Accessory nerve disorder is an injury to the spinal

accessory nerve The accessory nerve, also known as the eleventh cranial nerve, cranial nerve XI, or simply CN XI, is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles. It is classified as the eleventh of twelve pairs of cranial nerv ...

which results in diminished or absent function of the

sternocleidomastoid muscle The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck. The sternocleidomastoid is innervated by the access ...

and upper portion of the

trapezius muscle The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula. It moves the scapula and supports the ...

Signs and symptoms

Patients with spinal accessory nerve paralysis often exhibit signs of lower motor neuron disease such as diminished muscle mass,

fasciculation A fasciculation, or muscle twitch, is a spontaneous, involuntary muscle contraction and relaxation, involving fine muscle fibers. They are common, with as many as 70% of people experiencing them. They can be benign, or associated with more serio ...

s, and partial

paralysis Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...

of the sternocleidomastoid and trapezius muscles. Interruption of the nerve supply to the sternocleidomastoid muscle results in an asymmetric neckline, while weakness of the trapezius muscle can produce a drooping shoulder,

winged scapula A winged scapula (scapula alata) is a skeletal medical condition in which the shoulder blade protrudes from a person's back in an abnormal position. In rare conditions it has the potential to lead to limited functional activity in the upper ex ...

, and a weakness of forward elevation of the shoulder.

Causes

Medical procedures are the most common cause of injury to the spinal accessory nerve. In particular, radical neck dissection and cervical

lymph node biopsy Lymph node biopsy is a test in which a lymph node or a piece of a lymph node is removed for examination under a microscope (see: biopsy). The lymphatic system is made up of several lymph nodes connected by lymph vessels. The nodes produce white bl ...

are among the most common surgical procedures that result in spinal accessory nerve damage. London notes that a failure to rapidly identify spinal accessory nerve damage may exacerbate the problem, as early intervention leads to improved outcomes.

Diagnosis

The function of the spinal accessory nerve is measured in the

neurological examination A neurological examination is the assessment of sensory neuron and motor responses, especially reflexes, to determine whether the nervous system is impaired. This typically includes a physical examination and a review of the patient's medical hist ...

. How the examination is administered varies by practitioner, but it frequently involves three components: inspection,

range of motion Range of motion (or ROM), is the linear or angular distance that a moving object may normally travel while properly attached to another. It is also called range of travel (or ROT), particularly when talking about mechanical devices and in mechanic ...

testing, and strength testing. During inspection, the examiner observes the sternocleidomastoid and trapezius muscles, looking for signs of lower motor neuron disease, such as

muscle atrophy Muscle atrophy is the loss of skeletal muscle mass. It can be caused by immobility, aging, malnutrition, medications, or a wide range of injuries or diseases that impact the musculoskeletal or nervous system. Muscle atrophy leads to muscle weakness ...

and

. A

may also be suggestive of abnormal spinal accessory nerve function, as described above. In assessing range of motion, the examiner observes while the patient tilts and rotates the head, shrugs both shoulders, and abducts both arms. A winged scapula due to spinal accessory nerve damage will often be exaggerated on arm abduction. Strength testing is similar to range of motion testing, except that the patient performs the actions against the examiner's resistance. The examiner measures sternocleidomastoid muscle function by asking the patient to turn his or her head against resistance. Simultaneously, the examiner observes the action of the contralateral sternocleidomastoid muscle. For example, if the patient turns his or her head to the right, the left sternocleidomastoid muscle normally will tighten. To assess the strength of the trapezius muscle, the examiner asks the patient to shrug his or her shoulders against resistance. In patients with damage to the spinal accessory nerve, shoulder elevation will be diminished, and the patient will be incapable of raising the shoulders against the examiner's resistance.

Treatment

There are several options of treatment when

iatrogenic Iatrogenesis is the causation of a disease, a harmful complication, or other ill effect by any medical activity, including diagnosis, intervention, error, or negligence. "Iatrogenic", ''Merriam-Webster.com'', Merriam-Webster, Inc., accessed 2 ...

(i.e., caused by the surgeon) spinal accessory nerve damage is noted during surgery. For example, during a functional neck dissection that injures the spinal accessory nerve, injury prompts the surgeon to cautiously preserve branches of C2, C3, and C4 spinal nerves that provide supplemental innervation to the trapezius muscle. Alternatively, or in addition to intraoperative procedures, postoperative procedures can also help in recovering the function of a damaged spinal accessory nerve. For example, the

Eden-Lange procedure The Eden-Lange procedure is an orthopedic surgery, orthopedic procedure to alleviate the symptoms of Accessory nerve disorder, trapezius palsy when more conservative measures, such as spontaneous resolution and Neuroregeneration#Surgery, surgical ...

, in which remaining functional shoulder muscles are surgically repositioned, may be useful for treating trapezius muscle palsy.

References

External links

{{DEFAULTSORT:Accessory Nerve Disorder Peripheral nervous system disorders

Disorder Disorder may refer to randomness, non-order, or no intelligible pattern. Disorder may also refer to: Healthcare * Disorder (medicine), a functional abnormality or disturbance * Mental disorder or psychological disorder, a psychological pattern a ...