Scalp swellings are common in infants and have recently been reviewed by Williams et al
The most common scalp swellings are caput succedaneum and cephalhaematoma and both are more commonly associated with instrumental delivery or difficult labour.
The subaponeurotic or subgaleal space is the area between the scalp aponeurosis and peri-cranium extending from the supraorbital ridge to the nape of the neck from anteriorly to posteriorly and laterally to the ears. The subaponeurotic layer is made up of multiple sheets of vascularised connective tissue that are able to glide over each other. The highly vascular nature of this tissue increases the risk of bleeding which may be significant, and subgaleal or subaponeurotic haemorrhage occurs due to the rupture of emissary veins which are connections between dural sinuses and scalp veins. Haemorrhage can occur into this large space during delivery causing hypovolaemic shock early in the perinatal period. Subaponeurotic or subgaleal haemorrhage is most often associated with vacuum extraction or forceps delivery, but it can occur spontaneously.2 3
Subaponeurotic or subgaleal fluid collections are thought to be rare and present later. These four cases all presented within a 6-month period in a mid-sized district hospital with a birth rate of 3400 per year. These scalp fluid collections were clinically distinct with features typical for fluid in the subaponeurotic or subgaleal space, that is, mobile, compressible fluid collection with often a prominent fluid thrill. The fluid moved with the position of the head and clearly crossed suture lines. They were clinically very distinct from other scalp swellings in infancy. Although all cases in our series were born by emergency caesarean section and one of the four experienced a failed forceps delivery, but there were no unusual features in these cases that could be considered to be specifically relevant to the aetiology of subaponeurotic or subgaleal collection presenting after the first 2–3 weeks of life.
Hopkins et al4
reported a series of seven cases (six were infants and one a 7-year-old child) that presented over a 4-year period with subaponeurotic fluid collections. Mean age at presentation was 9 weeks. Of the six cases that presented in infancy, four were born via ventouse delivery while the remaining two were spontaneous vaginal deliveries. All six had skull x-rays and there was no evidence of fractures. Ultrasound of the head confirmed scalp fluid swellings with no intracranial extension or haemorrhage. The fluid was seen to cross the sutures and could be chased over the vault. They postulated that the cause of the swellings were small subaponeurotic bleeds at delivery which were masked by soft tissue swelling which may have gradually liquefied with further fluid accumulation due to exudation resulting in increase in size and later presentation. They also postulated that the there could have been a disruption in lymphatic drainage with resultant accumulation of fluid over several weeks. They aspirated fluid from the lesion in one case and identified clear fluid. All resolved spontaneously between 2 and 24 weeks.
Schoberer et al5
reported a series of five cases of subaponeurotic fluid collection, four of which were large in size, presenting at 7–8 weeks after birth. Four of the infants were delivered by ventouse extraction and one was delivered by caesarean section after failed external cephalic version. In all cases ultrasound showed a compressible lesion of low echogenicity with no cyst wall and no flow signals on colour-coded duplex sonography. One patient underwent MRI, three had CT scan and all had normal intracranial findings, with no extra-cranial connections, skull fractures or abnormal vascular markings. In this case series fluid was aspirated in three cases (twice in one case) and it was interesting to note that the fluid re-accumulated after aspiration on all three occasions. The fluid was serosanguinous in appearance and negative for microbiological studies. Further analysis of the fluid showed a high concentration of β-trace protein, and β2-transferrin was present in all aspirates within the normal range for CSF. They concluded that the fluid collections, as in the series by Hopkins et al
appeared to be related to traumatic labour, which was also supported by the serosanguinous nature of the fluid aspirates, and that the β2-transferrin and β-trace protein indicated the presence of CSF in all aspirates. They postulated that the origin of the CSF may have been due to micro-fractures undetectable by neuroimaging or disruption of emissary or diploic veins that connect intracranial venous sinuses with superficial veins of the scalp.
When considering the data available on all 15 cases that presented in infancy (excluding the 7-year-old boy of the Hopkin et al study) (), the common clinical finding at presentation was of a distinct, highly characteristic scalp swelling of short duration, detectable at a mean age of 7 weeks that resolves spontaneously on average 3–4 weeks later. There is a strong association with cephalic presentation and instrumental delivery with only 2/15 (13%) cases having normal delivery, 9/15 (60%) having ventouse or attempted ventouse delivery, 2/15 (13%) having forceps delivery and 6/15 (40%) being born via caesarean section. There is no history of significant scalp injury or swelling recorded on newborn examination. There is no associated skull fracture or intracranial haemorrhage and the prognosis is good with spontaneous resolution in all cases. This swelling is not associated with excessive increase in the head circumference as the swelling is very mobile, fluctuant and shifts with the position of the head. The fluid is serosanguinous in nature with some indication that it may originate from CSF, although the exact aetiology of the collection is not clear. It would appear that aspiration of the fluid is not helpful therapeutically or diagnostically and risks introducing infection. If the condition is diagnosed clinically with confidence there is no specific indication for imaging studies or therapeutic intervention.
Details of 15 cases of subaponeurotic fluid collections
Non-accidental head injury should always be considered in the differential diagnosis of children with spontaneous scalp swellings as this can commonly occur in the absence of any supporting history or physical examination. Subgaleal or subaponeurotic haemorrhage has been described in the pattern of injury associated with shaken baby syndrome and other non-accidental head injuries, but such infants are usually unwell in contrast to children with subaponeurotic fluid collections.
If imaging is to be considered in infants with subaponeurotic or subgaleal fluid collections when there are concerns regarding abusive head injury, then a skull x-ray should be performed as an initial investigation to rule out any evident fracture. Ultrasound is then a useful and simple investigation that will confirm the diagnosis of subaponeurotic or subgaleal collection but will not give any information regarding the nature of the fluid. MRI is then a better option to confirm the nature of the fluid as compared to CT because it does not involve radiation and is easier to perform in this age group (feed and wrap technique).
- Subaponeurotic fluid or subgaleal collection is a rare but important cause of scalp swelling in infants.
- It is different from subgaleal haemorrhage in newborns, which is a life threatening condition; subaponeurotic fluid collection also presents later in infancy and such children are very well at presentation.
- The aetiology remains uncertain but may be related to traumatic delivery, but it is unclear why it presents later.
- It is clinically very distinct from other scalp swellings and the fluid in the subaponeurotic or subgaleal space is very characteristic – it is ill defined, mobile, fluctuant and is not limited by sutures.
- It can be diagnosed clinically without the need for radiological investigations due to the characteristic nature of the swelling, but appropriate imaging studies should be carried out if there are any concerns regarding the nature of the swelling.
- As the swelling resolves spontaneously without any intervention, no treatment is needed.