Unilateral Diffuse Cortical Dysplasia: A Case Report
Authors: Hashizume Kiyotaka , Kiriyama Kenji , Kunimoto Masayuki , Maeda Takahiro , Tanaka Tatsuya , Miyamoto Masae , Miyokawa Naoyuki , Fukuhara Masakazu 
Published: August 2009

Purpose: A case of unilateral diffuse cortical dysplasia is presented, and the surgical strategy is discussed.

Case Report: A 6‐year‐old girl with moderate mental retardation had had intractable epilepsy for 4 years with daily complex partial or generalized seizures. Magnetic resonance imaging demonstrated a schizen‐cephaly in the right occipital lobe. The wall of the cleft showed isointensity as white matter, and a mass of gray‐matter intensity was identified under the wall. The gray‐matter intensity lesion continued into the thalamus and midbrain. There was no hippocampal formation. Diffuse polymicrogyria was seen in the ipsiiateral fronto‐parietotemporal lobes. an electroencephalogram (EEG) showed interictal spikes predominantly in the right frontal and central areas, and a phase reversal was found in the right central lead. The ictal EEG was successfully recorded 4 times with prolonged video‐EEG monitoring. However, the laterality and localization of the seizure onset were unclear. Invasive recording was impossible because of the mental retardation. On interictal single‐photon‐emission computed tomography (SPECT) with 99mTc‐ECD, the right occipital lesion showed normal perfusion as gray matter, and a mild low‐perfusion area was observed in the right frontal and parietal lobes. the ictal SPECT revealed a remarkable high‐perfusion area in the lesion, including the neighboring cortex. A large craniotomy was performed, and the right occipital, parietal, and temporal lobes were exposed. The schizencephalic cyst was covered with a thick arachnoid membrane and continued into the lateral ventricle. The dysplastic lesion appeared as a glassy yellowish white mass. Around the lesion, the cortex showed diffuse polymicrogyria. An electrocorticogram (ECoG) was recorded from the surface of the lesion and polymicrogyria. Interictal spikes were recorded frequently in the polymicrogyria, but sporadically in the lesion. The epileptogenic zone, including the dysplastic lesion, was resected. The medial resectable margin of the lesion was determined intraoperatively by using a neuronavigation system (Viewing Wand, ISG Technologies, Toronto, Canada). After the en bloc resection, the ECoG was recorded again at the resected margin. Although rare epileptic activity persisted in the anterior margin, additional resection was not carried out to avoid additional neurologic impairment. The patient tolerated the surgery well and showed no additional neurologic deficits postoperatively. For 2 weeks after the surgery, the patient still had a few seizures every day. However, the number of seizures gradually decreased by 4 weeks after the surgery and disappeared after the seventh week. Complete seizure control was obtained for 9 months postoperatively with the same an‐ticonvulsive therapy as that used before the surgery. Histologic examination revealed that the surface of the lesion was covered with a layer of subpial gliosis. Under the gliosis, the lesion consisted of complicated glial bundles and cortical islands. Some neurons were observed even in the glial bundle. The gray matter had no laminar structure and contained cytomegalic and polynuclear neurons. In the neighboring cortex that showed polymicrogyria, normal cortical columnar structure was preserved. However, the neuronal density was higher than that in the normal cortex.

Conclusions; Surgical indication for patients with diffuse cortical dysplasia is often neglected because of multiple seizure foci and mental disorders. However, it should be stressed that an excellent outcome is possible in some cases if the epileptic focus can be precisely defined. A neuronavigation system and intraoperative recording of the EcoG are useful for focus resection during surgery for epilepsy.