MR Neurography - Brachial Plexus

MR neurography uses nerve-selective, high-resolution and fluid-sensitive sequences with fat and vascular suppression to display the brachial plexus from the cervical roots to the terminal branches. It characterises traumatic, neoplastic, inflammatory and compressive plexopathies and, together with muscle denervation signal, localises and grades nerve injury.

Indications

Traumatic brachial plexopathy and suspected nerve root avulsion
Peripheral nerve sheath tumours (schwannoma, neurofibroma) and plexiform neurofibromatosis
Metastatic or direct tumour infiltration (e.g. Pancoast tumour, breast cancer)
Thoracic outlet syndrome with neurogenic symptoms
Radiation-induced versus recurrent tumour plexopathy
Inflammatory neuropathies (e.g. Parsonage-Turner syndrome) and post-surgical assessment

Contraindications & Cautions

Non-conditional pacemakers, ICDs, neurostimulators and ferromagnetic implants
Cochlear implants and unstable metallic intra-ocular foreign bodies
Severe claustrophobia without sedation
Gadolinium caution with eGFR <30 mL/min/1.73 m2 when contrast is needed for a mass
Pregnancy: unenhanced neurography can be performed; avoid gadolinium unless essential

Patient Preparation

MRI safety screening and removal of ferromagnetic objects
Position supine with arms by the side; consider arm abduction for suspected thoracic outlet syndrome
Explain the long acquisition times of 3D sequences and the need to remain still
Intravenous cannula when a tumour or inflammatory cause is suspected
Correlate with electrodiagnostic (EMG/NCS) findings to focus the examination

Technique & Parameters

Coronal and sagittal-oblique T1 for anatomy and fat planes around the plexus
Fat-suppressed T2 or STIR to highlight increased nerve signal and denervation oedema
3D isotropic nerve-selective sequences (e.g. 3D STIR SPACE, DW reversed-FISP/PSIF) with vascular suppression for maximum-intensity nerve reconstructions
High-resolution axial imaging through the interscalene, costoclavicular and retropectoral regions
Post-gadolinium fat-saturated T1 when a mass or inflammatory/neoplastic infiltration is suspected
1.5T or 3T with surface/phased-array coils covering the neck, plexus and axilla

Systematic Review

Trace each level: roots (C5-T1), trunks, divisions, cords (lateral, posterior, medial) and terminal branches
Assess nerve calibre, signal intensity, fascicular pattern and continuity
Look for pseudomeningoceles and absent/displaced roots indicating avulsion
Evaluate for a mass, its relationship to the nerve and enhancement pattern
Assess the interscalene triangle, costoclavicular space and retropectoral tunnel for compression
Review shoulder-girdle muscles for denervation oedema (subacute) or fatty atrophy (chronic)

Key Findings & Significance

Root avulsion: pseudomeningocele, empty nerve root sleeve and displaced/absent nerve root
Nerve sheath tumour: fusiform T2-hyperintense mass along the nerve with a target sign and split-fat sign, enhancing after contrast
Tumour infiltration: nodular or diffuse T2 signal and enhancement encasing the plexus (Pancoast, breast metastasis)
Radiation plexopathy: diffuse T2 signal without a focal mass, often with tissue fibrosis
Parsonage-Turner: hyperintense enlarged nerve segments with corresponding muscle denervation oedema
Thoracic outlet syndrome: nerve displacement/compression at the costoclavicular space, accentuated on abduction

Differential Considerations

Focal plexus mass: schwannoma, neurofibroma, malignant peripheral nerve sheath tumour, metastasis, lymphoma
Diffuse plexus signal/enhancement: radiation plexopathy, inflammatory neuritis, metastatic infiltration
Post-traumatic: root avulsion (pre-ganglionic) versus post-ganglionic rupture/stretch injury
Denervation muscle oedema: nerve injury, neuritis, or non-specific (recent activity)
Thoracic outlet compression: neurogenic, arterial or venous subtypes

Pearls & Pitfalls

Distinguishing pre-ganglionic (avulsion, with pseudomeningocele) from post-ganglionic injury is critical for surgical planning
The target sign and split-fat sign help identify a benign peripheral nerve sheath tumour
Rapid growth, ill-defined margins, heterogeneity and perilesional oedema raise concern for malignant transformation
Muscle denervation signal helps localise the level and chronicity of nerve injury
Provocative arm-abduction imaging increases sensitivity for neurogenic thoracic outlet syndrome

Structured Report

State field strength, nerve-selective sequences and whether contrast was given
Report the level and nature of the abnormality (roots to terminal branches)
Distinguish pre- from post-ganglionic injury in trauma and describe pseudomeningoceles
Characterise any mass and its relationship to the nerve and adjacent vessels
Describe muscle denervation and provide an impression correlated with EMG/NCS

References

Chhabra A, et al. MR neurography: technique and clinical applications. Radiographics
Wade RG, et al. Magnetic resonance imaging for detecting root avulsions in traumatic brachial plexus injury
ISMRM MSK/Peripheral Nerve Study Group recommendations on MR neurography
Van Es HW, et al. MRI of the brachial plexus. European Radiology

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.

MR Neurography - Brachial Plexus

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References