Tendon Jerk Trouble?


Q:"Is it possible to do tendon jerks? I've watched videos yet I'm not able to do them on patients. What do I do?"


A: The most common reason for poor demonstration of DTRs clinically is improper technique. 

One of the most important step is to completely expose the muscle who’s reflex is being tested.
For example, for a knee jerk – it is the contraction of the quadriceps muscle that should be looked for rather than the more optimistic jerking of the knee which will not be seen in most normal people or persons with diminished reflex, hence exposing the patients thigh is a key feature. 

YouTube videos often show demonstrations of exaggerated reflexes in patients suffering  from UMN lesions and hence one should not expect to reproduce the same level of findings in a normal patient.

Another common cause of failure with demonstration is that the patient is not relaxed or is concentrating on the procedure being performed. After a general explanation, mingle the specific instructions with questions or comments designed to get the patient to speak at some length about some other topic.

 If you cannot get any response with a specific reflex—ankle jerks are usually the most difficult—then try the following:

In the upper extremity, have the patient make a fist with one hand while the opposite extremity is being tested.

If the reflex being tested is the knee jerk or ankle jerk, have the patient perform the "Jendrassik maneuver," a reinforcement of the reflex. The patient's fingers of each hand are hooked together so each arm can forcefully pull against the other. The split second before you are ready to tap the tendon, say "pull."

In general, any way to distract the patient from what you are doing will enhance the chances of obtaining the reflex. Having the patient count or give the names of children are examples.

Lastly the hammer tap is extremely important to be performed properly. Use a brisk but not painful tap. Use your wrist, not your arm, for the action. In an extremity a useful maneuver is to elicit the reflex from several different positions, rapidly shifting the limb and performing the test. Use varying force and note any variance in response.

And lastly, practice on your friends till you get it right before heading to the wards! Practice is everything.


Ps: Here's one video you can watch if you haven't:


Answer by Pranav Hinduja.

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