Quick Facts
The epicranial aponeurosis is the aponeurotic layer of the scalp; the central tendon of the epicranius muscle, connecting the frontal and occipital bellies of the occipitofrontalis muscle, and the temporoparietalis muscles (Dorland, 2011).
Related parts of the anatomy
Structure
The epicranial aponeurosis is the third layer of the scalp and the strongest. It is a thin (approximately 0.5 mm), broad, and strong tendinous sheet that serves as an intermediate tendon between the occipital and frontal bellies of the occipitofrontalis muscle (Brennan, Mahadevan and Evans, 2015).
The epicranial aponeurosis is tightly bound to the overlying skin via a fibrous subcutaneous tissue. However, it is loosely connected to the underlying pericranium, thus allowing it to move freely, while carrying the skin with it.
Deep lacerations, or cuts, to the scalp can result in continuous bleeding. This is because the underlying epicranial aponeurosis is abundant in elastic fibers, which prevents the vessels in the overlying superficial fascia from retracting.
Key Features/Anatomical Relations
The epicranial aponeurosis is internal to the dense superficial fascia of the scalp and external to the loose connective tissue of the scalp.
Posteriorly, it blends with the occipital belly of the occipitofrontalis to insert into the superior nuchal line of the occipital bone. Anteriorly, it is continuous with the frontal portion of the occipitofrontalis muscle and blends with the eyebrows. Laterally, it blends with the temporalis fascia, as well as the anterior and superior auricular muscles and the temporoparietalis muscle.
The subaponeurotic space, or “danger space,” is a potential space deep to the epicranial aponeurosis. This space contains the loose connective tissue and the emissary veins that link the intracranial dural sinuses with the extracranial veins. Thus, localized infections within this space have the potential to spread intracranially. The subaponeurotic space is limited anteriorly by the frontal belly and posteriorly by the occipital belly of the occipitofrontalis muscle.
Function
The epicranial aponeurosis serves as a site of origin for the frontal bellies of the occipitofrontalis muscle and a site of insertion for the occipital muscles of the occipitofrontalis muscle. Additionally, it is loosely connected to the underlying loose connective tissue; thus it can move over it freely, carrying the skin and subcutaneous tissue.
List of Clinical Correlates
—Scalp lacerations
—Scalp infections
—Subgaleal hemorrhage
—Osteomyelitis
—Brain abscess
References
Brennan, P. A., Mahadevan, V. and Evans, B. T. (2015) Clinical Head and Neck Anatomy for Surgeons. CRC Press.
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
