View Full Version : Summary of double crush and electrodiagnostic testing

08-09-1996, 08:13 AM

The following is a summary of the responses I received from a posting I
placed on both the Biomechanics and Neuromuscular lists about 5-6 weeks ago.
I greatly appreciate all of the feedback I received.

I have included all messages as they were received, so I apologize for the
length. I have also included some messages (listed after the break) from
other contacts which I received. Several of these I did some minor edits on
to reduce size. The original posting is included at the end of the other

Thank you again to all who responded. You have been of great assistance.


************************ Original messages *******************************

I'm supervising a students who is investigating the neural tension testing
issues with carpal tunnel and radiculopathies. We are not looking at SEPs
for the reason that you report. However I suggest when you do find a
assessment technique then you may consider the position of the joints (Cx,
shld, elbow and wrist) the order and combination so called sensitizing
manoeuvres are applied. How you control for dependency between trials is
another issue since the 'tissues' time characteristics - mechanical
creep/hysteresis, accomodation, and (in the pathological situation)
sensitization should be considered.
Good luck in your studies.. we are testing in about 3 mths I'll contact you
if we find anything that my assist you.

Garry T Allison PhD. Lecturer,
School of Physiotherapy, email:iallison@info.curtin.edu.au
Curtin University of Technology, Tel. +61 9 351 3648
Selby Street, Shenton Park, Fax. +61 9 351 3636
Western Australia 6008
================================================== =======================

In response to your query re: recording evoked potentials. It is certainly
possible to do using surface recording electrodes, but you will probably
have to average approximately 2000 responses in order to clearly see the SEP
given its low amplitude. You may find the book by Rainer Spehlmann, Evoked
Potential Primer, Butterworth Publishers, 1985 to be helpful in terms of
setting up your recording parameters and providing normative data.

Good luck, I hope this helps

Brenda Brouwer, Ph.D

Brenda Brouwer, Ph.D
Graduate Coordinator
School of Rehabilitation Therapy
Queen's University
Kingston, ON
Canada, K7L 3N6
ph. 613-545-6087
FAX 613-545-6776

__________________________________________________ _________________________


I suggest you contact Dr. Benjamin Sucher at the Center for Carpal
Tunnel Studies in Paradise Valley, Arizona. He does not have email (I
don't think) so you'll have to call or write to him (see below).

Benjamin Sucher, D.O., P.C.
Center for Carpal Tunnel Studies
10555 N. Tatum Blvd., Suite A-104
Paradise Valley, AZ 85253
(602) 483-7387
(602) 483-3684 (fax)

He has done extensive research on both CTS and TOS and has
published extensively on both topics. Maybe he can help.

Good luck!


Richard N. Hinrichs, Ph.D.
Dept. of Exercise Science
Arizona State University

__________________________________________________ _________________________


First off, the thoracic outlet would involve mainly the ulnar nerve, and in
my 19 years of experience as a registered EMG tech, (15 of those years at
Columbia Presbyterian Medical Center in Manhattan), we found no evidence of
double crush involving median nerve at the wrist and supraclavicular fossa
(Erb point), stimulating the motor nerve orthodromically(being a purely EMG
tech means I don't do SSEP's), in spite of rather extensive testing for it
over the course of a few years in the early eighties, nor of ulnar
groove/thoracic outlet which is still tested at Erb point. This bing said, I
do exclude the more recently described conduction block neuropathies (though
I still think that's a new description for what used to be called
mononeuropathy multiplex, with a few new bells and whistles).

Further, at the discussion arising towards the end of this quest for double
crush involving two sites on the peripheral nerve, I vaguely recall that the
upshot of the *original* thesis (perhaps not by McComas) was a double crush
involving a cervical disc and a more peripheral site on the nerve originating
at that level. Not to throw a wet towel on your search, because I do believe
that SSEP's may uncover a link, but you must be certain that the entrapments
that you may find are exclusive to that nerve and not part of a generalized

You may want to go to the AAEM home page and search for minimonographs or
workshop handouts; I have not looked for this particular topic, but I'm
certain it is covered somehow. The URL is:

Regarding those who have been doing this kind of work, it seems in my own
little world that it was the orthopods and the physiatrists who actually
believed in the presence of a thoracic outlet syndrome; the very small
percentage of patients I have tested for thoracic outlet syndrome (again,
proximal stimulation of ULNAR motor nerves, recording ADM in the hand, and of
course doing segmental testing) has shown no blocks; working always with
Neurologists, we began to get fewer referrals for thoracic outlet, it seemed,
as time went on...and we uncovered no sensory abnormalities (agian,
orthodromic stimulation of finger, record wrist, all distal) that could not
be explained by a more distal block (carpal tunnel for the median nerve,
ulnar groove for the ulnar nerve most commonly), especially considering that
the involvement of the sensory nerve (measuring amplitude, which will be
affected first) has always been commensurate with the degree of compression
seen in the peripheral motor nerve.

Hope I made sense...I have been working in private practice for the past
three years and spend my days switching from layman's descriptions of what an
EMG entails to giving quick synopses of the results to whichever of three
Neurologists I am working with that day, so I consider myself somewhat
academically impaired in terms of discussion. Let me know how you make out
in your search, and I will discuss this in the interim with the EMGers with
whom I work (CPMC trained, so they are truly serious
electrodiagnosticians...not to fault anyone else...but I know their
background, having been there).

Good Luck!

Marylyn DeGregorio, R.EDT

__________________________________________________ __________________

Dear Kevin
I use median nerve SEPs for research in athletes, and have recently
started trying to look for compound action potentials over Erb's
point and vertebra C5, in order to clarify the farfields on the
cortical recordings (according to M.R.Nuwer, et al. IFCN
recommended standards for short latency somatosensory evoked
potentials, Electroencephalography and clinical neurophysiology 91 :
6-11, 1991). I haven't had much luck yet, despite averaging 500
responses, but am working on it. I would be surprised if you can
record compound action potentials in the brachial plexus
particularly without averaging. I have been very successful with
surface electrodes, as long as the impedence between electrodes is
less than 5 kOhms, so I'm not sure if the hassle of needle electrodes
is worth it. Increasing your pulse width (I use 0.2ms) will cause
"smearing" of your compound action potential, and makes it difficult
to measure latencies, but increasing the intensity will enlarge your
compound AP and make it more easily recognisable, I use just above
the motor threshhold (ie: get a thumb twitch).
An old reference (which you probably have) where they do just what
you are describing is J.E.Desmedt and G.Cheron, Central somatosensory
conduction in man : neural generators and interpeak latencies of the
far field components recorded from neck and right or left scalp and
earlobes. Electroencephalography and clinical neurophysiology. 50 :
382-403, 1980. See page 387 particularly.
I hope this helps a little.

@ "People who tell you that they like to