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View Full Version : Doctor's, how important are jerk reflexes during checkups?


diggleblop
12-15-2006, 01:17 PM
I have two herniated discs on L4 and L5. Yesterday I had an evaluation by a Doctor assigned by the Department of Labor assigned to my case.

When he was giving me a motor skills test everything was going decent until it was time to test my reflexes on my knees and ankles.

I had no reflex in either leg or ankle. Well, I wouldn't say 'no reflex', but he just kept saying, "Hmm, how odd, that's supposed to be your good leg and there's still no response." He just kept tapping with his little hammer and my legs didn't budge or make one jerk at all.

I basically had no reflex response in either leg or knee.

1. How important is that in his findings?

2. Does that let him know there is some sort of possible nerve damage?

3. What is the purpose of these reflex tests? Is that what they do, test nerves?

diggleblop
12-15-2006, 01:19 PM
Sorry about the typo. I'm in a hurry.

BlakeTyner
12-15-2006, 03:39 PM
Standard disclaimer, I'm not a doc. Just a guy who took neuropsychology as an undergrad.

As I recall, the foundation of our understanding of how the stream from the brain to the muscles (and vice versa) comes from the "reflex arc." At some point in time, someone working with animals noticed that stimulation to the leg caused a response, but not fast enough to be nearing the speed of electricity. Thus, the propagation of the action potential must come from some other means - chemical.

Okay, that's all well and good.

The doctor's reflex tests can be a pretty good early indicator of a neurological problem (and, my guess is, a regular physiological problem as well.) There are some diseases that cause the breakdown of the fatty myelin sheathes on some axons; the myelin acts as a sort of "supercharger" for the chemical transmission down the axon. Instead of having to travel the full length, activating the sodium-potassium pump all the way, the signal is able to "jump" from the gaps in myelin...nodes of Ranvier as I recall. If the myelin breaks down, the axon isn't able to compensate, and that's pretty bad.

Certain types of astrocytes produce/repair myelin, though I'm sure an astrocytoma could mess that up as well.

Anyway, I'm sure a doc will be along shortly with an educated medical answer, but the reflex arc is pretty important...

KarlGauss
12-15-2006, 05:40 PM
The nerves controlling the knee and ankle reflexes emerge from the spinal cord at L4 and S1 respectively.

So, if say the L4 disc has slipped sideways a bit, it may have pressed on the nerves controlling the knee reflex. Same for discs at S1 and the ankle reflex.

It is very, very common for people to lose these reflexes as they age. They can also be lost if, as may be the case in you, the nerves controlling them have been damaged (e.g. by a slipped disc).

By itself (or themselves), loss of those reflexes is pretty well meaningless. On the other hand, if a person has lost all their reflexes, or has symptoms (weakness or disturbed sensation) in the body area controlled by the same nerve as the one that controls the associated reflex, it may indicate a problem.

Loss of all reflexes could indicate something like diabetic nerve damage or, in fact, any cause of neuropathy. Loss of reflexes at say the ankle, coupled with inability to press down with the foot (plantar flexion) could indicate a more specific problem at S1.

On the other hand, increased reflexes, if focal (e.g. only involving half the body), could indicate things like strokes and multiple sclerosis.

diggleblop
12-15-2006, 06:07 PM
BlakeTyner, thank you, kind sir. Anyone wanna try in layman terms for a regular Joe such as myself. ;)

diggleblop
12-15-2006, 06:09 PM
KarlGauss, thanks so much. Thanks to both of you ! All others are welcome, too

Sapo
12-15-2006, 06:45 PM
I am in perfectly good health and have a good enough reaction time to play videogames and drive at unnecessarily high speeds. Still, I have never had those reflexes. The doctors have always been puzzled but make nothing of it and see no reason to go further on that.

KarlGauss
12-15-2006, 07:16 PM
I am in perfectly good health and have a good enough reaction time to play videogames and drive at unnecessarily high speeds. Still, I have never had those reflexes. The doctors have always been puzzled but make nothing of it and see no reason to go further on that.
I understand. Still, it's important to note that the "reflexes" we're talking about at the knee and ankle are very much unlike the "reflexes" you're referring to. The former are spinal reflexes whereas the quick "reflexes" of a hockey goalie or a crack video game player are something else entirely. In fact, they're not really reflexes in the medical sense of the word. More along the lines of 'quickly integarated and responsive' perception-motor functions.

diggleblop
12-15-2006, 08:04 PM
Exactly, KarlGauss, I mean in conjunction with a back injury, hat would it mean to a Doctor when he examines a patient that has no response to the knee and ankle reflex test.

KarlGauss
12-15-2006, 08:56 PM
I'm not sure if you're last post was a question to me, so my apologies if this one is superfluous.

First of all, let me make explicit that things like the ankle and knee reflexes are called deep tendon reflexes (DTRs).

If a doctor examines someone and finds that they have no ankle and knee reflexes there are a number of possibilities including:

1. All, or most, of the other DTRs throughout the body are absent (e.g. knee, ankle, biceps, tricpeps, quads, brachioradialis . . .). This could be normal or it could mean there is a diffuse neuropathy going on (such as that due to diabetes, or from chemotherapy, or with Gullian-Barre syndrome, . . .)

2. Only the ankle and knee DTRs are absent, the other DTRs are normal, and the patient is asymptomatic and has no other abnormal findings on physical exam and neurological testing. Again, this could be normal (as in a normal older person), or it could mean there has been some localized injury to the nerves governing those specific DTRs (e.g. disc problems in the past). Again, so long as the person is feeling fine with no symptoms, and so long as the rest of the physical and neurologic exams are normal, there's probably nothing else that needs to be done.

3. Only the ankle and knee DTRs are absent, the other DTRs are normal, but the patient does have symptoms and/or detectable abnormalities in the sensation or strength in that part of the body controlled by the same nerve as that for the absent reflex(es). So, in the case of an absent ankle reflex for example, the nerve controlling it is called S1. As it turns out, S1 also provides sensation to the sole of the foot as well providing strength to the foot for the movement of downward pressure (the same motion as "stepping on the gas"). If a person is checked and found to have diminished sensation on the sole of their foot, weakness in pushing the foot down at the ankle, and an absent ankle reflex, it strongly suggests that there's been an injury (or some other process) affecting the S1 nerve. The next step would probably be to actually look at the area where the S1 nerve is close to the disc, i.e. an MRI. This could show what has injured the S1 nerve (disc compression, a tumor, an abcess, etc.)

It's definitely worth your while to look at this picture (http://catalog.nucleusinc.com/imagesenlarged/7672W.jpg). Look at the picture called "L5-S1 Disc from Above". The front of the person is towards the top of the page, and the back of the person towards the bottom. Notice how the degenerating disc has 'leaked' out thereby encroaching on the nerve root just as it says towards the lower right of the picture.

Look also at the pictures in this link (http://hillsnz.tripod.com/). The page is very long and the pictures of relevance start about 1/4 of the way down and continue until about 3/4 of the way through. They do a super job of depicting various disc problems and associated nerve injuries/compressions.

NB. Throughout this post, for the purpose of clarity, I deliberately used the term "nerve" (as in S1 nerve) when we're actually talking about "nerve roots" (as in the S1 nerve root). But everything I said still applies.

Helen's Eidolon
12-15-2006, 10:44 PM
So if this doesn't diagnose any common and dangerous conditions, why is it done so routinely at checkups for kids?

diggleblop
12-15-2006, 11:16 PM
So if this doesn't diagnose any common and dangerous conditions, why is it done so routinely at checkups for kids?


Good question, maybe it's because kids don't complain of back aches as much as adults and it's one way to tell if they have damage.

Mama Zappa
12-17-2006, 07:58 AM
This doesn't quite tie to the OP, but *hyperactive* reflexes can be an indicator of some medical conditions also. When I was pregnant with Moon Unit, my blood pressure started creeping up and I was eventually diagnosed with pre-eclampsia. One screening they did was to check my various reflexes; as the disease progressed, my knees, elbows and ankles became more and more jumpy. I *think* (but am not sure) that this was because of the illness's effect on the central nervous system.

So, Diggleblop, evidently you're not pregnant :D

erm, I assume you're not.... I have the impression you're male, right?

diggleblop
12-18-2006, 10:22 PM
Correct, I am not pregnant. If I am, then it would be revolutionary.

Bryan Ekers
12-18-2006, 10:23 PM
I'd say it's very important to give the doctor something to do where he can claim to understand the significance but the patient cannot, increasing the medical mystique. :D

KarlGauss
12-18-2006, 10:44 PM
I'd say it's very important to give the doctor something to do where he can claim to understand the significance but the patient cannot, increasing the medical mystique. :D
There is actually a fair kernel of truth to this. There have been times when, having little or nothing to offer the patient, I tapped their reflexes simply to "consolidate" the physician-patient relationship ('the laying on of hands").

diggleblop
12-18-2006, 11:19 PM
There is actually a fair kernel of truth to this. There have been times when, having little or nothing to offer the patient, I tapped their reflexes simply to "consolidate" the physician-patient relationship ('the laying on of hands").


Is this phenomenon also similar to looking down the throat when the patient isn't complaining of any throat pain or cold? lol