Periventricular nodular heterotopia (PVNH) is described in the medical litterature as a a neuronal migration disorder. It is characterized by the presence of nodules of neurons (gray matter) in the wrong spot, specifically along the lateral ventricles instead of properly migrating to the cortex. It can also be referred to as BPH, BPNH, PNH or grey matter heterotopia.
The incidence of PVNH is unknown, and about 50% of occurences are genetically linked to the X-chromosome. The other 50% are thought to be spontaneous mutations. The genetic forms of PVNH are caused by mutation or deletion of one of the following genes: FLNA or ARFGEF2.
It is estimated that about 80% of patients affected by PVNH will suffer from seizures.
There appears to be 5 different distinguisable types of periventricular nodular heterotopia:
(1) bilateral and symmetrical;
(2) bilateral single-noduled;
(3) bilateral and asymmetrical - x-linked, with a female predominance and known familial cases of epilepsy. This form of PVNH is associated with the Xq28 chromosome and caused by a mutation in the Filamin A or 1 (FLNA) gene. Recent findings have demonstrated it is also associated with PVNH4 (PVNH with Ehlers Danlos variant) - the very form of PVNH my family is affected by. Medical reports allege that males show early lethality (in utero or soon after birth) although cases of FLNA mutations have been reported in boys (some showing mild symptoms and others very severe).
(4) unilateral: this form is not reported to have sex or familial prevalence it appears.
and (5) unilateral with extension to neocortex.
Generally, females present with seizures which appear at the average age of 14-15 years and the disease includes an increased risk for stroke and other vascular/coagulation problems. Intellectual delays are sometimes present as well as motor delays or physical impairments such as short digits.
It is important to note that people can have PVNH and have normal intelligence and live well.
To find out more about PVNH, visit the dedicated page on the Genetics Home Reference’s site (laymen’s term) or the one on the National Center for Biotechnology Information‘ site (more technical information).