Want to increase the sensitivity of your tendon reflex testing?
Try the Jendrassik maneuver (JM)
If you test your patients patellar reflex and their is a decreased or absent reflex, this may mean that there is compression/damage on the L3 or L4 (most likely) spinal level… or maybe your patient is overly conscious of the movement which could influence the test!
If you suspect this, the JM can help prevent you getting a false positive when testing key muscles. Heres how it is performed:
The patient interlocks his/her fingers in preparation.The patient is then instructed to clench their teeth (optional) and pull hands apart with strong force while keeping them locked. The patellar tendon must then be tapped immediately after to elicit the reflex. A response or a larger response may be observed, indicating some conscious/supraspinal inhibition.
How does it work?
The JM will heighten (exaggerate) lower limb tendon reflexes by countering some of the normal descending inhibition the brain sends to the reflex arc. It can also help prevent conscious inhibition of the reflex.
When you decrease inhibition, you increase excitability. Stroke patients have Upper Motor Neuron Lesions, and so in some cases this decreases (or removes) descending inhibition from the brain. This is why tendon reflexes in stroke and other UMNL patients have increased reflexes.