Background and objectives: Bedside sonographic duplex technique (SDT) may be used as an adjunct to cranial computed tomography (CCT) to monitor brain-injured patients after decompressive craniectomy (DC). The present study aimed to assess the value of SDT in repeated measurements of ventricle dimensions in patients after DC by comparing both techniques. Materials and Methods: Retrospective assessment of 20 consecutive patients after DC for refractory intracranial pressure (ICP) increase following subarachnoid hemorrhage (SAH), bleeding and trauma which were examined by SDT and CCT in the context of routine clinical practice. Whenever a repeated CCT was clinically indicated SDT examinations were performed within 24 hours and correlated via measurement of the dimensions of all four cerebral ventricles. Basal cerebral arteries including pathologies such as vasospasms were also evaluated in comparison to selected digital subtraction angiography (DSA). Results: Repeated measurements of all four ventricle diameters showed high correlation between CCT and SDT (right lateral r = 0.997, p < 0.001; left lateral r = 0.997, p < 0.001; third r = 0.991, p < 0.001, fourth ventricle r = 0.977, p < 0.001). SDT performed well in visualizing basal cerebral arteries including pathologies (e.g., vasospasms) as compared to DSA. Conclusions: Repeated SDT measurements of the dimensions of all four ventricles in patients after DC for refractory ICP increase delivered reproducible results comparable to CCT. SDT may be considered as a valuable bedside monitoring tool in patients after DC.