A string-like structure consisting of multiple axons leaving the spinal cord. An axon is an extension of a nerve cell. Multiple nerve cells form the brain and spinal cord, sending signals to control all functions of the human body.
Main Functions of Nerves in Musculoskeletal System is to provide sensory feedback to the brain. This feedback is interpreted and determines which signals are sent through the nerve axons
Types of sensory functions:
- Sensation of touch
- Joint position
Other functions include allowing muscles to perform motor functions. Also warning and preventing the body from being damaged by environmental factors via pain fibers. Pain fibers alert a person of environmental and internal pain, such as appendicitis or kidney stones
Brachial Plexus is a network formed from exiting neck nerves intermingling. It ends in specific nerves that control the entire upper limb; the shoulder, elbow, wrist and hand.
Five Major Nerves from the Brachial Plexus
Secondary Nerves from the Brachial Plexus
- Long thoracic
- Dorsal scapular
Symptoms of Nerve Pain
These symptoms are the hallmark of nerve pain, which continues with or without the use of our limbs. Rest pain, with symptoms of numbness, tingling or weakness, alerts an examiner that a nerve compression is most likely present.
If a muscle has a dense fascial cover, there is a change in pressure between the cover and the dense fascial edge. As a nerve glides repetitively between the fasical cover and fascial edge, the nerve can become compressed. This compression causes nerve swelling, which is called the edge effect.
Nerve compression syndromes are normally found in adults. It is rare to find nerve compression syndromes in patients younger than 20 years old.
Common Causes of Nerve Compression Syndromes
- Injury secondary to direct trauma
- Indirect injury of nerve stretching through pulling
- Repetitive use with poor body posture
- Medical conditions:Â Diabetes, Thyroid disorder and Kidney failure
With aging, the water content of cells decrease. This leads to decreasing tissue flexibility as the collagen type of tissue changes to the less flexible type. The elastin part of muscle and ligaments decrease as well, further decreasing muscle flexibility. Nerve compression in the neck and shoulder typically presents with pain in the neck and shoulder.
- A cool limb sensation
- Muscle weakness
- Discoloration of the arm and hand
- Functional limitations: Dropping objects, Inability to button shirts, comb hair or brush your teeth
Nerve pain has a constant presence occurring without the use of the limb but is often aggravated with use. Pain quality can vary from a dull ache to severe intolerable sharp stabbing pain. The temporal appearance is also variable and at times unpredictable, presenting without rhyme or reason. Examples of Nerve Compression Syndromes in Shoulder:
- Suprascapular nerve compression
- Quadrangular space syndrome
- Parsonage Turner syndrome
- Thoracic Outlet Syndrome
- Complex Regional Pain Syndrome
Suprascapular nerve compression typically occurs in two locations. When the suprascapular nerve exits the brachial plexus, it passes through the suprascapular notch. This space the suprascapular nerve travels through can become excessively tight, causing a dull constant ache in the shoulder. This ache is deep in quality and occurs at rest but is aggravated with use of the arm. The use of an EMG/NCS can be helpful in making the diagnosis, and diagnostic injections can be given in the office to confirm the diagnosis.
Spinoglenoid ganglion cyst causing compression of the suprascapular nerve
The suprascapular nerve can also be compressed in an area called the spinoglenoid notch from the presence of a ganglion cyst (fluid filled sack). A ganglion cyst most commonly arises from fluid leaking from the shoulder joint caused by a SLAP lesion. A SLAP lesion is a tear in the labrum which seals the glenoid rim. This type of compression results in the atrophy (withering away) of the muscle of the supraspinatus and infraspinatus. The compression of the spinoglenoid notch causes atrophy of the infraspinatus. The consequence of this compression is weakness of the rotator cuff muscles. These muscles raise the arm and allow the arm outside rotation.
Quadrangular space syndrome (QSS) is a rare condition often presenting with shoulder pain brought on by repetitive overhead activities. Other rarer causes include benign cysts or arterial aneurysms. QSS, like suprascapular nerve compression, is an axillary nerve compression arising from the brachial plexus. This axillary nerve is accompanied by the posterior humeral circumflex artery (PHCA) at the shoulder level. This neurovascular bundle can become compressed as it passes through the quadrangular space. A nerve conduction study can be of assistance but often times can be negative. A MR angiogram focusing on the area is helpful and treatment is symptomatic initially.
Parsonage Turner Syndrome, or brachial neuritis, is a rare syndrome of unknown cause; it is linked to a viral origin affecting the brachial plexus. The diagnosis is one of exclusion, requiring the ruling out of other causes.
Patients with this condition present with an insidious onset of intense shoulder pain progressing over a 2-3 day period and slowly dissipating after 2 weeks. This is followed by weakness in the shoulder and upper limb muscles, in some instances progressing to atrophy and paralysis. The majority of patients have complete resolution of their symptoms over time but it can take up to 2 years.
Treatment is symptomatic, focusing on maintaining limb mobility and electrical stimulation to maintain joint flexibility and muscle mass.
Thoracic Outlet Syndrome: Accessory Muscle Thoracic Outlet Syndrome: Accessory Rib
Thoracic Outlet Syndrome (TOS) also known as Thoracic Outlet Compression (TOC), is a nerve compression syndrome of the thoracic outlet. The thoracic outlet is where the brachial plexus exits the neck area to travel down the arm as individual nerves.
Common TOS/TOC Patient Histories
- History of either minor or major injury
- History of repetitive overhead activity
- History of administrative duties working in front of a computer
Types of Thoracic Outlet Compression
Vascular (2% of total cases)
1. Subclavian Artery Compression
2. Internal Jugular Vein Compression
Nerve Types (98% of total cases)
3. Neurogenic Thoracic Outlet Compression
- True neurogenic type occurs in less than 1% of patients.
- Nerve conduction study is often positive and confirms the diagnosis.
4. Disputed Neurogenic Thoracic Outlet Compression
- Most common type; comprises 97% of cases
- Pain occurs with and without use of the limb but is aggravated with use
- Patients present with pain in: Entire upper limb (shoulder, elbow, forearm, wrist and hand) and Neck
- Night awakening is common
- Rarely is there true muscle atrophy
- Limb may experience a cool sensation with mild discoloration
- Nerve conduction study is typically negative in this condition, but the history and physical exam findings are classic
A diagnostic injection can be given in the office with lidocaine at the inter-scalene level to confirm the diagnosis. If more than 50% of the pain is alleviated with the injection, and the rest of the clinical picture is present, without another diagnosis to explain the symptoms after a thorough workup, then a presumptive diagnosis of disputed neurogenic thoracic outlet compression is made.
Complex Regional Pain Syndrome (CRPS)
CRPS was previously known as Reflex Sympathetic Dystrophy. Causes of CRPS can occur as a consequence of minor and often insignificant trauma or a major violent trauma.
Types of Complex Regional Pain Syndrome:
Type I CRPS
- Believed to have a central neurogenic cause
- Theorized a genetic predisposition may exist
- Presents with a minor limb injury causing symptoms such as:
- Severe pain
- Limb swelling
- Loss of motion
- Poor function
Type II CRPS
- Also called â€œcausalgiaâ€
- A distinct nerve pathway compression is usually the cause.
Type III CRPS
- An unexplained pain syndromes that includes fibromyalgia.
It is very important to distinguish the different types of CRPS. For example, Type II CRPS has a higher response rate and if a nerve compression syndrome is identified as the cause, surgical decompression will resolve the symptoms.
Type I CRPS is a nonsurgical condition. However, there is the exception that an implantable nerve stimulator can be used to control pain when other conservative options are exhausted.
Symptoms in CRPS result from nerve dysfunction affecting the musculoskeletal system and blood vessels feeding the affected area.
Common CRPS Symptoms
- Severe constant pain
- Burning sensation
- Allodynia: severe hypersensitivity to touch
- Hyperpathia: exaggerated response to a minor stimulus
- Cool sensation
- Joint stiffness
- Muscle atrophy
- Changes to fingernails
- Loss of skin folds
- Hair growth
- Variance in appearance and color such as: shiny glossy look and mottled or a bluish discoloration due to the sympathetic fibers innervating the local blood vessels
The history and physical exam is the most important, along with a geographic palpation. Recommended Tests:
- Bone scans – Performed by placing a special dye in patientâ€™s vein. The dye circulates around the body and accumulates in areas of inflammation. It is positive in many conditions and so has very little usefulness in making a diagnosis of CRPS
- Plain x-rays – Plain films show osteopenia or decreased bone density but the simple lack of use of a body part will show this so this test adds very little to making an accurate diagnosis
- MRI scans
- Nerve conduction study (EMG/NCS) – Can be helpful if it is a Type II CRPS with a specific demonstrated nerve compression
- Stellate ganglion blocks – A stellate ganglion block is useful to rule out CRPS