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Topic

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Mandibular notch

The mandibular notch, also known as the sigmoid notch, is a deep curved depression located along the superior border of the mandibular ramus, between the coronoid process anteriorly and the condylar process posteriorly. It forms an important anatomical passage for neurovascular structures and serves as a key landmark in maxillofacial anatomy and imaging.

The notch allows transmission of the masseteric nerve and vessels from the infratemporal fossa to the deep surface of the masseter muscle. Its shape and depth vary among individuals and are influenced by mandibular development, dentition, and masticatory function.

Synonyms

  • Sigmoid notch of mandible

  • Mandibular incisure

  • Incisura mandibulae

Location and Structure

  • Position: Superior border of the mandibular ramus

  • Anterior boundary: Coronoid process

  • Posterior boundary: Condylar process

  • Shape: Smooth, concave, U- or V-shaped depression

  • Surface: Cortical bone with a thin underlying cancellous component

  • Orientation: Faces superiorly and slightly medially

Relations

  • Superiorly: Infratemporal fossa contents

  • Inferiorly: Mandibular ramus

  • Anteriorly: Coronoid process and temporalis tendon

  • Posteriorly: Condylar neck and temporomandibular joint

  • Medially: Lateral pterygoid muscle region

  • Laterally: Masseter muscle

Attachments and Transmitted Structures

  • Muscular relations:

    • Temporalis tendon attaches to the coronoid process anterior to the notch

    • Masseter muscle lies lateral to the notch

  • Transmitted structures:

    • Masseteric nerve

    • Masseteric artery and vein

  • Functional corridor: Provides unobstructed passage from infratemporal fossa to masseter muscle

Function

  • Serves as a neurovascular passage to the masseter muscle

  • Separates coronoid and condylar processes, allowing independent function

  • Acts as an anatomical landmark in TMJ imaging and surgery

  • Contributes to mandibular biomechanics during mastication

Clinical Significance

  • Important landmark in orthognathic surgery, mandibular fracture assessment, and TMJ procedures

  • Used as a reference point in panoramic radiography and CT-based mandibular measurements

  • Shape variations may be noted in developmental or functional mandibular adaptations

  • Assists in orientation during mandibular ramus reconstruction

MRI Appearance

T1-weighted images:

  • Cortical bone of the notch appears very low signal (black)

  • Underlying cancellous bone may show intermediate-to-bright marrow signal

  • Adjacent muscles (masseter, temporalis): intermediate signal

  • Fat planes in infratemporal fossa appear bright

T2-weighted images:

  • Cortical bone remains low signal

  • Marrow signal appears intermediate to mildly bright

  • Surrounding muscles show intermediate signal

  • Joint fluid of nearby TMJ (if included) appears bright

STIR:

  • Cortical bone remains dark

  • Marrow signal is intermediate-to-dark in normal conditions

  • Surrounding soft tissues show uniform signal without hyperintensity

  • Fat signal is suppressed, improving delineation of bone margins

T1 Fat-Saturated Post-Contrast:

  • Mandibular notch bone shows no intrinsic enhancement

  • Adjacent muscles enhance homogeneously

  • Neurovascular structures passing through the notch enhance normally

  • Clear delineation of cortical margins against enhancing soft tissue

CT Appearance

Non-Contrast CT:

  • Mandibular notch is clearly visualized as a smooth concave cortical depression

  • Cortex appears high attenuation (bright white)

  • Cancellous bone appears slightly lower in attenuation

  • Excellent depiction of notch depth, contour, and symmetry

  • Superior for evaluating osseous anatomy and mandibular morphology

Post-Contrast CT (standard):

  • Bone does not enhance

  • Adjacent muscles and soft tissues enhance uniformly

  • Neurovascular structures passing through the notch may enhance

  • Provides clear contrast between osseous and soft-tissue structures

X-Ray Appearance

Panoramic Radiograph (OPG):

  • Appears as a smooth radiolucent concavity between coronoid and condylar processes

  • Cortical margins are well-defined and continuous

  • Symmetry between right and left sides can be assessed

CT VRT 3D image

Mandibular notch CT 3d anatomy labelled image-img-00000-00000

CT image

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CT image

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X Ray image

Mandibular notch