Diagnosing a brachial plexus birth injury begins with examining a newborn's arm movements, reflexes, and muscle function. Repeated examinations help determine whether the nerves are recovering. Imaging and electrical nerve tests may be useful when the injury is severe or surgery is being considered.
Why early diagnosis matters
A newborn with brachial plexus damage may have difficulty moving one arm.
Some babies show obvious weakness immediately after delivery.
Others have more subtle movement differences.
The initial examination helps identify the affected muscles and possible nerve roots.
Early diagnosis also helps distinguish neurological weakness from pain caused by a fracture.
This distinction matters because the conditions require different follow-up.
An uncomplicated fracture may heal within several weeks.
A significant nerve injury may require months of monitoring and specialized treatment.
Evaluating shoulder and elbow movement
Doctors observe how the baby moves each arm.
They compare shoulder lifting, elbow bending, and arm rotation.
Weakness in these movements may suggest an upper brachial plexus injury.
In classic Erb's palsy, the baby may struggle to lift the shoulder or bend the elbow.
Hand movement may remain relatively normal.
The examination helps determine whether the injury is limited or more extensive.
Assessing wrist and hand function
Wrist and finger movements provide additional information.
Weakness in the hand may suggest lower-root involvement.
A baby with global brachial plexus palsy may have little movement throughout the arm.
Doctors assess grasp, finger motion, and overall muscle activity.
They also look for unusual resting positions.
The pattern of weakness can help identify the likely nerve distribution.
Understanding the Moro reflex
The Moro reflex is a normal newborn response to sudden changes in position or sensation.
A healthy response generally involves both arms moving outward and then inward.
A baby with a brachial plexus injury may show reduced movement on one side.
This is called an asymmetric Moro reflex.
However, a clavicle fracture can produce a similar response because movement causes pain.
The reflex therefore provides useful information but cannot establish the diagnosis by itself.
When imaging may be recommended
Not every newborn with arm weakness requires immediate advanced imaging.
The decision depends on the examination and suspected injury.
An X-ray may help identify a clavicle or upper-arm fracture.
Magnetic resonance imaging may be considered when clinicians suspect severe nerve-root damage.
Imaging can provide information about the nerve structures and surrounding tissues.
However, imaging findings must be interpreted alongside the child's symptoms and physical examination.
Electromyography and nerve conduction studies
Electromyography, often called EMG, evaluates electrical activity in muscles.
Nerve conduction studies assess how electrical signals travel through nerves.
These tests may help specialists evaluate nerve function and recovery.
Their usefulness depends on the child's age, the timing of testing, and the clinical question.
They are not necessary for every infant.
Specialists decide whether the results would change treatment planning.
Why repeated examinations are essential
A single examination cannot always predict recovery.
Some newborns show substantial improvement during the first weeks.
Others continue to have weakness despite appropriate care.
Repeated assessments document whether important movements are returning.
Persistent weakness may indicate a need for further specialist evaluation.
Early referral is particularly important when severe injury is suspected.
Common questions around diagnosis
Can doctors diagnose brachial plexus injury without an MRI?
Yes. The initial diagnosis is usually based on clinical examination.
Can a broken collarbone resemble nerve damage?
Yes. Pain from a fracture may reduce arm movement and affect reflexes.
Why does a baby need repeated examinations?
Serial assessments help clinicians evaluate nerve recovery and decide whether additional treatment is needed.
For more information, visit: https://birthinjuryadvocate.com/birth-injuries/brachial-plexus/
