Accessory Nerve Disorder

Patients with spinal accessory nerve palsy often show signs of lower motor neuron disease, such as decreased muscle mass, fasciculation, and partial paralysis of the sternocleidomastoid and trapezius muscles. Interruption of the innervation of the sternocleidomastoid muscle leads to an asymmetric décolleté, while weakness of the trapezius muscle can lead to drooping of the shoulder, pterygo-shaped scapula and weakness of the anterior shoulder lift. ^[3]

Medical procedures are the most common cause of spinal accessory nerve injuries. ^[4] In particular, radical neck dissection and cervical lymph node biopsy are some of the most common surgical procedures that cause damage to the spinal accessory nerve. ^[4] London notes that failure to quickly identify spinal accessory nerve damage can exacerbate the problem, while early intervention can improve outcomes. ^[four]

There are several treatment options when iatrogenic (that is, that occurred during surgery) damage to the spinal accessory nerve is noticed during surgery. For example, during the functional opening of the neck, in case of damage to the spinal nerve, the injury obliges the surgeon to be careful and preserve the branches of the C2, C3, C4 spinal nerves, which provide additional innervation of the trapezius muscle. ^[5] Alternatively, or in addition to intraoperative procedures, postoperative procedures may also help restore the function of the damaged spinal nerve. For example, the Eden-Lange procedure, in which the remaining functional shoulder muscles are surgically moved, can be useful in treating trapezius muscle paralysis. ^{[6] [7]}

The functions of the accessory nerve are determined through a neurological examination. Since the examination is carried out by various specialists, it often includes three components: examination, testing of the range of motion and strength testing.

During the examination, the expert observes the sternocleidomastoid and trapezius muscles, in search of signs of disease of the lower motor neurons, such as muscle atrophy and fasciculation. The pterygoid scapula may also suggest the abnormal function of the spinal accessory nerve, as described above.

When assessing the range of movements, the expert notes how the patient bends and rotates his head, shrugs and shrugs his hands. The pterygoid scapula due to damage to the spinal accessory nerve often protrudes strongly in the designated arm.

Strength testing is similar to testing a range of motion, with the difference that the patient performs the same actions under load, that is, against the resistance of the expert. The expert measures the function of the sternocleidomastoid muscle , asking the patient to turn his head against resistance. At the same time, the expert notes the effect of the opposite sternocleidomastoid muscle. For example, if a patient turns his head to the right, the left muscle is usually stretched.

To assess the strength of the trapezius muscle, the expert suggests the patient to shrug against resistance. In patients with damage to the spinal accessory nerve, the shoulder height will decrease, and the patient will be unable to raise his shoulders against the resistance of an expert.