[Prospects for conservative treatment of chronic subdural hematomas - investigation of the absorption process].

The most common treatment of chronic subdural hematomas is evacuation and irrigation via burr holes. The theory is that chronic subdural hematomas will undergo a natural healing process if such surgery is performed. However, there is no information concerning the course of hematoma absorption. In this work, 111In-DTPA was injected into the hematoma cavity before and after hematoma evacuation and irrigation in 12 cases of chronic subdural hematoma with comparatively mild symptoms. The radioactivity in the head was measure with time using a scintillation counter and the attenuation rate was obtained. The values measured hourly were expressed as ratios of the 1st measured value. Because of the properties of 111In-DTPA, this attenuation rate was considered to be the absorption rate of the liquid components of the hematoma. In 8 of the preoperative cases, the average measured values, were 84.8 +/- 12.6% after 3 hours, 77.3 +/- 12.1% after six hours, 34.5 +/- 13.8% after 24 hours and 13.3 +/- 13.5% after 48 hours. In six of the postoperative cases, the values were 70.4 +/- 14.3% after 3 hours, 47.8 +/- 10.8% after 6 hours, 12.4 +/- 6.7% after 24 hours and 3.6 +/- 2.0% after 48 hours. In a comparison between the two, the postoperative cases showed clearly advanced absorption with a significant difference at a risk factor of 0.1% or less in each case. This is because the osmotic pressure is the same for the liquid in the hematoma, the blood and the cerebrospinal fluid and an explanation based on this alone is difficult; it is necessary to consider colloid osmotic pressure. When the radioactivities in the liquid in the hematoma, blood and cerebrospinal fluid were measured, the values for the blood were always higher than those for the cerebrospinal fluid and most of the absorption of the hematoma is considered to originate in the vascular bed in the hematoma cavity (sinusoidal channel layer). Therefore, for the conservative treatment of chronic subdural hematomas, it is necessary to consider methods which promote absorption of the hematoma.