Herniation secondary to critical cerebrospinal fluid hypovolemia after supratentorial craniotomy: a single-center case series

Critical cerebrospinal fluid hypovolemia (CCSFH) is a rare postcraniotomy condition in patients with acute supratentorial brain injury, often mistaken for intracranial hypertension. This article aims to enhance awareness of CCSFH by describing its clinical and radiological characteristics.

Between January 2019 and November 2023, 330 consecutive patients with acute critical brain injury underwent supratentorial craniotomy. CCSFH diagnosis was based on three criteria: a decline in consciousness, head CT scans revealing midline shift of ≥ 5 mm, and rapid clinical or imaging presentation improvement within three days after implementing various treatments to increase CSF volume. Clinical and imaging features, treatment courses, and responses were analyzed. Midline shift on head CT scans was measured at four time points before and after surgery and compared using repeated measures ANOVA.

Fifteen patients (4.5%) developed CCSFH within 1 to 13 days post-surgery. Of them, seven patients exhibited a decline in consciousness or mental status, with three presenting anisocoria. The remaining eight had normal pupil sizes, complicating consciousness assessment due to postoperative sedation and analgesia. The average midline shift was 10.84 ± 2.83 mm during the CCSFH presentation, which showed a statistically significant difference from the initial postoperative measurement (p = 0.005) but not from the preoperative measurement (p = 0.536). Intracranial pressure ranged from 1–11 mmHg in five cases. The first four cases underwent an unplanned decompressive craniectomy as their conditions progressed to severe cingulate or transtentorial herniation, attributable to unawareness of cerebrospinal fluid hypovolemia before the second surgery. Drawing from the accumulated experiences, the subsequent eleven cases of CCSFH were promptly identified upon onset, and appropriate treatments were administered, with the supine position serving as the primary intervention modality. The CCSFH condition was successfully reversed in all patients.

CCSFH after craniotomy should be considered, and prompt identification and intervention are required in cases of clinical deterioration. The primary management strategy is placing the patient supine, along with stopping cerebrospinal fluid drainage, halting hyperosmotic diuretics, and administering intravenous hydration, often leading to favorable outcomes.