Epilepsy in the Elderly — Definition, Pathophysiology, Clinical Features, Investigations and Treatment

Epilepsy in the Elderly — Definition, Pathophysiology, Clinical Features, Investigations and Treatment Definitions (ILAE / IBE)

An epileptic seizure is a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.

Epilepsy exists when a seizure is confirmed and the brain shows an enduring tendency to recur. It is diagnosed with: two unprovoked or reflex seizures more than 24 hours apart; OR one unprovoked seizure with a ≥60% probability of another over the next 10 years; OR an epilepsy syndrome.

A seizure provoked by a transient factor acting on an otherwise normal brain does not count towards a diagnosis of epilepsy.

Status epilepticus (SE): more than 30 minutes of continuous seizure activity, or intermittent seizures without full recovery of consciousness between them. Shorter operational durations are now proposed.

Refractory epilepsy: failure of adequate trials of two tolerated, appropriately chosen antiepileptic drug (AED) schedules to achieve sustained seizure freedom.

Epilepsy is the third most common neurological disorder in older age groups. Incidence follows a U-shaped curve, highest at both ends of life. 25% of new-onset seizures occur after age 65.

Prevalence of active epilepsy at age ≥75 is about 1.5% (twice that of younger adults); in nursing homes it exceeds 5%.

SE incidence in the elderly is almost double the general population (86/100,000/year), rising with age, highest at ≥85 years. Non-convulsive SE (NCSE) occurs more often in the very old and critically ill.

Acute symptomatic seizures: stroke 30–54%, metabolic/electrolyte imbalance 10–15%, tumours 10%, trauma 10%, drug-related 10%, CNS infection 2–3%.

Epilepsy: cryptogenic 48–50%, stroke 40–53% (single largest identifiable cause), dementia 5–20%, tumours 4– 19%, trauma 1–3%.

Mechanism: cortical/subcortical injury → gliotic scar → a hyperexcitable focus. In Alzheimer's disease, amyloid-driven network hyperexcitability raises seizure risk. Consider also autoimmune limbic encephalitis (VGKC/LGI1 antibodies) and Hashimoto's encephalopathy.

Seizure onset is focal in 62–68% and generalised in 27–39%; for established epilepsy, focal 65%, generalised 13%, unknown 22%.

Presentation is subtle — brief episodes of confusion, unexplained falls, or stereotyped movements, often misdiagnosed as non-specific confusional states.

Typical auras (fear, epigastric rising sensation, déjà vu) are less common; non-specific auras such as dizziness predominate. The seizure focus is more often extratemporal, especially frontal.

The postictal period is prolonged — lasting hours to days. Todd's paresis may mimic stroke.

NCSE presents as altered mental status ranging from mild disorientation to confusion or coma, uncharacteristic behaviour or aphasia. More than half occur with acute medical illness — organ failure, drug toxicity, alcohol/benzodiazepine withdrawal, metabolic disturbance.

Diagnosis is clinical, based on an eyewitness description. The major difficulty is that older patients often cannot give an accurate history.

EEG sensitivity falls with age: epileptiform transients occur less often, activation procedures add little, EEG is normal in about one-third, and non-specific focal slowing is common even without seizures. A sleep or nap EEG is advised if the awake study is negative.

Inpatient video-EEG is the gold standard for characterising events and distinguishing epileptic from psychogenic non-epileptic attacks (6–15% of "uncontrolled epilepsy").

Brain imaging in every patient — MRI preferred over CT as it is more sensitive for stroke, TBI and structural lesions. Add ECG (exclude arrhythmic syncope), glucose, electrolytes, calcium, renal and liver function, and drug review.

Differential diagnosis: syncope, limb-shaking TIA, transient global amnesia, transient epileptic amnesia, hypoglycaemia, REM sleep behaviour disorder, periodic limb movement disorder, hypnic jerks, delirium, psychogenic attacks.

Because recurrence risk is high, treat after the first confirmed unprovoked seizure, especially with a brain lesion or epileptiform EEG.

An ideal AED for the elderly has linear pharmacokinetics, minimal hepatic metabolism, minimal drug interaction and renal excretion, and minimal impact on cognition, memory or mood — no such drug exists.

Start low, titrate slowly, use monotherapy first-line. Older patients often respond to lower doses (e.g. valproate dose reduced by 30–40%).

Preferred agents: lacosamide, lamotrigine and levetiracetam — these have the greatest likelihood of seizure freedom at 6 and 12 months. Lamotrigine is better tolerated than carbamazepine.

Avoid: phenytoin, carbamazepine, phenobarbital, primidone, valproate and benzodiazepines — chronic toxicity, interactions and neurotoxicity in hypoalbuminaemia.

Match the drug to comorbidity: in depression avoid levetiracetam (irritability), topiramate, phenobarbital, primidone and vigabatrin. In Alzheimer's disease, treat after a second episode; avoid polytherapy, which impairs cognition.

Epilepsy is one of the top 10 conditions related to frailty. Assess falls risk and provide bone protection — AEDs increase fracture risk. Use STOPP/START and Beers criteria to manage polypharmacy.

SE algorithm (Pathy's Box 51.1): treat within 5–10 minutes; IV glucose if hypoglycaemic. First line — lorazepam 0.1 mg/kg IV (2 mg/min), or diazepam 10 mg over 2 min, or midazolam 10 mg IM; repeat once at 10 min. Second line (established SE) — phenytoin 15 mg/kg (max 20 mg/min, with cardiac and BP monitoring), or valproate 15–30 mg/kg if cardiovascular comorbidity, or levetiracetam 20–30 mg/kg over 15 min. Refractory — midazolam or propofol infusion, then general anaesthesia and ventilation.

Prognosis is good — most newly diagnosed older patients become seizure-free on first AED monotherapy. Failure to become seizure-free within the first year predicts drug resistance. Epilepsy surgery and vagus nerve stimulation (27– 44% seizure reduction) are feasible in selected older patients.