Cystic hygroma

Description

Cystic hygromas (CH) are generally bilateral, thin-walled, uni-or multi-locular, fluid-filled cavities in the posterior aspect of the neck. They may be asymmetric or symmetric. Larger hygromas are often subdivided into a variable number of compartments by incomplete septa. The volume of the hygroma and the presence of septa are associated with higher incidence of chromosomal disease and poorer fetal prognosis. Hygromas are caused by failure of or delay in jugular lymphaticovenous communication, and they may regress and resolve if collateral routes develop or if jugular veins connect. The cavities may extend posteriorly from the upper part of the occipital bone to the level of the seventh cervical vertebra or scapular area; medially to beneath the sternocleidomastoid muscle; and rarely into the axilla or anterior chest wall. They form superficial to the musculature of the neck with a deeper extension to the proximal part of the internal jugular vein. Some cavities are continuous with intricate systems of irregular lymph channels, extending into the edematous connective tissue around adjacent anatomic structures, while other CH are well demarcated. CH are frequently reported in association with abnormalities of the major lymph trunks, leading to peripheral edema, pleural, pericardial and peritoneal effusions. CH is a non-specific malformation found in a number of unrelated conditions. Up to 76% of hygromas are associated with a chromosomal abnormality .Between 50 and 75% of all septated hygromas are cytogenetically abnormal, affected fetuses are also more likely to develop hydrops and less likely to be liveborn. The most common abnormality associated with a septated hygroma is Turners syndrome and with non-septated, trisomy 21. For these reasons fetal chromosome analysis is essential. Within the group that are chromosomally normal are a number of single gene disorders and patterns of malformations resulting from in utero exposure to known teratogens. The most common of these is Noonan syndrome. This diagnosis should be suspected even when the CH resolves, and a search made for accompanying anomalies, such as cardiac defects. Spontaneous regression has been reported which, if it occurs by 20 weeks gestation may be associated with a good prognosis. Only 9% of cases result in healthy children with normal karyotypes, the remaining 91% being either terminated (89%) or liveborn (2%) but with chromosomal abnormality or malformation. However a recent analysis of cases reported to a congenital malformation registry may suggest that more care should be taken with prenatal diagnosis and the counselling given. Of 89 diagnoses made prenatally 50% were incorrect at postmortem and of the 63% of the 89 that were terminated for cystic hygroma only 25% were confirmed.