54 yo female with history of a childhood seizure. Now experienced an event with an aura followed by loss of consciousness and observed tonic-clonic movements.

CT head; MR T1-w pre and/or post contrast; MR Coronal T2-w spin echo and MR FLAIR; MR diffusion

CT Head
1. Negative noncontrast CT

T1-w MR pre and post
1. Subtle evidence of hyperemia along the left parahippocampal gyrus consistent with recent seizure activity.

MR Coronal T2-w spin echo and MR FLAIR
1. Evidence of recent (i.e. acute phase), but not hyperacute bilateral hippocampal post seizure injuries. Changes are more obvious on the left than the right and the findings are mainly centered in the posterior body and tail of both hippocampi. The subtlety of the findings could reflect a very limited post seizure injury or post seizure events being ofset in their timeframe. Currently, both sides are in the later acute to subacute phase, based on the fading hyperintense edema and the reappearance of the myelinated tracts, especially on the right.
 
MR Diffusion (DWI)
1. There is a small focal area of  positive MR diffusion is evident in the posterior body-tail transition zone and tail of the left hippocampus. This area is likely, overtime, to proceed to tissue necrosis.
 
MR susceptibility is not available

1. There is evidence of bilateral hippocampal abnormality, but they are discordant in severity or timeline. The changes in the right hippocampus are subtle mainly with effacement of the internal white matter tracts and only minimal cytogenic edema. The changes in the left are much more prominent. These include edema, effaced white matter tracts, and MR diffusion water restriction in the mid body of the left hippocampus. There is a history of childhood seizure event, but, there is no evidence of chronic mesial sclerosis. It is not clear if a single seizure occurred worse on the left vs. the right, or the right hippocampal changes are from a recent but not concurrent seizure event. Nevertheless, having bilateral hippocampal post ictal changes is significant and supports the possibility of progression to epilepsy if not treated.

MR Flair is often not abnormal in cases of acute or subacute post seizure activity. It is usually positive in mesial temporal sclerosis. MR Flair should not be depended on to evaluate hippocampal post seizure injuries in the hyperacute, acute, or subacute time-frames.

Bilateral abnormal changes inplies a significant depth and duration of the seizure event. However, in this case, the extent of injury differs between sides. This is a common finding. Often one hippocampus can be abnormal in all 5 subsegments, while the contralateral side involves only one or a few segments. Thus, careful assessment of post seizure injury needs to be determined in every case to recognize the full extent of the hippocampal injury.