A case of focal cortical dysplasia type Ib atypically showing reversible intensity changes on magnetic resonance imaging which could be affected by epileptic discharge activity.

Focal cortical dysplasia (FCD) was first described as a distinct neuropathological entity in 1971 by Taylor and colleagues. FCD is thought to be an embryological migration disorder and is thus considered a non-progressive, unchangeable disease throughout life. A 9-year-old right-handed boy was referred from a local hospital for medically intractable epileptic seizures. Serial magnetic resonance images (MRI) showed intensity changes that indicated exacerbation and remission. After presurgical evaluations including intracranial video-electroencephalogram monitoring, we performed a lesionectomy aided by MRI and epileptic focus resection. He has been free from seizures for more than 3 years. Neuropathological findings showed FCD type Ib. We surgically treated a patient with FCD, which showed MRI intensity changes indicating exacerbation and remission. Although FCD type Ib is generally invisible on MRI, in this patient, changes in intensity on MRI made FCD type Ib visible.