Numbness in the left shoulder is often caused by low-urgency conditions that can be treated by your primary care doctor, and range from common issues like a pinched nerve in the neck to uncommon conditions like brachial plexopathy. Read more below to learn 7 possible causes of numbness in the left shoulder, possible treatment options, and more.
Symptoms of left shoulder numbness
Most people describe numbness as a loss of sensation or feeling in a body part. People often feel this numbness in the leg after sitting in the same position for too long; they may refer to the sensation as “pins and needles” or the “leg falling asleep.”
However, these symptoms can also occur in the left shoulder and can signal conditions that range from benign to severe. As a result, it is important to follow up with your doctor and get appropriate care as soon as you notice symptoms.
Common characteristics of left shoulder numbness
Characteristics associated with left shoulder numbness may include:
- Weakness: You may have difficulty or be unable to move the arm in different planes (forward, backward, up or down). You may experience difficulty performing daily tasks that involve other parts of the arm such as grasping with the hand.
- Loss of sensation: In addition to numbness, you may not be able to feel sensations such as heat or cold or pain from a pinprick.
Common accompanying symptoms
Left shoulder numbness can be associated with many different conditions and symptoms can vary. Symptoms associated with left shoulder numbness may include:
- Pins and needles sensation
- Sensitivity to touch
A complicated branching system of nerves called the brachial plexus controls the upper arm. This plexus of nerves starts from the cervical spinal cord, travels down the neck, over the first rib, and into the armpit to provide innervation to not only the arm and hand but also the chest and shoulder.
The axillary nerve, a branch of the brachial plexus, primarily controls sensation (also called cutaneous innervation) of the upper arm. The supraclavicular nerves also control part of the area over the shoulders — these are not part of the brachial plexus but also branch from the cervical spinal cord.
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Causes of left shoulder numbness
Left shoulder numbness is the result of injury, compression or irritation primarily of the axillary nerve, but such symptoms also result from injury, compression or irritation of the other nerves in that area. Thus, causes that result in left shoulder numbness are varied, but can be divided into the following categories:
Left shoulder numbness can be a result of trauma such as the following.
- Direct injury: Direct injury to the muscles and bones of the upper arm in the form of dislocations, fractures, and even sprains can also result in injury to the nerves of the upper arm resulting in numbness and other associated symptoms such as tingling and pain.
- Compressive injury: Surprisingly, the axillary nerve is very susceptible to compression from non-traumatic causes. For example, compression of the brachial plexus and in turn the axillary nerve by anatomical structures in the area such as the first rib or clavicle can result in a constellation of symptoms including numbness of the upper arm. This is known as thoracic outlet syndrome.
- Entrapment: Very rarely, the axillary nerve may become trapped as it runs through a small space (the quadrilateral space) made by the teres minor muscle at the top, the humerus bone on one side, the long head of the triceps muscle on the other side, and the teres major muscle at the bottom. See an image of this space and its relationship to the axillary nerve here.
Systemic disease may lead to left shoulder numbness, such as the following.
- Metabolic: Dysfunction in the processes that your body uses day-to-day, for example, glucose and insulin dysregulation in diabetes, can damage the peripheral nerves causing numbness in one upper arm and other parts of the body (this condition is known as peripheral neuropathy).
- Tumors: Very rarely, cancerous and noncancerous growths in the body can directly grow and compress nerves in the upper arm, including the axillary nerve.
This list does not constitute medical advice and may not accurately represent what you have.
Repetitive strain injury of the shoulder ("swimmer's shoulder")
Repetitive strain injury of the shoulder is caused by consistent repetitive use.
Top Symptoms: shoulder pain from overuse, shoulder weakness, shoulder numbness
Symptoms that always occur with repetitive strain injury of the shoulder ("swimmer's shoulder"): shoulder pain from overuse
Symptoms that never occur with repetitive strain injury of the shoulder ("swimmer's shoulder"): severe shoulder pain, shoulder injury
Brachial plexopathy (shoulder nerve issue)
The brachial plexus is a web of nerves between the neck and shoulder, connecting the spinal cord nerves to the arm. There is one web on each side of the neck. Any injury that forces the shoulder to stretch down, and the neck to stretch up and away, can damage these nerves and cause brachial plexopathy.
Sports injuries and car accidents are often involved. Inflammation, tumors, and radiation treatment can also damage the brachial plexus.
Milder symptoms include numbness and weakness in the arm, with a shocklike stinging or burning sensation. A more severe injury can cause paralysis and loss of feeling in the arm, with pain in some parts of the arm, hand, and shoulder.
These symptoms should be seen by a medical provider since permanent damage can result if the injuries are not treated.
Diagnosis is made through electromyography (EMG) testing, CT scan, MRI, and sometimes angiogram.
Treatment usually involves rest and physical therapy. Surgery may be necessary to remove scar tissue or repair the damaged nerves.
Top Symptoms: pain in one arm, shoulder pain that shoots to the arm, arm weakness, numbness in one arm, shoulder pain
Symptoms that never occur with brachial plexopathy (shoulder nerve issue): pain in the front middle part of the neck
Urgency: Primary care doctor
Pinched nerve in the neck
A pinched nerve in the neck is also called cervical radiculopathy. It means that a nerve in the neck, at a point where it branches off from the spinal cord, is being compressed by the surrounding bones, muscles, or other tissues.
It can be caused by a traumatic injury, such as from sports or an automobile accident, especially if the injury results in a herniated disk. It may also arise from the normal wear and tear of aging.
Symptoms include sharp, burning pain with numbness and tingling from the neck to the shoulder, as well as weakness and numbness into the arm and hand.
Diagnosis is made through patient history, physical examination, and simple neurological tests to check the reflexes. Imaging such as x-ray, CT scan, or MRI may be done, as well as electromyography to measure nerve impulses in the muscles.
A pinched nerve in the neck often improves with simply a few days or weeks of rest. Physical therapy, nonsteroidal anti-inflammatory drugs, and steroid injections into the spine can all be very helpful.
Top Symptoms: pain in one shoulder, spontaneous shoulder pain, pain that radiates down arm, pain in the back of the neck, severe shoulder pain
Urgency: Primary care doctor
Carpal tunnel syndrome is a condition of numbness and tingling in the hand and arm caused by compression of the mediannerve as it travels through the carpal tunnel. Causes include overuse of the wrist and hand, especially highly repetitive activities such as typing or wo..
Fibromyalgia is a set of chronic symptoms that include ongoing fatigue, diffuse tenderness to touch, musculoskeletal pain, and usually some degree of depression.
The cause is not known. When fibromyalgia appears, it is usually after a stressful physical or emotional event such as an automobile accident or a divorce. It may include a genetic component where the person experiences normal sensation as pain.
Almost 90% of fibromyalgia sufferers are women. Anyone with rheumatic disease, such as rheumatoid arthritis or lupus, may be more prone to fibromyalgia.
Poor sleep is often a symptom, along with foggy thinking, headaches, painful menstrual periods, and increased sensitivity to heat, cold, bright lights, and loud noises.
There is no standard test for fibromyalgia. The diagnosis is usually made when the above symptoms go on for three months or more with no apparent cause.
Fibromyalgia does not go away on its own but does not get worse, either.
Top Symptoms: fatigue, arthralgias or myalgias, anxiety, depressed mood, headache
Symptoms that always occur with fibromyalgia: arthralgias or myalgias
Urgency: Primary care doctor
Thoracic outlet syndrome
The "thoracic outlet" is the space on either side of the base of the neck where nerves, arteries, and veins travel beneath the collarbone. If these become compressed or damaged, the condition is called thoracic outlet syndrome or TOS.
The most common causes are trauma, such as a car accident or fall; and repetition or overuse, such as a sports injury.
Symptoms vary depending on the structures being compressed:
- Neurogenic TOS affects the nerves. It is the most common form and creates numbness, tingling, pain, and weakness in the arms, hand, and fingers.
- Vascular TOS affects the arteries and veins. It creates the same symptoms as neurogenic TOS as well as cold, pale hands and arms with weak pulse.
It is important to see a medical provider about these symptoms so that the damage does not become permanent.
Diagnosis is made through patient history, physical examination, imaging such as x-ray or ultrasound, and sometimes nerve conduction and blood flow studies.
Treatment involves physical therapy, pain relievers, and sometimes surgery.
Top Symptoms: pain in one shoulder, spontaneous shoulder pain, arm weakness, arm numbness, pain in one shoulder blade
Urgency: Primary care doctor
Chronic idiopathic peripheral neuropathy
Peripheral neuropathy refers to the feeling of numbness, tingling, and pins-and-needles sensation in the feet. Idiopathic means the cause is not known, and chronic means the condition is ongoing without getting better or worse.
The condition is most often found in people over age 60. Idiopathic neuropathy has no known cause.
Symptoms include uncomfortable numbness and tingling in the feet; difficulty standing or walking due to pain and lack of normal sensitivity; and weakness and cramping in the muscles of the feet and ankles.
Peripheral neuropathy can greatly interfere with quality of life, so a medical provider should be seen in order to treat the symptoms and reduce the discomfort.
Diagnosis is made through physical examination; blood tests to rule out other conditions; and neurologic and muscle studies such as electromyography.
Treatment involves over-the-counter pain relievers; prescription pain relievers to manage more severe pain; physical therapy and safety measures to compensate for loss of sensation in the feet; and therapeutic footwear to help with balance and walking.
Top Symptoms: distal numbness, muscle aches, joint stiffness, numbness on both sides of body, loss of muscle mass
Urgency: Primary care doctor
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Left shoulder numbness treatments and relief
At home treatment for left shoulder numbness can be as simple as resting the arm and being mindful of your arm’s positioning when it is and is not in use. However, if your left shoulder numbness persists, you should see a medical professional for an evaluation.
You can treat temporary symptoms of numbness with simple lifestyle changes:
- Sleep habits: An activity as simple as sleeping on the back with the arms above the head can temporarily compress the axillary nerve, resulting in the familiar sensation of the “arm falling asleep.” Try to be cognizant of how you sleep and make yourself as comfortable as possible.
- Moving: Avoid repetitive motions or cramped positions that put unnecessary pressure on your shoulders.
- While resting: Often you can find relief by improving your posture, buying a support for your back while typing, or taking breaks throughout the day in order to lessen compression and irritation of the nerves in your arms/shoulders.
When to see a doctor
However, if you experience frequent, persistent episodes of left shoulder numbness, visit your doctor to find the exact cause of your condition in order to get appropriate treatment. Depending on the cause, your doctor may first suggest other lifestyle modifications such as:
- Regular exercise: Maintaining an optimal weight with exercise as well as a balanced diet can prevent and control metabolic diseases such as obesity and diabetes. Medications: Your doctor may be able to give you a prescription that can treat tingling and other symptoms related to numbness in the upper shoulder.
- Physical therapy: If your shoulder numbness is due to anatomical conditions or trauma that cause compression of the nerves and blood vessels leading to your arm and hand, your doctor may suggest therapy to help take the pressure of these body parts, which also may improve your range of motion and posture.
- Surgery: If other treatments are ineffective and your symptoms continue to progress or worsen, your doctor may recommend looking into surgical options to combat your symptoms.
When it is an emergency
If you experience any symptoms of speech difficulty, facial drooping, or weakness to the point you cannot raise your arm call 911 immediately. These could be signs of a stroke.
FAQs about left shoulder numbness
Will the numbness in my left shoulder affect the use of my hand?
The numbness in your left shoulder may be associated with problems moving the arm and hand. The axillary nerve is both a motor and sensory nerve, so it provides innervation that controls movement in addition to sensation. You may have some weakness and difficulty externally rotating or abducting the shoulder, but since other muscles can help with these movements, your difficulty should not be severe. If compression or injury of the brachial plexus results in injury to other nerves, you may also experience difficulties moving the hand.
Why am I only feeling symptoms in only my left shoulder?
You are only feeling numbness in one upper arm because the nerve in that specific shoulder is affected whereas the nerve in the other arm has not.
Is numbness in the left shoulder life-threatening?
Usually, numbness in the left shoulder is not life-threatening, especially if it is related to compressive etiologies such as lying on the arm for too long. However, numbness in the left shoulder may be a sign of a stroke, which is a life-threatening condition that requires immediate attention.
Will the numbness spread from my left shoulder to other parts of my arm or upper body?
If your symptoms are due to compression of the axillary nerve via the brachial plexus, your symptoms may spread to other parts of the arm and hand depending on which other branches and nerves of the plexus are affected.
How long will the numbness last?
Decompression of the axillary nerve from non-traumatic causes usually results in very fast relief. Decompression in this context can be attained by moving the arm from the offending position or shaking out the shoulder.
Questions your doctor may ask about left shoulder numbness
- How would you explain the cause of your shoulder pain?
- Let's do a physical exam. Can you turn your hand over from the backside to the frontside?
- Have someone push down on your arm as you hold it out. Can you resist? (This is known as the axillary nerve test.)
- Straighten your elbow while someone else pushes against that movement. Can you overcome the other person's resistance?
Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.
- Brachial Plexus Injuries. American Academy of Orthopedic Surgeons: OrthoInfo. Reviewed June 2015. OrthoInfo Link
- Peripheral nerve injury in the upper extremity. University of Michigan: Michigan Medicine. Michigan Medicine Link
- Thoracic outlet syndrome. University of Rochester Medical Center. URMC Link
- Neal SL, Fields KB. Peripheral nerve entrapment and injury in the upper extremity. American Family Physician. 2010;81(2):147-155. AAFP Link