Introduction
The suprascapular nerve arises from the upper trunk of the brachial plexus and supplies the supraspinatus and infraspinatus muscles. It is a mixed nerve (sensory and motor) that gives sensory branches to acromioclavicular and glenohumeral joints, and motor branches to the supraspinatus and infraspinatus muscles (two of the four muscles that make the shoulder joint). The suprascapular artery and vein run along with the nerve to provide the blood supply. The anatomy and the course of the nerve make it susceptible to injury as it passes through the suprascapular and spinoglenoid notches. The most common site of compression of the suprascapular nerve is at the suprascapular notch.
What Is Neuropathy?
Damage to the nerve that leads to pain, weakness, numbness, or a tingling or pricking sensation is called neuropathy. It is usually caused by injuries, infections, and exposure to toxins. It is diagnosed by electromyography and managed by medications, or some severe cases may require surgical intervention.
What Is Suprascapular Neuropathy?
Severe shoulder pain and dysfunction due to suprascapular nerve entrapment are called suprascapular neuropathy. It was first described in 1936 by Frenchman Andre Thomas and further defined in the year 1959 by Kopell and Thomson. It is a rare cause of shoulder pain, mainly related to the anatomy and course of the suprascapular nerve. It occurs in people around 40 years of age, especially in athletes and people playing overhead sports. It is characterized by pain, infraspinatus muscle impairment, suprascapular muscle atrophy, and weakness.
What Are the Causes of Suprascapular Neuropathy?
Some of the causes of suprascapular neuropathy include:
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Overhead sports injuries, such as basketball, baseball, volleyball, etc., due to repeated throwing activities that involve backward and forward rotations of the scapula, resulting in suprascapular nerve compression. Repeated throwing activities may increase compression and damage the nerve.
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The presence of cysts or tumors at the suprascapular or spinoglenoid notch compresses the nerve.
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Paralabral cysts (fluid-filled cavities) associated with glenohumeral instability (shoulder joint instability) may compress the nerve.
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In some rare cases, trauma may lead to fractures of the suprascapular notch resulting in damage to the suprascapular nerve or post-traumatic arthritis (inflammation of the joint following trauma).
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Shoulder injections or anesthetic injections administered, and surgical procedures involving a posterior approach to the shoulder may damage the nerve.
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Rotator cuff muscle tears (shoulder muscles that help in movement) may also lead to suprascapular nerve injury.
What Are the Signs and Symptoms of Suprascapular Neuropathy?
Some of the signs and symptoms of suprascapular neuropathy include:
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Vague shoulder pain and discomfort and difficulty in shoulder movement.
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Pain worsens on the movement of the shoulder and upper arm.
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Heaviness or weakness of the shoulders and upper arm.
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Pain radiating to the neck and arms.
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Atrophy of the shoulder muscles (wasting of muscles and shrinkage).
How Is Suprascapular Neuropathy Diagnosed?
Diagnosis of suprascapular neuropathy is quite challenging as the clinical presentation is mostly similar to other shoulder pathologies; hence must be considered in patients with unexplained shoulder pain, especially in overhead sports athletes. A complete medical history is taken, which includes previous shoulder surgeries, history of trauma, overhead activities, and previously administered anesthetic shoulder injections; it is followed by a thorough physical examination. The patient usually presents with deep dull, continuous pain and is non-specific in nature. In some cases, it may radiate to the neck and arm, associated with suprascapular muscle atrophy and weakness in elevating the arm and rotation. Pain and tenderness are noted, which increase due to stretching the nerve on movement. A fast-acting anesthetic is injected locally into the spinoglenoid notch, and pain relief confirms the diagnosis of the nerve entrapment. Radiological investigations include:
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X-rays to rule out fractures and arthritis and a magnetic resonance imaging scan (MRI) may reveal inflammation of the supraspinatus or infraspinatus muscle, atrophy, presence of cysts, or any other lesions compressing the nerve.
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Ultrasonography may be recommended in some cases, as it is less expensive than an MRI scan, and the presence of any cysts or parascapular ganglia masses can be identified.
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Electromyography is the gold-standard diagnostic test for suprascapular neuropathy, which helps to detect the injury level and nerve conduction velocity (NCV). It shows the presence of sharp waves, fibrillations, and increased latency, suggesting the denervation of the supraspinatus or infraspinatus muscles. However, in some rare cases, such as chronic neuropathic pain, it may show negative results.
How Is Suprascapular Neuropathy Managed?
Suprascapular neuropathy can be managed by non-surgical and surgical methods. Non-surgical methods are advised in most cases of suprascapular neuropathy due to overuse of the muscles, with the absence of rotator cuff muscle injury and no compression of the nerve, and may not be helpful to patients with long-duration symptoms or muscle atrophy. It includes
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Nonsteroidal inflammatory drugs to relieve pain, such as Ibuprofen, Acetaminophen, etc.
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Activity modification and a comprehensive physical therapy program include muscle strengthening exercises and range of motion exercises for around six months.
Surgical management is necessary in cases of rotator cuff tears, suprascapular nerve compression, muscle atrophy, or a poor outcome following a non-surgical treatment. It includes
The surgical release of the suprascapular nerve, irrespective of the electromyography findings, is done in symptomatic patients through an open or an arthroscopic approach.
Open Approach:
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Suprascapular Notch Decompression: A transverse skin incision is done either parallel to the scapular spine or a curved incision medial to the acromioclavicular joint, the trapezius muscle is split by blunt dissection, and the supraspinatus muscle is identified. The suprascapular nerve bundle and the transverse scapular ligament are located. The transverse scapular ligament is released, and the suprascapular nerve is freed; further decompression may be needed in some cases, which is performed by deepening or widening the suprascapular notch.
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Supraglenoid Notch Decompression: It is done by making a skin incision three centimeters medial to the posterolateral corner of the acromion and extending downwards towards the posterior axillary skin fold. The deltoid muscle is split by a blunt dissection, and the fascia is opened. The spinoglenoid notch is exposed by dislocating the infraspinatus muscle belly, and a consistent ligamentous structure is then visible. The spinoglenoid ligament is cut from the scapular spine edge, and the suprascapular nerve is released. If a ganglion cyst is present in this area, it is also excised after ligament release.
Arthroscopic Approach: It is a quick and safe procedure but requires a high degree of expertise due to the proximity of the neurovascular structures, and the suprascapular artery and nerve are identified and protected. A blunt dissection is made around the transverse scapular ligament, arthroscopic scissors are introduced, and the ligament is cut to release the suprascapular nerve. Any soft tissue lesions present are then treated. Complications may rarely occur in some cases due to injury to the blood vessels and suprascapular nerve during dissection. The surgical treatment is followed by rehabilitation therapy by muscle strengthening exercises after four to eight weeks to improve the range of motion.
Conclusion
An injury to the suprascapular nerve due to repeated overhead activities, followed by nerve compression, is called suprascapular neuropathy. It is a rare condition associated with vague shoulder pain that increases on movement and sometimes radiates to the neck and the upper arm. It is usually diagnosed by electromyography and nerve conduction studies and managed by conservative or surgical treatments, followed by rehabilitation therapy.
