Brachial Plexus Injury: Symptoms, Nerve Involvement, and Functional Impacts

The brachial plexus is a critical network of nerves responsible for motor control and sensory function in the upper limb. It gives rise to three major peripheral nerves: the median nerve, radial nerve, and ulnar nerve. When a severe trauma leads to complete disruption of the brachial plexus, the consequences are profound—resulting in total paralysis of the affected arm along with a complete loss of sensation. This type of injury often stems from high-impact accidents such as motorcycle crashes, childbirth complications, or penetrating injuries.

Understanding the Role of Key Nerves in Brachial Plexus Function

Each of the three primary nerves originating from the brachial plexus governs distinct regions of the arm and hand. Damage to any one of these nerves produces specific clinical manifestations that help clinicians diagnose the extent and location of the injury. Understanding these patterns is essential for timely intervention and effective rehabilitation planning.

Median Nerve Involvement: Loss of Hand Grip and Palm Sensation

When the brachial plexus injury affects the median nerve, patients typically experience numbness in the palm, particularly in the thumb, index, middle, and part of the ring finger. One of the most noticeable functional deficits is the inability to form a strong grip or make a full fist. This occurs because the median nerve controls key muscles involved in flexion of the fingers and opposition of the thumb. Without proper signaling, fine motor skills deteriorate significantly, impacting daily activities like holding utensils or turning keys.

Radial Nerve Damage: Wrist and Finger Extension Challenges

Injury extending into the radial nerve pathway results in characteristic symptoms such as numbness on the back of the hand and an inability to straighten the fingers or extend the wrist—commonly referred to as "wrist drop." The thumb may also lose its ability to abduct or lift upward. These impairments stem from the radial nerve's role in innervating the extensor muscles of the forearm. Individuals with this type of damage often struggle with tasks requiring pushing motions or lifting objects with an open hand.

Ulnar Nerve Dysfunction: Claw Hand and Impaired Finger Mobility

Damage affecting the ulnar nerve typically leads to numbness in the little finger and the outer half of the ring finger. Over time, muscle atrophy in the hand can cause a distinctive deformity known as "claw hand," where the fourth and fifth fingers curl inward due to unopposed muscle pull. Additionally, coordination between fingers diminishes, making actions like typing, playing instruments, or buttoning shirts extremely difficult. This condition highlights the ulnar nerve's crucial role in fine motor control and intrinsic hand muscle function.

Diagnosis and Clinical Importance of Early Detection

Accurate diagnosis of brachial plexus injuries involves a combination of physical examination, electromyography (EMG), nerve conduction studies, and advanced imaging such as MRI or CT myelography. Identifying which nerve pathways are compromised allows healthcare providers to tailor treatment strategies, including physical therapy, surgical repair, or nerve grafting procedures.

Early intervention significantly improves long-term outcomes. Delayed treatment can lead to permanent muscle atrophy, joint contractures, and irreversible loss of function. Therefore, anyone experiencing sudden weakness, numbness, or loss of movement in the arm following trauma should seek immediate medical evaluation.

In summary, brachial plexus injuries present with a spectrum of neurological deficits depending on the severity and location of nerve damage. Recognizing the distinct patterns associated with median, radial, and ulnar nerve involvement enables more precise diagnosis and targeted therapeutic approaches, ultimately enhancing recovery prospects for affected individuals.