HIV-negative encephalitis and meningoencephalitis in the elderly

Introduction. The elderly are at a higher risk of infectious pathologies, which represent the third cause of primary mortality over 65 years and the leading cause of incidental mortality. The aim of a prospective longitudinal study conducted from April 1, 2012 to August 31, 2015 was to compare the epidemiological, clinical, biological, and etiological characteristics of encephalitis and meningoencephalitis in the elderly with those of young adults.
Methods. Patients aged over 28 days with suggestive symptoms of encephalitis were included from three medical departments (resuscitation, infectious diseases, and pediatrics) based on established inclusion and exclusion criteria. Patients seropositive for HIV and children under 15 years of age were excluded. Based on age, two groups were formed: group A (under 65 years old) and group B (65 years old and above), and were compared epidemiologically, clinically, and in terms of evolution.
Results. Out of 141 files that met the inclusion criteria, 38 were excluded (age ≤ 15 years). The average age for groups A and B were 36.27 ± 13.9 years (extremes: 17-64 years) and 72.55 ± 5.6 years (range: 66-83 years), respectively. In group B, progressive onset was the main feature (54.5%), associated with behavioral disorders (81.8%) and focal neurological disorders (81.8%). A significant part of these patients also had respiratory signs (36.8%), while in group A, behavioral disorders, focal and diffuse neurological disorders represented 49.6%, 45.5%, and 29.3% of cases, respectively. Out of 92 (65.2%) patients in group A, 44 (47.8%) had confirmed and/or probable viral etiologies, 31 (33.7%) had confirmed and/or probable bacterial etiologies, 3 (3.3%) had parasitic etiologies, 29 had confirmed co-infections, and 42 (45.7%) were treatable.
Conclusion: The study highlights the frequency of encephalitis and meningoencephalitis of viral origin in the elderly. The diagnosis remains difficult and any neurological sign recent onset and evolving in a febrile context should suggest the diagnosis.