Background: Decompressive craniectomy (DC) is a life-saving intervention for malignant cerebral venous thrombosis (CVT). Earlier studies have shown increase in cerebral oxygenation after DC in traumatic brain injury but similar studies are lacking in CVT. We hypothesized that regional cerebral (tissue) oxygen saturation (rSO(2)) on the side of CVT is lower than the contralateral side and improves after DC. Materials and Methods: In this prospective cohort study, rSO(2) was monitored using near-infrared spectroscopy technique, before and after DC on both cerebral hemispheres. Data regarding factors likely to affect rSO(2) such as systolic blood pressure, partial pressure of oxygen and carbon dioxide in blood (PaO2 and PaCO2), and hemoglobin were simultaneously collected. The primary outcome measure was pre-post change in rSO(2) on the ipsilateral cerebral hemisphere. The secondary outcomes were in-hospital mortality and duration of postoperative hospital stay. Results: Seventeen patients underwent DC during the 6-month study period. Their mean age was 39.2 +/- 12.4 years. The pre-post DC change in rSO(2) on the hemisphere with CVT was significant (mean difference=3.6%; 95% confidence interval, 1.5-5.7; P=0.002). One patient died in the hospital. There was no difference in the duration of postoperative hospital stay (10 d [range, 6 to 21 d] vs. 14 d [range, 1 to 30 d], P=0.92) between patients with preoperative ipsilateral rSO(2) 60%. There was no correlation between PaO2, PaCO2, systolic blood pressure, and hemoglobin with rSO(2). Conclusions: Patients with malignant CVT had a lower rSO(2) on ipsilateral side of the lesion, which improved significantly after DC. Preoperative rSO(2) was not correlated with the duration of hospital stay.