subgaleal

Subgaleal refers to a potential anatomical space in the scalp, located between the galea aponeurotica and the pericranium. It is part of the loose connective tissue layer that allows the scalp to move over the skull. In infants, this space can be relatively large and extensible, which has clinical significance in the context of birth trauma and certain head injuries.

Anatomy and boundaries

The subgaleal space spans the calvaria and is continuous across the scalp, extending around the forehead, vertex, and occipital region. It communicates across suture lines and with adjacent loose areolar layers, making it capable of spreading fluid or blood widely. In adults the space is typically small and contained, but in newborns its potential size increases the impact of trauma or hemorrhage within it.

Subgaleal hemorrhage

Subgaleal hemorrhage is the accumulation of blood within the subgaleal space. It is most commonly associated with birth trauma, particularly vacuum-assisted delivery or forceps use, though it can occur with blunt head injury or bleeding disorders. The daytime presentation includes diffuse, boggy scalp swelling that can cross suture lines, sometimes accompanied by pallor, tachycardia, hypotension, and signs of hypovolemia. Because the space can hold a large volume of blood, substantial hemorrhage can occur before external signs become severe.

Diagnosis and management

Diagnosis is primarily clinical, supported by imaging such as ultrasound to assess the extent of fluid or bleeding. Laboratory tests may show a falling hemoglobin/hematocrit and coagulopathy if present. Management focuses on hemodynamic stabilization and restoration of circulating volume, often requiring blood products, airway support, and intensive monitoring. Treating underlying causes and preventing ongoing blood loss are also essential. Subgaleal hemorrhage carries risk of significant morbidity and mortality without prompt recognition and treatment.