The Leading Cause: Cerebrovascular Disease
For patients over 65, the brain becomes more vulnerable to various insults, making new-onset seizures more likely to be symptomatic, meaning they are caused by an underlying condition. Leading the list of these conditions is cerebrovascular disease, particularly stroke. A stroke, whether ischemic (caused by a blood clot) or hemorrhagic (caused by a bleed), damages brain tissue, disrupting normal electrical activity and creating an 'epileptic focus'.
Studies show that seizures can occur both shortly after a stroke (early-onset) or months to years later (late-onset epilepsy). The risk of developing late-onset epilepsy is markedly increased when the stroke affects the cerebral cortex. Hemorrhagic strokes have also been associated with a higher incidence of seizures compared to ischemic strokes. Early identification of a seizure after a stroke is critical, as it can indicate a greater risk of future seizures and warrants careful management.
Other Common Underlying Causes
While stroke is the most prevalent, several other conditions contribute significantly to new-onset seizures in the elderly. A comprehensive evaluation is essential to pinpoint the correct etiology and develop an appropriate treatment plan.
Traumatic Brain Injury (TBI)
Head trauma accounts for a substantial percentage of late-onset epilepsy, with the incidence of falls and other head injuries increasing with age. Even a seemingly minor head injury can lead to a seizure, especially if the individual is on blood thinners. The resulting damage can lead to gliosis (scar tissue formation), which can irritate the surrounding brain tissue and trigger seizures long after the initial injury has healed.
Brain Tumors
Both primary brain tumors and metastases from other cancers can cause seizures in older adults, and they are the second most common cause after stroke. Seizures are often the first presenting symptom of a brain tumor, making a neurological evaluation crucial for any senior experiencing a new-onset seizure. The location and type of tumor can influence seizure risk, with low-grade and cortical tumors being particularly prone to causing electrical disturbances.
Neurodegenerative Diseases
Progressive conditions like Alzheimer's disease and other dementias are increasingly recognized as risk factors for late-onset seizures and epilepsy. Research suggests a bidirectional relationship between AD and epilepsy, with seizures potentially accelerating cognitive decline. Seizures in these patients can be subtle, sometimes manifesting as unusual behaviors or confusion, and may go unrecognized.
Metabolic and Toxic Causes
Acute metabolic disturbances are a common precipitating factor for seizures in older hospitalized patients.
- Electrolyte imbalances: Hyponatremia (low sodium) and hypocalcemia (low calcium) are frequent triggers.
- Blood sugar extremes: Both hypoglycemia (low blood sugar) from insulin use and nonketotic hyperglycemia can induce seizures, particularly in diabetic patients.
- Drug-related: Withdrawal from alcohol or sedative medications, as well as certain drugs that lower the seizure threshold (e.g., some antibiotics, antidepressants), can cause seizures.
The Role of a Neurological Workup
Given the varied causes and often subtle presentation of seizures in the elderly, a thorough diagnostic workup is essential. This may include:
- Detailed Medical History: Collecting information from both the patient and caregivers is vital, as memory issues in seniors can obscure details of the event.
- Electroencephalogram (EEG): A routine EEG is a first step, but a longer ambulatory or video EEG may be necessary to capture infrequent seizure activity.
- Brain Imaging: High-quality brain imaging, such as an MRI, is critical to identify structural causes like a stroke, tumor, or old head injury.
- Blood Tests: Screening for metabolic imbalances is standard procedure to rule out toxic or metabolic causes.
Seizure Presentation: Older vs. Younger Patients
| Feature | Older Adults (over 65) | Younger Adults |
|---|---|---|
| Primary Cause | Predominantly symptomatic (e.g., stroke, tumor) | Often idiopathic or genetic |
| Type | More likely to be focal (partial) seizures | Often more generalized |
| Symptoms | Subtle, non-classic signs like confusion, dizziness, or odd sensations; often misdiagnosed | Classic auras and more overt tonic-clonic activity |
| EEG Results | Higher likelihood of a normal routine EEG, necessitating longer monitoring | More likely to show clear epileptiform discharges on routine EEG |
| Postictal State | Can last for hours or even days, potentially misinterpreted as cognitive decline | Typically lasts minutes to an hour |
Navigating Treatment and Risks
Managing seizures in the elderly presents unique challenges. Anti-seizure medications (ASMs) may have different pharmacokinetics in older adults, and potential drug-drug interactions with other medications are a concern. Newer ASMs are generally preferred due to better tolerability and fewer side effects. The goal is to achieve seizure control while minimizing side effects and optimizing overall quality of life. Lifelong treatment is often recommended, especially for late-onset seizures linked to permanent structural brain abnormalities.
Conclusion: Prioritizing Neurological Assessment
In summary, while many factors can lead to a first-onset seizure in a patient over 65, cerebrovascular disease, particularly stroke, stands out as the most common underlying cause. Traumatic brain injury, brain tumors, and neurodegenerative disorders are also significant contributors. Due to the potential for subtle symptoms and misdiagnosis, a thorough neurological workup is essential for any senior with new-onset seizure activity. Early intervention targeting the underlying cause is the best way to prevent recurrence and improve long-term outcomes. For more detailed clinical guidelines on late-onset epilepsy management, a resource such as this review on the topic can be helpful: https://clue.mgh.harvard.edu/for-physicians/clinical-management-of-late-onset-unexplained-epilepsy/.
