Provoked seizures are usually generalized tonic-clonic seizures.
19 A comprehensive review of systems may elicit history of nocturnal enuresis, encopresis, tongue-biting, or any sudden cognitive decline, suggestingseizures.
20
The physical examination concentrates on evaluating any injuries sustained during the spell and finding evidence of focal neurologic deficits or signs of systemic illness, with special attention to physical findings suggestive of cerebrovascular or atherosclerotic disease. Injuries due to a fall onto an outstretched hand are a sign of initial preservation of consciousness, which is unlikely with a seizure.
21 Orthostatic vital signs coupled with a history of dimming vision preceding the attack are more consistent with a diagnosis of syncope, as opposed to seizure.
22
Testing
In general, the imaging modality of choice for evaluating suspected seizures is MRI because of its sensitivity for finding subtle or small lesions. Emergent CT is required when any of the following are present: new focal neurologic deficits, persistently altered mental status, a recent history of trauma, persistent headache, anticoagulant use, immunocompromised status, or fever.23 Routine laboratory evaluation in an elderly person
with suspected seizures should include a CBC; tests to measure electrolytes, calcium, magnesium, phosphorus, BUN, creatinine, and glucose; liver function tests; and toxicology screening.7,20 Lumbar puncture is indicated when encephalitis, meningitis, or cancer is suspected.7
EEG is essential, but results should be interpreted with care as older patients often have nonspecific abnormalities consistent with diffuse atherosclerotic changes. They also have a lower incidence of interictal epileptiform activity than is seen in persons with epilepsy overall, which further decreases the utility of EEG.24 One-time EEG has a relatively low sensitivity (50%); performing multiple tests increase the diagnostic yield.25 The gold standard of EEG diagnosis is the actual recording of a seizure, but this can be difficult without relatively frequent seizure activity. Prolonged video EEG or ambulatory EEG monitoring may clarify the diagnosis in patients with repeated periods of altered mental status, dizziness, or paroxysmal movements.2,16
Differential diagnosis
The differential diagnosis of seizures in the elderly is listed in Table 5. Once seizures are diagnosed, you must determine whether the seizures are provoked (unlikely to recur without the provoking stimulus) or unprovoked (usually symptomatic and likely to recur without treatment).
Provoked seizures are usually of the generalized tonic-clonic type.19 If provocation has been ruled out but the patient is having generalized tonic-clonic seizures, the ictal events are probably partial seizures that secondarily generalize. New-onset idiopathic generalized tonic-clonic seizures in older adults are rare19 except in patients with Alzheimer's disease, who usually have generalized seizures due to the global brain pathology of that disease. Epilepsy will develop in approximately 20% of patients with Alzheimer's disease by their fifth year after diagnosis.26
Treatment and follow-up
Up to 80% of older adults who have had a single seizure are likely to have another.1,27 Because of this high recurrence risk, some advise initiating antiepileptic drug (AED) treatment after only one symptomatic seizure when a cortical lesion has been identified via neuroimaging.19
When selecting the initial AED, consider seizure type, pharmacokinetic profile, possible drug interactions, other medical conditions, efficacy, expected adverse effects, and cost14 (see the table “Comparative characteristics of first- and second-generation antiepileptic drugs” on the Web). Counsel the patient about potential adverse effects that may be related to the medication and the likelihood of success with treatment.
Long-term thinking is very important. New-onset seizures in elderly patients are often controlled with relatively modest dosages of whichever AED is first selected.19 Thus the primary consideration for successful treatment is tolerability,15,28 and clinicians should choose the initial drug with this in mind.4,29
Normal physiologic changes of aging alter the pharmacokinetic profiles of many AEDs. Older adults have lower circulating protein concentrations (leading to a higher proportion of active free drug at an equivalent serum drug level), decreased renal elimination, altered distribution volumes, impaired hepatic metabolism, and decreased enzyme inducibility.10,29 There are alterations in the GI absorption of highly insoluble AEDs such as phenytoin and carbamazepine.29
Common AED side effects such as dizziness, somnolence, increased tremor, and unsteadiness are especially troublesome in the elderly, who often have disequilibrium or gait problems at baseline. These problems are usually dose-dependent and can be minimized with slow titration, but note that the elderly tend to experience side effects at serum drug levels that are not considered high in other age groups.11 Soporific phenobarbital is a particularly unsuitable choice.30 Additional areas of concern for older patients are chronic adverse effects such as osteoporosis, peripheral neuropathy, and weight gain, common with the use of first-generation AEDs.12 These adverse effects have not been noted with second-generation AEDs.31
Cognitive or other neurologic deficits are also common in seniors,32,33 and formal cognitive function testing before initiating treatment is important.1 Lamotrigine, gabapentin, levetiracetam, pregabalin, and zonisamide are desirable first choices for treatment because of their most favorable cognitive profiles.29 The increased expense of this new generation of AEDs may well be offset by decreased costs due to adverse drug effects.29