Cystic hygroma

Cystic hygroma


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.


CH may be diagnosed by ultrasound, possibly as early as 10 weeks gestation but with a mean of 19 weeks. The posterolateral position and cystic appearance are characteristic. Larger CH are frequently divided by random, incomplete septa. They often have a dense midline septum, representing the nuchal ligament, which provides a useful landmark to differentiate CH from other craniocervical masses. Smaller, non-septated CH may be located anterolaterally. Non-septated CH appear to have a better prognosis: they frequently regress prior to 16 weeks gestation; the risk of associated chromosome abnormality is lower; and relatively good neonatal outcome can be expected. By contrast, septated CH are often associated with a chromosome anomaly. Generalized hydrops accompanies 60-90% of septated CH, even where the karyotype is normal. In these cases, the outlook is grave, with the majority ending in spontaneous miscarriage, intrauterine death or early neonatal death. Only 7% of continuing pregnancies result in liveborn infants. Transvaginal ultrasonography enables very early detection of CH. Diagnostic confusion at this gestation can occur because of the existence of ‘nuchal blebs’, posterior occipital fluid collections, which are common under 10 weeks, and which usually resolve by 11 weeks. These could represent temporary accumulation of lymph, and may be a normal variant in the development of lymphaticovenous communication. Maternal serum or amniotic fluid alpha-fetoprotein estimation has been used to aid diagnosis of CH. However, the concentration of alpha-fetoprotein is inconsistent and adds little to the sonographic findings. Alpha-fetoprotein concentration in hygroma fluid is often markedly elevated. Congenital heart defects, particularly those associated with decreased left heart blood flow, such as coarctation of the aorta and bicuspid aortic valve, are often found in association with CH. Other malformations observed in rare instances include hydronephrosis, double ureter, horseshoe kidney, bilateral renal agenesis, two vessel cord, intrauterine growth retardation and polysplenia syndrome. The diagnosis of CH should be sonographically assured, and distinguished from other craniocervical masses. A detailed search for other malformations, growth retardation and generalised hydrops should be performed

Differential Diagnosis

The identification of a posterior cranial mass will prompt consideration of the following: Most encephaloceles are located in the occipital area. An underlying bony defect is the rule, but may be difficult to demonstrate when small. The mass is seen to derive from, and move with, the fetal head. It may be cystic, solid or a combination. Tumours such as teratomas are likely to have a solid or complex appearance. The twin sac of a blighted ovum will lack the typical septations of a CH. Nuchal edema or thickening can occur as a consequence of jugulolymphatic obstruction, prior to the development of fullblown CH, or may simply represent delayed opening of the jugulolymphatic connection. In the latter situation, the oedema/thickening should resolve promptly. Cystic lymphangioma has a more complex appearance than CH, and is both cystic and solid. It is not associated with jugulovenous lymphatic obstruction and will not resolve. It is often anterior, causing the fetal head to be retroflexed; the principal concern is difficulty during delivery. Diagnostic errors may occur because of misinterpretation of a segment of umbilical cord behind the neck, an adjacent subchorionic cyst, or, in the first trimester, when part of the amnion has not yet merged with the chorion.

Sonographic Features

Single or multiloculated fluid-filled cavity, usually in the posterior nuchal region

Lack of solid component Internal septation common, particularly in the midline

Intact skull and spinal column

Associated Syndromes

  • Achondrogenesis type II
  • Chromosomal
  • Cowchock
  • Cumming
  • De Lang
  • Distichiasis-lymphedema
  • Down
  • Edwards
  • Familial
  • Fryns
  • Klinefelter
  • Lethal multiple pterygium
  • Noonan
  • Nuchal blebs
  • Patau
  • Roberts
  • Teratogens
  • Tetraploidy
  • Turner


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