Chronic subdural hematoma: the dementia-like condition that surgery can often reverse

Maybe you are the one searching, not the patient: an elderly parent has become confused over a few weeks, started dragging a leg, "suddenly got old" — and a CT scan found a chronic subdural hematoma. Here is the fact families most need first: among the conditions that can make an older person decline this way, this is one of the most treatable. The standard treatment for chronic subdural hematoma in elderly patients is burr hole surgery — a small drainage procedure usually done under local anesthesia — and many patients improve dramatically within days. It is sometimes called the "treatable dementia," because symptoms that looked like dementia can lift once the fluid is drained. About 1 in 10 come back and need a second drainage; and if things worsen sharply over hours to a day or two, treat it as an emergency — the box above tells you when.

What a chronic subdural hematoma is

"Chronic subdural hematoma" means a collection of old, liquefied blood and fluid that has built up slowly in the space between the brain and its tough outer membrane (the dura). The word chronic simply means it formed gradually — over weeks — which is what sets it apart from the acute subdural hematoma seen right after a serious head injury.

The trigger is often a minor head knock — bumping a door frame, a small fall — that happened weeks to months earlier and that the patient may not even remember. Because the brain shrinks slightly with age, the small bridging veins on its surface are stretched, and a trivial injury can start a slow ooze that grows over weeks. This is why it is, above all, a condition of older adults — and why it is so often mistaken, at first, for ordinary aging or dementia.

Symptoms — slow, and easy to mistake for aging

Because the fluid builds up over weeks, the symptoms creep in rather than strike, which is exactly why they are so often put down to "just getting old." There is usually no single dramatic moment. The common features are:

• confusion, memory trouble, apathy, or a flattened personality — the "dementia-like" picture
• unsteady walking, a wide or shuffling gait, and falls
• weakness or clumsiness on one side of the body (an arm or a leg)
• headache, often mild but persistent
• slurred speech or trouble finding words
• daytime drowsiness

Two things matter here. First, which symptoms appear depends on where the fluid is pressing and on which side (it can be one side or both). Second — and this is the key distinction of this whole page — the pace tells you something. A decline unfolding over weeks (not years) in an older person is one of the patterns that should prompt a scan, because it can be this, and this is treatable. When symptoms instead worsen sharply over hours to a day or two, that is a different and more urgent situation — see When to seek help immediately, below.

Causes and risk factors

The mechanism is a slow one. On the surface of the brain, small bridging veins tear slightly and ooze; because an older brain has shrunk a little, there is more room for fluid to collect and more stretch on those veins, so even a light knock can start the process. The collection then enlarges over weeks, partly because the membrane that forms around it grows fragile, leaky vessels of its own. The risk factors fall into two groups: the medical ones that can be acted on, and the ones that are simply background.

Medical / modifiable:

• Blood-thinning medication (anticoagulants and antiplatelet drugs) — a major risk factor, and one that also shapes how surgery is timed.
• Heavy alcohol use — linked both to falls and to the brain changes that raise the risk.

Background (not modifiable):

• Older age — the risk climbs steeply after about 70. In Japan's national database, chronic subdural hematoma is overwhelmingly a disease of older adults.
• Male sex — it is roughly two to three times more common in men.
• Brain atrophy — from age, and also from long-standing heavy drinking, which is why those two overlap.

None of these condemns a hematoma to grow or to need surgery — they lean on the odds, nothing stronger. How they play out for one patient is a question for the doctor who can see the scans.

Tests and diagnosis — what each one shows

The diagnosis is usually quick and clear-cut.

• Head CT — the workhorse. A non-contrast CT takes only minutes, needs no dye, and shows the collection of fluid, which side(s) it is on, how large it is, and whether it is pushing the brain across the midline. For an older person who has declined over weeks, this is the single most useful test — and it is why doctors reach for it.
• MRI — sometimes added to judge the age of the blood, to study both sides in detail, or when the picture is not clear-cut on CT.

Because the scan answers the question so directly, the hardest part is usually not the imaging but the decision to do it. That is why the "decline over weeks in an older person" pattern is worth taking seriously rather than waiting it out.

How Japan typically treats it

Japan, as one of the world's most aged societies, sees an enormous number of these cases — a national administrative database study analyzed more than 63,000 Japanese cases, and drainage of a chronic subdural hematoma is among the most frequently performed operations in Japanese neurosurgery. The typical approach looks like this:

• Small and symptom-free: observation is legitimate. A thin hematoma causing no symptoms may simply be followed with repeat CT, because some resolve on their own.
• Causing symptoms: burr hole surgery. Through a small scalp incision, an opening about the size of a coin is made in the skull, the old fluid is washed out, and a soft drain is usually left in place for a day or so. It is commonly done under local anesthesia with light sedation, typically takes under an hour, and — importantly for the very elderly — avoids the risks of general anesthesia. Hospital stays in Japan are commonly around one to two weeks, shorter in some centers — a reflection of a cautious inpatient follow-up culture that keeps a close eye on the very elderly rather than a sign of a bigger operation.
• A Japanese habit you may not see elsewhere: Kampo medicine. Many Japanese neurosurgeons prescribe goreisan, a traditional herbal (Kampo) medicine thought to help fluid reabsorb, either alongside surgery or for small hematomas under observation. I should be honest about the evidence: a multi-center randomized trial (Journal of Neurotrauma, 2018) did not show a statistically significant reduction in recurrence. It is widely used and well tolerated, but it is an adjunct with limited proof — not a substitute for surgery when surgery is needed.

The honest part: about 1 in 10 come back

Burr hole surgery works, but the fluid re-accumulates in roughly 10% of patients (reports range from about 5% to 20%), typically within the first few months. A recurrence is usually handled with a second drainage — frustrating, but rarely dangerous when caught early, which is why follow-up scans matter.

This is also where the field has genuinely moved in the last few years. A catheter procedure called middle meningeal artery (MMA) embolization blocks the small artery that feeds the hematoma's leaky membrane. Two randomized trials published in the New England Journal of Medicine — EMBOLISE (2024) and STEM (2025) — tested adding it to the initial operation, not as a treatment for a hematoma that has already come back, and found it lowered the later reoperation rate: in EMBOLISE, from about 11% to about 4%, with STEM pointing the same way and earlier systematic reviews agreeing. Using embolization for hematomas that have already recurred, or that carry a high risk of doing so, is a separate, increasingly common real-world practice — though how far to widen the indication is still being worked out. It is not yet routine everywhere, in Japan as elsewhere.

Outlook and follow-up

For most people this is one of the more hopeful stories in neurosurgery. After a symptomatic hematoma is drained, many patients improve markedly within days — steadier on their feet, clearer in their thinking — and a good number return close to how they were before. Two honest qualifiers belong here:

• Not every symptom is from the fluid. If part of the decline was underlying dementia or an old stroke, draining the hematoma lifts only the part the fluid was causing.
• Recurrence is common enough to watch for (about 10%, as above), so follow-up imaging matters. A repeat CT in the weeks after surgery is usual, and any return of symptoms prompts another look.

Recovery in the very elderly can be slower, and some need a period of rehabilitation to get walking again. The individual outlook depends on age, general health, how long the symptoms were present, and how much of the decline the hematoma was actually causing — best judged by the treating team following the case.

Everyday life during recovery and observation

Two situations come up. If a small hematoma is being observed rather than operated on, life generally continues, with attention to two things: avoiding another head injury — falls are the main enemy in this age group — and reviewing any blood-thinning medication with the prescribing doctor. If surgery has been done, most people are up and walking within days, and ordinary activity resumes gradually as the surgeon advises.

Falls prevention deserves a special mention, because both the trigger and the recurrence so often involve a knock to the head. Keeping the home safe — good lighting, removing trip hazards, handrails, and reviewing medications that cause dizziness — is one of the few things a family can act on directly. Reducing heavy alcohol use helps on both counts, since it raises the risk and contributes to falls. Specific limits on driving, work, and exercise depend on how much has recovered and belong with the treating doctor.

When to seek help immediately

Keep this section within reach for the moments when you cannot tell what you are looking at. A chronic subdural hematoma has two speeds, and they call for two different responses.

Worsening over hours to a day or two — treat it as an emergency. If an older person with a known or suspected hematoma shows any of the following coming on sharply, put the reading aside and get care the same day — call your local emergency number or go straight to an emergency department. These can mean the hematoma is enlarging and pressing dangerously on the brain:

• progressing weakness or paralysis on one side — a worsening facial droop, or an arm or leg giving way
• a sudden drop in alertness — hard to wake, very drowsy, far more confused than before, or unresponsive
• repeated vomiting
• a new seizure
• a rapid worsening of walking, or a sudden inability to stand or walk
• (and, as with any brain emergency, a sudden severe headache)

Slow, dementia-like change over weeks — see a doctor soon, but don't wait it out for months. The more common presentation is quieter and easy to blame on aging: gradual confusion, apathy, mild unsteadiness, or a persistent dull headache developing over weeks. This is not a call-an-ambulance situation — but it should not be left to drift, either. Arrange a prompt medical assessment, because a head CT can settle it quickly, and if it is a hematoma, it is treatable.

And if you cannot tell which speed you are seeing, let a doctor make that call rather than the calendar.

The decision, honestly framed

Compared with most brain surgery, the stakes here are inverted: the operation is small, and the cost of not treating a symptomatic hematoma — pressure on the brain of an already frail person — is usually the larger risk. That said, three honest caveats belong in any family's thinking. First, not every symptom reverses: if some of the decline is underlying dementia or a prior stroke, draining the fluid fixes only the part the fluid was causing. Second, blood thinners cut both ways — they usually must be paused for surgery, yet they are often protecting the heart or preventing stroke, and the timing of restarting them is a genuine judgment call between doctors. Third, recurrence is common enough that one operation is sometimes not the end of the story. None of this changes the headline — this is one of the most rewarding conditions a neurosurgeon treats — but families decide better knowing the full shape of it.

Questions worth taking back to the doctor

Frequently asked questions

Could my parent's confusion be a chronic subdural hematoma instead of dementia?

It is possible, and it is exactly why doctors order a head CT when an older person declines over weeks rather than years. A chronic subdural hematoma can mimic dementia — confusion, apathy, unsteady walking — but unlike most dementias it is often reversible with surgery. Only imaging can tell the two apart, so a prompt medical assessment is the right first step.

What warning signs mean we should go to the emergency room right away?

Chronic subdural hematoma usually changes slowly, but a sharp worsening over hours to a day or two is a red flag. Seek emergency care the same day if an older person develops progressing weakness or paralysis on one side, becomes suddenly very drowsy or hard to wake, vomits repeatedly, has a new seizure, or rapidly loses the ability to walk. These can signal the hematoma enlarging. Slow, dementia-like changes over weeks are less urgent but still deserve a prompt medical assessment rather than months of waiting.

Is burr hole surgery safe for someone in their 80s or 90s?

It is generally considered one of the least invasive, best-tolerated operations in neurosurgery: a small opening in the skull, commonly done under local anesthesia with sedation, typically in under an hour. Age alone rarely rules it out — surgeons operate on patients in their 90s when the hematoma is causing symptoms. The individual risks still depend on overall health and medications, which is a discussion for the treating team.

How often does a chronic subdural hematoma come back after surgery?

Roughly 10% of patients (reports range from about 5% to 20%) need a repeat procedure because fluid re-accumulates. A recurrence is usually treated with a second drainage. Separately, a catheter procedure called middle meningeal artery embolization has emerged: randomized trials (EMBOLISE and STEM) tested adding it to the initial surgery — not as a treatment for recurrence — and found it lowered the later reoperation rate, in EMBOLISE from about 11% to about 4%. Using it for hematomas that have already come back, or that are at high risk, is becoming an option too, though how far to widen the indication is still being worked out. It is not yet offered at every hospital, so availability is worth asking about.

My parent takes blood thinners. How does that change things?

Blood thinners (anticoagulants and antiplatelet drugs) are a major risk factor for chronic subdural hematoma, and they usually need to be paused around surgery. The difficult question is when to restart them, because they are often protecting the heart or preventing stroke. There is no universal answer — it is a case-by-case balance struck between the neurosurgeon and the prescribing doctor, and it is one of the most important questions a family can ask.

Can I discuss my parent's situation with a Japanese neurosurgeon online?

Yes. Japan Medical Bridge arranges one-on-one video consultations in English with a Japanese neurosurgeon, where you can hear how cases like your parent's are commonly managed in Japan. The session offers background, not a diagnosis or medical advice — treatment decisions belong to your family and the treating doctors.