The prognosis for fetuses with apparent Dandy-Walker syndrome or its variant is often grim but can vary widely. Pinpointing the variations with sonography can help doctors better advise patients, according to a presentation at the American Institute of Ultrasound in Medicine conference in April.
Researchers from Massachusetts General Hospital and Brigham and Women's Hospital, both in Boston, shared the results of the first large study outlining the sonographic diagnosis of the syndrome.
"Counseling patients is problematic. The outcomes vary widely and there is a host of associated anatomic and karyotypic abnormalities," said presenter Dr. Jeffrey Ecker.
Dandy-Walker syndrome (DW) is a congenital brain malformation involving the fourth ventricle and cerebellum. It is defined as an enlargement of the fourth ventricle, an absence of the cerebellar vermis, and cyst formation in the posterior fossa. Hydrocephalus may also be present, according to the National Institute of Neurological Disorders and Stroke.
Symptoms, which often occur in early infancy, include slow motor development and progressive macrocrania. Dandy-Walker syndrome has a high association with other central nervous system structural anomalies, including agenesis of the corpus callosum and malformations of the face, limbs, digits, and heart. Dandy-Walker Variant (DWV) is a less severe posterior fossa anomaly.
In the latest study, 99 scans performed between 1992 and 1999 were retrospectively evaluated. In the 50 fetuses with DW, 86% had sonographically identifiable anomalies. In the remaining 49 cases with DWV, 85% had anomalies detected with sonography.
"In making the diagnosis of DWV, we were careful to confirm diagnosis on ultrasound performed after 18 weeks gestation," Ecker said, noting that DWV may not show until after the 17th week.
The most common anomalies were ventriculomegaly, which was found in 32% of fetuses with DW and 27% of those with DWV; cardiac defects were apparent in 38% of the DW cases and 41% of DWV. Abnormal karyotypes (chromosomal characteristics in individual cells) were found in 46% of DW fetuses and 36% of those with DWV.
The outcomes for DW were as follows: 41 patients elected termination, there were five neonatal deaths, one normal survivor at six-week follow-up, two abnormal survivors, and nine patients lost to follow-up. Of those nine patients, two had known karyotype abnormalities, Ecker reported.
Among the 49 cases of DWV, 20 elected termination and three fetuses died in utero. A total of 13 were lost to follow-up. Ecker said his team suspected many of these patients elected termination. There were 13 survivors, of which seven were normal at six weeks follow-up, although six had isolated findings of DWV.
"Isolated DWV appears to have the highest chance of leading to a normal outcome," Ecker said. "All patients with sonographic diagnosis of DW and DWV should consider amniocentesis, even those with isolated DWV."
A second study presented at the AIUM by Canadian researchers looked at outcomes after prenatal ultrasound findings of DWV. Thirty cases of DWV were identified on prenatal sonography done at the Children's and Women's Health Centre in Vancouver. Of those 30 patients, ten fetuses had isolated DWV. Four of those cases resulted in a number of complications, including toxoplasmosis and Joubert syndrome after birth. The remaining fetuses are developing normally at two to seven years of follow-up, the paper reported.
By Shalmali Pal
AuntMinnie.com staff writer
May 2000
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