Subdural Hygroma after Management of Ruptured Intracranial Aneurysms: Incidence, Associated Factors, Clinical Course, and Management Options

To evaluate incidence, associated factors, clinical course, and management options of subdural hygroma in patients treated for aneurysmal subarachnoid hemorrhage (aSAH). From January 2013 until June 2022, 336 consecutive patients with aSAH underwent treatment in our center. No one case was excluded from the study cohort. Computed tomography (CT) examinations were performed at admission, immediately after surgery and on the first postoperative day, and subsequently in case of any neurological deterioration or, at least, once per week until discharge from the hospital. Subsequent CT examinations were on discretion of specialists in rehabilitation facility, referring physicians, or neurosurgeons at the outpatient clinic. The length of radiological follow-up starting from CT at admission ranged from 1 to 3,286 days (mean, 673 ± 895 days; median, 150 days). Subdural hygromas developed in 84 patients (25%). An average interval until this imaging finding from the initial CT examination was 25 ± 55 days (median, 8 days; range, 0 – 362 days). Evaluation in the multivariate model revealed that patient age > 72 years (P < 0.0001), cerebrospinal fluid (CSF) shunting (P < 0.0001), and microsurgical clipping of ruptured intracranial aneurysm (RIA; P < 0.0001) are independently associated with the development of subdural hygroma. In 54 of 84 cases (64%) subdural hygromas required observation only. Increase of the lesion size with (5 cases) or without (10 cases) appearance of midline shift was associated with patient age < 72 years (P = 0.0398), decompressive craniotomy (P = 0.0192), and CSF shunting (P = 0.0009), while evaluation of these factors in the multivariate model confirmed independent association of only CSF shunting (P = 0.0003). Active management of subdural hygromas included adjustment of the shunt programmable valve opening pressure, cranioplasty, external subdural drainage, or their combination. Overall, during follow-up (mean, 531 ± 824 days; median, 119 days; range, 2 – 3,285 days) after the start of observation or applied treatment, subdural hygromas demonstrated either decrease (50 cases) or stabilization (34 cases) of their sizes, and no one lesion showed progression again. The clinical course of subdural hygromas in patients treated for aSAH is generally favorable, but occasionally these lesions demonstrate progressive enlargement with or without appearance of midline shift, which requires active management.