Spinal Accessory Nerve Palsy - Causes, Symptoms, Diagnosis, and Treatment.

What Is Spinal Accessory Nerve Palsy?

The spinal accessory nerve is a cranial nerve emerging from the base of the skull through the jugular foramen (a small opening at the base of the skull), and it travels downwards to supply the sternocleidomastoid (SCM) and trapezius muscles of the neck. Spinal accessory nerve injury usually occurs during a neck dissection surgery. Injury to the nerve results in a condition called spinal accessory nerve palsy (SANP). The superficial nature and the length make the spinal accessory nerve more susceptible to injury. Injury to the spinal accessory nerve could be incidental, from blunt trauma, or, more commonly, from an injury during surgical procedures.

What Causes Injury to the Spinal Accessory Nerve?

• Iatrogenic Causes - That means the injuries made by medical or surgical procedures or by a medical practitioner. The surgical procedures that may cause a spinal accessory nerve injury include lymph node biopsies, neck surgeries for tumor removal, neck dissection, and cosmetic surgeries.

• Penetrating Trauma - Including gunshot or knife wounds.

• Neurological Causes - A tumor at the base of the skull involving the jugular foramen (the cranial nerve emerges from the skull through the jugular foramen) can compress the nerve leading to spinal accessory nerve palsy.

• Sports Injuries - Such as wrestling, hockey stick blow, a sling note, and a whiplash injury.

What Are the Symptoms of Spinal Accessory Nerve Palsy?

• Pain is the most common complaint in the spinal accessory nerve injury. Pain along with weakness of the involved shoulder is mostly observed. The pain may radiate to the neck, upper back, and arm on the affected side. The pain is increased while taking weight in that arm. The combination of pain and weakness would limit movements of the affected shoulder.

• Depressed shoulder girdle or shoulder drooping.

• Atrophy of the trapezius muscle (trapezius is a pair of large muscles located at the back of the neck).

• Paralysis or weakness of sternocleidomastoid muscle.

• Winging of the scapula (shoulder blade). The scapular bone becomes more prominent on the affected side.

• Restricted movement of the affected side shoulder.

How to Diagnose Spinal Accessory Nerve Palsy?

Spinal accessory nerve palsy is initially diagnosed with a physical examination of the patient. Medical history is very important in the case of spinal accessory nerve palsy as it gives information about any surgical procedure in the neck region. Other than this some imaging techniques used in the diagnosis of spinal accessory nerve palsy is as follows;

• Electromyography (EMG) - It is a diagnostic method used to evaluate the electrical activity of the muscle. This technique helps to diagnose any problem regarding the muscle and the nerve supplying the muscle. A series of EMGs can determine the degree of muscle damage.

• High-Resolution UltraSonography (HRUS) - It is used for the confirmation of the target nerve and to visualize the structures around the nerve. Ultrasound helps to diagnose any changes to the muscles, such as atrophy. Ultrasound guidance can be used in injections and administration of medications to avoid complications.

• Goniometry - Used to evaluate shoulder movements such as flexion and abduction.

What Is the Management of Spinal Accessory Nerve Palsy?

Management of spinal accessory nerve palsy is determined by the cause of the nerve injury. For severe cases, immediate treatment is recommended. Usually, the management consists of two methods, medical and surgical.

Medical Management:

Medical management is indicated in cases with mild symptoms like pain and mild dysfunction of the scapula, and in cases with clinical improvement of shoulder functions.

Short-term medications for pain relief and improvement of shoulder functions are;

• Non steroidal anti inflammatory drugs (NSAIDs).

• Local anesthesia for regional nerve blocks.

• Transcutaneous nerve stimulation.

These methods are not recommended for the long term management of spinal accessory nerve palsy.

Rehabilitation:

Rehabilitation is recommended to improve movements of the shoulder girdle to avoid shoulder dysfunction. The following rehabilitative measures are recommended;

• Avoid carrying heavy weights on the affected side.

• Place the affected hand in the pocket of the pants to get significant relief from pain and discomfort.

• An arm sling is recommended for pain relief.

• Use of an orthosis (an external device like braces or splint) can help decrease pain and weakness.

Physical Therapy:

Physical therapy is essential for recovery from spinal accessory nerve injury. It is critical in patients who refuse surgical treatment or who are unsuitable for surgery. Physical therapy is more successful if started within one month of surgery and done up to three months. However, it also works well for late-diagnosed spinal nerve injury as well. Physical therapy shows significant improvement in pain, movement of shoulder, and overall quality of life. Physical therapy reduces stiffness of the shoulder joint resulting from malalignment.

Surgical Management:

Surgical treatment is indicated only in cases with no improvement in clinical examination or serial electromyography. Other indications are severe pain and shoulder dysfunction, and dense paralysis. The surgical procedures are the following;

• Primary nerve anastomosis.

• Neurolysis.

• Nerve graftings such as autograft and Neurotube.

• Eden-Lang muscle transfer.

In patients with obvious injury to the spinal accessory nerve immediate reconstruction surgery is needed. For patients who do not respond to nerve repair or surgery, muscle or tendon transfer is recommended to stabilize the scapula. Scapulothoracic fusion is one such procedure.

What Are the Complications of Spinal Accessory Nerve Palsy?

• Neck pain.

• Asymmetric shoulders.

• Weakness in the neck area.

• Inability to shrug the shoulder.

• Graft failure due to a fibrous growth over the graft.

• Morbidity of the donor site in nerve grafting.

Conclusion

Spinal accessory nerve (SAN) function after an injury is influenced by factors such as the type of neck surgery, the extent of the injury, radiation therapy, the time gap between trauma and repair, and the length of the graft. An early and accurate diagnosis and appropriate management determines the outcome of the spinal accessory nerve palsy. The importance of physical therapy should be stressed in patients undergoing nerve repair surgery. Proper follow-up is necessary after the treatment. With timely diagnosis and treatment, patients with spinal accessory nerve palsy can improve the quality of their life and lead a pain free and functional life.