Introduction: MRI data is essential for early diagnosis and evaluation of surgical indication in patients with Rasmussen syndrome (RS). In the present study, we examined the status and evolutionary changes in MRI lesions to identify the MRI characteristics of RS.
Methods: MRI of 15 RS patients was examined regarding frequency and distribution of atrophic lesions on T1-weighted images and high intensity lesions on FLAIR or T2-weighted images.
Results: In 13 patients, atrophic lesions were observed predominantly in the frontal lobes with various extent of involvement. High intensity lesions were also observed in 13 patients. High intensity lesions were significantly more prevalent in the cortex of patients with later onset and were present in the insula in 37.5% of epilepsia partialis continua (EPC) type patients and in 57.1% of non-EPC type. Early MRI showed various combinations of atrophic lesions or high intensity lesions in seven of nine patients who underwent MRI examinations within one year of their first seizure. Serial MRI revealed high intensity lesions with characteristic features of regression (20.0% of patients), fluctuation (regression followed by reappearance; 33.3%) and expansion (46.7%). Appearance and reappearance of high intensity lesions in the cortex and/or subcortical white matter were associated with aggravation of seizures. Bilateral high intensity lesions were observed in three patients with unilateral epileptogenic foci, who were successfully treated by surgical intervention.
Conclusion: Dynamic evolutionary changes in lesions (regression, fluctuation and expansion of high intensity lesions), as observed on MRI, may be a diagnostic feature of Rasmussen syndrome.