Pre/Post Ganglionic

Pre/Post Ganglionic

Preganglionic vs. Postganglionic pathologyIdentifying pre-ganglionic nerve root from post-ganglionic nerve root or plexus pathology is based on the presence of normal or abnormal evoked sensory nerve(s) action potential.In pre-ganglionic nerve root pathology, the evoked sensory nerve action potential will remain preserved because of the fact that the pathway from the nerve cell body proximally, and dendrites distally remains intact.  This physiologic unit remains undisturbed, and electrically viable.  If the nerve has been disrupted or avulsed between the cell body and peripheral twigs, the nerve will become electrically unexcitable, with eventual attenuation or unevokable sensory response.

Radiculopathy usually affects the nerve root proximal to the ganglion, plexus pathology distal to the ganglion.   For example, upper trunk or C5,C6 post-ganglionic pathology will cause attenuation of the evoked lateral antebrachial cutaneous nerves.  Lower trunk or post-ganglionic C8,T1 nerve root pathology will affect the evoked ulnar sensory response and medial antebrachial cutaneous response.

In both instances, EMG spontaneous abnormalities, silence upon volition will be observed from the affected muscles. The evoked motor response will be reduced or absent, as the site of pathology will disrupt the continuity between the anterior horn cell body within the spinal cord and the distal nerve twigs.

postganglionic

C8,T1 post ganglionic avulsionabsent ulnar sensory response
absent evoked ulnar motor response
EMG spontaneous abnormalities*
EMG silence upon volition*
C8, T1 preganglionic avulsionnormal ulnar sensory response
absent evoked ulnar motor response
EMG spontaneous abnormalities*
EMG silence upon volition*
*C8,T1 myotome limb muscles

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Ray Jurewicz
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E-mail: rj@NerveStudy.com Web Site design by Larry Berman and Chris Maher

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