MRI abnormalities following febrile status epilepticus in children: the FEBSTAT study

Abstract

Objective: The FEBSTAT study is a prospective study that seeks to determine the acute and long-term consequences of febrile status epilepticus (FSE) in childhood.

Methods: From 2003 to 2010, 199 children age 1 month to 5 years presenting with FSE (>30 minutes) were enrolled in FEBSTAT within 72 hours of the FSE episode. Of these, 191 had imaging with emphasis on the hippocampus. All MRIs were reviewed by 2 neuroradiologists blinded to clinical details. A group of 96 children with first simple FS who were imaged using a similar protocol served as controls.

Results: A total of 22 (11.5%) children had definitely abnormal (n = 17) or equivocal (n = 5) increased T2 signal in the hippocampus following FSE compared with none in the control group (p < 0.0001). Developmental abnormalities of the hippocampus were more common in the FSE group (n = 20, 10.5%) than in controls (n = 2, 2.1%) (p = 0.0097) with hippocampal malrotation being the most common (15 cases and 2 controls). Extrahippocampal imaging abnormalities were present in 15.7% of the FSE group and 15.6% of the controls. However, extrahippocampal imaging abnormalities of the temporal lobe were more common in the FSE group (7.9%) than in controls (1.0%) (p = 0.015).

Conclusions: This prospective study demonstrates that children with FSE are at risk for acute hippocampal injury and that a substantial number also have abnormalities in hippocampal development. Follow-up studies are in progress to determine the long-term outcomes in these children.

Figure 1. Hippocampal abnormality following febrile status epilepticus (FSE)

Coronal T2 MRI of 20-month-old child with focal FSE. Seizure was intermittent with total duration of 360 minutes, total convulsive time of 81 minutes, and duration of longest convulsion of 60 minutes. MRI performed 1 day after the episode of status demonstrates increased T2 signal throughout the right hippocampus (arrow) which is also slightly larger than the left side. No other abnormalities are noted.

Figure 2. Extrahippocampal temporal lobe abnormality following febrile status epilepticus (FSE)

MRI of 11-month-old child with focal FSE. Seizure was continuous and lasted 120 minutes. MRI performed 3 days after the episode of FSE. Note increased T2 signal and enlargement of the right hippocampus (arrow in A), accompanied by increased T2 signal in the right amygdala (B) and right mesial temporal cortex (C).

Figure 3. Hippocampal malrotation (HIMAL) in child with febrile status epilepticus (FSE)

MRI of 40-month-old child with generalized FSE. Seizure was intermittent with total duration of 120 minutes, longest convulsion of 25 minutes, and total convulsive time of 50 minutes. Child had a prior complex febrile seizure (not status) at 24 months. MRI performed 4 days after the episode of status demonstrates the HIMAL abnormality. There is incomplete rotation of the left hippocampus (arrow) with normal size and signal intensity but abnormally rounded shape and blurred internal architecture.