Accessory nerve disorder
Encyclopedia
Injury to the spinal accessory nerve
can cause an accessory nerve disorder or spinal accessory nerve palsy, which results in diminished or absent function of the sternocleidomastoid muscle
and upper portion of the trapezius muscle
.
s, and partial paralysis
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
, and a weakness of forward elevation of the shoulder.
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.
. How the examination is administered varies by practitioner, but it frequently involves three components: inspection, range of motion
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
and fasciculation
. A winged scapula
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.
Accessory nerve
In anatomy, the accessory nerve is a nerve that controls specific muscles of the shoulder and neck. As part of it was formerly believed to originate in the brain, it is considered a cranial nerve...
can cause an accessory nerve disorder or spinal accessory nerve palsy, which results in diminished or absent function of the sternocleidomastoid muscle
Sternocleidomastoid muscle
In human anatomy, the sternocleidomastoid muscle , also known as sternomastoid and commonly abbreviated as SCM, is a paired muscle in the superficial layers of the anterior portion of the neck...
and upper portion of the trapezius muscle
Trapezius muscle
In human anatomy, the trapezius is a large superficial muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae and laterally to the spine of the scapula...
.
Presentation
this type of Patients with spinal accessory nerve palsy often exhibit signs of lower motor neuron disease such as diminished muscle mass, fasciculationFasciculation
A fasciculation , or "muscle twitch", is a small, local, involuntary muscle contraction and relaxation visible under the skin arising from the spontaneous discharge of a bundle of skeletal muscle fibers...
s, and partial paralysis
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
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
Winged scapula
A winged scapula is a condition in which the shoulder blade, or shoulder bone, protrudes from a person’s back in an abnormal position. It is a rare condition with the potential to lead to limited functional activity in the upper extremity with which it is adjacent. It can affect a person’s ability...
, 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 biopsyLymph 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 .The lymphatic system is made up of several lymph nodes connected by lymph vessels. The nodes produce white blood cells that fight infections...
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.
Treatment
There are several options of treatment when iatrogenic (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, in which remaining functional shoulder muscles are surgically repositioned, may be useful for treating trapezius muscle palsy.Assessing function
The function of the spinal accessory nerve is measured in the neurological examinationNeurological examination
A neurological examination is the assessment of sensory neuron and motor responses, especially reflexes, to determine whether the nervous system is impaired...
. How the examination is administered varies by practitioner, but it frequently involves three components: inspection, range of motion
Range of motion
Range of motion , is the distance that a movable object may normally travel while properly attached to another object. It is also called range of travel, particularly when talking about mechanical devices and in mechanical engineering fields...
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
Muscle atrophy, or disuse atrophy, is defined as a decrease in the mass of the muscle; it can be a partial or complete wasting away of muscle. When a muscle atrophies, this leads to muscle weakness, since the ability to exert force is related to mass...
and fasciculation
Fasciculation
A fasciculation , or "muscle twitch", is a small, local, involuntary muscle contraction and relaxation visible under the skin arising from the spontaneous discharge of a bundle of skeletal muscle fibers...
. A winged scapula
Winged scapula
A winged scapula is a condition in which the shoulder blade, or shoulder bone, protrudes from a person’s back in an abnormal position. It is a rare condition with the potential to lead to limited functional activity in the upper extremity with which it is adjacent. It can affect a person’s ability...
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.