This study is aimed at improving reporting in Chronic Subdural Haematoma (CSDH) research studies, through development of a standardised Core Outcome Set (COS), a unified CSDH Definition and set of Data Elements (DE) for reporting.

The study design includes a Delphi survey process from two main stakeholder groups: Health-Care Professionals or Researchers (HCPR) and Patients or carers. HCPR, patients and carers will all be invited to complete the survey on the COS, only the HCPR survey will include questions on definition and DE. Results of the Delphi Survey will be discussed at a final consensus meeting before results are confirmed and published.

Chronic subdural haematoma (CSDH) is a collection of blood and fluid surrounded by membranes that accumulates on the brain surface over weeks to months. It predominately affects older people and often has a delayed association with a preceding head trauma.

There has been significant growth in the number of CSDH publications in recent years mirroring progress in potential management options but there is wide variation in how and when patient outcome is measured amongst studies. Much could be gained by agreeing a minimum set of standardized outcomes that should be measured and reported in all CSDH studies, known as a Core Outcome Set (COS).

The overall study design includes a Delphi survey process.This is a process whereby all outcomes and data elements from the CSDH literature and expert opinion are presented to a large group of patients, carers and HCPR via a survey. Each survey participant has the opportunity to rank the elements and outcomes in levels of importance to them, and the survey is then repeated including presentation of the results from the first round, in order to attempt to gain agreement between participants on what is important. All elements are then reviewed at a final "consensus" meeting

Inclusion Criteria:

All invited participants who provide consent to take part in 2 rounds of survey

Healthcare Professionals, Researchers, patients and carers.

Protocol submitted for open publication prior to commencing study. Final study report will be published at end of study including full anonymised survey responses.