Brachial Plexus Injury: Symptoms, Causes, and Diagnosis Explained
Brachial plexus injury is a condition that affects the network of nerves responsible for sending signals from the spine to the shoulder, arm, and hand. These injuries often result from trauma, such as car accidents, sports injuries, or childbirth complications. Other causes include compression from tumors, inflammation, or scar tissue formation due to previous surgeries or infections. When these vital nerves are damaged, it can lead to a range of physical impairments, making early diagnosis and treatment essential.
Understanding the Brachial Plexus Anatomy
The brachial plexus is formed by spinal nerves originating from C5 to T1—specifically, the fifth cervical nerve (C5) through the first thoracic nerve (T1). Each of these nerve roots plays a distinct role in motor control and sensory function throughout the upper limb:
Nerve Functions Breakdown
C5 Nerve: Primarily innervates the muscles that control shoulder abduction and elbow flexion. It also provides sensation to the lateral (outer) side of the upper arm. Damage here may cause weakness in lifting the arm sideways.
C6 Nerve: Governs wrist extension and biceps function, with sensory input to the thumb and outer forearm. A patient with C6 impairment might struggle to lift their thumb or rotate the forearm outward.
C7 Nerve: This nerve is crucial for elbow extension, wrist flexion, and movement of the middle finger. Weakness in gripping or extending the arm could indicate C7 involvement.
C8 Nerve: Controls fine motor skills in the hand, particularly those involving the ring and little fingers, as well as sensation along the inner forearm. Issues like difficulty holding small objects may point to C8 damage.
T1 Nerve: Responsible for handgrip strength and sensation on the medial (inner) lower arm. Injury to this nerve can lead to diminished dexterity and a feeling of heaviness in the hand.
Common Symptoms of Brachial Plexus Damage
Symptoms vary depending on which part of the nerve network is affected. Typical signs include numbness, tingling, burning sensations, or complete loss of feeling in parts of the arm or hand. Motor deficits such as muscle weakness, inability to move the shoulder, elbow, or fingers, and even paralysis in severe cases are common. For example, if someone cannot lift their thumb, it often indicates an issue with the C6 nerve root. Similarly, difficulty extending the middle finger may signal C7 dysfunction.
How Is Brachial Plexus Injury Diagnosed?
A definitive diagnosis usually begins with a thorough medical history and physical examination, focusing on trauma or repetitive strain. The gold standard for confirming nerve damage is electromyography (EMG), often combined with nerve conduction studies (NCS). These tests measure electrical activity in muscles and the speed of nerve signals, helping pinpoint the location and severity of the injury.
In some cases, imaging techniques like MRI or CT myelography are used to visualize structural abnormalities such as herniated discs, tumors, or scar tissue compressing the nerves. If initial treatments fail or the injury mechanism suggests significant internal damage, surgical exploration—known as nerve exploration—may be recommended to assess and potentially repair the affected nerves.
Why Early Intervention Matters
Timely evaluation by a neurologist or orthopedic specialist is critical. Delayed treatment can lead to permanent muscle atrophy, joint stiffness, and irreversible loss of function. With proper care, including physical therapy, medication, or surgery when necessary, many patients experience meaningful recovery and improved quality of life.
If you're experiencing unexplained arm weakness, persistent numbness, or reduced mobility after an injury, don't ignore these warning signs. Seek professional medical advice promptly to determine the underlying cause and begin an effective treatment plan.