Transient MR signal changes in patients with generalized tonicoclonic seizure or status epilepticus: Periictal diffusion-weighted imaging

BACKGROUND AND PURPOSE: Our purpose was to investigate transient MR signal changes on periictal MR images of patients with generalized tonicoclonic se izure or status epilepticus and to evaluate the clinical significance of th ese findings for differential diagnosis and understanding of the pathophysi ology of seizure-induced brain changes. METHODS: Eight patients with MR images that were obtained within 3 days aft er the onset of generalized tonicoclonic seizure or status epilepticus and that showed seizure-related MR signal changes had their records retrospecti vely reviewed. T1- and T2-weighted images were obtained of all eight patien ts. Additional diffusion-weighted images were obtained of five patients dur ing initial examination. After adequate control of the seizure was achieved , followup MR imaging was performed. We evaluated the signal changes, locat ion of the lesions, and degree of contrast enhancement on T1- and T2-weight ed images and the signal change and apparent diffusion coefficient (ADC) on diffusion-weighted images. We also compared the signal changes of the init ial MR images to those of the follow-up MR images. RESULTS: The initial MR images revealed focally increased T2 signal intensi ty, swelling, and increased volume of the involved cortical gyrus in all ei ght patients. The lesions were located in the cortical gray matter or subco rtical white matter in seven patients and at the right hippocampus in one. T1-weighted images showed decreased signal intensity at exactly the same lo cation (n = 6) and gyral contrast enhancement (n = 4). Diffusion-weighted i mages revealed increased signal intensity at the same location and focally reduced ADC, The ADC values were reduced by 6% to 28% compared with either the normal structure opposite the lesion or normal control. Follow-up MR im aging revealed the complete resolution of the abnormal T2 signal change and swelling in five patients, whereas resolution of the swelling with residua l increased T2 signal intensity at the ipsilateral hippocampus was observed in the other two patients. For one of the two patients, hippocampal sclero sis was diagnosed. For the remaining one patient, newly developed increased T2 signal intensity was shown. CONCLUSION: The MR signal changes that occur after generalized tonicoclonic seizure or status epilepticus are transient increase of signal intensity a nd swelling at the cortical gray matter, subcortical white matter, or hippo campus on periictal T2-weighted and diffusion-weighted images. These findin gs reflect transient cytotoxic and vasogenic edema induced by seizure. The reversibility and typical location of lesions can help exclude the epilepto genic structural lesions.