Seizures and epilepsy in elderly patients of an urban area of Iran: clinical manifestation, differential diagnosis, etiology, and epilepsy subtypes

Etiology

Unlike younger individuals between the ages of 35–64 years where the most common cause of acute symptomatic seizures is drug withdrawal, systemic metabolic disorders represent the most common identifiable cause of acute symptomatic seizure in the elderly [13]. Compared to the published work of Waterhouse and Towne [1] our findings suggest that metabolic derangement may be a more common cause of seizure in the elderly than stroke, particularly within the Iranian population. Further, our findings may suggest that the Iranian population may differ from the US population [14], as they found that CVD was the most common etiology associated with elderly seizure. In agreement with previous studies, hypoglycemia secondary to excessive insulin use and non-ketotic acidosis was the most common metabolic cause of seizures [15, 16]. Finally, our study found that only 2 % of seizure cases were associated with substance abuse or pharmacologic misadventures. When compared to other studies [17], this rate is roughly five times less than general population and may be a result of cultural differences between Iranian and British society.

Our findings suggest that CVD is the most common cause of epilepsy in the elderly Iranian population, and this is consistent with other reports in the medical literature of both Iranian and non-Iranians. In one recent study of the northern Iranian region, 17.3 % of patients presenting with acute stroke developed at least one seizure within two years of their stroke [18]. Such findings suggest that measures should be undertaken to reduce the rate of CVD through lifestyle modification and early preventative measures to control hypertension and hyperlipidemia.

Clinical manifestations and diagnosis

Significant differences in the clinical manifestations of seizure exist between younger and older patients and are postulated to be a major cause of delayed diagnosis. Since tonic–clonic seizures are uncommon [19], elderly patients may present with atypical symptoms, even though 75 % of patients exhibited generalized tonic–clonic seizures, making it the most common clinical symptom. It might be related to the inclusion of more patients with classic symptoms, or because relatively few of the practitioners in our region are well-educated on epilepsy in the elderly, which can cause misdiagnosis and delayed treatment. Spitz et al. [20] reported that correct diagnosis is frequently delayed in the elderly, mainly because of lack of awareness of partial seizures by the public and healthcare providers and the concept of trying to attribute all of the patients’ symptoms to a single diagnosis. 30 % of the time or more, people are unaware of their seizures [21] and only go to hospital when classic symptoms are manifested.

The reason seizures manifest differently in older patients than in younger, is because of the anterior frontal cortical areas of the brain affected in stroke patients [11]. Over 20 % of patients suffered from impaired consciousness and impaired alertness, which is significantly different from those in younger patients. Ramsay and Pryor [22] reported that often patients describe seizures as altered mentation, periods of staring, unresponsiveness, or blackout spells in the elderly. These factors make it more difficult to diagnose epilepsy correctly in elderly patients.

Differential diagnosis

Epilepsy is often misdiagnosed in younger patients and even more commonly in the elderly. Our study found that the majority of elderly patients with seizure or epilepsy were initially misdiagnosed, and this finding is consistent with previous reports. Ramsay et al. [23] reported that alternative diagnoses were altered mental status (41.8 %), confusion (37.5 %), blackout spells (29.3 %), memory disturbance (17.2 %), syncope (16.8 %), dizziness (10.3 %), and dementia (6.9 %). The particular challenges of differential diagnosis in elderly patients demand special attention. The diagnosis of epilepsy in elderly patients is limited by four factors: (1) many patients cannot produce an exact history of their seizures, and are often difficult to observe; (2) the epilepsy is often misdiagnosed because of insufficient epileptic knowledge from primary care providers; (3) cognitively impaired elderly individuals are often unwilling or unable to cooperate during examinations, and (4) diagnosis is limited by the cognitive compromise as a result of neurological or psychiatric comorbidities in the elderly [24].

Epileptic seizure types

Our study showed that the most common epileptic seizure type for older patients in our region was generalized epileptic seizure, in disagreement with previous reports that implicate complex partial seizures as the most common cause [19]. The reasons for this incongruent finding are unclear, but may be a result of a lack of video-EEG monitoring in the city of Qom, as paroxysmal events often require video-EEG monitoring [1]. In contrast, generalized tonic–clonic seizures are easier to identify in the absence of video-EEG monitoring.

Status epilepticus

Our results showed that SE was much more common than has been reported in the medical literature. SE is estimated to occur in between 1.3 and 12.3 % of adult epileptic patients [3]. SE was probably more common in our study partly, because our patient population was biased towards individuals who were admitted with symptomatic seizures. Consistent with other reports, anoxia was the most common cause of SE in older patients. However, Wu et al. [25] showed that the prevalent etiology of SE was a delayed effect of brain injury or stroke, in older Californian patients.

In older patients, the etiology of SE is one of the major determinants of mortality, in addition to patient age and duration of SE [26]. Our SE patients had a mortality rate of about 60 %, which is higher than the previous studies in adults, which vary from 2.5 % to about 20 % [27]. The highest mortality was found in SE patients with anoxia, with a mortality rate of about 84 %, which is in agreement with the earlier studies [26].

Several limitations exist in our study. First, our study was not strictly population-based, even though it was the first study of this type in an urban area of Iran. Cases were found by screening medical records, and this presumably excludes some patients who had not been admitted to a hospital or clinic. Second, the accuracy of our findings is complicated by the fact that older people are more prone to live alone and are thus, less reliable regarding medical history. Finally, video-EEG monitoring was not available to us, and may thus, limit our ability to classify seizure types in older patients.