What Causes Seizures in Elderly With No History?

Cerebrovascular disease, particularly stroke, is the single most common cause of new-onset seizures in older adults who have never had one before. But it is far from the only trigger. Neurodegenerative conditions like Alzheimer’s disease, metabolic disturbances, medication side effects, head injuries from falls, brain tumors, and even autoimmune inflammation can all provoke a first seizure after age 60. People in this age group actually have the highest rate of new-onset epilepsy of any demographic, which surprises many who think of seizures as primarily a childhood problem.

Why Seizures Become More Common With Age

The aging brain accumulates vulnerabilities. Blood vessels stiffen and narrow, neurons gradually decline, the blood-brain barrier becomes leakier, and the body’s ability to regulate electrolytes and clear medications slows down. Each of these changes independently lowers the threshold at which brain cells fire abnormally. People over about 60 face a sharply increasing risk of both one-off symptomatic seizures and ongoing epilepsy, and the growing size of the older population means more people are affected every year.¹ An international task force on epilepsy in older adults confirmed this pattern across wealthier countries, though noted it is less consistently observed in lower-income settings, possibly due to differences in the types of diseases people survive into old age and how thoroughly seizures get detected.²

One important distinction matters for everything that follows: a single seizure triggered by an identifiable, reversible problem (like a sodium crash or a medication reaction) is called an acute symptomatic seizure. It does not mean the person has epilepsy. Epilepsy involves recurrent, unprovoked seizures or a high likelihood of recurrence. Many first seizures in older adults turn out to be acute symptomatic events that resolve once the underlying trigger is corrected.³

Stroke and Cerebrovascular Disease

Stroke is the dominant cause of late-life seizures, accounting for the largest share of identifiable cases. Both ischemic strokes (blocked blood flow) and hemorrhagic strokes (bleeding in the brain) can trigger seizures, but the timing matters. Seizures that happen within the first week or so of a stroke tend to be brief, focal, and driven by the acute metabolic chaos the stroke creates in surrounding brain tissue. Once that acute phase resolves, these early seizures often do not return.⁴

Late post-stroke seizures are a different story. These appear months or even years after the stroke and stem from permanent structural scarring in the brain that creates a focus of abnormal electrical activity. The majority of people who develop late post-stroke seizures go on to have recurrent episodes, meaning they develop epilepsy. This is one reason doctors pay close attention to any seizure-like event in someone with a history of stroke, even a mild one the person may not remember having.

What catches many families off guard is that a person can have “silent” cerebrovascular disease, small strokes or chronic small-vessel damage that never produced obvious symptoms, yet still have enough accumulated brain injury to provoke a seizure. Early seizures after stroke have also been linked to a roughly fourfold higher risk of developing dementia within three years, suggesting that post-stroke seizures may be a marker of broader brain vulnerability.⁵

Alzheimer’s Disease and Other Neurodegenerative Conditions

Alzheimer’s disease is a recognized risk factor for seizures, though the connection is underappreciated by both patients and clinicians. The neurodegeneration itself creates an imbalance between excitatory and inhibitory circuits in the brain, which can tip certain networks into seizure activity.⁶ Research in animal models of Alzheimer’s has shown that the hallmark protein deposits, amyloid and tau, are linked to cortical hyperexcitability that may actually precede noticeable memory loss.⁷

This means a seizure in an older adult could, in some cases, be an early signal of a neurodegenerative process that has not yet been diagnosed. The relationship runs both directions: people with epilepsy are more likely to develop dementia, and people with certain forms of dementia, particularly Alzheimer’s and vascular dementia, are at significantly higher risk of developing epilepsy.⁸ This bidirectional link makes cognitive screening especially important when an older adult presents with a first seizure, even if they seem mentally sharp.

Metabolic Disruptions and Electrolyte Problems

Older adults are particularly vulnerable to metabolic seizures because their kidneys and hormonal systems are less efficient at maintaining the body’s chemical balance. Acute electrolyte imbalances can provoke seizures as their sole symptom, with no other warning signs. The most frequent culprits are low sodium (hyponatremia), low calcium, and low magnesium.⁹

Low sodium is especially common in older people and can be triggered by common medications like certain diuretics (water pills) and antidepressants. Dehydration, which older adults are prone to because thirst signals weaken with age, can concentrate or dilute electrolytes unpredictably. Kidney disease, liver failure, and severely uncontrolled blood sugar (either very high or very low) can all cross the seizure threshold as well.

The good news is that metabolic seizures are often entirely reversible. Once the underlying chemical imbalance is corrected, the seizures stop and do not recur, as long as the metabolic problem does not return. These do not count as epilepsy and usually do not require long-term seizure medication.

Medications and Substance Withdrawal

The sheer number of medications older adults take creates a minefield for seizure risk. Some drugs directly lower the seizure threshold, meaning they make the brain more susceptible to abnormal electrical activity. Common offenders include certain antibiotics (fluoroquinolones like ciprofloxacin, carbapenems), some antidepressants (particularly bupropion and tricyclics at high doses), antipsychotics, and the pain medication tramadol. Even drugs not traditionally thought of as neurological, like the immunosuppressants used after organ transplant, can provoke seizures.

Withdrawal from alcohol and benzodiazepines (medications like diazepam or lorazepam commonly prescribed for anxiety or sleep) is another well-recognized seizure trigger in this age group.¹⁰ An older person who has been taking benzodiazepines for years and suddenly stops, whether intentionally or because they forgot to refill a prescription, can develop life-threatening withdrawal seizures. Similarly, a long-term heavy drinker who abruptly stops consuming alcohol faces the same risk. These withdrawal seizures can occur even in someone who has never had a seizure in their life.

Age-related declines in kidney and liver function also change how drugs are processed. A medication dose that was safe at age 50 may build up to toxic levels at age 75 because the body clears it more slowly. This slow drug accumulation is an underrecognized source of first seizures in elderly patients, especially when multiple medications interact with each other.

Falls and Traumatic Brain Injury

Falls are the most common cause of traumatic brain injury in older adults, since both balance and protective reflexes degrade with age.¹¹ When an older person falls and hits their head, the aging brain is more vulnerable to damage than a younger one. Brain atrophy that happens naturally with aging means there is more space between the brain and the skull, which allows the brain to move more during impact. This makes subdural hematomas (blood collecting between the brain and its outer covering) and contusions more common in older people after even relatively minor falls.

A seizure can follow a head injury by days, weeks, or months. In some cases the initial fall seemed minor enough that no one sought medical attention, only for a seizure to appear later as a slow bleed or scar tissue develops. Anticoagulant medications (blood thinners), which are extremely common in older adults with heart conditions, increase the risk of intracranial bleeding after head trauma and therefore indirectly raise the seizure risk after a fall.

Brain Tumors

Both primary brain tumors and metastases (cancers that have spread to the brain from elsewhere in the body) can cause first-time seizures in older adults. Tumors irritate surrounding brain tissue and disrupt normal electrical signaling. In some cases, a seizure is the first symptom that reveals a previously unknown tumor. Slower-growing tumors like meningiomas are more common in older adults and may be present for years before they grow large enough to trigger a seizure. Metastatic brain lesions from lung, breast, or skin cancers are another important consideration, since the incidence of many cancers rises with age.³

Autoimmune Encephalitis

One of the more recently recognized causes of late-life seizures is autoimmune encephalitis, a condition where the immune system mistakenly attacks proteins in the brain. This has emerged as an important diagnosis to consider in older adults whose seizures cannot be explained by stroke, tumor, or metabolic problems.¹²

In one study of 225 patients with late-onset seizures, about 4% met criteria for definite autoimmune encephalitis based on specific antibodies found in their spinal fluid and blood. Several antibody types were identified, and in some cases the autoimmune attack was driven by an underlying cancer that had not yet been diagnosed. Three patients in that study were newly found to have small cell lung cancer after the antibody testing pointed toward a paraneoplastic process.¹³ While 4% may sound small, it matters enormously for those individuals because autoimmune encephalitis is treatable with immunotherapy, and missing the diagnosis means ongoing seizures and cognitive decline that could have been prevented.

Sleep Apnea and Nighttime Oxygen Drops

Obstructive sleep apnea is extremely common in older adults and has been linked to seizure risk through a mechanism most people would not think of: repeated drops in blood oxygen levels during sleep. Several pathways have been proposed, including direct oxygen deprivation to the brain, reduced cardiac output during apneic episodes, and fragmented sleep that activates abnormal electrical activity.¹⁴

A large community-based study found that people whose oxygen saturation dipped below 80% during sleep had roughly a threefold higher risk of developing late-onset epilepsy compared to those without such drops, and this association held even after accounting for other risk factors like stroke, diabetes, and dementia.¹⁵ Interestingly, the overall severity of sleep apnea (measured by the standard apnea-hypopnea index) did not predict seizure risk. It was specifically the depth of oxygen desaturation that mattered. This suggests that treating sleep apnea aggressively, particularly preventing severe oxygen dips, could potentially lower seizure risk in vulnerable older adults.

Why Seizures in Older Adults Are Easily Missed

Many people picture a seizure as a dramatic convulsion with loss of consciousness and full-body shaking. That type does occur in older adults, but a surprising number of seizures in this age group look nothing like it. Nonconvulsive status epilepticus, a condition where the brain is in continuous seizure activity without obvious convulsions, is particularly tricky. Its symptoms can include confusion, personality changes, difficulty speaking, subtle repetitive movements, or simply staring blankly. In an older person, these signs are easily attributed to a urinary tract infection, a medication side effect, “just getting old,” or early dementia.¹⁶

This diagnostic challenge is compounded by the fact that older patients often have multiple medical problems that produce overlapping symptoms. A person with pre-existing cerebrovascular disease, mild cognitive impairment, and several medications may present with confusion that has four plausible explanations, and seizure may not be the first one anyone considers. An EEG (electroencephalogram) is needed to confirm nonconvulsive seizure activity, but getting timely access to EEG monitoring can be difficult, especially outside large medical centers.

What Happens After a First Seizure

When an older adult has a first seizure, the diagnostic workup typically starts with a CT scan to quickly rule out emergencies like bleeding or a large mass. If that initial scan is negative, MRI offers a much more detailed look at the brain and is recommended as the follow-up imaging study.¹⁷ Blood tests check for metabolic and electrolyte abnormalities, kidney and liver function, glucose levels, and medication levels. An EEG records the brain’s electrical activity looking for patterns that suggest a seizure focus or ongoing subclinical seizures. In certain cases, a lumbar puncture (spinal tap) may be performed to check for infection or autoimmune antibodies.

A question families often face is whether a single seizure needs to be treated with long-term medication. In one retrospective study, about a quarter of older patients who had a first seizure experienced a recurrence within one year, and about a third within two years. Starting anti-seizure medication cut the risk of recurrence roughly in half. Doctors frequently started medication even when imaging and EEG were unrevealing, suggesting that clinicians often weigh the potential consequences of another seizure in a frail older person (falls, fractures, injury) heavily in their decision-making.¹⁸

Treatment Challenges in Older Adults

Choosing the right seizure medication for an older person is considerably more complicated than for a younger adult. Many anti-seizure medications demonstrate similar effectiveness at controlling seizures, so the deciding factors tend to be side effects, drug interactions, and how well the person tolerates the treatment. Older adults are more vulnerable to side effects like dizziness, drowsiness, falls, bone loss, and cognitive dulling, all of which can seriously affect quality of life and independence.¹⁹

Drug interactions pose a particular problem. Older enzyme-inducing medications like carbamazepine and phenytoin can interfere with blood thinners, heart medications, and chemotherapy drugs. Newer agents like levetiracetam and lamotrigine tend to have fewer interactions but come with their own concerns. Levetiracetam can cause irritability and behavioral changes, while lamotrigine requires very slow dose increases to avoid a dangerous skin reaction. Current evidence favors starting at lower doses than in younger adults and increasing slowly, because the aging body processes these drugs more slowly and reaches effective blood levels at lower doses.

Cognitive Impact and the Link to Dementia

A first seizure in later life is not just a neurological event to manage in the moment. It may also be a signal of broader cognitive vulnerability. Research on people with late-onset unexplained seizures (where no clear cause is found) has shown that these individuals are more likely to have subtle cognitive impairment, particularly in verbal memory, compared to age-matched peers without seizures.²⁰ The same study found lower volumes in the amygdala, a brain structure involved in memory and emotion, suggesting underlying neurodegeneration that had not yet crossed the threshold for a clinical dementia diagnosis.

The bidirectional relationship between epilepsy and dementia described earlier has practical implications for follow-up care. After a first seizure, cognitive monitoring over subsequent years can catch emerging decline early, when interventions to support daily functioning and plan for the future are most useful. It does not mean that everyone who has a late-life seizure will develop dementia, but the risk is elevated enough that it deserves attention.

Mortality and the Stakes of Getting It Right

The broader health implications of new-onset epilepsy in older adults are sobering. A large study found a five-year mortality rate of about 63% for older adults diagnosed with incident epilepsy, a figure driven largely by the serious underlying conditions (stroke, dementia, cancer) that caused the seizures in the first place rather than by the seizures alone.²¹ This does not mean seizures themselves are a death sentence, but it underscores that a first seizure in an older person is a red flag that demands thorough investigation. The seizure is often the visible tip of a larger iceberg, and what matters most is identifying and treating whatever lies beneath it.