Arms often feel numb when raised, a common sensation. This temporary numbness typically arises from the body’s intricate network of nerves and blood vessels responding to positional changes. Understanding the underlying anatomy helps clarify why certain arm movements can lead to this sensation.
The Pathways of Sensation and Supply
Arm sensation and function rely on nerves and blood vessels from the neck and chest. The brachial plexus, a nerve network from spinal nerves C5 to T1, extends from the spinal cord through the neck and armpit into the upper limb. These nerves control muscle movement and provide sensory input like touch, temperature, and pain in the shoulders, arms, and hands.
Blood supply to the arms comes from an arterial system starting with the subclavian artery in the chest, continuing as the axillary artery in the armpit, and then the brachial artery down the arm. This system, including radial and ulnar arteries in the forearm, supplies oxygen and nutrients. Veins, like the subclavian vein, return deoxygenated blood to the heart.
Why Raising Your Arms Causes Compression
Raising arms can temporarily narrow anatomical spaces, compressing nerves and blood vessels. The thoracic outlet, a space between the collarbone (clavicle) and first rib, is one such area. When the arm is elevated, especially overhead, this space constricts, temporarily pinching the brachial plexus and subclavian artery and vein.
Compression reduces blood flow and interferes with nerve signals, causing numbness or tingling. Everyday activities like sleeping with an arm overhead, prolonged overhead work, or certain exercises can create enough pressure for these temporary symptoms. This is similar to a limb “falling asleep” from sustained pressure.
Beyond Temporary Pressure: Underlying Conditions
Persistent or recurring arm numbness, beyond temporary elevation, may signal an underlying condition. Thoracic Outlet Syndrome (TOS) involves nerve or blood vessel compression in the thoracic outlet. Neurogenic TOS, the most common, compresses the brachial plexus, causing numbness, tingling, and weakness, worsened by arm elevation. Venous TOS compresses the subclavian vein, leading to arm swelling or discoloration. Arterial TOS compresses the subclavian artery, reducing blood flow and making the arm feel cold.
Other conditions can also cause arm numbness worsened by elevation. Cervical radiculopathy, or a “pinched nerve” in the neck, results from nerve compression or irritation where it branches from the spinal cord. This can stem from arthritis, bone spurs, or a herniated disc, causing pain, numbness, and weakness radiating into the arm. Nerve entrapment syndromes, like cubital tunnel syndrome (ulnar nerve at elbow) or Guyon’s canal syndrome (ulnar nerve at wrist), cause numbness and tingling in the hand and forearm, aggravated by certain arm positions. Quadrilateral Space Syndrome involves axillary nerve and artery compression in the shoulder, leading to numbness and weakness with overhead arm movements.
When to Seek Professional Guidance
Consult a healthcare professional if arm numbness when raised becomes regular or concerning. Seek medical evaluation if numbness is persistent, not just with arm elevation, or if accompanied by pain, muscle weakness, or skin color changes like paleness or bluish discoloration. Medical attention is also warranted if numbness significantly impacts daily activities or sleep, or if you experience difficulty moving your arm or stiffness.
Seek immediate medical help if numbness appears suddenly, is severe, or follows a head, neck, or back injury. Urgent “red flag” symptoms include numbness affecting an entire arm or leg, difficulty walking, talking, or thinking, loss of muscle control, or numbness spreading throughout the body. These warning signs require prompt medical assessment to rule out serious conditions.