Putting 'CSF-Shift Edema' Hypothesis to Test: Comparing Cisternal and Parenchymal Pressures After Basal Cisternostomy for Head Injury.

Abstract

Increased brain edema in head injury is due to shift of cerebrospinal fluid (CSF) from cisterns at high pressure to brain parenchyma at low pressure. By opening basal cisterns and decreasing the increased cisternal pressure, basal cisternostomy (BC) results in reversal of CSF shift from parenchyma to cisterns, leading to decreased brain edema. Though the CSF-shift edema hypothesis is based on pressure difference between cisterns and brain parenchyma, the relationship of these pressures has not been studied. A prospective clinical study was conducted from November 2018 to March 2020 including adult patients with head injury who were candidates for standard decompressive hemicraniectomy (DHC). All patients had neurological assessment and head computed tomography preoperatively and postoperatively. All patients underwent BC with DHC. Postoperatively, parenchymal and cisternal pressures and neurological condition were monitored hourly for 72 hours. Nine (5 men, 4 women) patients with head injury (mean age, 45.7 years; range, 25-72 years) underwent DHC-BC. Median Glasgow Coma Scale score of patients at admission was 8 (range, 4-14), and median midline shift on computed tomography was 8 mm (range, 7-12 mm). There was a significant difference between opening (25.70 ± 10.48 mm Hg) and closing (11.30 ± 5.95 mm Hg) parenchymal pressures (t₉ = 3.963, P = 0.003). Immediate postoperative cisternal pressure was 1-11 mm Hg and was lower than immediate postoperative parenchymal pressure in all except 1 patient. Postoperatively, if cisternal pressure remained low, parenchymal pressure also decreased, and patients showed clinical improvement. Patients showing increased cisternal pressure showed increased parenchymal pressure and clinical worsening. Our study supports the CSF-shift edema hypothesis. Following DHC-BC, cisternal pressure is lowered to near-atmospheric pressure, and its relationship to parenchymal pressure predicts the future course of patients by reversal or re-reversal of CSF shift.