Background Chronic subdural hematoma (cSDH) is one of the most common neurosurgical diseases with a significant financial burden. Current management includes observation for mild or asymptomatic patients and surgical drainage for moderate and severe patients. However, surgical drainage is associated with a 15% reoperation rate and a mortality of up to 10%. Middle meningeal artery embolization (MMAE) is a promising minimally invasive alternative with an estimated surgical recurrence rate of 6.8% and 4.6% for standalone MMAE and combined MMAE and surgery respectively. However, randomized data is lacking for this emerging therapy.

Methods CHESS is a NIH-funded, prospective, multi-center, randomized, open label clinical trial. Patients with a moderately symptomatic cSDH (de novo or recurrent), defined as 4/5 weakness or better, gait instability, or mild aphasia, will be randomized in a 1:1 ratio to standalone MMAE with particles (PVA or embospheres) or surgical drainage. The composite primary outcome is the proportion of patients that require rescue surgery or die within 180 days. The primary hypothesis is that the proportion of that require surgery or die within 180 days after randomization is lower by 13% or more for the MMAE treated group compared to surgical drainage. For an effect size of 13%, assuming that the proportion of subjects that will require surgery or die is 25% in the surgical drainage group, a type I error probability of 0.05, a type II error probability of 0.15, and a dropout/crossover rate of 10%, the sample size of 394 patients was estimated. One interim analysis for overwhelming efficacy and futility will be performed assuming a group sequential design of O’Brien and Fleming boundary. Safety outcomes include the proportion of subjects with ischemic strokes, serious/life threatening adverse events, worsening neurological status or development of new disabling neurological symptoms, seizures, and cranioneuropathy (blindness and facial paralysis) within 180 days of randomization. Exploratory outcomes include volumetric reduction in hematoma size, change in Quality of Life, cognition, headache, and mRS at 180 days.

Discussion CHESS is designed to be the first US randomized controlled trial to provide evidence on the safety and efficacy of standalone MMAE vs surgical drainage. Innovative features of this design include the use of particles as the embolic agent and the inclusion of recurrent, in addition to de novo, cSDHs.

Disclosures P. Kan: 1; C; 1U18EB029353-01/NIH, Siemens Research Grant. 2; C; Imperative Care, Stryker Neurovascular. 4; C; Vena Medical. A. Thomas: None. M. Selim: None. A. Qureshi: None. R. Martin: None. C. Cassarly: None. F. Siddiq: None.