What is drift in the upper extremity?

Upper Extremity Drift: Definition and Clinical Significance

Upper extremity drift refers to the involuntary downward movement of an outstretched arm, often accompanied by pronation, which serves as a clinical sign of subtle upper motor neuron weakness or other neurological disorders. 1, 2

Types of Upper Extremity Drift

• Pronator drift: The most common form, characterized by downward movement of the outstretched arm accompanied by pronation (palm rotation downward), indicating upper motor neuron weakness on the affected side 2

• Drift without pronation: A specific pattern where the arm drifts downward without pronation, highly specific for conversion disorder (functional neurological disorder) with a sensitivity of 100% and specificity of 93% 2

• Midline hand drift: A less common pattern where the outstretched hand(s) drift toward the midline of the body, potentially indicating neurocognitive disorders including Parkinson disease dementia, Lewy body dementia, or vascular dementia 3

Clinical Testing Technique

To properly assess for upper extremity drift:

• Position the patient seated or standing 2
• Ask them to extend both arms forward with palms facing upward (supinated) 2
• Instruct them to close their eyes and maintain this position for 10-30 seconds 2
• Observe for any downward movement and/or pronation of either arm 2

Clinical Significance and Interpretation

Pronator Drift (with pronation)

• Indicates subtle upper motor neuron weakness, often due to stroke or other central nervous system lesions 1
• May be present before other obvious signs of weakness are detectable 4
• Often accompanied by other upper motor neuron signs such as hyperreflexia or Hoffmann's sign 4

Drift Without Pronation

• Highly specific for conversion disorder (functional neurological symptom disorder) 2
• Can help differentiate between organic and functional neurological disorders at the bedside 2

Midline Hand Drift

• Associated with neurocognitive disorders, even in early stages 3
• May be present in patients with mild cognitive impairment before frontal release signs appear 3
• Most commonly seen in Parkinson disease dementia, Lewy body dementia, and vascular dementia 3

Clinical Applications in Stroke Rehabilitation

Upper extremity drift assessment is particularly valuable in stroke evaluation and rehabilitation:

• Serves as an early indicator of motor recovery potential 5
• Helps guide rehabilitation strategies for upper extremity function 5
• Can be used to monitor progress during task-specific training and other rehabilitation interventions 5

Related Rehabilitation Approaches

For patients with upper extremity weakness manifesting as drift:

• Task-specific practice is strongly recommended to improve motor function and activities of daily living 5
• Constraint-induced movement therapy may be beneficial for those with some preserved wrist and finger extension 5
• Robotic therapy can be considered for those with moderate to severe upper limb paresis 5
• Neuromuscular electrical stimulation may improve motor outcomes in patients with minimal volitional movement 5

Pitfalls and Caveats

• Fatigue can cause drift in healthy individuals, so brief testing periods (10-30 seconds) are recommended 2
• Bilateral drift may indicate bilateral weakness or a non-neurological cause such as fatigue 1
• Always interpret drift in the context of other neurological findings 3
• Similar testing can be performed for lower extremities (rotator drift) to assess for subtle leg weakness 4