Drift without pronation sign
Introduction and Test Justification
The purpose of the Drift without pronation sign is to differentiate between conversion disorder and organic weakness in patients presenting with upper limb signs. The sign is considered particularly reliable in milder cases of paresis, as it highlights a dysfunction in supination that arises even in mild pyramidal tract lesions.[1]
Interpretation may be challenging in cases of severe paresis. In cases of rapid drift due to severe paresis, the downward fall of the limb occurs too rapidly for the examiner to clearly identify whether a pronation movement has taken place.[2] To navigate this difficulty, clinicians may instead observe the final resting position of the hand for example, whether it lands on the patient's knee in a pronated or supinated position to determine the presence or absence of pronation.[2]
Technique
Step 1: Seat the patient comfortably in front of the examiner with both arms stretched out forward.
Step 2: Place the arms in a full supination position with palms facing upward and fingers adducted.
Step 3: Instruct the patient to close their eyes and maintain the outstretched position for as long as possible, with a minimum duration of 10 seconds.
Step 4: Carefully observe the arms for any downward drift and closely monitor for any pronation movement during the drift.
Step 5: In cases of rapid drift due to severe paresis, observe the final resting position of the hand on the patient's knee, noting whether it is in a pronated or supinated position.
Interpretation
A positive sign is recorded when the arm drifts downward with no pronation and the final hand position remains in supination.
A negative sign is recorded when the arm drifts downward with pronation present and the final hand position is in pronation.[2][3]
Evidence
Validation Study: Drift without pronation was validated in a study examining 26 patients with upper extremity functional limb weakness and 28 controls with organic neurological weakness. In this unblinded study, all patients with functional limb weakness exhibited drift without pronation, resulting in strong diagnostic accuracy[6]:
Sensitivity: 100%
Specificity: 93%
Diagnostic Significance: The sign is considered positive when a downward drift occurs in the absence of pronation in the affected upper extremity. The high sensitivity and specificity values confirm it as a reliable clinical tool for differentiating functional limb weakness from organic neurological weakness.[6]
Summary
The Drift without pronation sign is a clinical test used to differentiate between conversion disorder and organic weakness in the upper limb, particularly in mild paresis. Patients extend their arms in full supination for ten seconds while the examiner watches for downward drift and pronation. A positive result indicates drift without pronation; a negative result shows pronation. Validated studies report 100% sensitivity and 93% specificity, confirming its effectiveness in distinguishing functional from organic limb weakness.
References
- ↑ Tremolizzo L, Susani E, Riva MA, Cesana G, Ferrarese C, Appollonio I. Positive signs of functional weakness. Journal of the neurological sciences. 2014 May 15;340(1-2):13-8.
- ↑ 2.0 2.1 2.2 Daum C, Aybek S. Validity of the “Drift without pronation” sign in conversion disorder. BMC neurology. 2013 Apr 1;13(1):31.
- ↑ Lalitha LP, Acharya PT, Javali M, Mehta A, Rangaiah P. Functional Neurological Disorders: A Comprehensive Review. The Journal of the Association of Physicians of India. 2025 Jul;73(7):e17-23.
- ↑ Youtu.be. Available at: https://youtu.be/o8zkr3tmszQ?si=Od7UWSL_sSRlumYw (Accessed: May 14, 2026).
- ↑ Youtu.be. Available at: https://youtu.be/2MkNKTXp7L8?si=PqtBhaCiBkEfXYV6 (Accessed: May 14, 2026).
- ↑ 6.0 6.1 Dolbow J, El-Azzouni S, Zhang Y, Geiger C. A practical guide to assessing functional motor weakness: a review of validated techniques. Journal of Neurology. 2025 Jun;272(6):427.