Abnormal Muscle Tone in the Arm

CLINICAL DIAGNOSTIC MANUAL

Abnormal muscle tone in the arm refers to any alteration in the degree of tension or resistance that muscles provide to passive movement. Muscle tone can be increased (hypertonia) or decreased (hypotonia), and these alterations can significantly affect arm function and mobility. The causes of abnormal muscle tone are varied and may include neurological, muscular, or central nervous system disorders. Identifying the underlying cause is essential to provide appropriate treatment and improve the patient’s quality of life.

Condition	Clinical Symptoms and Signs	Suspected Diagnosis	Confirmatory Diagnosis
Cerebellar lesion	Hypotonia, intention tremor, ataxia, dysmetria, dysarthria, nystagmus	Clinical history, neurological exam	Brain MRI, cerebellar coordination tests
Primary muscle disease	Hypotonia, proximal muscle weakness, difficulty climbing stairs or lifting objects, possible muscle pain	Clinical history, physical exam, signs of myopathy	Elevated CPK, muscle biopsy, genetic studies
Upper motor neuron lesion	Spastic hypertonia, weakness, exaggerated reflexes, Babinski sign	Clinical history, neurological exam	Brain and spinal MRI, nerve conduction studies
Parkinson’s disease	Rigidity, bradykinesia, resting tremor, postural instability	Clinical history, neurological exam	Neurological evaluation, response to levodopa therapy