Holoprosencephaly: A review

Holoprosencephaly (HPE) is a brain malformation characterized by incomplete cleavage of the cerebral hemispheres and deep brain structures. Epilepsy is a common problem in children with HPE and a vast majority will have abnormal EEGs. A variety of EEG findings, including spike-and-slow-wave complexes, hypsarrhythmia, isoelectric patterns, periodic discharges, fast anterior rhythms, posterior gradient flattening, asynchronous high amplitude rhythmic activity, and paroxysmal hypersynchronous patterns, are reported in the literature. About half of the children with HPE evaluated at Texas Scottish Rite Hospital for Children have epilepsy. These children have various seizure types; however, there are some consistent EEG findings such as hypersynchronous theta during sleep, hypersynchronous theta while awake, hypersynchronous beta during sleep, and episodic attenuation of cerebral activity, in addition to a spectrum of epileptiform discharges. This article is a review of the clinical and neuroimaging features of HPE and includes discussion of what is known about EEG findings in the disorder.