Contralateral progression after unilateral evacuation of bilateral chronic subdural hematomas: the volume relation ratio as prognostic factor?

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Unilateral evacuation of bilateral chronic subdural hematomas (bcSDHs) is associated with higher retreatment rates than an initial bilateral intervention. One reason for that is a possible progression in the size of the contralateral side after unilateral treatment. Thus, the authors focused their study on finding predictors of the need for contralateral retreatment. All patients who had undergone unilateral or bilateral evacuation of bcSDHs in the Department of Neurosurgery at the University Hospital of St. Poelten during a 5-year period (7/2012 to 6/2017) were retrospectively identified. The preoperative hematoma volume was calculated using the XYZ/2 method. Of a total of 103 patients with bcSDHs, 61 patients underwent bilateral evacuation and 42 patients underwent unilateral evacuation. The retreatment rate after bilateral evacuation was significantly lower than that after unilateral evacuation (14.8% vs 31%, respectively; p = 0.049). Contralateral retreatment after unilateral evacuation was necessary in 9 patients (21.4%). The preoperative contralateral hematoma volume was significantly higher in those patients who needed contralateral retreatment after initial unilateral evacuation (68.4 cm3 vs 27.4 cm3, respectively; p < 0.001). Furthermore, the so-called volume relation ratio created by dividing the smaller by the larger hematoma volume was significantly higher when contralateral retreatment became necessary (0.56 vs 0.21, respectively; p < 0.001). Patients needing evacuation of bcSDHs should be considered for primary bilateral evacuation if the hematoma volume on the smaller side is greater than 40 cm3 and the subsequent volume relation ratio is greater than 0.4.