Inflamed or injured accessory nerve: causes, symptoms, diagnosis, treatment

The accessory nerve  is the eleventh of the twelve cranial nerves (XI cranial nerve) and is a motor nerve that has thepeculiarity of being equipped with both spinal root (which originates from the spinal cord) and a cranial root (which originates from the medulla oblongata). Its main function is the motor function relative to the shoulder-trapezium-neck area, therefore any inflammation or injury, determines more or less serious alterations to these movements. However, inflammation of the accessory nerve is rare.

Causes and risk factors

The causes of inflammation of the accessory nerve are related to fractures of the skull base (for example in the event of falls or road or sports accidents) or compression of the nerve by external structures, such as bones or tumors, or iatrogenic damage.

  • In “high” inflammations / lesions there is weakness / paralysis of the sternocleidomastoid muscle, without alteration of sensitivity. The causes are mostly due to tumors or fractures of the skull base. High lesions are very rare.
  • In “low” inflammations / lesions there is weakness / paralysis of the trapezius muscle. The most frequent cause in this case is accidental nerve injury during a lymph node biopsy or a cut or fire injury.


As already mentioned in the previous paragraph, lesions / inflammations of this nerve can lead to the establishment of an ipsilateral weakness / paralysis in the trapezius muscle, a difficulty in elevating the scapula and in some movements of the sternocleidomastoid muscle (neck) and therefore in rotation of the head. The patient’s clinical picture is well characterized by the “oscillating position” of the scapula, furthermore the elevation of the arm beyond 90 ° is seriously compromised.


The doctor comes to the suspicion of inflammation of the accessory nerve only with a   thorough history (collection of patient data, his symptoms, his habits, the pathologies of his family …), associated with an objective examination that includes head, neck and chest . Differential diagnosis can often be helped only thanks to instrumental tests such as ultrasound, CT and / or magnetic resonance imaging, associated with general laboratory tests. Diagnosis may need the advice of a neurologist, orthopedist and neurosurgeon.


There is no single cure that resolves inflammation of the accessory nerve : the specific treatment is set up on the basis of the upstream cause that caused the inflammation. In some cases the inflammation gradually decreases spontaneously. A nerve injury is generally considered to be a very serious condition with poor prognosis and almost never spontaneous recovery. The treatment of the lesion is neurosurgical and consists in the suture of the two nerve stumps by means of nerve grafts. Unfortunately, it often happens that one of the nerve stumps cannot be found with impossibility to reconstruct the nerve: in these cases it is possible to resort to decidedly more complicated surgical interventions, such as the transposition of other muscles such as the rhomboid muscles and the elevator of the scapula.


by Abdullah Sam
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