Re: Undetected lesions of the spine

Posted By aradia on October 27, 1998 at 17:19:54:

In Reply to: Re: Undetected lesions of the spine posted by CCF Neurology MD - AY on October 27, 1998 at 15:49:16:






: : I know that it is possible to have undetected lesions of the spine, but is it also
: : possible to have undetected compression of the nerves of the spine?  The data that
: : I have to give to you is a negative brain and full spinal mri, all bloodwork negative,
: : negative or normal(ana, sed rate 5, etc.) emg normal, abnormal sep posterial tibial popliteal fossa & p17 absent,
: : (n45 48.0, 47.8), (p37 43.2, 42.8),   Numbness in right calf, ankle, foot, upper left back quadrant, spread to
: : left calf, ankle, and foot. Dizziess and many other symptoms.  Neurologist feels
: : sep supports early stages of ms, ordered baer, vep, then spinal tap after that to rule
: : out spinal vasculitis, infection, etc.  He stated the sep is one of the most
: : positive tests in determining early ms.  My husband has mentioned nerve compression
: : several times, and the neuro has dismissed it with the testing.  My argument, is
: : the question above, if there can be undetected lesions, could that also apply to
: : undetected nerve compression?
Thank you

Please pardon my misunderstanding of your information.  EMG's sometimes do no pick up nerve compression,
does that apply to the SSEP test as well?
Thank you
Aradia



  


: : : Thanks for your question.  A compression of the nerves - either at the
: neural foramina, where the nerve roots exit the spine; or more peripherally
: in the limbs - will generally result in alterations in the EMG/NCS.  However,
: there are a number of caveats with that generalization: Subtle/minor
: entrapments (compressions) can initially go undetected by the test, depending
: on how the different bundles of nerve fibers are organized within a major
: nerve trunk;  the EMG/NCS does not detect well lesions to slower-conducting/
: unmyelinated fiber (which transmits pain); certain peripheral nerves are
: technically difficult to evaluate using EMG/NCS due to either nerve or
: muscle location.  Given these restrictions, the clinician should use his/her
: judgement in the interpretation of the EMG/NCS results.
I hope this information is helpful.  Best of luck.
This information is provided for general medical education purposes only.
: Please consult your doctor regarding diagnostic and treatment options.




Thanks for your feedback.  There are a number of limitations why a SSEP
is not an adequate test for detection of nerve root compressions:
- A discrete lesion at a single nerve root may not cause a prolongation in
latency of the SSEP recorded over the spine or scalp because any slowing
of conduction in the compressed segment of the nerve fibers traversing
the involved nerve root is masked by the normal velocity of conduction in
the long pathway from the point of the peripheral stimulation to the site
at which the responses are generated.
- When the SSEP is elicited by stimulation of a multisegmental nerve trunk
any slowing of conduction caused by a lesion involving a single nerve root
will be obscured by the normal conduction speed in fibers traversing the
adjacent, unaffected roots.
- Abnormal SSEP do not suggest either the age or nature of the underlying
pathology and provide only limited information regarding the precise location
of lesions between the dorsal root ganglion and the spinal cord.
I hope this information is helpful.  Best of luck.
This information is provided for general medical education purposes only.
Please consult your doctor regarding diagnostic and treatment options.
Thank you very much for your information, however, confusion has now set in.
You referred to lesions in discussing the SSeP.  Would that also include nerve
compression from a bulging disc or is that something completely different?  
I am so sorry to bother you, just trying to grasp the idea on whether or not
I could possibly have nerve compression by a bulging disc vs. an undetected lesion
which is what the doctor thinks per the ssep test.  He says that the compression
has been pretty well ruled out by the mri's stating bulging discs, but no nerve
impingement.  My husband seems to think, that if there is a possibility of "undetected
lesions", then what is the possibility of "undetected nerve impingement".  I thank you
in advance for your answers which have been helpful, unfortunately my brain is not
comprending them :).
Aradia