiological findings, and surgical results in a large series of the patients treated at the same institution. 500 consecutive patients (359 men and 141 women) with CSDH were treated by burr hole craniostomy with closed system drainage from January 1987 through February 1999. Causes, clinical and computed tomographic findings, surgical results, re-expansion of brain after surgery, and hematoma recurrence were statistically analyzed to elucidate the potential risks of CSDH. Most patients (89.4%) had good recovery, 8.4% showed no change, and 2.2% worsened. Six patients (1.2%) died, three due to disseminated intravascular coagulation. Recurrence of hematoma was recognized in 49 patients (9.8%), at 1 to 8 weeks (3.5 ± 1.9 weeks) after the first operation. The brain reexpansion rate at one week after operation was 45.0 ± 21.4% in patients with hematoma recurrence and significantly lower than 55.3 ± 19.1% in patients without recurrence (p º 0.001). Old age, preexisting cerebral infarction, and persistence of subdural air after surgery were significantly correlated with poor brain re-expansion (p º 0.001). Twenty-seven patients (5.4%) suffered postoperative complications, of which 13 cases were acute subdural hematoma caused by incomplete hemostasis of the scalp wound and four cases were tension pneumocephalus. Careful hemostasis and complete replacement of subdural hematoma by normal saline to prevent influx of air into the subdural space will further improve the surgical outcome for patients with CSDH.

Chronic subdural hematoma (CSDH) tends to occur in elderly patients with a history of mild head injury at a few months prior to the onset of symptoms. Intracranial arachnoid cyst is believed to be congenital and sometimes becomes symptomatic in pediatric patients. These two distinct clinical entities sporadically occur in the same young patient. Twelve of 541 cases of CSDH surgically treated in our institution had associated arachnoid cyst. The clinical and radiological characteristics of the cases of CSDH associated with arachnoid cyst were retrospectively analyzed and compared with those of CSDH without arachnoid cyst. Arachnoid cysts were located in the middle fossa (eight cases), convexity (two cases), and posterior fossa (two cases). Three cysts were less than 20 mm in diameter. The 12 patients with CSDH and arachnoid cyst (mean age 27.8 +/- 19.7 years) were significantly younger (p < 0.001) than the patients with CSDH without arachnoid cyst (69.5 +/- 13.7 years). Five of the 12 patients were pediatric cases (< 15 years old). The clinical symptoms were also significantly different. The most frequent symptom was headache followed by vomiting in the patients with arachnoid cyst, while gait disturbance and hemiparesis predominated in patients without arachnoid cyst. Hematoma evacuation through burr holes improved the symptoms in all patients with arachnoid cyst. We conclude that even a small arachnoid cyst can be a risk factor for CSDH after mild head injury in young patients and symptoms of increased intracranial pressure are common. Hematoma evacuation is adequate at first operation. If the preoperative symptoms persist, additional arachnoid cyst surgery should be considered. The present results also suggest that CSDH formation may be preceded by subdural hygroma caused by the rupture of arachnoid cyst.

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Highly pathogenic infectious bursal disease virus (IBDV) strains (Ehime/91, DV86) and a moderately pathogenic strain (J1) were compared in order to clarify the association between the pathogenicity of IBDV and viral antigen distribution. Virus target cells in the bursa, thymus, spleen, and bone marrow were examined by transmission electron microscopy. Although all strains caused similar bursal atrophy, the highly pathogenic strains brought about a greater decrease in the thymic weight index and more severe lesions in the cecal tonsil, thymus, spleen, and bone marrow. Immunohistochemical detection of IBDV antigen in tissues from chickens infected with Ehime/91 and DV86 strains showed a higher frequency of antigen-positive cells in the spleen and bone marrow. Transmission electron microscopy indicated the presence of viral particles in the cytoplasm of epithelial reticular cells in the thymus and monocytes in the bone marrow. The results show that pathogenicity of field strains of IBDV correlates with lesion production in non-bursal lymphopoietic organs. The results also suggest that pathogenicity of IBDV may be associated with virus antigen distribution in non-bursal lymphopoietic organs.