CLINICAL PRESENTATION — Most seizures in elderly patients are partial onset, with or without secondary generalization. When generalized, the partial onset may be unobserved or unrecognized, and the patient incorrectly classified as having primary generalized seizures. Late-onset primary generalized epilepsy, while rare, has been described in older individuals. It is possible that these were lifelong conditions, previously undiagnosed.
Complex partial seizure was the most common seizure type in older patients in the VACS#428 (a clinical trial of antiepileptic medications in elderly people with epilepsy); 38.3 percent of patients experienced complex partial seizures. In contrast to younger patients, complex partial seizures in the elderly are more often extratemporal, usually frontal, in origin, and therefore have an "atypical" clinical presentation. Classic descriptions of seizure aura, such as deja vu and olfactory hallucinations, are uncommon. Patients may instead report antecedent symptoms that are atypical and nonspecific, such as vaguely localized paresthesias, dizziness, and muscle cramps. Observers often note episodic confusion, sleepiness, or clumsiness rather than motor manifestations such as tonic or clonic movements, or automatisms. Postictal states are frequently more prolonged in elderly patients.
Because of the "atypical" symptomatology, elderly patients with seizures may be frequently misdiagnosed. In the VACS#428, 73.3 percent of patients ultimately diagnosed with epilepsy had a different referral diagnosis. These included altered mental status, confusion, blackout spells, memory disturbance, syncope, dizziness, and dementia. In another series, transient ischemic attack (TIA), depression, and metabolic or psychiatric disorders were also among the initial misdiagnoses. Misdiagnosis is more common in patients with partial complex and partial simple seizures than with generalized tonic-clonic seizures. Despite the known association of seizures and cerebrovascular disease, a history of stroke or TIA was associated with a 1.7-year delay to diagnosis. Similarly, comorbid dementia can obscure the recognition of seizures.
Dementia and epilepsy — Alzheimer disease (AD) is a risk factor for epilepsy. Between 9 to 16 percent of patients with AD will develop seizures, usually in the later stages of disease, a rate 10 times otherwise expected. A premorbid diagnosis of either AD or non-Alzheimer dementia are more common in patients presenting with a first unprovoked seizure compared with age-matched hospitalized controls (OR=6 and 8, respectively). A prospective cohort study of 233 patients with newly diagnosed AD found that younger age at onset and more severe dementia were independent risk factors for incident epilepsy.
Seizures in the setting of dementia account for 9 to 17 percent of elderly people with epilepsy. Dementia may coexist and possibly interact with other causes of epilepsy. In a prospective study, preexisting dementia increased the risk of post-stroke epilepsy. In another retrospective case series, 40 percent of patients with dementia and seizures had another potential structural cause (usually stroke) for their seizures.
IMPORTANT DIFFERENTIAL DIAGNOSIS
Delirium or acute toxic-metabolic encephalopathy may be difficult to distinguish from partial complex seizures and nonconvulsive status epilepticus (NCSE), particularly in a patient with baseline neurologic impairment. Episodic, dramatic changes in mental status with a return to normal or baseline cognition strongly suggest seizures, but the presentation may be more subtle.
When present, stereotyped motor movements or automatisms suggest seizure. However, tremor, asterixis, and myoclonus are not uncommon in delirium. Hallucinations may be a feature of either condition. Causes of delirium and seizures overlap, and delirium and seizures can coexist. EEG can identify or exclude seizures in this setting.
SUMMARY AND RECOMMENDATIONS
• A first seizure is not uncommon in elderly persons and can represent an acute symptomatic seizure, a provoked event that is not expected to recur in the absence of that trigger or new-onset epilepsy, a condition in which recurrent unprovoked seizures are expected in the absence of treatment.
• In this age group, acute symptomatic seizures are most often seen in the setting of acute stroke and metabolic encephalopathy. Cerebrovascular disease and degenerative dementia are common causes of epilepsy in the elderly, but one-third to one-half of cases are of cryptogenic origin.
• The overwhelming majority of late-onset epilepsy is partial or localization-related and presents with partial complex seizures, with and without secondary generalization.
• Clinicians should maintain a high level of suspicion for possible seizures in older patients presenting with intermittent or fluctuating confusional states. The usual clues to the possibility of underlying seizures are often absent.
• Considerations in the differential diagnosis of seizures in older patients include syncope and transient cerebral ischemia, as well as other disorders.
Reference:
http://www.uptodate.com/online/content/topic.do?topicKey=epil_eeg/6024&selectedTitle=2%7E150&source=search_result
available on 10/06/2010
