Peripheral Nerves: The Plexi

Learning OutcomesAt the end of this sessions you should be able to….

• Discuss the points at which the brachial and lumbosacral plexi and their major branches are vulnerable

• Discuss the effects of mononeuropathy of the major nerves

• Explain the effects of damage to the brachial plexus trunks

• Discuss the difference between injury at the level of the spinal nerve and at the level of the peripheral nerve

• Discuss reasons for relative frequency of injury to nerve roots and peripheral nerves in the upper and lower limbs

Overview

• Review the anatomy of the cervical, brachial and lumbosacral plexi

• Course of the plexi and nerves and sites of vulnerability

• Distribution of the peripheral nerves and effects of injury (case studies)

Some Terminology…

• Radiculopathy = result of damage to nerve root– May be little sensory loss due to overlap of

dermatomes– Main symptom = perception of sharp, burning pain

in dermatomal distribution (‘shooting pains’)• Mononeuropathy = result of damage to a single

peripheral nerve– Signs and symptoms can include

paraesthesia/anaesthesia and paresis/paralysis

Cervical Plexus (ventral rami)

• Arises from the ventral rami of C1-C4 (some contribution from C5)

• Lies deep to SCM, anterolateral to levator scapulae & middle scalene

• Supplies skin and muscles of head, neck, shoulders, & chest• Phrenic nerve (C3 -5) supplies motor and sensory fibers to

diaphragm– Irritation phrenic nerve -> hiccups– If both phrenic nerves severed, diaphragm paralyzed, respiratory

arrest• Cervical plexus runs parallel to accessory and hypoglossal

nerves.

Cervical Plexus (continued)

• Lesser occipital n

• Great auricular n

• Transverse cervical n

• Supraclavicular n

• Phrenic n

• Other branches supply muscles of the neck

Cervical PlexusRef: Marieb & Hoehn , Human Anatomy & Physiology(7th edn)

Brachial PlexusRef: Drake et al (2005), Gray’s Anatomy for Students Flash Cards, Elsevier

Where/how might the brachial plexus be injured? (think trunks, divisions, cords)

Vulnerable Sites for Upper Limb NervesRef: Patten (1977) Neurological Differential Diagnosis

Vulnerable Sites for Lower Limb NervesRef: Patten (1977) Neurological Differential Diagnosis

Clinical Considerations

• Key question when PPW neurological symptoms is whether those symptoms are in the territory of a single nerve root or the territory of a single peripheral nerve or its branches

• In upper limb, motor symptoms are more reliable than sensory