Intraoperative Ultrasonography during Drainage for Chronic Subdural Hematomas: A Technique to Release Isolated Deep-seated Hematomas--Technical Note.

After the drainage of chronic subdural hematomas (CSDHs), residual isolated deep-seated hematomas (IDHs) may recur. We introduce intraoperative ultrasonography to detect and remove such IDHs. Intraoperative ultrasonography is performed with fine transducers introduced via burr holes. Images obtained before dural opening show the CSDHs, hyper- and/or hypoechoic content, and mono- or multilayers. Images are also acquired after irrigation of the hematoma under the dura. Floating hyperechoic spots (cavitations) on the brain cortex created by irrigation confirm the release of all hematoma layers; areas without spots represent IDHs. Their overlying thin membranes are fenestrated with a dural hook for irrigation. Ultrasonographs were evaluated in 43 CSDHs (37 patients); 9 (21%) required IDH fenestration. On computed tomography scans, 17 were homogeneous-, 6 were laminar-, 16 were separated-, and 4 were trabecular type lesions. Of these, 2 (11.8%), 3 (50%), 4 (25%), and 0, respectively, manifested IDHs requiring fenestration. There were no technique-related complications. Patients subjected to IDH fenestration had lower recurrence rates (11.1% vs. 50%, p = 0.095) and required significantly less time for brain re-expansion (mean 3.78 ± 1.62 vs. 18 ± 5.54 weeks, p = 0.0009) than did 6 patients whose IDHs remained after 48 conventional irrigation and drainage procedures. Intraoperative ultrasonography in patients with CSDHs facilitates the safe release of hidden IDHs. It can be expected to reduce the risk of postoperative hematoma recurrence and to shorten the brain re-expansion time.