Not All New Scalp Bulges Are Concerning

A previously healthy 6-week-old male presents to the emergency department for new posterior scalp swelling, which the parents noticed earlier that morning (Video 1; Figure 1). They do not recall a preceding trauma, injury, or fall that could affect the area. Aside from the scalp swelling, he is otherwise acting averagely, breastfeeding well, and is easily consolable. The results of his review of systems are otherwise negative. Parents do not note any rashes, bruising, bleeding, or wounds.He was born at 40 weeks’ gestation via a vacuum-assisted cesarean delivery for failure to progress. Per routine care, he received intramuscular vitamin K. At birth, he had an occipital caput succedaneum that resolved by day 2 of life. He otherwise has no additional birth or medical history. The surgical history is significant for a circumcision without any complications. He lives with his mother and father, who are his primary caregivers. There are no new social stressors.In the emergency department, the patient is afebrile and hemodynamically stable with age-appropriate vital signs. His weight is 5.1 kg (46th percentile), length is 57.7 cm (27th percentile), and head circumference is 40.3 cm (79th percentile), which all track along his prior growth percentiles. On examination, he is well appearing and has an open, flat, and soft anterior fontanelle. There is a 4 × 4-cm soft, fluctuant fluid collection over the superior occiput that crosses suture lines. The overlying skin is not erythematous, warm, or tender to the touch, and there is no visible bruising. The patient’s lingual frenulum is intact. A fundoscopic examination confirms bilateral red reflex. The results of his neurologic examination are normal: he demonstrates equal, spontaneous movement of all 4 extremities with grossly normal strength throughout.A noncontrast computed tomography (CT) scan of the head shows nonspecific edema at the midline vertex scalp without acute intracranial pathology or underlying skull fractures (Figure 2). The patient is discharged home and parents are given strict return precautions and advised to follow-up with their pediatrician.The differential diagnosis of scalp swelling in the immediate newborn period includes subgaleal hemorrhages, caput succedaneums, and cephalohematomas. However, new-onset scalp swelling that develops weeks after delivery is highly concerning for nonaccidental trauma (NAT), resulting in a subgaleal or subaponeurotic hemorrhage. In this otherwise healthy, well-appearing infant with no other examination findings, the diagnosis was a benign etiology of scalp swelling known as delayed subaponeurotic fluid collection (DSFC).1–8DSFC is characterized by spontaneous delayed onset of scalp swelling in early infancy. It characteristically presents as a soft, nontender, mobile, fluctuant swelling of the scalp with a palpable “fluid thrill” on examination.9,10 The reported typical age of onset is between ages 3.5 and 18 weeks.1,5 There are no clearly reported incidence rates, but fewer than 50 instances of DSFC have been described.5 The exact etiology and what accounts for the delayed presentation is unknown. DSFC has been associated with a history of difficult labor or birth trauma. The vast majority of described instances occurred in infants who had instrument-assisted deliveries or placement of scalp electrodes during delivery or who needed emergency cesarean deliveries.1–9 DSFC is a benign entity characterized by progressive swelling, followed by spontaneous resolution between 1 and 20 weeks after diagnosis.1–9Several mechanisms have been proposed to explain how DSFC develops. Hopkins et al postulated that DSFC may arise because of disrupted lymphatic drainage.1 Schoberer et al hypothesized that DSFC may occur because of microfractures that disrupt cerebrospinal fluid (CSF) drainage pathways following traumatic births.8 This theory is supported by analysis of aspirated fluid from instances of DSFC that demonstrate presence of proteins, including β-trace and β2-transferrin, typically found in CSF.3,6–8DSFC is primarily a clinical diagnosis and can be differentiated from other causes of scalp swelling by history, physical examination, and judicious use of laboratory and imaging studies.2,5,6 The differential diagnoses include cephalohematomas, caput succedaneums, and subgaleal hemorrhages, which all present similarly with scalp swelling. Both cephalohematomas and caput succedaneums present immediately after birth. Cephalohematomas are confined to suture lines, which differentiate them from DSFC. Although caput succedaneums can cross suture lines, they are immobile and not ballotable on examination, which helps distinguish them from DSFC. Subgaleal hemorrhages are indistinguishable from DSFC by physical examination because both are mobile and easily compressible, and the swelling crosses suture lines. Subgaleal hemorrhages can be present immediately after birth, particularly in the setting of a traumatic birth, or they can have a delayed presentation. The delayed presentation is concerning for trauma, either accidental or NAT, and is typically the result of a significant closed head injury. These infants are generally unwell and typically have evidence of other injuries. The bleeding can be so extensive that it results in hemorrhagic shock.5 Leptomeningeal cysts (LMCs) can also present with delayed nontender progressive scalp swelling caused by herniation of brain elements through a posttraumatic skull fracture with a concurrent dural tear.11 LMCs usually develop from a fall-related incident in children younger than 3 years, most commonly involve the parietal scalp, and can be soft or firm on palpation.11 Because of the inciting trauma, children with LMCs will typically present with other neurologic deficits or seizures.11Laboratory studies are rarely helpful, but complete blood count and clotting studies can be considered if there is concern for an underlying coagulopathy. Imaging is not typically recommended because the history, vitals, and examination findings alone should be sufficient for clinicians to diagnose DSFC. However, should imaging be used, a head CT or magnetic resonance imaging (MRI) scan can be helpful to confirm the fluid collection location and evaluate for any underlying skull fractures or intracranial injuries.5 An MRI scan is superior because it avoids radiation exposure and can better distinguish between a benign fluid collection and a hematoma. However, access to MRI scans may be a barrier. With a CT scan, the density of the fluid should be low, like water.5 In either case, a CT or MRI scan of infants with DSFC will confirm a subaponeurotic or subgaleal collection. Aspiration of the fluid collection is not routinely recommended because it increases the risk of bleeding and infection, the fluid tends to reaccumulate rapidly, and aspiration does not change the timeline for spontaneous resolution.1,3,5–7DSFC is a benign entity that will spontaneously resolve within 1 to 20 weeks of presentation and has no known long-term sequelae.1,2,4,6,7,9 The most important task for the diagnosing clinician is differentiating DSFC from NAT. Reassuringly, no published reports of DSFC have been associated with an acute injury. In the absence of other findings, pursuing skeletal surveys or referring to child protective services is unnecessary and not recommended. However, if the subaponeurotic fluid collection persists beyond the typically expected resolution period, an MRI scan is recommended to evaluate for a persistent communication between the CSF and the subaponeurotic or subgaleal space.The infant’s scalp swelling spontaneously resolved over 4 weeks without any recurrence.DSFC is a rare, benign etiology of postnatal scalp swelling.DSFC can be distinguished from other common causes of scalp swelling, including caput succedaneum and cephalohematoma, based on timing of onset, location, and physical examination characteristics.DSFC must be distinguished from subgaleal hemorrhages, which, if arising later in infancy, raises suspicion for NAT.Advanced imaging with a CT or MRI scan is not necessarily needed to diagnose DSFC if the history and examination are reassuring.The authors would like to thank Drs Lawrence Ma, Ronnie Chen, and Paritosh Khanna for their time and expertise.