Ultrasound of the septum pellucidum. Recognition of evolving fenestrations in the hydrocephalic infant.

Fenestrations of the septum pellucidum may be noted in hydrocephalic infants. This finding and its changing image was noted in six premature infants evaluated by neurosonography over time periods ranging from weeks to months. Breaks in the septum were noted to occur from 14 days to 23 weeks after the sonographic diagnosis of hydrocephalus. Some of these fenestrations were noted to increase in size and/or become bilateral over time. The awareness of evolving fenestrations and their late-stage images helps avoid confusion with partial and complete agenesis of the septum pellucidum and their possible associated neuroanatomical abnormalities.