Neonatal subependymal cysts detected by sonography: prevalence, sonographic findings, and clinical significance.

OBJECTIVE: Cranial sonography in neonates occasionally shows subependymal cysts. These cysts may be due to a variety of pathologic disorders, but they also occur as an "isolated" condition without an obvious cause in some patients. Assessment of the clinical significance of these lesions has been difficult because of the limited duration of follow-up, the informal nature of neurodevelopmental evaluation, and the heterogeneous cohort of patients previously reported. Accordingly, the purposes of this study were to provide more complete and longer neurodevelopmental followup and to describe the prevalence and sonographic characteristics of isolated subependymal cysts detected on cranial sonograms in neonates.
MATERIALS AND METHODS: In a 4 1/2-year period, more than 4000 cranial sonograms were obtained at our institution. We retrospectively determined that 17 neonates (59 studies) had sonographic evidence of an isolated subependymal cyst. A high-resolution real-time mechanical sector transducer was used to obtain the sonograms. No subjects had clinical or sonographic evidence of intercurrent hemorrhage, infarct, infection, or congenital abnormalities. Neurodevelopmental outcome was independently determined. In particular, premature infants who weighed less than 1500 g at birth were longitudinally assessed by a multidisciplinary developmental team. A general quotient was derived in nine subjects by using the Griffith Mental Developmental Scales.
RESULTS: Subependymal cysts were often tear shaped, 2-11 mm in size, and located either at the caudothalamic groove or along the anterior aspect of the caudate nucleus. Most subjects (n = 15) who had the cysts were born prematurely (mean gestational age, 31 weeks; range, 25-34 weeks). Results of follow-up were available in 14 infants 2-41 months old (mean, 22 months; median, 21 months). Development was considered to be normal in 13 of the 14 subjects; one term infant referred because of mild dysmorphic features had a mild global delay. The general quotient for corrected age, determined in nine subjects, had a mean of 111 (range, 103-120; normal, > 83). Fifteen neonates had at least two cranial sonographic examinations. In seven patients, serial examinations showed that cysts had resolved or diminished in size (on average 23 weeks after the initial sonographic study). In the other eight, no change in the size of the cyst was observed, but the mean interval between the first and last sonograms was only 14 days.
CONCLUSION: Cranial sonograms of neonates occasionally show isolated subependymal cysts, usually in premature infants. In most cases, no serious neurodevelopmental complications occur. Many cysts resolve after a variable period.