Interhemispheric subdural hematomas (IHSDHs) are thought to be rare. Surgical management of these lesions presents a challenge as they are in close proximity to the sagittal sinus and bridging veins. IHSDHs are poorly characterized clinically and their exact incidence is unknown. There are also no clear guidelines for the management of IHSDH.

This is a retrospective review of all admitted patients with a diagnosis of traumatic brain injury over a 4-year period at a Level I trauma centre. Clinical characteristics of all patients with subdural hematoma (SDH) and IHSDH were collected.

Of 2165 admissions, 1182 patients had acute traumatic SDHs, 420 patients had IHSDHs (1.9% of admissions and 35.5% of SDH), 35 (8.3% of IHSDH) were ≥8 mm in width. IHSDH was isolated in 16 (3.8%) of the cases. Average age was 61.7 ± 21.5 years for all IHSDHs and 77.1 ± 10.4 for large IHSDH (p < 0.001). For large IHSDH, a transient loss of consciousness (LOC) occurred in 51.5% of individuals, post-traumatic amnesia (PTA) in 47.8% of cases, and motor weakness in 37.9% of patients. Five of the large IHSDH patients presented with motor deficits directly related to the IHSDH, and weakness resolved in four of these five individuals. None were treated surgically. Progression of IHSDH width occurred in one patient.

IHSDHs are often referred to as rare entities. Our results show they are common. Conservative management is appropriate to manage most IHSDHs, as most resolve spontaneously, and their symptoms resolve as well.