Post-Infectious ADEM after HSV-1 Encephalitis in an Elderly Patient with Latent Tuberculosis: A Case Report
Abstract
Background: Acute disseminated encephalomyelitis (ADEM) is a demyelinating disorder typically seen in children after an infectious trigger. Its occurrence in older adults, especially after herpes simplex virus type 1 (HSV-1) encephalitis, is uncommon and carries a less predictable course. Management is further complicated when the patient has latent tuberculosis, since high-dose corticosteroids, the standard ADEM treatment, can reactivate dormant infection. We report such a case, in which the diagnosis moved through several competing possibilities before treatment had to account for this added risk. Case Summary: A 60-year-old hypertensive woman presented unconscious (GCS 3/15), after a few days of fever and headache. Her history included tuberculosis treated five years earlier. Initial CT brain suggested stroke, but preceding fever and altered sensorium argued against it. CSF analysis and PCR confirmed HSV-1 encephalitis, and she was started on intravenous acyclovir; her condition improved to GCS 11/15 by day 11. On day 13, her condition deteriorated again to GCS 4/15. Pulmonary embolism was considered given a raised D-dimer, but excluded on CT pulmonary angiography. MRI brain instead showed multifocal white matter lesions consistent with post-infectious ADEM. High-dose corticosteroids were started, and given her latent tuberculosis history, anti-tuberculous therapy was added as prophylaxis against reactivation. She improved markedly within four days and was discharged fully oriented, remaining stable at six-week follow-up. Conclusion: Post-infectious ADEM should be considered whenever a biphasic decline complicates encephalitis in an elderly patient. Characteristic MRI findings are central to the diagnosis, and autoantibody screening, alongside other investigations, helps exclude close differentials such as NMDAR encephalitis and multiple sclerosis. In patients with latent tuberculosis, clinicians must weigh the risk of reactivation against the need for immunosuppressive therapy in ADEM. Key Words: Encephalomyelitis, HSV-1 Encephalitis, Elder, Tuberculosis.