L. T. Kurland

The Risk of Epilepsy Following Febrile Convulsions

Neurology 1979;29:297–303

The risk of unprovoked seizures after encephalitis and meningitis

A population-based cohort of 714 survivors of encephalitis or meningitis between 1935 and 1981 was followed in order to evaluate the risks of unprovoked seizures after CNS infections. The 20-year risk of developing unprovoked seizures was 6.8%, and the ratio of observed to expected cases of unprovoked seizures was 6.9. The increased incidence of unprovoked seizures was highest during the first 5 years after the CNS infection but remained elevated over the next 15 years of follow-up. The type of CNS infection and the presence or absence of seizures during the acute phase of the CNS infection greatly influenced the risks of subsequent unprovoked seizures. The 20-year risk of developing unprovoked seizures was 22% for patients with viral encephalitis and early seizures, 10% for patients with viral encephalitis without early seizures, 13% for patients with bacterial meningitis and early seizures, and 2.4% for patients with bacterial meningitis without early seizures. The 20-year risk of 2.1% for patients with aseptic meningitis was not increased over the general population incidence of unprovoked seizures.

THE THERAPEUTIC IMPACT OF TEMPORAL ARTERY BIOPSY

To evaluate the clinical usefulness of temporal artery biopsy in the diagnosis of giant-cell arteritis we followed up all 134 residents of Olmsted County, Minnesota, who had temporal artery biopsies between 1965 and 1980. Initial biopsies were positive for giant-cell arteritis in 46 cases and negative in 88. A history of jaw pain or claudication and the findings of a palpably abnormal temporal artery were significantly more common in the patients whose biopsy specimens showed giant-cell arteritis. Over a median follow-up period of 70 months (range 1-192) only 8 of the 88 biopsy-negative patients had clinical courses requiring long-term, high-dose corticosteroid therapy for giant-cell arteritis. In this population-based study temporal artery biopsy correctly predicted the subsequent need for corticosteroid therapy in 94% of cases: these findings indicate that biopsy should be done before patients are committed to long-term corticosteroid therapy.

Risk of Recurrence After an Initial Unprovoked Seizure

Summary: A cohort of 424 patients was followed to determine the patterns of risk for recurrence after an initial unprovoked seizure. Overall, the risk of recurrence was 36% by 1 year, 48% by 3 years, and 56% by 5 years. The risk of subsequent seizures was lower for patients with idiopathic seizures than for those whose seizures had a presumed etiology. Among cases for which initial seizure was classified as idiopathic, EEG abnormalities, abnormal neurologic examination findings, and initial partial seizures were identified as significant independent predictors of higher recurrence risks.

Cholecystectomy and carcinoma of the colon.

After cholecystectomy the concentration of secondary bile acids in the bile increases. These bile acids have been incriminated in the pathogenesis of carcinoma of the colon. Hence the hypothesis that cholecystectomy predisposes to the development of carcinoma of the colon. To test this hypothesis, 1681 residents of Rochester, Minnesota (460 males and 1221 females), who underwent cholecystectomy during 1950-69, were followed up. Carcinoma of the colon developed in a higher-than-expected number of patients. However, the association was significant only in females (relative risk 1.7; 95% confidence interval 1.1-2.5) and even stronger for right-sided carcinoma of the colon (relative risk 2.1; 95% confidence interval 1.1-3.6). These data support the hypothesis that cholecystectomy may be a predisposing factor in the development of cancer of the colon in women.

Brain injury and neurologic sequelae: A cohort study of dementia, parkinsonism, and amyotrophic lateral sclerosis

We reviewed the medical records of 821 Olmsted County residents who had suffered head trauma with presumed brain injury between 1935 and 1974 and were more than 40 years old at the time of their last medical assessment. These patients were followed over 15,000 person-years for dementia and other degenerative neurologic diseases. The standardized morbidity ratio (SMR) for dementia was 1.06, and the SMR for dementia of the Alzheimer type was 1.00. These values are not significantly elevated and are inconsistent with studies that suggest that head trauma is a risk factor for Alzheimers disease. In addition, the SMRs for parkinsonism (1.04), Parkinsons disease (0.94), and amyotrophic lateral sclerosis (1.05) were not significantly elevated, providing no evidence that head trauma is a risk factor for these disorders. However, these latter results are based on smaller total case numbers.

Lack of association between Alzheimer's disease and education, occupation, marital status, or living arrangement

Using the resources of the Rochester Epidemiology Project, we conducted a case-control study of sociodemographic characteristics using the incidence cohort of patients with Alzheimers disease (AD). During the conduct of ongoing studies of AD in Rochester, we identified new cases of AD as they occurred during 1975-1979 (N = 241). We selected one age- and sex-matched control from among all registrations for care in this community during the year of onset for each case. There was little difference between cases and controls for educational attainment, marital status, type of dwelling, living arrangement, or occupation. We were unable to confirm low educational level as a risk factor for AD in this population. Future attempts to identify etiologic risk factors for dementing illness should probably move toward other areas of research.

Prevalence of medically diagnosed dementia in a defined United States population: Rochester, Minnesota, January 1, 1975

Using the centralized diagnostic data resource for the population of Rochester, Minnesota, we determined the prevalence of medically diagnosed dementia for this community. There were 289 individuals with dementia who were residing in Rochester on January 1, 1975:208 women and 81 men. The overall age-and sex-adjusted rates per 100,000 population were 342 for all dementias and 227 for Alzheimers disease. Prevalence rates increased with age for both sexes. Limiting the denominator to persons ≥,65 years, age-adjusted rates per 100,000 population for men and women were 3,452 and 3,466 (or about 3.5%), respectively, for dementia and 2,007 and 2,675 (2.0 and 2.7%), respectively, for Alzheimers disease.

Is the incidence of dementing illness changing? A 25‐year time trend study in Rochester, Minnesota (1960‐1984)

We performed a time trend study of incidence of dementing illness in Rochester, Minnesota. We ascertained age- and sex-specific incidence rates for the five quinquennia, 1960 through 1984. The incidence rates sharply increased with advancing age, reaching a high of 2,922/100,000 person years in the group 85 years and older. For dementia caused either solely or predominantly by Alzheimers disease, this figure was 2,600/100,000 person years for the oldest age group. There were no significant differences in the incidence of dementing illness between men and women. In the oldest age groups in the last two quinquennia of study, there appears to be a trend toward increasing incidence rates. Over the years, the proportion of cases attributed to dementia due to unknown causes has decreased while the proportion of cases attributed to Alzheimers disease has increased.

The risk of seizure disorders among relatives of children with febrile convulsions

We studied the risk for seizure disorders among relatives of probands with febrile convulsions. The risk for febrile convulsions was raised in siblings, offspring, and nieces and nephews of probands. Risks to siblings were higher if one or both parents also had febrile convulsions, or the proband had no identified neurologic abnormality before the febrile convulsion, if the proband had recurrent febrile convulsions, or the febrile convulsions were complex. The risk for epilepsy was raised in siblings of probands, but not in other relatives. If the proband had febrile convulsions followed by epilepsy, risk to siblings for febrile convulsions and for epilepsy was significantly higher than when probands had either condition alone.