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Acute nerve compression and the compound muscle action potential.

Stecker MM, Baylor K, Chan YM - J Brachial Plex Peripher Nerve Inj (2008)

Bottom Line: The ability to detect statistically significant changes in the CMAP at low force levels using other descriptors of the CMAP including duration, latency variation, etc alone or in conjunction with amplitude and velocity measures was investigated.However, these other parameters did not allow for earlier detection of significant changes.On the other hand, ischemic and stretch injuries are associated with larger changes in conduction velocity for a given value of CMAP amplitude reduction.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurology, Geisinger Medical Center, Danville, PA 17822 USA. mark_stecker@yahoo.com

ABSTRACT
Detecting acute nerve compression using neurophysiologic studies is an important part of the practice of clinical intra-operative neurophysiology. The goal of this paper was to study the changes in the compound muscle action potential (CMAP) during acute mechanical compression. This is the type of injury most likely to occur during surgery. Thus, understanding the changes in the CMAP during this type of injury will be useful in the detection and prevention using intra-operative neurophysiologic monitoring. The model involved compression of the hamster sciatic nerve over a region of 1.3 mm with pressures up to 2000 mmHg for times on the order of 3 minutes. In this model CMAP amplitude dropped to 50% of its baseline value when a pressure of roughly 1000 mmHg is applied while, at the same time, nerve conduction velocities decline by only 5%. The ability to detect statistically significant changes in the CMAP at low force levels using other descriptors of the CMAP including duration, latency variation, etc alone or in conjunction with amplitude and velocity measures was investigated. However, these other parameters did not allow for earlier detection of significant changes. This study focused on a model in which nerve injury on a short time scale is purely mechanical in origin. It demonstrated that a pure compression injury produced large changes in CMAP amplitude prior to large changes in conduction velocity. On the other hand, ischemic and stretch injuries are associated with larger changes in conduction velocity for a given value of CMAP amplitude reduction.

No MeSH data available.


Related in: MedlinePlus

Changes in relative CMAP duration as a function of relative CMAP amplitude.
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Figure 5: Changes in relative CMAP duration as a function of relative CMAP amplitude.

Mentions: In all cases where a CMAP was recordable, the maximum velocity was never less than half of its initial value. In order to better elucidate the changes in the CMAP, figures 4 and 5 show the normalized CMAP velocity and CMAP duration respectively from each recorded potential as a function of the normalized CMAP amplitude. In both of these cases, no change in the measured parameters greater than 10% occurs until the CMAP amplitude is reduced by over 80%. Similar effects of the mean latency and latency variance are noted.


Acute nerve compression and the compound muscle action potential.

Stecker MM, Baylor K, Chan YM - J Brachial Plex Peripher Nerve Inj (2008)

Changes in relative CMAP duration as a function of relative CMAP amplitude.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2245939&req=5

Figure 5: Changes in relative CMAP duration as a function of relative CMAP amplitude.
Mentions: In all cases where a CMAP was recordable, the maximum velocity was never less than half of its initial value. In order to better elucidate the changes in the CMAP, figures 4 and 5 show the normalized CMAP velocity and CMAP duration respectively from each recorded potential as a function of the normalized CMAP amplitude. In both of these cases, no change in the measured parameters greater than 10% occurs until the CMAP amplitude is reduced by over 80%. Similar effects of the mean latency and latency variance are noted.

Bottom Line: The ability to detect statistically significant changes in the CMAP at low force levels using other descriptors of the CMAP including duration, latency variation, etc alone or in conjunction with amplitude and velocity measures was investigated.However, these other parameters did not allow for earlier detection of significant changes.On the other hand, ischemic and stretch injuries are associated with larger changes in conduction velocity for a given value of CMAP amplitude reduction.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurology, Geisinger Medical Center, Danville, PA 17822 USA. mark_stecker@yahoo.com

ABSTRACT
Detecting acute nerve compression using neurophysiologic studies is an important part of the practice of clinical intra-operative neurophysiology. The goal of this paper was to study the changes in the compound muscle action potential (CMAP) during acute mechanical compression. This is the type of injury most likely to occur during surgery. Thus, understanding the changes in the CMAP during this type of injury will be useful in the detection and prevention using intra-operative neurophysiologic monitoring. The model involved compression of the hamster sciatic nerve over a region of 1.3 mm with pressures up to 2000 mmHg for times on the order of 3 minutes. In this model CMAP amplitude dropped to 50% of its baseline value when a pressure of roughly 1000 mmHg is applied while, at the same time, nerve conduction velocities decline by only 5%. The ability to detect statistically significant changes in the CMAP at low force levels using other descriptors of the CMAP including duration, latency variation, etc alone or in conjunction with amplitude and velocity measures was investigated. However, these other parameters did not allow for earlier detection of significant changes. This study focused on a model in which nerve injury on a short time scale is purely mechanical in origin. It demonstrated that a pure compression injury produced large changes in CMAP amplitude prior to large changes in conduction velocity. On the other hand, ischemic and stretch injuries are associated with larger changes in conduction velocity for a given value of CMAP amplitude reduction.

No MeSH data available.


Related in: MedlinePlus