Objectives We are conducting a feasibility and pilot phase randomised controlled trial (RCT) to address the top uncertainty about cavernomas, does treatment with surgery (neurosurgery or stereotactic radio- surgery) improve outcome, compared to treatment without surgery?

Methods Feasibility study and pilot phase, parallel group,pragmatic RCT involving ~60 participants. Par- ticipants are randomised 1:1 to treatment with surgery or treatment without surgery. The primary clinical outcome is symptomatic intracranial haemorrhage or new persistent focal neurological deficit. Collabora- tors keep screening logs capturing characteristics of patients screened, eligible,approached, consented and randomised. A Quinte T recruitment intervention is evaluating screening logs and audio recordings of recruitment discussions and interviews with recruiters and patients.

Results The first site opened in August 2021.14 (47%) of our target of 30 sites are currently active.Six sites are pending activation. The first patient was recruited in September 2021.on 14 January, of 35 patients screened,17 (49%) were approached to assess eligibility, 10 (29%) were eligible, and three (9% of those screened and 5% of the n=60 target ) were randomised.

Conclusions We are grateful to neurologists for supporting this multidisciplinary collaboration to demons- trate the feasibility of resolving the top uncertainty about brain cavernoma in a definitive main phase trial.