Subdural hygroma is an accumulation of a cerebrospinal fluid-like fluid in the subdural space. It is a common epiphenomenon after a traumatic brain injury (TBI), but it may also occur after brain surgeries. A total of 17 patients in a prospective case series with subdural hygromas were analyzed. A male predominance (82.4%) was found. The mean age was 58.6 years. Traumatic brain injury was the main mechanism (76.5%); however, other mechanisms, such as post-craniotomy (17.6%), post-chronic subdural hematoma drainage (5.9%), and post-ventricle shunt (5.9%), were also observed. Incidental findings were diagnosed in 11.8% of the cases (mainly in elderly patients). Four patients required subdural shunt (23.5%)all of them had TBI. Small subdural effusions were present in 35.5% of the cases. The mean time from admission to diagnosis was 6.1 days. The majority of the cases must have involved lesions of the dura-arachnoid interface since TBIs were the main causes of hygroma. The findings of incidental hygroma in elderly patients and its development after a ventricle shunt suggest that brain atrophy also plays a significant role in subdural hygroma formation.