• Hypothalamic hamartoma;
  • Volumetric magnetic resonance imaging;
  • Brain measurement;
  • Cerebral dysgenesis;
  • Epilepsy surgery

Summary: Purpose: We tested the hypothesis that widespread extralesional abnormalities of cerebral structure exist in association with apparently isolated hypothalamic hamartomata, providing a structural basis for the poor response of seizures to removal of the hamartoma or other apparently focal epilepto-genic zones present.

Methods: High-resolution magnetic resonance imaging (MRI) brain scans of 2 patients with hypothalamic hamartomata were quantified by determination of regional distribution and symmetry of distribution of cortical gray matter and subcortical matter volumes. The results were compared with normal ranges for the distribution of such tissues in 33 controls.

Results: Both patients had abnormalities of distribution of gray and subcortical matter, whereas control subjects did not. These abnormalities were beyond the hamartoma itself, in areas of cerebrum that on visual inspection alone appeared completely normal.

Conclusions: Extralesional abnormalities of cerebral structure are present in the cerebrum of patients with hypothalamic hamartoma, as in most patients with other dysgeneses. These abnormalities may explain the poor outcome of epilepsy surgery in patients with this form of dysgenesis. These preliminary findings require further investigation.