MRI Anatomy Flashcards · Neuro

Brachial Plexus Anatomy

Learn to identify every labeled structure on a Brachial Plexus MRI, plane by plane.

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Brachial Plexus anatomy, structure by structure

Brachial plexus MRI is one of the harder studies a technologist will set up, and reading it starts with knowing where the nerve roots live. This reference walks through every structure in our brachial plexus flashcard deck on the coronal plane, with a plain-language definition, how each root looks on MRI, and the pathology you will actually run into at the scanner. The plexus is built from the C5 through T1 roots; this deck labels the four cervical roots (C5, C6, C7, C8) that you trace as they leave the spine.

Brachial plexus roots (C5-C8)

The five spinal nerve roots (C5 through T1) that form the brachial plexus. Each root leaves the spine through its neural foramen and runs between the anterior and middle scalene muscles before the roots merge into trunks (C5 and C6 form the upper trunk, C7 the middle trunk, and C8 with T1 the lower trunk). Coronal STIR is the workhorse sequence here: the fat suppression knocks out the bright neck fat so the normal nerves stand out as smooth, slightly bright cords.

Brachial Plexus Roots: C5

The most superior root of the brachial plexus, the C5 spinal nerve, which joins C6 to build the upper trunk.

On MRI: Best traced on coronal STIR/T2 as the highest of the obliquely descending nerve cords; fat suppression makes the normal root slightly bright against the dark suppressed neck fat. It emerges from its neural foramen and runs into the gap between the anterior and middle scalene muscles.

Common pathology: Traction or avulsion injuries from shoulder/arm trauma (an upper-trunk pattern is the classic Erb palsy distribution), pseudomeningocele at an avulsed root, and tumor or nodal encasement in the supraclavicular region.

Tip: On the coronal STIR, count the roots from the top down: the highest cord exiting toward the upper trunk is C5.

Brachial Plexus Roots: C6

The second root from the top, the C6 spinal nerve, which combines with C5 to form the upper trunk.

On MRI: Sits just below C5 on coronal STIR/T2, following the same oblique course out of its neural foramen and through the interscalene triangle. Normal roots are smooth and uniform in caliber; fat-suppressed sequences keep them conspicuous.

Common pathology: Frequently involved with C5 in upper-trunk (Erb) injuries and stretch injuries; also a site for inflammatory plexitis (Parsonage-Turner) and nerve-sheath tumors such as schwannoma.

Brachial Plexus Roots: C7

The middle root of the plexus, the C7 spinal nerve, which continues on its own as the middle trunk.

On MRI: Lies centrally among the roots on coronal STIR/T2 and is the single root that becomes the middle trunk rather than pairing with a neighbor. Trace it from its foramen laterally into the scalene corridor toward the supraclavicular fossa.

Common pathology: Involved in stretch and avulsion injuries and in radiation-induced plexopathy; abnormal T2/STIR brightness or thickening of the root is a clue to denervation or infiltration.

Brachial Plexus Roots: C8

The lowest cervical root of the plexus, the C8 spinal nerve, which joins the T1 root to form the lower trunk.

On MRI: The most inferior root visible on these coronal STIR/T2 images, coursing toward the lower trunk near the first rib and subclavian vessels. Fat suppression helps separate the low-lying root from adjacent vessels and apical fat.

Common pathology: Lower-trunk injuries (the Klumpke pattern) from arm hyperabduction or birth trauma, and compression in thoracic outlet syndrome or by a Pancoast (superior sulcus) tumor at the lung apex.

Tip: The lowest root running toward the first rib and subclavian region is C8; pair it mentally with T1 to remember the lower trunk.

Frequently asked questions

Which plane and sequence are best for brachial plexus MRI?

The coronal plane is the workhorse for following the roots, trunks, and divisions along their oblique course from the spine toward the axilla, and an oblique sagittal is added to see the roots and trunks in cross-section. Coronal STIR (or another fat-suppressed T2) is the key sequence: suppressing the bright neck and shoulder fat makes the normal nerves stand out as smooth, slightly bright cords.

What structures are labeled in this brachial plexus deck?

This deck labels the four cervical nerve roots of the brachial plexus on coronal images: C5, C6, C7, and C8. The full plexus also includes the T1 root and the trunks, divisions, cords, and terminal branches; the roots are the foundation you trace first before following them into the upper, middle, and lower trunks.

How do the roots combine into the trunks of the plexus?

C5 and C6 join to form the upper trunk, C7 continues alone as the middle trunk, and C8 joins T1 to form the lower trunk. Each root leaves the spine through its neural foramen and passes between the anterior and middle scalene muscles before merging, which is why the interscalene region is such an important landmark on the images.

Why is STIR used for the brachial plexus?

STIR is a fat-suppression technique that nulls the abundant fat in the neck, supraclavicular fossa, and axilla. With the fat dark, the normal nerves appear relatively bright and easy to trace, and abnormal nerves that are swollen or inflamed light up even more, which makes STIR sensitive for plexopathy, traction injury, and tumor involvement.

Do I need an account to use these brachial plexus MRI flashcards?

No. The interactive flashcards and this full labeled reference are open to use, with no account required to start. Creating an account lets you save your progress across devices and track which packs you have mastered.

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Brachial Plexus Anatomy