LAUSR

OBJECTIVE Reversible splenium lesions during febrile illness (RESLEF) are found in a spectrum. There are two types of corpus callosum (CC) lesions: CC-only type, with limited lesions and the CC (+) type, with extensive white-matter lesions. This retrospective study aimed to describe the differences in clinical findings between CC-only and CC (+) lesions and the association between onset age and clinico-radiological features in RESLEF. METHODS Fifty-two episodes of CC-only or CC (+) lesions accompanied by neurological symptoms, e.g., seizures, delirious behavior (DB), and disturbance of consciousness (DC), from January 2008 to October 2019 were included. We analyzed the etiology (pathogen), clinical course, laboratory data, magnetic resonance imaging and electroencephalography findings, therapy, and prognosis. RESULTS The rate of DC in the CC (+) was significantly higher than that in the CC-only group (5/6 [83%] vs 7/46 [15%]; p = 0.0016). The median number of seizures in the CC (+) was also significantly higher than that in the CC-only group (4 [0-7] vs 0 [0-7]; p = 0.034). Further, in RESLEF, the median onset age (months) in the seizure was significantly lower than that in the no-seizure group (39 [12-74] vs 83 [28-174]; p = 0.0007). The median onset age (months) in the DB was significantly higher than that in the no-DB group (74.5 [26-174] vs 28 [12-139]; p = 0.003). CONCLUSIONS In RESLEF, CC (+) is a more severe neurological symptom than CC-only. Furthermore, the onset age is related to the type of neurological symptoms that appear.