Posterior quadrantic dysplasia or hemi-hemimegalencephaly: a characteristic brain malformation.

INTRODUCTION: Posterior quadrantic dysplasia (PQD), a developmental malformation involving the temporal, parietal, and occipital lobes of one cerebral hemisphere, leads to intractable epilepsy.
OBJECTIVE: To characterize the clinical features of 19 patients with PQD and analyze the postsurgical outcome of those who underwent resection of dysplastic tissue.
METHODS: The extent and nature of the malformation were primarily assessed with high-resolution brain imaging. Fourteen patients underwent complete or partial temporoparieto-occipital resection or temporal resection associated with parieto-occipital disconnection. Postoperative follow-up period ranged from 8 months to 7 years. The authors used the Engel classification for postoperative outcome.
RESULTS: All patients were sporadic. Clinical features included infantile spasms, partial seizures, mental retardation, mild hemiparesis, and visual field defects. Neuroimaging localized the malformation within the posterior cerebral quadrant contralateral to the neurologic deficit and demonstrated hemi-hemimegalencephaly in 14 of 19 patients and multilobar cortical dysplasia in 5 of 19 patients. The authors observed class I outcome in six patients. Two patients had class II and four patients had class III outcome. Class IV outcome was seen in two patients. After surgery, two patients developed mild hemiparesis, and two developed a visual field defect.
CONCLUSIONS: Widespread cortical dysplasia is more frequent in the posterior quadrant. In our series, posterior quadrantic dysplasia represents either hemi-hemimegalencephaly or multilobar cortical dysplasia. Individuals with posterior quadrantic dysplasia share a spectrum of clinical features. The intractable epilepsy in these patients may be alleviated by a large quadrantic temporoparieto-occipital resection.