Brachial plexus injuries

Brachial plexus injuries are a spectrum of upper limb neurological deficits secondary to partial or complete injury to the brachial plexus, which provideprovides the nerve supply of upper limb muscles. 

Anatomy

The brachial plexus can be organized into 5 zones; spinal nerve roots, trunks, divisions, cords and terminal branches. 3 trunks (upper, middle and lower), 3 cords (lateral, posterior and medial) and 5 terminal branches (musculocutaneous, radial, axillary, median and ulnar nerves). 

Injuries can be classified as preganglionic, post ganglionic and mixed. Each injury has its own treatment plan.

Clinical manifestationspresentation

Trauma, usually by motor vehicle accidents, involves severe traction on the upper limb which leads to partial or complete nerve avulsion.:

• C5, C6/C6 involvement leads to paralysis of shoulder and biceps muscles. When
• C7 is also involved, the paralysis extends to wrist and hand muscles.
• C8, T1/T1 involvement leads to paralysis of the forearm flexors and hand intrinsic muscles.

Also, birth (obstetric) injuries can involves the upper trunk leading to an Erb's paralysis palsy.

Radiographic features

Conventional (fluoroscopic) myelography

Conventional myelography is performed via intrathecal injection of iodinated contrast media. Nerve roots can be demonstrated as well as the leakage of contrast into the meningocelemeningocoele. 

Advantages include high spatial resolution and absence of CSF flow artefacts and disadvantages. Disadvantages include improper filling of the meningocelemeningocoele sac in the presence of dural scar, intra and post procedural complications e.g. hematoma, infection, allergic reaction and headache. 

Nowadays myelography is almost always performed in conjunction with CT myelography.

CT myelography

Widely replaces conventional myelography as it utilizes less contrast agent and hence less contrast reaction. Advantages include ability to detect partial root avulsion, excellent visualization of bony structures, no CSF flow artetactsartifacts and multiplanar reconstruction. Disadvantages include high radiation dose, poor visualization of lower brachial plexus due to bony artefacts, pre- and post procedural complications. Brachial plexus injuries can be classified into 6six types by CT myelography.

Conventional MRI

Together with direct visualization of nerve root and sleeves, alsospinal cord injuries e(e.g. edema in acute stage, myelomalacia in chronic stage and cord hematoma) can be demonstrated. Post contrast enhancement of nerve root suggest functional impairment even if it appears continuous. Abnormal enhancement of paraspinal muscles is an indirect sign of root avulsion.

MR myelography

This uses steady state coherent gradient echo sequences which imply high contrast to noise ration andratio and reduce flow artefacts. itIt can easily identify nerve roots and meningocelemeningocoele sac even if there are intradural scars.

Diffusion weighted neurography

A recent modality which can demonstrate post ganglionicpostganglionic injuries as discontinuation of injured nerves.

ManagementTreatment and prognosis

Depends on the site of injury and degrees of damage. Preganglionic injury is repaired by nerve transfer. Post ganglionic Postganglionic injury is treated by nerve graft or conservative.