Supratrochlear Lymph Nodes: Anatomy, Location, Function, Imaging

Topic

Supratrochlear lymph nodes

The supratrochlear lymph nodes, also known as epitrochlear lymph nodes, are small, superficial lymph nodes located superior and medial to the medial epicondyle of the humerus, in the subcutaneous tissue just anterior to the medial intermuscular septum. They typically number one to three and form part of the superficial lymphatic network of the upper limb.

These nodes are clinically important because they drain the ulnar aspect of the forearm, hand, and little and ring fingers. Enlargement of supratrochlear lymph nodes is an early sign of infections, lymphatic obstruction, or systemic diseases such as lymphoma, HIV, or syphilis.

Synonyms

Epitrochlear lymph nodes
Cubital lymph nodes
Medial elbow lymph nodes

Location and Structure

Situated approximately 3–4 cm above the medial epicondyle, along the basilic vein in the subcutaneous tissue.
Typically 1–3 nodes present, oval or kidney-shaped, measuring 3–8 mm in normal individuals.
Surrounded by loose connective tissue and fat, occasionally associated with small superficial veins and lymphatic vessels.
Covered by deep fascia and overlying skin; readily palpable in pathological enlargement.

Relations

Anteriorly: Subcutaneous fat and skin of the medial aspect of the elbow.
Posteriorly: Medial intermuscular septum and brachialis muscle.
Medially: Basilic vein and accompanying superficial lymphatics from the ulnar forearm.
Laterally: Biceps tendon and brachial artery (deeper).
Superiorly: Connects to lymphatics ascending toward the lateral group of axillary lymph nodes.
Inferiorly: Receives afferents from lymphatics of the forearm and hand.

Lymphatic Drainage

Afferent vessels: Drain lymph from the ulnar side of the forearm and hand, particularly the medial two digits and hypothenar region.
Efferent vessels: Ascend alongside the basilic vein, pierce the deep fascia at the mid-arm, and drain into the lateral (humeral) group of axillary lymph nodes.
Acts as a relay station between superficial hand lymphatics and the deep axillary system.

Function

Filtration: Removes pathogens, debris, and foreign particles from lymph before it reaches the axillary nodes.
Immune surveillance: Contains macrophages, B and T lymphocytes involved in immune response.
Early sentinel node: First site of lymphatic involvement in infections or systemic disease of the forearm and hand.

Clinical Significance

Lymphadenopathy: Enlargement indicates local infection (hand, forearm) or systemic disease (HIV, syphilis, tuberculosis, lymphoma).
Palpation site: Located approximately 3 cm above the medial epicondyle, best felt with the forearm partially flexed.
Infection drainage: Commonly enlarged in cellulitis, abscess, or traumatic wounds of the ulnar aspect of the hand.
Malignancy: May be involved in melanoma or squamous cell carcinoma metastasis from the forearm or hand.
Imaging role: MRI and CT help assess nodal enlargement, necrosis, or perinodal inflammatory changes.

MRI Appearance

T1-weighted images:
- Normal node: intermediate signal with central fatty hilum (bright center) and low-signal cortex.
- Enlarged reactive node: mildly hypointense cortex with preserved fatty hilum.
- Malignant node: loss of fatty hilum, uniformly low-to-intermediate signal.
T2-weighted images:
- Normal: intermediate-to-bright signal cortex with a bright hilum.
- Reactive nodes: mild T2 hyperintensity due to cortical thickening and edema.
- Malignant nodes: heterogeneous hyperintensity, irregular margins, and absence of central hilum.
STIR:
- Normal node: intermediate signal with visible hilum.
- Pathology: bright hyperintense signal in edema, inflammation, or metastatic infiltration.
Proton Density Fat-Saturated (PD FS):
- Normal: intermediate-to-dark cortical signal with distinct fatty hilum.
- Inflamed node: bright cortical rim and surrounding perinodal hyperintensity.
- Useful for identifying edema, necrosis, or perinodal inflammatory changes.
T1 Fat-Sat Post-Contrast:
- Normal: mild homogeneous enhancement, preserving fatty hilum.
- Reactive lymphadenitis: diffuse homogeneous enhancement with maintained shape.
- Malignant node: heterogeneous or peripheral enhancement, absent hilum, possible central necrosis.

CT Appearance

Non-Contrast CT:

Normal nodes: small, oval, soft-tissue densities (20–40 HU) with surrounding fat.
Typically <10 mm short-axis diameter.
Reactive or malignant nodes: enlarged, rounded, and denser with possible perinodal fat stranding.

Post-Contrast CT (standard):

Normal node: mild homogeneous enhancement.
Reactive lymphadenitis: uniform enhancement, surrounding inflammatory fat changes.
Metastatic or necrotic node: heterogeneous enhancement, central low-density necrotic core, irregular borders.
Helpful in evaluating infection, malignancy, trauma, and lymphatic obstruction.

MRI images

CT image

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