To report a case of medically refractory nonconvulsive status epilepticus in a patient with amyloid-related imaging abnormalities (ARIA) with lecanemab.

Recent studies have shown promising results for amyloid-lowering antibodies in the treatment of early-stage Alzheimer's disease. FDA approval was granted for lecanemab in 2023. Amyloid-related imaging abnormalities (ARIA), including ARIA-E (edema) and ARIA-H (hemosiderin), have been reported as potential side effects. Although usually asymptomatic, ARIA may cause headaches, visual disturbances, confusion, and dizziness. Seizures have been reported in aducanumab-induced ARIA. Here, we report a case of lecanemab-induced ARIA resulting in nonconvulsive status epilepticus (NCSE). 

NA

An 84-year-old ApoE4 carrier female with a history of Alzheimer's disease on lecanemab with a recent diagnosis of ARIA-E (moderate) and ARIA-H (mild) presented with acute progressive confusion. Patient was diagnosed with asymptomatic ARIA by screening MRI eight weeks after lecanemab initiation. MRI revealed two distinct areas of edema in the left occipital and right temporal lobes, and four new microhemorrhages. The next lecanemab infusion was held. Two weeks later patient awoke with disorientation and slow, unsteady gait prompting ER presentation where aphasia and left gaze preference were observed. The patient subsequently had a 40-second bilateral tonic-clonic seizure with spontaneous resolution. The seizure was treated with lorazepam IV and levetiracetam IV load. Continuous EEG showed focal NCSE in the right temporal region (maximal at P4/T6/O2) corresponding to the known ARIA-E location, which continued after a second dose of lorazepam with loading of lacosamide. After loading of valproic acid, EEG continued to be on the ictal end of the ictal-interictal continuum suggesting medically refractory status epilepticus. MRI brain showed slight expansion of ARIA-E and stable ARIA-H compared to MRI completed two weeks prior. The patient was treated for severe ARIA with three days of high-dose methylprednisolone.

Lecanemab-induced ARIA may lead to medically refractory focal status epilepticus.