Perdarahan Subgaleal

01Pathophysiology

The scalp has five anatomical layers, classically memorized by the mnemonic SCALP: Skin, Connective tissue (dense), Aponeurosis (galea aponeurotica), Loose areolar tissue, and Periosteum (pericranium). Subgaleal hemorrhage occurs when blood collects in the loose areolar tissue layer, which lies between the galea aponeurotica above and the periosteum below.

This layer is critically important because it is a potential space with no anatomical boundaries that limit expansion. It extends from the orbital ridges anteriorly to the nuchal ridge posteriorly, and from one temporal fascia to the other laterally. Because of this vast extent, this space can accommodate up to 260 mL of blood, which is nearly the entire circulating blood volume of a term neonate (approximately 80 mL/kg).

The bleeding originates from the emissary veins that traverse this space, connecting the dural sinuses to the superficial scalp veins. During vacuum-assisted delivery, the negative pressure applied to the fetal scalp generates shearing forces that tear these bridging veins. This is why vacuum extraction is the single most important risk factor. Forceps delivery can also cause similar vascular disruption, though to a lesser degree.

Once the veins are torn, blood dissects freely through the loose connective tissue. Unlike a cephalohematoma, where the periosteum is tightly adherent to the skull at the suture lines and confines bleeding to a single bone, there is no such barrier in the subgaleal space. The hemorrhage spreads diffusely, leading to progressive swelling that crosses suture lines and fontanelles. This uncontained bleeding is what makes subgaleal hemorrhage a life-threatening emergency: the neonate can lose a fatal volume of blood into the scalp before the clinician realizes the severity.

The downstream consequence is hypovolemic shock. As blood volume drops, the neonate becomes tachycardic, pale, and hypotensive. The consumption of clotting factors at the bleeding site can trigger disseminated intravascular coagulation (DIC), which worsens the hemorrhage and creates a dangerous feedback loop of bleeding and coagulopathy.

02Classification and Clinical Manifestation

Subgaleal hemorrhage does not have formal staging in the way that many diseases do, but it is clinically useful to understand it in terms of severity based on estimated blood loss, which drives presentation and urgency.

It is also essential to understand where subgaleal hemorrhage fits among the three extracranial neonatal hemorrhages, as this is one of the most commonly tested comparisons:

03Diagnostic Workup

Clinical diagnosis is paramount. In the exam setting, the vignette will describe a neonate born via vacuum-assisted delivery who develops a progressively enlarging, fluctuant scalp swelling crossing suture lines within hours of birth. This clinical picture alone should trigger the diagnosis.

The best initial step is not imaging but rather clinical recognition and monitoring. Serial head circumference measurements are the most practical bedside tool. A commonly tested correlation is that each 1 cm increase in head circumference corresponds to roughly 40 mL of accumulated blood. This means a 2 to 3 cm increase may signal the loss of 80 to 120 mL, which in a 3 kg neonate (total blood volume around 240 mL) represents a loss of 33 to 50% of circulating volume.

Simultaneously, serial hematocrit measurements will show a progressive decline. The coagulation panel is ordered not only to detect DIC but also to identify underlying coagulopathies (such as factor deficiencies or vitamin K deficiency bleeding) that may have predisposed the infant to the hemorrhage in the first place.

Cranial ultrasound is the best initial imaging modality because it is portable, radiation-free, and can be performed at the bedside in the NICU. It visualizes the fluid collection well and can also evaluate for intraventricular or subdural hemorrhage. CT scan is reserved for cases where the diagnosis is unclear, where intracranial pathology is suspected, or when surgical intervention is being considered. CT provides superior anatomical detail and can detect skull fractures.

04Management and Treatment

Acute stabilization is the priority. The "next best step" when you recognize a neonate in hemorrhagic shock from subgaleal hemorrhage is volume resuscitation with isotonic crystalloid (normal saline) followed immediately by packed red blood cell transfusion. Do not wait for lab confirmation before initiating resuscitation if the clinical picture is clear.

Correction of coagulopathy runs in parallel. Fresh frozen plasma replaces the consumed clotting factors, and cryoprecipitate is added if fibrinogen is critically low. Vitamin K should be confirmed or re-administered. These interventions break the cycle of consumptive coagulopathy and ongoing hemorrhage.

There is no role for surgical evacuation in most cases. The hemorrhage is venous and diffuse, not a localized arterial bleed amenable to ligation. Management is entirely supportive and resuscitative. However, if there is an associated intracranial hemorrhage or depressed skull fracture, neurosurgical consultation is warranted.

Long-term considerations are generally favorable for survivors. Once the acute phase is managed, the hematoma resorbs over days to weeks. During resorption, the breakdown of red blood cells produces unconjugated bilirubin, so the infant should be monitored for hyperbilirubinemia and treated with phototherapy as needed. Follow-up should include neurodevelopmental assessment, particularly if the infant experienced prolonged hypotension or required prolonged resuscitation.

Contraindication to note: In a neonate with suspected or confirmed coagulopathy, avoid any procedures that could worsen bleeding (such as unnecessary scalp punctures or aggressive scalp manipulation). Also, if DIC is present, platelet transfusion alone without FFP/cryoprecipitate is insufficient because the coagulation cascade itself is disrupted.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students lose points on subgaleal hemorrhage questions is by confusing it with cephalohematoma. Both are post-delivery scalp swellings, and both are associated with instrumental delivery. The critical discriminator is whether the swelling crosses suture lines. If the vignette says the swelling crosses suture lines and the baby is becoming hemodynamically unstable, it is subgaleal hemorrhage, not cephalohematoma. If the swelling is confined to one bone and the baby is otherwise stable, it is cephalohematoma.

A second common trap is confusing subgaleal hemorrhage with caput succedaneum because both cross suture lines. The key here is timing, character, and trajectory. Caput is present at birth and resolves; subgaleal hemorrhage develops after birth and worsens. Caput is pitting edema; subgaleal hemorrhage is fluctuant collected blood.

Another tested pearl: exam writers love to test whether you know the volume significance of the subgaleal space. When a vignette provides a head circumference that has increased by several centimeters over hours, you should immediately calculate approximate blood loss (1 cm = ~40 mL) and recognize the severity of the situation.

Finally, do not forget the association between subgaleal hemorrhage and underlying coagulopathy. A vignette may describe a neonate without a history of instrumental delivery who develops diffuse scalp swelling. In this scenario, the question is testing whether you will investigate for an inherited bleeding disorder such as hemophilia or for vitamin K deficiency bleeding as the underlying cause.

The core competency being tested is your ability to localize the anatomical layer of bleeding (subcutaneous vs. subperiosteal vs. subaponeurotic), connect that localization to clinical behavior (crossing suture lines, hemodynamic compromise), and initiate the correct sequence of resuscitative management.