Ref2242ed to as they acute brachial neuropathy and neuralgic amyotrophy.
It is a syndrome of unknown cause.
Risk factors include; post-operative status, post-infectious, post-traumatic or post-vaccination.
It manifests most likely from an autoimmune inflammation of unknown cause of the brachial plexus.
Occurs in about 1.6 people per 100,000 per year.
Patients experience severe shoulder or arm pain followed by weakness and numbness.
Associated with winged scapula.
The pain is of sudden onset and radiates from the shoulder to the upper arm.
Affected muscles become weak and atrophied, and in advanced cases, paralyzed.
Occasionally, there will be no pain, but atrophy and weakness.
Sometimes patients experience pain, not ending in paralysis.
MRI may assist in diagnosis.
It involves neuropathy of the suprascapular nerve in 97% of cases, and variably involves the axillary and subscapular nerves.
The muscles usually involved are the supraspinatus and infraspinatus, which are both innervated by the suprascapular nerve.
Involvement of the deltoid is more variable, as it is innervated by the axillary nerve.
Despite its wasting and at times long-lasting effects, in most cases recovery is usually good in 18–24 months, depending on how old the patient is.