Symptoms and Clinical Manifestations of Brachial Plexus Injuries
The brachial plexus is a critical network of nerves responsible for transmitting signals from the spinal cord to the shoulders, arms, and hands. When damage occurs to this complex system—commonly referred to as brachial plexus injury—the consequences can significantly impact motor function, sensation, and overall upper limb mobility. These injuries are among the most frequent types of peripheral nerve trauma, often resulting from high-impact accidents, birth complications, or surgical complications. Understanding the distinct patterns of symptoms based on the affected nerve roots is essential for accurate diagnosis and effective treatment planning.
Upper Brachial Plexus Injury: Key Signs and Functional Impairments
Injuries affecting the upper portion of the brachial plexus—typically involving the C5 and C6 nerve roots—lead to specific neurological deficits. This type of injury commonly results in paralysis or weakness of several key nerves, including the axillary, musculocutaneous, suprascapular, and dorsal scapular nerves, along with partial involvement of the median nerve.
Motor Function Limitations
Patients with upper brachial plexus damage experience significant challenges in shoulder and elbow movement. The inability to abduct or elevate the arm is one of the hallmark signs due to deltoid and supraspinatus muscle dysfunction. Additionally, flexion at the elbow becomes severely impaired because of biceps and brachialis muscle weakness, which are innervated by the musculocutaneous nerve. Although wrist flexion and extension may still be possible, these movements are typically weakened. Forearm rotation—both supination and pronation—is also compromised, further limiting daily activities.
Sensory and Neurological Deficits
Sensation across the lateral and anterior aspects of the upper arm and forearm is often diminished or completely lost. This sensory loss primarily affects the areas supplied by the affected nerves, leading to numbness or reduced sensitivity on the extensor surface of the arm. While finger movements generally remain intact since the lower nerve roots (C8–T1) are spared, patients may still report subtle coordination issues due to disrupted proprioception.
In severe cases, partial or complete paralysis of the upper extremity may occur, particularly in the shoulder and proximal arm regions. However, reflexive or passive joint movements usually remain unaffected, distinguishing neurologic impairment from musculoskeletal injury.
Lower Brachial Plexus Injury: Impact on Hand Function and Sensation
When the lower brachial plexus—specifically the C8 and T1 nerve roots—is damaged, the clinical picture shifts dramatically. This type of injury predominantly affects hand function and fine motor control, often resulting in what is known as Klumpke's paralysis.
Hand and Finger Dysfunction
The most noticeable consequence is the loss of intrinsic hand muscle function. The ulnar nerve, along with portions of the median and radial nerves, may become partially or fully paralyzed, leading to profound weakness or complete inability to flex or extend the fingers. As a result, grip strength deteriorates, and fine motor tasks such as writing, buttoning clothes, or handling small objects become extremely difficult or impossible.
Over time, disuse leads to visible atrophy of the small muscles within the hand, giving the hand a characteristic "claw-like" appearance. This muscular wasting is a clear indicator of chronic nerve damage and underscores the importance of early intervention.
Sensory Loss and Skin Involvement
Sensation along the medial aspect of the forearm and hand—particularly the little and ring fingers—is typically absent or severely reduced. This numbness corresponds to the dermatomal distribution of the ulnar nerve and adjacent cutaneous nerves such as the medial brachial and medial antebrachial cutaneous nerves. Patients often describe a persistent tingling, burning, or complete lack of feeling in these regions, increasing the risk of unnoticed injuries or infections.
Notably, shoulder, elbow, and wrist joints often retain relatively normal range of motion, which helps differentiate lower brachial plexus injuries from more extensive upper limb neuropathies.
Total Brachial Plexus Avulsion: A Severe Neurological Emergency
In the most extreme cases, complete brachial plexus injury—often caused by traumatic avulsion or severe stretching—results in total paralysis of the entire arm. This condition involves all nerve roots from C5 to T1 and presents with a flaccid, lifeless upper limb.
Complete Motor Paralysis
All voluntary movements in the shoulder, arm, and hand are lost. The patient cannot initiate any active motion at the major joints, including abduction, flexion, or rotation. Despite this, passive joint manipulation remains pain-free and mechanically intact, confirming that the limitation is neurological rather than structural.
An interesting exception is the preservation of shoulder shrugging, which may still be possible due to the accessory nerve (cranial nerve XI) controlling the trapezius muscle. This residual movement can be diagnostically valuable in assessing the extent of nerve damage.
Widespread Sensory Loss
Sensation over nearly the entire upper limb is abolished. The only area that may retain some feeling is the medial upper arm, thanks to the intercostobrachial nerve—a sensory branch originating from the second intercostal nerve—which lies outside the brachial plexus network. Elsewhere, patients report complete anesthesia, making them vulnerable to burns, cuts, and pressure sores without awareness.
Early diagnosis through electromyography (EMG), nerve conduction studies, and advanced imaging like MRI is crucial. Timely surgical reconstruction or nerve grafting may offer the best chance for functional recovery, especially when performed within the first six months post-injury.
In conclusion, brachial plexus injuries present in varying forms—upper, lower, or total—each with distinct symptom profiles. Recognizing these patterns enables healthcare providers to tailor interventions effectively, improving long-term outcomes for patients suffering from these debilitating conditions.