What causes sudden onset seizures in the elderly?

New-Onset Seizures in the Elderly: Etiologies and Evaluation

The most common causes of new-onset seizures in elderly patients are cerebrovascular disease (stroke and small vessel disease), cerebral atrophy, neurodegenerative disorders, brain tumors, and metabolic disturbances, with cerebrovascular disease being the leading structural cause. 1, 2

Primary Structural Causes

Cerebrovascular Disease (Most Common)

• Stroke and cerebrovascular disease are the leading identifiable causes of late-onset seizures in elderly patients, accounting for the majority of cases with identified etiology 1, 2
• Small vessel disease and chronic cerebral ischemia contribute significantly to seizure risk in this population 2
• Cerebral atrophy, often related to chronic vascular changes, is frequently identified on neuroimaging 2

Brain Tumors

• Primary and metastatic brain tumors represent an important cause of new-onset seizures in the elderly, particularly in patients without vascular risk factors 1, 2
• Brain imaging reveals potentially epileptogenic abnormalities in approximately 59% of elderly patients with first unprovoked seizures 2

Neurodegenerative Disorders

• Primary neurodegenerative disorders including Alzheimer's disease and other dementias increase seizure risk 1
• The relationship between neurodegeneration and epilepsy is bidirectional and increasingly recognized 1

Traumatic Brain Injury

• Head trauma, including remote injuries, can manifest as new-onset seizures years after the initial insult 1
• Falls are common in the elderly and may result in subdural hematomas or other traumatic lesions 1

Metabolic and Acute Symptomatic Causes

Electrolyte Abnormalities

• Hyponatremia, hypocalcemia, and hypomagnesemia are significant seizure triggers that must be identified and corrected 3
• Hypocalcemia can trigger seizures at any age, even in patients with no prior seizure history 3
• Hyperglycemia and other glucose abnormalities can provoke seizures 3

Medication-Related Causes

• Non-compliance with antiseizure medications in patients with known epilepsy significantly increases recurrence risk 3
• Certain prescribed medications lower seizure threshold, with tramadol being a notable example 3
• Polypharmacy in elderly patients increases risk of drug interactions that may precipitate seizures 4

Other Metabolic Factors

• Uremia and renal dysfunction can cause provoked seizures 3
• Endocrine disorders including hypoparathyroidism and hypothyroidism may contribute through associated electrolyte disturbances 3

Critical Diagnostic Approach

Immediate Neuroimaging

• The American College of Emergency Physicians recommends performing neuroimaging of the brain in the ED for patients with first-time seizures 5
• Urgent neuroimaging is particularly indicated when there is history of malignancy, immunocompromise, anticoagulation therapy, new focal deficits, or age older than 40 years 5

Essential Laboratory Testing

• Obtain serum glucose and sodium levels on all patients with first-time seizures 6
• Check calcium, magnesium, and renal function to identify metabolic causes 3
• Pregnancy testing for women of childbearing age 6

EEG Findings

• Abnormal EEGs are present in approximately 26% of elderly patients with first seizures, with higher rates in the late-onset group 2
• However, EEG abnormalities are less common than in younger patients, and normal EEG does not exclude epilepsy 2

Clinical Presentation Nuances

Seizure Semiology in the Elderly

• Elderly patients most commonly present with focal seizures with impaired consciousness (55.9%), which are often subtle and may be missed 7, 2
• Younger patients more typically have focal to bilateral tonic-clonic seizures 2
• Status epilepticus occurs in approximately 10% of cases, more commonly in late-onset seizures 2

Recognition Challenges

• Seizures in older adults are often so subtle they are not recognized or treated, yet 25% of first-time seizures occur in this age group 7
• Post-ictal confusion may be attributed to dementia or delirium rather than recognized as seizure-related 7

Important Caveats

• Once an older adult has one seizure, they are at significantly higher risk for recurrent seizures and epilepsy diagnosis 7
• The incidence of epilepsy peaks in the elderly population, now representing the third most common neurologic problem in this age group 8
• Cryptogenic cases (unknown cause despite workup) remain common, though less so than in younger patients 2, 4
• In-hospital mortality can occur, with nine patients dying during follow-up in one recent study of late-onset seizures 2