What is jendrassik's manoeuvre ?

lt is also known as -reinforcement’.

When the deep reflexes or jerks are not elicited by routine manoeuvre, reinforcement is applied for better response.

Ask the patient to do the following

• To make a fist with the ipsilateral hand,
• To hook the fingers of two hands together and then pull them as hard as possible,
• To clench the teeth,
• To push the knees hard together.

It is very important to remember that this phenomenon lasts for less than a second. Hence the

patient is asked to do the manoeuvre almost synchronously with the tapping of the tendon (the

procedure must be demonstrated to the patient before tapping the tendon).

Reinforcement (to make some strong voluntary muscular effort) acts by the following .

• Increasing the excitability of the anterior horn cells,
• Increasing the recruitment of gamma-fibres, i.e. increasing the sensitivity of the muscle spindle primary sensory endings to stretch (increased gamma fusimotor drive).

Always perform the Jendrassik's manoeuvre before declaring a tendon reflex absent .