Subdural Hematomas 101

New procedure provides improved options for blood clots affecting the brain

Written by John Ferrari 

From concussions to strokes to trauma, neurologists and neurosurgeons diagnose, treat and manage a galaxy of conditions, all affecting the most complex mechanism we know: the brain. Among the injuries that can affect the brain, subdural hematomas are among the more common, and range from mild, or even asymptomatic, to potentially life-threatening. Now, as Torrance Memorial Medical Director of Neurosurgery Paula Eboli, M.D., explains, there’s a new way to treat this affliction.

What is a subdural hematoma?

A subdural hematoma (SDH) is bleeding that has occurred inside the bone, underneath the dura [one of the membranes that surrounds and protects the brain] but outside the brain itself. There are both acute and chronic SDHs. Acute SDHs refer to bleeding that has occurred recently, while chronic SDHs are essentially the evolution of the acute SDH over time: there was bleeding there at some point, and now that bleeding has evolved into a mix of blood and fluid. Clots can range in size from a few millimeters to more than a centimeter.

What causes an SDH?

Sometimes when we diagnose a chronic SDH, the patient can identify a trauma that may have caused it – a fall or some other injury to the head ­– but SDHs can be spontaneous, too. Anything that causes bleeding in the area between the dura and brain can lead to an acute SDH, and can then evolve into a chronic SDH over a period of some weeks.

Are there any risk factors associated with SDHs?

Older individuals tend to be more prone to SDHs because they are more likely to bleed. Also, as we age our brains shrink,; this means there’s more room between the bone and the brain, and this can make bleeding into the subdural space easier. Other risk factors for SDHs include antiplatelet and anticoagulant medications, a history of falls, trauma to the head and alcoholism.

How can SDHs affect the brain?

When an SDH is acute the area of bleeding is usually small, but when the clot starts to dissolve, typically weeks after the initial bleeding occurred, it liquifies and becomes larger; potentially causing pressure against the brain. The effects of the pressure can range from no symptoms at all to headaches, seizures, numbness or weakness, amongst other symptoms, depending on the size of the hematoma and the area of the brain that is being compressed. If the hematoma is large it can even cause brain herniation, where the pressure causes brain tissue to shift. That is potentially life threatening.

How are SDHs diagnosed?

In asymptomatic patients they often are what we call incidental findings. We run a brain scan for a different reason – for example, after a fall or other potential trauma to the head – and the scan reveals a chronic SDH. Usually it’s a CT scan – that’s the scan we typically order in a routine case – but it could be an MRI, too. That said, we do also order scans when we suspect a chronic SDH or a similar condition affecting the brain is causing symptoms the patient is having.

Are there any early symptoms or warning signs to watch out for?

Chronic SDHs can cause headaches, loss of balance, numbness, weakness confusion, etc., but those symptoms may also be related to different conditions. When we order a CT scan or MRI in these cases, we’re trying to find out exactly what is causing the symptoms.

What are the treatment options for chronic SDHs?

If they’re small and asymptomatic, often we opt to just monitor them – the clots do usually clear on their own with time. If they are causing symptoms, there are two treatment options. The more traditional is craniotomy and evacuation of the SDH. In patients with mild symptoms and not a significant mass effect, middle meningeal artery (MMA) embolization is an option. Often the two are performed either before or after each other.

What does craniotomy and evacuation entail?

This essentially drains the SDH. This procedure can carry a high recurrence rate, between approximately 5% and 20%. Recurrence happens for different reasons but sometimes after the hematoma is drained, the brain does not re expand quickly and a cavity remains where the hematoma was. There can be rebleeding into the cavity, forming a recurrent SDH.

What is middle meningeal artery embolization?

MMA is an endovascular procedure. We guide a catheter from an access point in the wrist or groin up through the common carotid artery, into the external carotid artery and then into the middle meningeal artery. Then we embolize – we block – the middle meningeal artery, decreasing blood supply to the membrane adjacent to the SDH. This prevents discharge of fluid into the subdural cavity, allowing the body to slowly reabsorb the subdural hematoma. It takes a while to see results from this procedure ­– two, four, or even six weeks – so it’s for cases where the symptoms are not severe, and we can wait for the chronic SDH to clear up on its own potentially preventing any additional bleeding.

How do the two procedures work together?

MMA by itself is generally indicated for those with mild symptoms, and hematomas that are small or moderate in size with no significant mass effect. This procedure can also be performed as an adjunct to surgical intervention to prevent recurrence, which can happen with an evacuation. On the other hand, an evacuation clears the hematoma immediately, and can treat larger hematomas, so the two procedures are complementary: the evacuation removes the existing hematoma, and the MMA helps to prevent recurrence.

For how long have you been doing these procedures?

We’ve been performing MMAs at Torrance Memorial for over a year now. It’s a fairly new procedure, and there are still ongoing trials, but there is a lot of data that support it. Performing an MMA embolization requires a neurointerventionalist, as well as a surgical team to support the procedure and a surgical angio suite equipped for it. We have a state-of-the-art suite, as well as neurointerventionalists and other medical staff to perform MMAs. Patients remain in the hospital ICU overnight before being released. Chronic SDHs are pretty common, so the ability to treat them with MMA embolization is really a benefit for our population.