Neurosurgery notes/Anatomy/Peripheral nerves anatomy/Brachial plexus

Brachial plexus

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Peripheral nerves anatomy

General

  • The nerve roots exit from the spinal cord and emerge in the posterior triangle of the neck where they then form the upper (C5– C6), middle (C7), and lower trunks (C8– T1)
notion image

Pre and postfixed brachial plexus

  • Tubbs 2009
      • The possibility of prefixed (C4 contribution) or postfixed (T2 contribution) brachial plexus variants must be considered, necessitating careful imaging review for C4 or T2 root pathology.
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      • Prefixed brachial plexus has been described as having a contribution to the plexus from C4 without a significant contribution from T1
        • Incidence of a prefixed plexus: 25% to 48%
        • A prefix brachial plexus allows a C5/6 disc causing a c7 radiculopathy.
      • Postfixed brachial plexus has been described as having a T2 contribution without a significant contribution from C5.
        • Incidence of a postfixed plexus: 2% to 5%.
      • intradural interconnections may lead to misinterpretation of spinal levels harboring pathological entities of the spinal axis
        • C4 might innervate the deltoid as well
      Showing interconnections between the dorsal roots of C-4 and C-5 (upper arrow) and C-5 and C-6 (lower arrow), both on the left side.
      Showing interconnections between the dorsal roots of C-4 and C-5 (upper arrow) and C-5 and C-6 (lower arrow), both on the left side.

Quadrangular space, triangular space & triangular interval

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Superior
Inferior
Medial
Lateral
Contents
QS
Teres minor
Teres major
Long head of triceps
Humeral shaft
Axillary Nerve & Posterior circumflex humeral artery
TS
Teres minor
Teres major
-
Long head of triceps
Scapular Circumflex Artery
TI
Teres major
-
Lateral head of triceps
Medial head of triceps
Profunda Brachii Artery + Radial Nerve
Image