Development of a prognostic scoring system to predict risk of reoperation for contralateral hematoma growth after unilateral evacuation of bilateral chronic subdural hematoma.

Bilateral chronic subdural hematoma (bCSDH) is frequently drained unilaterally when the contralateral CSDH is small and asymptomatic. However, reoperation rates for contralateral CSDH growth can be high. We aimed to develop a prognostic scoring system to guide the selection of suitable patients for unilateral drainage of bCSDH. Data were collected retrospectively across three tertiary hospitals from 2010 to 2017 on all consecutive bCSDH patients aged 21 or above. Predictors of reoperation were identified using multivariable logistic regression. A prognostic score was developed and internally validated. 240 bCSDH patients were analyzed. 98 (40.8%) underwent unilateral and 142 (59.2%) underwent bilateral evacuation. Clinical outcomes were comparable between the unilateral and bilateral evacuation groups. Within the unilateral evacuation group, 4 (4.1%) had a reoperation for contralateral CSDH growth. Reoperation for contralateral CSDH was predicted by preoperative use of anticoagulants (OR = 15.0, 95% CI: 1.49-169.15, p = 0.017). Complete resolution of contralateral CSDH was predicted by its preoperative maximum width, with a cut-off of 9 mm producing the highest sensitivity and specificity (OR = 4.17 for ≤9 mm, 95% CI: 1.54-11.11, p = 0.004). Using our prognostic score, reoperation rate for contralateral CSDH was 1.6%, 3.6%, 16.7%, and 50.0% in low-risk, moderate-risk, high-risk and very high-risk patients, respectively. With each increase of 1 in the prognostic score, patients were 4 times as likely to undergo reoperation for contralateral CSDH (OR = 3.98, 95% CI: 1.36-13.53, p = 0.013). Our proposed risk score may be used as an adjunct in clinical decision making for bCSDH patients undergoing unilateral evacuation.