Why subdural hematomas form.

The usual mechanism

Bridging veins cross from the brain’s surface to the dural venous sinuses. When the brain shifts—after a fall, a blow, or even a sudden jolt—those veins can tear. Blood then spreads in the potential space beneath the dura.

In an older brain that has lost volume, the veins are already stretched. A minor fall that would not trouble a younger adult can be enough. That is a major reason chronic subdural hematoma is a disease of aging as much as a disease of trauma.

Risk factors

• Older age and brain atrophy.
• Falls, prior head injury, or repeated injuries.
• Anticoagulant or antiplatelet medication.
• Heavy alcohol use.
• Bleeding or clotting disorders.
• Prior subdural hematoma.
• In some patients, over-drainage of cerebrospinal fluid.

Having a risk factor is not a diagnosis. It is a reason to take new neurologic symptoms seriously and to mention them to the treating team.

Blood thinners

Medicines that reduce clotting save lives when they prevent stroke or another clot. They also raise the chance that a bleed, once started, will be larger. The response is not to stop them from a website. See the dedicated blood thinners guide.

When there is no clear injury

Occasionally no fall is remembered. That does not make the collection imaginary. Older adults may not recall a minor event, and some bleeds declare themselves only when membranes continue to leak. The work-up still starts with the exam and the scan, not with proving a story of trauma.

What you can change—and what you cannot

Fall-prevention, vision and footwear checks, home-safety changes, and honest medication lists are practical. Age is not modifiable. Secondary prevention after a diagnosed hematoma is individualized: blood-thinner strategy, follow-up imaging, and, in chronic collections, discussion of drainage and MMA embolization to reduce recurrence.