Accessory Nerve Cranial Nerve 11
The Spinal Accessory Nerve (SAN) or Cranial Nerve 11 is termed a cranial nerve as it was originally believed to originate in the brain. It has both a cranial and a spinal part, though debate still rages regarding if the cranial part is really a part of the SAN or part of the vagus nerve.  The cranial part , along with the cranial nerves 9 and 10, supplies innervation to the soft palate, larynx and pharynx. The spinal part supplies innervation to the Sternocleidomastoid and Trapezius muscles.
The spinal part on the SAN arises from C1- C5/6 nerve roots.
The smaller cranial part originates from the lateral aspect of the medulla oblongata.
Cranial Portion: travels from medulla up to jugular foramen to exit and join the vagus nerve on its way to supply the soft palate, larynx and pharynx.
Spinal Portion: Travels upwards as the C1-C5/6 spinal root section join together and exit out the jugular foramen, with the cranial portion. It goes on to supply the Sternocleidomastoid and Trapezius muscles.
Contributes to the supplying of the soft palate, larynx and pharynx muscles ( with larger contributions from cranial nerves 9 and 10 )
Sensory - surrounded by controversy
As the Trapezius and sternocleidomastoid muscles are derived from the pharyngeal arches some believe they must carry special visceral efferent information and other argue that they must contain general somatic efferent information.
Injury to the SAN causes varying degrees of disfunction to the Trapezius muscle and the Sternocleidomastoid muscle.
The various causes of injury include
- neck trauma
- wrenching injury to arm or neck
- surgical procedures such as lymph node biopsy, parotid surgery, carotid surgery and jugular vein cannulation.
- Radiation therapy to the lymph nodes in the neck
- Aneurysms of the internal carotid artery
- Fracture of the atlas bone or hyoid due to direct trauma
- The following conditions may affect nerve function eg Pharyngo-cervical-brachial variant of Guillain-Barre-syndrome, Sandifer syndrome, Eagle-syndrome, Diphtheria (infection), Poliomyelitis or Tetanus (both situations that rarely can affect the XI nerve), botulism, and sarcoidosis. Other causes are diabetes, vitamin B12 deficiency, and tumours.
A thorough medical and objective history should be carried out to determine the reasons for damage and the extent of the damage.
Imaging tests such as EMG often ordered
Observe for any wasting of muscles
Look for any lateral winging of scapular
Muscle testing of Trapezius and Sternocleidomastoid is essential
See video clip below for more details
Traditional physiotherapeutic methods are the mainstay of treatment. This is directed at restoring function to the shoulder girdle with emphasis on sternocleidomastoid and trapezius muscle. Methods employed may include:
- Taping eg McConnell taping to facilitate trapezius action
- Use of acute brief low frequency electrostimulation eg TENS, has been found in some studies to be beneficial in axonal growth
- Sling use several hours a day to help with pain management
- Cervical PNF patterns extension to flexion with rotation and Scapular PNF patterns from anterior depression to posterior elevation
- Hydrotherapy program
- Strengthening exercises for whole shoulder girdle with particular focus on Trapezius and SCM
- Stretching of muscles, nerves and soft tissues in the shoulder and neck deemed necessary
- Proprioceptive training
- Home exercise program individually tailored
- Flossing and gliding of CN11
- see also Nerve Injury Rehabilitation Physiotherapy
If physiotherapy is not successful other options are then considered including
- Nerve surgery, nerve grafting, nerve regeneration
- Tendon of muscle transfers to stabilise scapular eg scapulothoracic fusion, Modified Eden Lange Procedure
Surgical options comprise nerve surgery, nerve grafting, and nerve regeneration. Other treatment options include tendon or muscle transfer to stabilise scapula, employed for patients not responding to nerve repair or surgery. One of the widely used surgical procedures is scapulothoracic fusion.
To learn more on the ways that nerves heal after injury watch the great 8 minutes video clip below
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