Advanced Assessment of Reflexes

by Stephen Holt, MD, MS

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    00:00 Alright so guys we've finished our assessment of strength and again weakness could be found in upper motor neuron and lower motor neuron issue so it's not particularly helpful in that regard other than characterizing the severity of somebody's weakness. The real deciding factor is going to be the result of reflex testing. So, as a route to jump into reflex testing, it's good to orient ourselves to our tools and so let's take a look here. This is probably the most common reflex hammer that I see used by many medical students and health practitioner students of various types. This is known as a Taylor hammer and it's lightweight, it's small, it's easy to carry around, and to be frank I hate it. It's my least favorite kind of hammer. It doesn't have enough weight to it to really get good reflexes.

    00:45 That being said in a pinch, like I said, it's really easy to carry around, it's nice to have with you. In contrast, this is a Tromner hammer, it's got a lot more weight to it, a lot more give when you're really applying it to the tendons and most importantly it's not as hard on the tip so you can really bang on your fingers without, you know, ultimately causing yourself discomfort. So I find the Tromner hammer to be very useful to have around.

    01:09 Sometimes they also come with the ability to test pinprick or the ability to test light touch as well on the back of the hammer. Okay, so with that, let's jump into reflex testing.

    01:26 So just as we wanted to know which muscle groups were associated with which nerve roots, we also want to know which nerve roots are associated with which reflexes.

    01:35 So, the first reflex we're going to look at is C5. Just like C5 controlled biceps strength, it also controls the deep tendon reflex of the biceps tendon and so I'm going to put my finger on the tendon here and I can feel that very palpable cord of the biceps tendon and then I'm going to apply a swing as follows. When we think about the strength of the reflex, there's a range that we have from 0-4. The normal range is typically 2 and 3. So 2 being the lower end of normal and 3 being the upper end of normal. That being said, a 1 out of 4 reflex is also quite normal particularly if it's the same on the other side. In contrast, a 4 out of 4 reflex is hyperreflexia whether or not it's associated with clonus and then a 0 out of 4 reflex is essentially a mute reflex. Now as you might imagine, a patient who has a lower motor neuron problem and is not getting any input to that muscle, you're going to have a 0 out of 4 reflex or certainly an attenuated one. In contrast, if it's an upper motor neuron problem with the lower motor neuron firing with reckless abandon without any inhibition, you're going to have hyperreflexia and more leaning towards the 3 or 4 out of 4 on the spectrum. So again, this is the biceps tendon reflex and I'm applying a good swing to my hammer. It's really to make sure I'm getting the full weight of my reflex hammer at C5. Now I moved down to the brachioradialis muscle. I'm going to palpate on the belly of the brachioradialis muscle here which is going to insert on to the radial styloid. And there's just a subtle bit of pronation that you could see as his wrist curved inward. You can tilt the hand, the wrist out a little bit more and then you might see a little bit more of that pronation happening. That was C6. Next, we'll do C7, which is the triceps reflex and there's a lot of different ways to do this depending upon what position the patient might be in. I find it's really easy to just actually hold the forearm and hit the triceps muscle in this way. By doing that, I'm getting contraction of the base of his triceps which I can actually even feel in my forearm here. Other times I see people try and "relax your arm" come around the patient which is certainly a reasonable thing to do. It depends how uncomfortable it is for the patient and whether it's convenient for you but you can also do it like this and I'll get the same result which you can see as his hand moves out towards the side. So that was C5, C6, C7, very straightforward. And now moving on to the lower extremities. There are 2 reflexes we're going to look for down there. Since this was L2 for strength, this is L3 which is going to be a significant portion of the knee jerk deep tendon reflex or quadriceps reflex. I usually palpate where the tibial tuberosity is and I know that I'm going to go right above the tibial tuberosity as such. Great. So that, I would say is a 3 out of 4 reflex on the right and comparing with the left. Those are about the same depending about the strength of my hammer. So, as you can see he may have had a 1 to 2 out of 4 reflex up in his biceps, but as long as that's symmetric up there and even if it's a little bit higher downstream that's okay. It's really when you're looking for asymmetry that would be more concerning. So the next deep tendon reflex in the lower extremity is the ankle reflex and this is going to be L5-S1, which is involved in the plantarflexion of the foot. I'm going to basically put his ankle at approximately 90 degrees of dorsiflexion. I'm going to hit a few centimeters above the calcaneus. And you can see a nice downward plantarflexion there in his right foot. In some instances, it can be difficult to wrap around to tap on the Achilles tendon particularly in a bedbound patient so we can actually do this maneuver simply by putting your hand underneath the patient's foot and hitting on your feet as shown here. I'm getting just as much of a response with this approach as I would by trying to find and hit the tendon. So, sometimes you may come across a patient who appears to have no evidence of reflexes particularly in the lower extremities and we said those are mute reflexes. If you really want to bring out those reflexes because particularly in elderly patients they can be very subtle. There is a trick called the Jendrassik maneuver which helps to accentuate those lower extremity reflexes.

    06:23 This is an effort to trying to distract the descending input from the cortex from inhibiting the action of this spinal reflex. "So what I'm going to have you do Sean is I just want you to put your fingers together like this. And then I'm going to again check your knee reflex" while he is pulling his hands apart. "And I don't want you to pull your hands apart until we're ready to go." "So now, go ahead and pull your hands apart." And he already had a robust reflex but simply doing that Jendrassik maneuver "and you can relax." Further exaggerates that maneuver whether you're looking at the knee jerk reflexes or the ankle jerk reflexes. That can be a useful way to augment those reflexes. I've seen even some neurologist will not only have the patient do this Jendrassik maneuver but also have their head turn from side to side while they're doing it. And if that doesn't bring out the reflex in the lower extremities, then nothing will. The last test looking for upper motor neuron dysfunction is to perform the plantar reflex also known as the extensor reflex also known as the Babinski and all we're going to do is apply some in a hockey stick maneuver and simply go in that kind of slow approach. It should take a few seconds to fully navigate around the sole of the foot and you're looking for, in abnormal circumstance he would have his feet, his toes would flare upwards like this. Whereas as you saw in his case, all he did was his toes sort of plantarflexed a bit, which is completely normal.

    About the Lecture

    The lecture Advanced Assessment of Reflexes by Stephen Holt, MD, MS is from the course Assessment of the Neuromuscular and Neurological System (Nursing).

    Included Quiz Questions

    1. 3
    2. 2
    3. 1
    4. 4
    1. C6
    2. C5
    3. C7
    4. C8
    1. When there is no evidence of reflexes in the lower extremities
    2. When there is hyperreflexia in the lower extremities
    3. When there are high normal reflexes in the lower extremities
    4. When there are low normal reflexes in the lower extremities

    Author of lecture Advanced Assessment of Reflexes

     Stephen Holt, MD, MS

    Stephen Holt, MD, MS

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