Transient mesial temporal abnormalities associated with partial seizures of temporal lobe origin

ABSTRACT

Seizure induced transient brain CT or MRI abnormalities following status epilepticus have previously been reported. However, focal transient imaging abnormalities involving hippocampus or mesial temporal lobe as a consequence of seizure are rare findings. We report 2 patients with transient mesial temporal abnormalities on MRI associated with partial seizure of temporal lobe origin. A 59-year-old man with a 4-month history of occasional epigastric rising sensation had developed frequent olfactory hallucination 7 days prior to presentation. On brain MRI, T2 signal was increased in the right mesial temporal region, and the lesion showed mild mass effects and partial enhancement after gadolinium injection. Interictal spikes were noted from right nasopharyngeal electrode, but there was no clinical or electrical evidence of status epilepticus during prolonged scalp/sphenoidal EEG monitoring. His seizures were successfully controlled by phenytoin. T2 high signal was markedly decreased and prior enhancement was no longer seen on brain MRI done 5 weeks later. A 33-year old woman with a 6 month history of occasional vacant staring and oral automatism with amnesia complained progressive memory impairment. Right amygdala and hippocampal head was enlarged and showed T2 high signal without contrast enhancement. EEG with sphenoidal electrodes showed right sphenoidal spikes. Her seizures were controlled by carbamazepine and brain MRI became unremarkable 6 weeks later. Suggested mechanisms and significance of the transient imaging abnormalities following seizures will be briefly reviewed.