Summary Objective This retrospective study was designed to assess the impact of corpus callosotomy (CC) in patients with intractable West syndrome (WS) without lesions on magnetic resonance imaging (MRI). Methods This study involved 56 patients with WS who underwent CC between January 2000 and December 2014. Seizure outcomes and changes in psychomotor development were analyzed. Results Mean age at the onset of epilepsy and at the time of CC was 5.1 and 22.6 months, respectively. Mean duration of epilepsy before CC was 17.6 months. Video‐electroencephalography (EEG) monitoring showed bilateral ictal and interictal abnormalities before CC. Mean follow‐up duration was 36.6 months. At final follow‐up, seizure outcomes after CC were seizure‐free in 18 patients (32.1%), excellent (E: >80% reduction in seizure frequency) in 15 (26.8%), good (G: >50% reduction) in 10 (17.9%), and poor (P: <50% reduction) in 13 (23.2%). Epileptic spasms (ES) were eliminated in 24 patients (42.9%). However, tonic seizure (TS) outcomes were poor (P < 0.05). Of preoperative predictive factors related to seizure outcome, developmental delay before epilepsy onset correlated with poor outcome (P < 0.05). One year post‐CC, 6 patients (10.7%) had no epileptic abnormality on EEG, 19 (33.9%) had lateralized epileptic abnormalities, and 31 (55.4%) had bilateral asynchronous epileptic abnormalities. All patients without epileptic discharge achieved seizure freedom. Fifteen of 19 (78.9%) patients in the lateralized group and 12 of 31 (38.7%) in the bilateral asynchronous group had worthwhile outcomes (F + E). The patterns of EEG changes after CC correlated with seizure outcome (P < 0.01). Progressive declines in developmental quotient were prevented in patients with worthwhile outcomes. Significance CC represents an important therapeutic option for patients with WS without resectable MRI lesions. Transcallosal seizure bilateralization is critical for bilateral ES generation. Early identification of potential CC candidates and surgical intervention are important for better seizure control and cognitive capacity preservation before severe developmental delay development.

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We report a case of brain surface angiocentric glioma in a 6-year-old Japanese boy with medically intractable partial epilepsy. MRI showed somewhat ill-defined high-signal lesions on fluid-attenuated inversion recovery and T2-weighted imagings of the right occipitoparietal cortex. At surgery, a yellowish tumor was localized in the superficial cortex. Histologically, the tumor was predominantly composed of elongated astrocytic cells forming rings around blood vessels. Tumor cells circumferential to vessels predominanted in low cellurarity areas, whereas radial alignment with perivascular pseudorosettes was observed in more cellular regions. These perivascular pseudorosettes closely resembled those of ependymoma. The tumor cells showed variable cytoplasmic immunoreactivity with GFAP. These findings were more likely monomorphous angiocentric glioma, which was first described by Wang et al. in 2005. However, in our case the tumor had a small foci of polymorphous appearance and a comparatively high MIB-1 labeling index (8%). Therefore, the present case may be an atypical form of monomorphous angiocentric glioma. However, no de novo anaplastic monomorphous angiocentric glioma similar to our case has yet been reported in the literature. It remains to be determined whether the behavior of monomorphous angiocentric glioma is an example of benign biological characteristics or whether it more closely resembles a low-grade malignant tumor.