A 17-year-old boy comes to the emergency department because of fever, worsening headache, and swelling of the scalp 5 days after sustaining a contaminated laceration during a football game. The wound is located over the parietal scalp. Temperature is 38.9°C (102.0°F), blood pressure is 112/70 mm Hg, pulse is 108/min, and respirations are 18/min. Physical examination shows erythema and fluctuance surrounding the laceration. MRI shows inflammation tracking from the scalp toward a dural venous sinus through emissary veins.
Infection most likely spread through which of the following scalp layers?
The correct answer is:
C) Loose areolar connective tissue
The scalp consists of five layers remembered as skin, dense connective tissue, aponeurosis, loose areolar connective tissue, and pericranium. The loose areolar connective tissue layer is the “danger area” of the scalp because it contains emissary veins that connect superficial scalp veins with intracranial dural venous sinuses. Infection in this layer can therefore spread intracranially and cause serious complications such as dural venous sinus thrombosis or meningitis. This patient’s infected scalp laceration with extension through emissary veins identifies the loose areolar layer as the involved anatomic plane.
Answer choice A: Aponeurosis, is incorrect. The aponeurosis, or galea aponeurotica, connects the frontalis and occipitalis muscles and helps move the scalp. Lacerations involving this layer can gape due to tension, but the aponeurosis itself is not the main layer through which emissary veins transmit infection to dural venous sinuses.
Answer choice B: Dense connective tissue, is incorrect. The dense connective tissue layer contains blood vessels and nerves of the scalp and helps keep cut vessels open, which can lead to profuse bleeding from scalp lacerations. It is not the “danger area” associated with intracranial spread through emissary veins.
Answer choice D: Pericranium, is incorrect. The pericranium is the periosteum of the skull and lies deep to the loose areolar connective tissue. Subperiosteal collections are usually limited by cranial sutures because the pericranium attaches at suture lines, but this layer is not the principal route for infection spread through emissary veins.
Answer choice E: Skin, is incorrect. The skin is the most superficial layer of the scalp and contains hair follicles, sebaceous glands, and sweat glands. Although the infection may begin at the skin surface, intracranial spread through emissary veins occurs through the deeper loose areolar connective tissue layer.
Key Learning Point
The loose areolar connective tissue layer is the danger area of the scalp because emissary veins in this layer can transmit infection from the scalp to dural venous sinuses.
