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Submandibular lymph nodes

Submandibular lymph nodes are a group of small, oval to bean-shaped lymphatic structures located within the submandibular triangle, beneath the body of the mandible and along the facial vein and submandibular gland. They are part of the cervical lymphatic chain and play a critical role in draining lymph from the oral cavity, floor of the mouth, anterior tongue, cheeks, and part of the nasal cavity. These nodes vary in size, typically measuring less than 1 cm in healthy adults, and may be palpable if enlarged. Structurally, each node has a capsule, cortex, and medulla, with afferent lymphatic vessels entering at the periphery and efferent vessels exiting at the hilum.

Synonyms

  • Submandibular lymph node group

  • Submaxillary lymph nodes

  • Level I cervical lymph nodes (Level Ib)

Function

  • Filter lymphatic fluid from the oral cavity, lips, anterior tongue, floor of mouth, and cheeks

  • Trap and destroy pathogens, bacteria, and tumor cells

  • Initiate immune responses through lymphocyte activation in the cortex and medulla

  • Serve as key landmarks in head and neck oncology and surgery

MRI Appearance
T1-weighted images:

  • Nodes appear as oval to round structures of intermediate signal intensity, slightly darker than surrounding fat

  • The fatty hilum of normal nodes is hyperintense, providing a natural contrast

  • Pathologically enlarged nodes may lose the fatty hilum and appear more homogeneous

  • Surrounding submandibular fat is hyperintense, delineating node borders

T2-weighted images:

  • Normal nodes show intermediate signal, while fluid or edema in reactive nodes appears hyperintense

  • Useful for detecting reactive enlargement, cystic degeneration, or neoplastic infiltration

STIR (Short Tau Inversion Recovery):

  • Suppresses fat signal to highlight edema, inflammation, or tumor

  • Normal lymph nodes remain intermediate signal; reactive or metastatic nodes appear bright hyperintense

  • Particularly helpful for detecting early or subtle nodal pathology in the submandibular region

CT Appearance

  • Submandibular lymph nodes appear as soft tissue density oval structures in the submandibular triangle

  • The surrounding subcutaneous fat is hypodense, providing natural contrast

  • Nodes with fatty hilum may show a central hypodense area

  • Enlarged or pathological nodes appear as homogeneous or heterogeneous soft tissue densities, sometimes with necrotic centers

  • CT is particularly useful for evaluating nodal size, number, shape, internal architecture, and relation to adjacent structures, such as the submandibular gland and mandible

MRI images

Submandibular lymph nodes mri sagittal image -img-00000-00000