Jendrassik Manoeuvre

Original Editor - Misha Ahir
Top Contributors - Misha Ahir, Vidya Acharya and Ewa Jaraczewska

Purpose

The Jendrassik Maneuver is a clinical technique used to reinforce or enhance tendon reflexes. It was first described by Hungarian physician Ernő Jendrassik in 1885. The purpose of the manoeuvre is to facilitate the elicitation of deep tendon reflexes, minimise voluntary suppression of reflexes by distracting the patient, and differentiate between true neurological deficits and voluntary inhibition of reflexes. This technique is especially useful in anxious patients, particularly the patellar (knee-jerk) reflex. It is commonly used in neurological examinations when reflexes are difficult to elicit or appear diminished.

Technique

The patient is usually seated with legs dangling freely over the edge of the examination table. The patient is instructed to interlock the fingers of both hands in front of them. The patient then pulls the hands apart vigorously by attempting to pull them away from each other without letting go. While the patient is focused on the hand movement, the examiner taps the tendon (e.g., patellar tendon) with a reflex hammer.

This manoeuvre diverts attention and increases central facilitation of the reflex arc, often making the reflex response more pronounced. A study has standardised the manoeuvre with teeth clenching, and teeth clenching alone is optimal to enhance the Achilles tendon reflex.

Jendrassik manoeuvre relates to Grade 1+ reflex in the standard grading system on a five-level scale and it equals diminished or present only with reinforcement.

Evidence

While the exact mechanism is debated, several theories exist with evidence. Scientific studies and clinical observations support the use of the Jendrassik Manoeuvre as an effective method to enhance deep tendon reflexes:

• Neurophysiological Basis: The manoeuvre increases gamma efferent activity to muscle spindles and reduces presynaptic inhibition of the reflex arc, thereby increasing motor neuron excitability.
• Studies using electromyography (EMG) have shown that the amplitude and latency of reflex responses are significantly altered by performing the manoeuvre.

Conclusion

Jendrassik manoeuvre facilitates the monosynaptic reflexes. The effects of the manoeuvre last 1 sec–6 sec and are maximal for only 300 msec. The Jendrassik manoeuvre is clinically significant because it transforms a potentially unreliable clinical sign into a more accurate diagnostic tool, helping clinicians distinguish between normal variation, anxiety-related suppression, and true neurological pathology. This has direct implications for patient care, reducing both false positives and false negatives in neurological assessment. Research also supports that it can make absent ankle reflexes appear 70% of the time in elderly patients.