What are the anatomical relationships and structures enclosed or associated with the investing layer of the deep cervical fascia (DCF)?

Anatomical Relationships of the Investing Layer of Deep Cervical Fascia

Direct Answers to Each Statement

1. Splits to enclose the sternomastoid muscle: TRUE

• The investing layer of the deep cervical fascia (DCF) does split to enclose the sternocleidomastoid muscle 1
• This is a well-established anatomical relationship, though recent anatomical studies suggest the traditional description may be incomplete in certain regions 2, 3

2. Attached to the ligamentum nuchae: TRUE

• The investing layer attaches posteriorly to the ligamentum nuchae 1
• This posterior attachment is part of its circumferential course around the neck

3. Continues as the axillary sheath: TRUE

• The investing layer of DCF continues inferiorly and laterally to form the axillary sheath 1
• This represents the anatomical continuity of fascial planes from neck to upper extremity

4. Splits to enclose the thyroid gland: FALSE

• The thyroid gland is enclosed by the pretracheal (middle) layer of deep cervical fascia, not the investing layer 1
• The investing layer is the most superficial of the three DCF layers, while the pretracheal layer is the intermediate layer 1

5. Splits to enclose the submandibular gland: TRUE

• The superficial layer of deep cervical fascia (investing layer) splits into two layers to encapsulate the submandibular gland 4
• The deeper portion of this split fascia is in close contiguity with the hyoglossus muscle 4

Important Anatomical Caveats

Controversy Regarding Traditional Descriptions

• Recent anatomical research challenges the classical teaching that the investing layer forms a complete, continuous sheet around the neck 2, 3
• Studies using E12 sheet plastination demonstrate that no single connective tissue sheet extends directly between the sternocleidomastoid muscles in the anterior cervical triangle 2
• The investing layer is incomplete between the sternocleidomastoid and trapezius muscles, with the intervening space occupied by fatty tissue continuous with subcutaneous tissue 3

Clinical Implications

• The discontinuity of the investing fascia explains why superficial cervical plexus blocks work equally well whether placed deep or superficial to the fascia 2
• Deep potential spaces in the neck are directly continuous with subcutaneous tissue due to gaps in the investing layer 2
• This anatomical reality is important for understanding infection spread patterns and surgical approaches 3

Three-Layer Organization of Deep Cervical Fascia

• Superficial (investing) layer: Most superficial, enclosing SCM and trapezius 1
• Middle (pretracheal) layer: Intermediate layer enclosing thyroid gland 1
• Deep (prevertebral) layer: Deepest layer 1, 5