INTRODUCTION

A wide variety of lesions affect the scalp. They may be identified as palpable masses or as incidental findings in radiological studies. The differential diagnosis is broad, and radiologic evaluation is often requested.

Most scalp and skull lesions in children are benign.— Lipomas, epidermoid cysts, dermoid cysts and trichilemmal cysts are the most common diagnoses.

ANATOMY OF THE SCALP

—It consists of five layers: Fig. 1

1. Skin ⇒ Is especially thick in the region epicranial.

2. Dense connective tissue ⇒ Contains nerves, lymphatics and vessels.

3. Epicranial aponeurosis (galea aponeurotica) ⇒ Is a thin tendinous structure that bridges the paired occipital and frontal bellies of the occipitofrontalis muscle.

4. Loose connective tissue ⇒ Provides a plane of access in craniofacial and neurosurgical procedures. This layer is also called the "danger zone" because of the ease by which infectious agents can spread  into other layers or through emissary veins into the intracranial compartment.

5. Pericranium ⇒ Periosteum of skull bones.

A mnemonic for the layers of the scalp is:

S: Skin

C: Connective tissue

A: Aponeurosis

L: Loose connective tissue

P: Periosteum

SEMIOLOGY OF LESIONS OF THE SCALP

According to Hymen LA et al., three layers are distinguishable radiologically on normal and pathologic MRI and CT imaging: Fig. 2

1. Skin
2. The subcutaneous layer
3. Galea/subgaleal/periosteum complex

Lesions may be subdivided by their location within the scalp: Fig. 3

1. Skin/Connective tissue.

2. Subgaleal, between the galea aponeurosis and the skull periosteum.

3. They may include several or all layers of the scalp.