Accessory nerve palsy is a clinical syndrome caused by various factors such as irritation, involvement, or compression of the accessory nerve. The accessory nerve consists of a cranial root and a spinal root; it exits the cranial cavity through the jugular foramen and travels to the neck, where it innervates the sternocleidomastoid muscle and the trapezius muscle. The sternocleidomastoid muscle is primarily innervated by the C2 nerve, while the upper part of the trapezius muscle is innervated by the accessory nerve, and its lower part is innervated by the C3–C4 nerves.
The primary secondary cause of accessory nerve palsy is nasopharyngeal carcinoma, but diphtheria, acute and chronic pharyngeal infections, tumors, vascular diseases, syringobulbia, lesions near the intracranial medulla oblongata, and compression, invasion, or inflammatory irritation from cervical tumors can also lead to accessory nerve palsy.
I. Diagnostic Key Points
Isolated accessory nerve palsy is rare clinically. In unilateral accessory nerve palsy, weakness of the sternocleidomastoid muscle readily occurs, followed by atrophy. As a result, the patient is completely unable to turn the chin toward the healthy side, but can easily turn it toward the affected side. In bilateral sternocleidomastoid palsy, the head assumes a forward-flexed position. Paralysis of the trapezius muscle is not obvious because its upper portion is innervated by the accessory nerve, while its lower portion is innervated by the C3–C4 spinal segments. Therefore, in pure accessory nerve palsy, only the upper half of the trapezius is paralyzed, manifesting as downward and lateral displacement of the shoulder. When both upper limbs are hanging down, the fingers on the affected side descend lower than those on the healthy side. In paralysis of the upper trapezius, the vertebral border of the scapula abducts, and the superior angle abducts more prominently than the inferior angle.
II. Treatment
(I) Acupoints and Needling Methods
1. Tianyou (TE16) (affected side): Located inferior and posterior to the mastoid process, on the posterior border of the sternocleidomastoid muscle, level with the angle of the mandible, approximately midway between Tianrong (SI17) and Tianzhu (BL10). A 30-gauge filiform needle of 2 cun in length is selected. After routine local disinfection, the needle is inserted toward the spine to a depth of approximately 1.8 cun. Needling sensation: local distension and pain, or radiation to the shoulder and back.
2. **BL11 (Dazhu) on the affected side**: Located 1.5 *cun* lateral to the depression below the spinous process of the first thoracic vertebra (T1). Use a 30-gauge, 1.5 *cun* filiform needle. After routine local disinfection, insert obliquely toward the spine to a depth of approximately 1.2 *cun*. Needling sensation: local distention and pain.
3. **BL10 (Tianzhu)** (affected side): Located 1.3 cun lateral to **GV15 (Yamen)** and at the lateral border of the trapezius muscle. Use a 30-gauge, 2-cun filiform needle. After routine local disinfection, insert perpendicularly to a depth of approximately 1.6 cun. Needle sensation: local distension and pain.
**4. LI4 (Hegu) – Affected side:** Located on the dorsum of the hand, between the 1st and 2nd metacarpal bones, near the radial midpoint of the 2nd metacarpal bone. Use a 30-gauge, 2-cun filiform needle inserted approximately 1.8 cun toward SI3 (Houxi). Needling sensation: Distension and pain in the palm.
(II) Methods
Select the affected side or both sides. The patient takes a sitting position. The aforementioned acupoints are needled according to standard technique. Electroacupuncture is applied to the neck points, but LI4 (Hegu) is not connected to the electroacupuncture device. The needles are retained for 40 minutes and then removed. Treatment is given once daily, with 10 sessions constituting one course. A 5-day rest is taken before the next course.
3. Commentary
Simple accessory nerve palsy can be effectively treated with electroacupuncture to prevent atrophy of the sternocleidomastoid and cervical trapezius muscles and to promote functional recovery. However, in cases accompanied by severe secondary conditions, the primary focus should be on resolving the underlying secondary lesions before administering electroacupuncture, which can still yield satisfactory results.