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Please explain reflex pathology

Posted by Raina on August 03, 1999 at 09:20:58
Hi there-
I have a couple of questions regarding pathological reflexes. I have a basic understanding that an abnormal babinski reflex is when the big toe dorsiflexes and the smaller toes fan out. A normal one is when the toes bend down and not up. My question is: What pathological significance is it when both toes don't do anything (they don't dorsiflex or bend down).
Also what significance do symmetrical brisk reflexes have when there is an abnormal babinski sign present? Please advise and thanks in advance- Raina

Posted by Raina on August 03, 1999 at 09:24:26
Hi again-
I forgot to add another question. What significance do symmetrical brisk reflexes have when there is a normal plantar reflex? Thanks again! Raina

Posted by CCF Neuro[P] MD, RPS on August 03, 1999 at 12:29:40
Dear Raina:
See the previous posting.
CCF Neuro MD

Posted by Helen Stone on August 03, 1999 at 19:46:48
Dear Doctor,
I've been curious about the Babinski since going to Duke Hospital this past January when it seemed that ten thousand interns, residents, fellows, doctors, all wanted to perform the Babinski on the same day!
I did not understand your explanation.  Can you please elucidate?

Posted by CCF Neuro[P] MD, RPS on August 04, 1999 at 13:14:33
Tell me what you do not understand and I will elaborate.
CCF Neuro MD

Posted by Helen Stone on August 10, 1999 at 00:41:34
Thank you for answering.  I've just read and re-read all of this trying to find a question to ask you.  If I have all of this right, there are 3 possibilities for the Babinski :  1) toe points up; 2) toe points down or 3) toe does not respond.  At the same time reflexes (WHICH ONES?) may be  A) present  or B) absent.  Again if I have it right, 1) toe points up i and  A) reflexes present  = normal.  I'm assuming here that "brisk reflexes" = normal reflexes, but where? Isn't the Babinski a reflex?
I am unsure of the meaning of the other possibilities:  1 B, 2 A, 2 B, 3 A, 3 B.
I know that you said that one of these usually means the patient is nervous, that one of them means a break in the some kind of pathway.
I apologize for my denseness.  Consider me hopeless if you like and don't answer if you wish, although I would really like to understand this.  I have CIDP, no reflexes in knees or ankles and have never understood which kind of Babinski I have or what it means.  Only know it hurts.
Helen Stone

Posted by CCF Neuro[P] MD, RPS on August 10, 1999 at 12:18:00
Dear Helen:
Yes, the Babinski is a reflex.  The name Babinski is given only to the big or large toe response to stimulation of the nerve root L5 using the bottom of the foot (actually the side of the foot).  The stimulation is usually given to the bottom of the foot.
The large or big toe either goes up or down when the bottom of the food is stroked.  This is called the plantar response.  The name Babinski, is when the toe goes upward or in the extensor direction when the bottom of the foot is stroked.  When the toe goes downward or in the flexor direction then the plantar response is normal.  
When the toe goes up or in the extensor direction (positive Babinski) then this means that there is a lesion in the pyrimidal or motor tracts in the central nervous system.  One usually sees hyperactive reflexes in this condition.
Now, if the toes go upward and there are normal reflexes in the lower extremities then this is usually a sign of a normal patient who is nervous and the plantar response is misread (a withdrawal reflex was elicited and not a true plantar response).
The absence of reflexes is common in CIDP and this is due to demyelination of the large sensory fibers Ia.  The knee reflex is the patellar reflex and the ankle reflex is known as the ankle reflex.  Only the elicitation of the large toe by stimulating the bottom or side of the foot is known as the Babinski response, if the toe is upward.
I hope this helps you.
CCF Neuro MD

Posted by Helen Stone on August 11, 1999 at 13:22:16
Thank you for your explanation.  I think I understand, at least I hope I do.  In my case with having CIDP, I know I have no knee (patellar) or ankle reflexes in either leg, and I assume I have no Babinski response in the left foot since that is the one that was tested over and over again.  It makes sense that the same disease process of demyelination that eliminated the knee and ankle reflexes would also have eliminated the Babinski reflex response.  I will check this out with my neurologist.
Helen Stone

Posted by CCF Neuro[P] MD, RPS on August 11, 1999 at 16:25:27
Theoretically, you should not have a Babinski reflex.  This would indicate that you have a central lesion, whereas CIDP is a peripheral demyelinating lesion disease.  As previously explained, the Babinski reflex shows pyramidal tract (or upper motor neuron, central) disease process.  Having CIDP does not have central involvement.  Your big toe reflex may be absent or equivocal but not upgoing.
CCF Neuro MD

Posted by Helen on August 16, 1999 at 20:27:45

Thank you for your patience.  I now see why I was so dense!  I was mistakenly under the impression that the Babinski was a TEST rather than a REFLEX with TWO outcomes possible:  toes up or toes down with toes down being normal.  Thank you very much,

Posted by CCF Neuro[P] MD, RPS on August 17, 1999 at 20:53:39
Hope things are clear.
CCF Neuro MD

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