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    Related Topics

    From Lymphatic System

    SALT
    Skin-associated lymphoid tissue.
    Posterior Mediastinal Nodes
    Drain posterior thoracic structures.
    MALT
    Mucosa-associated lymphoid tissue.
    Popliteal Lymph Nodes
    Drain the foot and leg.
    Red Bone Marrow
    Produces lymphocytes; site of B-cell maturation.
    Pharyngeal Tonsil
    Located in the nasopharynx (adenoids).
    Preaortic Nodes
    Located in front of the aorta.
    Lingual Tonsils
    Located at the base of the tongue.
    Peyer’s Patches
    Lymphoid nodules in the small intestine.
    Lateral Axillary Nodes
    Located along the humerus in the axilla.
    Subscapular Axillary Nodes
    Located along the posterior chest wall.
    Superficial Cervical Lymph Nodes
    Drain superficial structures of the head and neck.
    Intestinal Trunk
    Drains lymph from the intestines.
    Pectoral Axillary Nodes
    Located along the anterior chest wall.
    Axillary Lymph Nodes
    Drain the upper limbs and chest wall.
    Lumbar Trunk
    Drains lower limbs and pelvic organs.
    Thymus
    Primary lymphoid organ for T-cell maturation.
    Subclavian Trunk
    Drains lymph from the upper limbs.
    Anterior Mediastinal Nodes
    Drain anterior thoracic structures.
    Paratracheal Nodes
    Located lateral to the trachea.
    Mesenteric Lymph Nodes
    Drain the intestines and abdominal structures.
    Parotid Lymph Nodes
    Drain the lateral face and scalp.
    Iliac Lymph Nodes
    Include external, internal, and common iliac nodes.
    Jugular Trunk
    Drains lymph from the head and neck.
    Cisterna Chyli
    Dilated sac at the start of the thoracic duct.

    Mastoid Lymph Nodes

    Reviewed by our medical team

    Drain the posterior scalp and ear.

    1. Overview

    The mastoid lymph nodes—also known as the retroauricular lymph nodes—are a small group of superficial lymph nodes situated behind the ear. They are part of the superficial lymphatic drainage system of the head and neck. These nodes help filter lymph from nearby regions such as the posterior scalp, external ear, and posterior auricle, playing a role in detecting and responding to local infections and other immune challenges.

    2. Location

    Mastoid lymph nodes are located in the retroauricular region, specifically:

    • Posterior to the auricle (external ear)

    • Overlying the mastoid process of the temporal bone

    • Within the superficial fascia, deep to the posterior auricular muscle and superficial to the sternocleidomastoid muscle’s superior portion

    They typically number one or two nodes and lie near the posterior auricular vein. They receive lymph from the posterior-lateral aspects of the scalp and auricle and drain into the superior deep cervical lymph nodes.

    3. Structure

    Each mastoid lymph node is a small, encapsulated, bean-shaped structure composed of organized lymphoid tissue. Structural components include:

    • Cortex: Contains follicles rich in B lymphocytes for humoral immunity.

    • Paracortex: Primarily composed of T lymphocytes and dendritic cells.

    • Medulla: Contains plasma cells and macrophages within medullary cords and sinuses.

    • Afferent lymphatics: Enter the convex surface, bringing lymph from superficial scalp and auricular regions.

    • Efferent lymphatics: Exit from the hilum and drain into the superior deep cervical lymph node group.

    4. Function

    The mastoid lymph nodes perform critical immune and drainage functions in the localized region of the head:

    • Lymph filtration: Remove pathogens, dead cells, and foreign particles from lymph collected from the scalp and auricle.

    • Immune activation: Serve as a site for antigen presentation, lymphocyte activation, and initiation of immune responses.

    • Lymph relay: Serve as intermediary nodes connecting superficial lymphatics to deeper cervical nodes.

    5. Physiological Role(s)

    Although small in size, mastoid lymph nodes play an essential role in local and systemic physiology:

    • First line of defense: Provide early immune response to infections or injuries of the posterior scalp and ear.

    • Early warning site: Participate in detecting pathogens or neoplastic cells entering the lymphatic system from the nearby skin and mucosa.

    • Drainage balance: Prevent accumulation of lymphatic fluid in the scalp and retroauricular region.

    • Collaboration with nearby nodes: Work in coordination with occipital, parotid, and cervical lymph nodes for efficient regional immune monitoring.

    6. Clinical Significance

    Lymphadenopathy

    Mastoid lymphadenopathy refers to the enlargement and tenderness of these nodes, typically due to local infection or inflammation. Causes include:

    • Scalp infections: Such as tinea capitis or bacterial folliculitis

    • Otitis externa or otitis media: Infections of the external or middle ear

    • Rubella (German measles): Often causes tenderness of retroauricular and occipital lymph nodes

    • Postauricular trauma or insect bites

    Clinically, enlarged mastoid nodes are often palpable behind the ear and may be tender or mobile depending on the underlying cause.

    Malignancy

    Although less common, mastoid lymph nodes can become involved in:

    • Metastatic spread from skin cancers of the scalp or ear (e.g., melanoma, squamous cell carcinoma)

    • Lymphomas: May present as persistent, non-tender nodal enlargement

    Persistent enlargement warrants further evaluation, possibly including ultrasound, fine needle aspiration, or biopsy.

    Diagnostic Evaluation

    Assessment of mastoid lymph nodes may include:

    • Palpation: Routine part of head and neck examination, especially in cases of fever or local scalp/ear complaints

    • Ultrasound: Used to evaluate size, shape, vascularity, and internal structure of superficial nodes

    • Blood tests: Helpful in identifying viral or bacterial causes of lymphadenopathy (e.g., rubella, EBV, streptococcal infections)

    Surgical Relevance

    In rare cases requiring lymph node excision (e.g., for biopsy or persistent infection), care must be taken to avoid injury to the nearby posterior auricular nerve and external jugular vein. In surgeries involving mastoid bone (e.g., mastoidectomy), inflammation of these nodes may also be encountered or secondarily involved.

    Did you know? The lymphatic system is responsible for maintaining fluid balance by collecting excess fluid from tissues and returning it to the bloodstream.