Chronic Subdural Hematoma: Toward a New Management Paradigm for an Increasingly Complex Population.

Chronic subdural hematoma (cSDH) is a frequent yet poorly studied entity. Patients with cSDH are increasingly using antithrombotic medication, are now older, and present with a variety of clinical symptoms, including incidental discoveries. Despite this increasing complexity, management has remained roughly unchanged since the late 1990s. We review here the state of cSDH research under way at Université de Sherbrooke and around the world with a focus on studies addressing specific gaps in the current evidence base. We show that evidence is lacking at many decision points in the typical cSDH patient treatment algorithm. No definition of cSDH is universally accepted, and a formal definition project, along with suggested common data elements to be reported in future trials (CODE-CSDH: formal cSDH definition project) is ongoing. An amendment to International Statistical Classification of Diseases and Related Health Problems (ICD-11) has also been proposed to improve classification and registry research. Within the cSDH clinical assessment, evidence for the occurrence of nonepileptic, stereotypical, and intermittent symptoms (NESIS) is emerging. The GENESIS study (Generation Evidence on the etiology and management of NESIS) will test etiological and therapeutic hypotheses for this patient subpopulation. For patients at high risk of recurrence, the TRACS (TXA for cSDH) and EMMACS studies (Embolization of the Middle Meningeal Artery in Chronic Subdural Hematoma study) are, respectively, assessing the use of tranexamic acid and meningeal artery embolization. The overarching vision is that patients with cSDH might be stratified for operative versus conservative treatment based on the need for mass effect removal, then be offered adjuvant therapies based on their risk of recurrence and thrombotic complications. We believe that such tailoring of therapy to each individual should help improve outcomes.