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Mastoid lymph nodes

Mastoid lymph nodes, also known as posterior auricular lymph nodes, are small, superficial lymph nodes located over the mastoid process, just posterior to the auricle and along the posterior aspect of the ear. They are typically 1–4 mm in size and embedded within the subcutaneous tissue and fascia overlying the mastoid bone. These nodes are part of the facial and cervical lymphatic network and primarily drain lymph from the posterior scalp, auricle, external auditory canal, and posterior ear region, eventually draining into the superficial cervical lymph nodes. Mastoid lymph nodes are not palpable under normal conditions, but become evident when enlarged due to infection, inflammation, or metastatic disease.

Synonyms

  • Posterior auricular lymph nodes

  • Retroauricular lymph nodes

  • Mastoid region lymph nodes

Function

  • Filter lymph from the posterior scalp, auricle, external ear canal, and posterior ear

  • Initiate immune response by trapping pathogens or foreign particles

  • Serve as an early indicator of scalp or ear infections when enlarged

  • Drain lymph into superficial cervical lymph nodes, maintaining lymphatic continuity

Location

  • Positioned superficially over the mastoid process, posterior to the auricle

  • Embedded within the subcutaneous fat and posterior cervical fascia

  • Usually bilateral, lying along the course of the posterior auricular vein

MRI Appearance

T1-weighted images:

  • Mastoid nodes appear as small, oval hypointense to intermediate signal structures within subcutaneous fat

  • Surrounded by hyperintense fat, which provides natural contrast

  • Pathological nodes may appear enlarged or show cortical irregularity

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal nodes may demonstrate mild homogeneous enhancement

  • Enlarged or inflamed nodes show marked homogeneous or heterogeneous enhancement, highlighting cortex and fatty hilum

  • Useful for detecting early metastatic involvement or inflammation

T2-weighted images:

  • Nodes show intermediate to slightly hyperintense signal, with surrounding fat bright

  • Edema or inflammatory infiltration appears hyperintense, making pathology conspicuous

  • Fatty hilum (if present) may appear slightly hyperintense relative to cortex

STIR (Short Tau Inversion Recovery):

  • Fat suppression enhances visualization of edema or pathology

  • Normal nodes appear low to intermediate signal, while inflamed or metastatic nodes appear hyperintense

  • Particularly useful for detecting subtle lymphadenopathy in the mastoid/postauricular region

CT Appearance:

  • Nodes appear as small soft tissue density structures overlying the mastoid process

  • Surrounded by air in the external auditory canal and mastoid air cells, providing natural hypodense contrast

  • Enlarged or pathological nodes appear as well-defined or irregular soft tissue masses

MRI images

Mastoid lymph nodes mri axial image -img-00000-00000

MRI images

Mastoid lymph nodes mri axial image -img-00000-00000_00001