Progression of brain damage after status epilepticus and its association with epileptogenesis: a quantitative MRI study in a rat model of temporal lobe epilepsy.
OBJECTIVE
This study examined the hypothesis that neurodegeneration continues after status epilepticus (SE) ends and that the severity of damage at the early phase of the epileptogenic process predicts the outcome of epilepsy in a long-term follow-up.


METHODS
SE was induced in rats by electrical stimulation of the amygdala, and the progression of structural alterations was monitored with multiparametric magnetic resonance imaging (MRI). Absolute T2, T1rho, and diffusion (Dav) images were acquired from amygdala, piriform cortex, thalamus, and hippocampus for < or = 4.5 months after SE. Frequency and type of spontaneous seizures were monitored with video-electroencephalography recordings. Histologic damage was assessed from Nissl, Timm, and Fluoro-Jade B preparations at 8 months.


RESULTS
At the acute phase (2 days after SE induction), quantitative MRI revealed increased T2, T1rho, and Dav values in the primary focal area (amygdala), reflecting disturbed water homeostasis and possible early structural damage. Pathologic T2 and T1rho were observed in mono- or polysynaptically connected regions, including the piriform cortex, midline thalamus, and hippocampus. The majority of acute MRI abnormalities were reversed by 9 days after SE. In later time points (> 20 days after induction), both the T1rho and diffusion MRI revealed secondarily affected areas, most predominantly in the amygdala and hippocampus. At this time, animals began to have spontaneous seizures. The initial pathology revealed by MRI had a low predictive value for the subsequent severity of epilepsy and tissue damage.


CONCLUSIONS
The results demonstrate progressive neurodegeneration after SE in the amygdala and the hippocampus and stress the need for continued administration of neuroprotectants in the treatment of SE even after electrographic seizure activity has ceased.
National Bio-NMR Facility and Department of Biomedical NMR, University of Kuopio, Kuopio, Finland.
Jaak
J
Nairismägi
Olli H J
OH
Gröhn
Mikko I
MI
Kettunen
Jari
J
Nissinen
Risto A
RA
Kauppinen
Asla
A
Pitkänen
D000679:Amygdala / Q000503:physiopathology; D000818:Animals; D001921:Brain / Q000473:pathology* / Q000503:physiopathology; D004558:Electric Stimulation; D004569:Electroencephalography / Q000706:statistics & numerical data; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis / Q000473:pathology* / Q000503:physiopathology; D005500:Follow-Up Studies; D006624:Hippocampus; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008991:Monitoring, Physiologic; D009410:Nerve Degeneration / Q000473:pathology / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012720:Severity of Illness Index; D013226:Status Epilepticus / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D013788:Thalamus / Q000473:pathology / Q000503:physiopathology; D014743:Videotape Recording