Evidence for nodular epileptogenicity and gender differences in periventricular nodular heterotopia

To determine whether clinical differences between the sexes seen in periventricular nodular heterotopia (PNH) have structural correlates on imaging.

PNH is the most common dysgenesis associated with hippocampal sclerosis (HS). Women with PNH have normal intellect; men may have mental retardation and other changes. Familial PNH, seen in women, is linked to Xq28-a region also abnormal in a sporadic male infant with PNH and retardation-suggesting sexual differences in gene expression. Epilepsy associated with PNH may be refractory to drugs, and surgery for associated HS does not stop seizures, suggesting intrinsic epileptogenicity of PNH.

Quantitative MRI analysis was performed using established techniques for detecting subtle structural changes in 13 female patients (11 sporadic and two familial) and four male patients (sporadic).

There is structural heterogeneity in PNH, even in patients with bilateral PNH. On MRI, men have more cerebral abnormalities beyond PNH than control subjects or female patients (p < 0.005).

The findings support the concept of intrinsic epileptogenicity of PNH. There may be additional structural abnormalities relevant to seizure generation, especially in men. Structural heterogeneity, and widespread abnormalities, may need consideration when patients are referred for surgical treatment or when additional studies of patients with PNH are conducted.