Adult-onset epilepsy with startle-induced seizure after febrile infection-related epilepsy syndrome: A case report

Startle-induced seizure is a rare type of reflex seizure triggered by unexpected sensory stimuli that often occurs in children with early acquired cerebral lesions or brain malformations. We report a unique case of adult-onset epilepsy with startle-induced seizures. A 24-year-old woman had suffered high fever and focal to bilateral tonic–clonic seizures. A diagnosis of febrile infection-related epilepsy syndrome (FIRES) was made based on the febrile infection occurring 7 days to 24 h before the onset of status epilepticus, which met all criteria for cryptogenic new-onset refractory status epilepticus (NORSE) according to the cryptogenic NORSE score. Immunotherapy and several antiseizure medications resulted in transient resolution of the seizures. Four months later, she experienced startle-induced seizures triggered by unexpected stimuli, such as auditory, visual, or unexpected events, and manifesting as initial tachycardia followed by right ear deafness, right hemifacial dysesthesia, eye deviation to the right, and tonic–clonic convulsions. Ictal electroencephalography revealed left temporal initial rhythmic delta activity, followed by rhythmic theta activity. The patient was diagnosed with startle epilepsy associated with FIRES and continued to receive anti-seizure medications. Claustrum-insular-operculum lesions may have been the epileptic focus in this case, in contrast to previous cases of epilepsy with startle-induced seizures originating in a frontoparietal network. This case indicates a new category of adult-onset post-FIRES epilepsy with startle-induced seizures.