brachial plexus imaging

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BRACHIAL PLEXUS IMAGING

IMAGING of BRACHIAL PLEXUSDR. SUMIT KAMBLEDM RESIDENTGMC, KOTA

ANATOMY

Magnetic resonance imaging (MRI) of brachial plexus

Diagnostic accuracy of MRI is relatively high- 87.8%.

Accuracy being 93.3% for mass lesions, 87.2% for traumatic brachial plexus injuries, 83.3% for entrapment syndrome, and 83.7% for post-treatment evaluation.

Supraclavicular LesionsInvolve nerve roots and trunks in scalene triangleMore common and more severe than lesions at other sites.

Common pathologies in the supraclavicular-Brachial plexitis (Parsonage-Turner syndrome), Traumatic injury,Neoplasms (metastasis, nerve sheath tumor, neurocutaneous syndrome, pancoast tumor),TOS.

Normal Oblique sagittal T1-weighted anatomy Roots (supraclavicular plexus)

Retroclavicular LesionsInvolve brachial plexus divisions.

Isolated lesions in the divisions are rare.

Retroclavicular plexus

Infraclavicular LesionsAffect cords and terminal branch nerves3 times less commonly seen than supraclavicular lesions

Have better prognosis and earlier recovery than supraclavicular lesions.

Common causes Radiation neuropathy, Humeral fracture-dislocation, Gunshot injury, and iatrogenic injuries.

Infraclavicular plexus

Normal sagittal anatomy Roots lateral to intervertebral foramina

Axial T1-weighted image

Trunks of the brachial plexus (arrowheads) posteriorSubclavian artery (solid black arrow)Vein (open arrow).

Coronal T1-weighted image

T2 STIR coronal image

NON TRAUMATIC BRACHIAL PLEXOPATHYRadiation fibrosis Inflammatory plexitis Breast cancerLung cancerBenign tumors LymphangiomaDesmoidNeurofibromaLipoma

Other malignant tumorsNeurofibrosarcomaEwing sarcomaEccrine sarcomaOsteosarcomaMesotheliomaMalignant fibrous histiocytomaMetastatic melanoma

Inflammatory PlexitisMay be idiopathic ,or could be associated with viral or bacterial infection or vaccination

Affect the lower brachial plexus.

Presents with acute onset of unilateral shoulder pain followed by flaccid paralysis of the shoulder and para-scapular muscles.

Often runs a self-limiting course.

MRI shows diffuse swelling and increased T2W signal in affected nerves .

There can be mild oedema of the affected muscles particularly supra and infraspinatus

STIR Coronal shows swollen and hyperintense right sided cords

Nerve sheath tumour involving brachial plexusInclude schwannoma, neurofibroma ,plexiform neurofibroma and malignant peripheral nerve sheath tumour.

Have an ovoid form and the nerve can often be seen entering and leaving the tumour.

Similar in signal intensity to muscle on T1W and show markedly increased signal intensity on T2W .Enhance with IV Gadolinium and may demonstrate cystic areas

Nerve sheath tumour T1W fat sat post Gadolinium Coronal image

Pancoast Tumour involving brachial plexusNon small cell lung carcinomas arise in lung apex and invade lower brachial plexus, subclavian vessels, upper ribs and vertebral bodiesPresent with pain in shoulder and arm, weakness and atrophy of the muscles of the hand and Horner's syndrome (involvement of stellate ganglion).

MRI is used to examine local extension of the tumour towards brachial plexus, subclavian vessels, vertebral bodies and intervertebral foramina.

T1W Coronal shows a lobulated hypointense mass

T1W Axial shows a lobulated hypointense mass

Metastatic infiltration of brachial plexusBreast carcinoma is most common .Other sources include lung carcinoma and head and neck cancer.

Low signal on T1 weighted images and high signal on T2 weighted images and also shows enhancement post gadolinium.

Metastasis from carcinoma breast Coronal T1W images shows spiculated focal mass lesion involving the left cords

Lymphoma involving brachial plexusBrachial plexus can be compressed or infiltrated by enlarged lymph nodes or a nodal mass .

Lymphoma of the paravertebral lymph nodes can extend through intervertebral foramina and extend to extradural space.

T2W sagittal - lobulated hyperintense paravertebral lesion involving the roots lateral to the intervertebral foramina

Radiation induced brachial plexopathy

Upper brachial plexus involvement with lymphoedema and lack of pain and a latency period of less than 1 year - radiation induced brachial plexopathy.

Horner's syndrome, lower brachial plexus involvement, severe pain, hand weakness and a latency period of more than 1 year is more suggestive of tumour involvement

Low signal on T1 weighted images and of high signal on T2 weighted images

Does not enhance post gadolinium.

Often causes architectural distortion and diffuse thickening of brachial plexus without the presence of a focal mass.

Coronal T1W image shows architectural distortion of rightsided cords with diffuse thickening

Surgical ligation involving brachial plexus

TRAUMATIC BRACHIAL PLEXOAPTHYMost common causes- Motor vehicle crashes Obstetric injuries. Sports injury, gunshot wound, rucksack injury,Iatrogenic traction injuries during anesthesia.

ClassificationPreganglionic, Postganglionic,Combination of both.

Post ganglionic injuries- better prognosis Pre-ganglionic - surgical repair is difficult, Poor prognosis

Pre-ganglionic injuriesOften cause nerve root avulsions with or without an associated pseudomeningocele (cerebrospinal fluid collection due to a dural tear).

Presence of a psuedomeningocele is highly suggestive, but not pathognomonic of a preganglionic lesion.

Signal intensity changes are observed in spinal cord in approximately 20% of patients.

Hyperintense areas on T2-weighted images suggest edema in acute phase and myelomalacia in the chronic phase.

Enhancement of intradural nerve roots and root stumps suggests functional impairment of nerve roots despite morphologic continuity.

Abnormal enhancement of paraspinal muscles is an accurate indirect sign of root avulsion injury (show enhancement as early as 24 hours)

Axial contrast-enhanced T1-weighted MR image demonstrates markedenhancement of the spinal cord surface at the right root exit zone

Axial T2-weighted MR Axial contrast-enhanced T1-weighted MR

Postganglionic brachial plexus

2D sequences and with the 3D STIR SPACE sequence can reliably detect masses that compress or stretch the plexus such as post-traumatic hematomas, clavicular fractures, focal or diffuse fibrosis and post-traumatic neuromas.

Allows the visualization of postganglionic ruptures of nerve roots, cords and trunks of the brachial plexus.

Edema and fibrosis of the brachial plexus can manifest as thickening of the plexus.

TOS (Entrapment Syndrome)Results from dynamic compression of the BPL, the subclavian artery, or the subclavian vein in the cervicothoracobrachial region.

Neurogenic TOS is most common, comprising 95% of all TOS cases.

Causative agents for TOS - Cervical rib, Elongated C7 transverse process, Exostosis of the first rib or clavicle, Excessive callus of the clavicle or first rib, Congenital fibromuscular anomalies, Muscle hypertrophy (scalenus, subclavius, or pectoralis minor muscles), Posttraumatic fibrosis of the scalene muscles.

Three possible sites of compression Interscalene triangle Costoclavicular space between first thoracic rib and the clavicleRetropectoralis minor space.

Functional 3D STIR MR with postural maneuvers (upper limb raised), are helpful in analyzing dynamically induced compression patterns.

Sagittal T1-weighted image (arm in neutral position)Normal costoclavicular space Normal retropectoralis minor space

Sagittal T1-weighted images with arm in hyperabduction

Sagittal T1-weighted images with arm in neutral and hyperabducted positions reveals compression of subclavian artery and brachial plexus in costoclavicular space due to a cervical rib

Coronal T2

MR NeurographyIndications1) Patients with nonspecific shoulder and arm pain or weakness, in which EMG and traditional MR imaging of the spine are inconclusive

2) To confirm nerve abnormalities in patients under consideration for surgery for TOS;

3) To exclude recurrent malignancy/confirm radiation plexopathy;

4) To characterize and evaluate the extent of space-occupying lesions

5) To evaluate and differentiate a simple stretch injury from higher grade nerve injury;

7) To exclude nerve re-entrapment/persistent impingement in failed surgery cases, 8) Guidance in perineural and scalene medication injections.

3D STIR SPACE sequence, in which nerves appear bright against a dark fat-suppressed background, is mainly considered as MRN

Entire plexus, from its origin at the spinal cord till its terminal branches can be traced.

MRN in cases of trauma is done 6 weeks or later after the injury so that plexus is not obscured by edema and/or haemorrhage

3D STIR SPACE sequence allows excellent background fat suppression and isotropic multiplanar and curved planar reconstructions.

3D T2 SPACE images focuses on cervical spinePre-ganglionic intradural nerve segments are best identified on this sequence.

Coronal three-dimensional Short Tau Inversion Recovery(STIR) Sampling Perfection with Application optimised Contrasts using a varying flip angle Evolutions(SPACE) image showing normal brachial plexus on both sides

Coronal three-dimensional STIR SPACE image

Magnetic resonance myelography (MRM)Use - diagnosis of traumatic meningoceles and nerve root avulsion.

Diagnos