Arm and Shoulder Weakness

CLINICAL DIAGNOSTIC MANUAL

Arm and shoulder weakness can result from various pathologies affecting muscles, peripheral nerves, or motor neurons. This weakness can be acute or progressive and may be unilateral or bilateral.

Loss of strength in the arm and shoulder can significantly interfere with daily activities and the patient’s quality of life. Identifying the underlying cause is crucial for appropriate management and treatment of the weakness, achieved through detailed clinical evaluation and specific complementary tests.

Condition	Clinical Symptoms and Signs	Suspected Diagnosis	Confirmatory Diagnosis
Progressive muscular atrophy	Weakness and muscle atrophy worsening over time, muscle mass loss, fasciculations, cramps	Clinical history, physical exam, progressive weakness	EMG, nerve conduction studies, muscle biopsy
Motor neuron disease	Progressive weakness, muscle atrophy, fasciculations, hyperactive reflexes, spasticity, dysarthria	Clinical history, neurological exam	EMG, brain and spinal MRI, nerve conduction studies
Primary muscle disease	Proximal muscle weakness, myopathy, difficulty climbing stairs or lifting objects, possible muscle pain	Clinical history, physical exam, signs of myopathy	Elevated CPK, muscle biopsy, genetic studies
Brachial plexus injury	Weakness and atrophy of shoulder and arm muscles, loss of reflexes, paraesthesias, pain	Clinical history, neurological exam	EMG, brachial plexus MRI, nerve conduction studies
Cervical radiculopathy	Neck pain radiating to the arm, muscle weakness and atrophy, loss of reflexes, paraesthesias	Clinical history, neurological exam	Cervical MRI, nerve conduction studies
Amyotrophic lateral sclerosis (ALS)	Progressive weakness and atrophy, fasciculations, spasticity, dysarthria, dysphagia	Clinical history, neurological exam	EMG, brain and spinal MRI, nerve conduction studies
Myasthenia gravis	Fluctuating muscle weakness, ptosis, diplopia, fatigue worsening with repetitive use, improving with rest	Clinical history, edrophonium test, signs of muscle fatigue	Antibody tests (AChR, MuSK), EMG, repetitive stimulation test