Median Nerve SSEP:- Is there a relationship between Median Nerve SSEP & Level of Spinal Cord Injury?

This case study was conducted by the American Spinal Cord Injury Association (ASIA) on patients with Quadriplegia. The question asked was is there a relationship between median nerve SSEP changes and level of spinal cord injury?.

The answer is yes, neuromonitoring of median nerve SSEPs conducted on 14 quadriplegic patients and 8 normal individuals. Amplitude and latency analysis of waveforms N9, N13 and N20 was conducted. N9 responses were present in all the patients and normal subjects, both amplitude and latency were similar in both groups.

On the other hand, N13 was absent in Quadriplegia patients?
N20 was absent in C5 patients with Quadriplegia? but it was present in C6-7 patients, though the amplitudes were decreased with normal latency. Did you notice these waveform changes in your recording?.

Read further:

Original Article

Spinal Cord (2009) 47, 372–378; doi:10.1038/sc.2008.147; published online 20 January 2009

Relationship between median nerve somatosensory evoked potentials and spinal cord injury levels in patients with quadriplegia

M I F de Arruda Serra Gaspar¹, A Cliquet Jr^2,3, V M Fernandes Lima⁴ and D C C de Abreu¹

Methods:

Fourteen individuals with quadriplegia and 8 healthy individuals were evaluated. Electrophysiological assessment of the median nerve was performed by evoked potential equipment. The injury level was obtained by ASIA. N₉, N₁₃ and N₂₀ were analyzed based on the presence or absence of responses. The parameters used for analyzing these responses were the latency and the amplitude. Data were analyzed using mixed-effect models.

What's New in Pediatric Orthopaedics???- Review by Kim and Noonan

In the latest issue of the journal JB and JS,  authours Young-Jo Kim, MD, PhD¹ 

and Kenneth J. Noonan, MD published their reviews on"Pediatric Orthopaedics". 

They discuss about the recent advancements in the field of Pediatric Orthopadics 

with emphasis on various spine deformity, neurological disorders in childrens with 

appropirate surgical methods used. They have done an excellent review of the literature, 

the 82 references listed can be useful for those in the Pediatric Ortho as well as for 

Neurophysiologists. There is a section on basic science applications and in another 

section on spine, they talk about effectiveness of Intraoperative monitoring 

using motor evoked potentials.

The effectiveness of spinal cord monitoring during spinal deformity surgery was recently reported in two large studies (involving >1000 patients), with the incidence of spinal cord injury approaching 1%^66,67. Transcranial motor-evoked potentials are exquisitely sensitive to threatened spinal cord function, andtheir use together with traditional somatosensory evoked potentials improves the accuracy of spinal cord monitoring. Somatosensory evoked potentials may not detect all problems and may not detect problems as rapidly as transcranial motor-evoked potentials do⁶⁷, and the sensitivity of transcranial motor-evoked potentials has led some centers to abandon somatosensory evoked potentials in favor of motor monitoring alone. For instance, Hsu et al.⁶⁸ reported 100% sensitivity for the detection of a clinically important neurological event in a consecutive series of 144 patients. The authors defined a neurological event as either a new postoperative deficit or a 50% decrease in the monitoring potential over a one-minute period. The rapidity with which motor monitoring detects spinal cord compromise makes it a valuable tool for sagittal plane correction, and prompt detection of a problem can lead to its resolution before a permanent deficit results^69,70.

The Journal of Bone and Joint Surgery (American). 2009;91:743-751.doi:10.2106/JBJS.H.01689

Spinal Cord integerity risk & Tibial single Trial SSEP?

Single trial Tibial Somatosensory SSEP along with H-reflex can be used to monitor the spinal cord integerity and function during surgical procedures that put the cord in risk. The following article
describes how this combination of a single trial SSEP can be
useful?.

When spinal cord functional integrity is at risk during surgery, intraoperative neuromonitoring is recommended.

Tibial Single Trial Somatosensory Evoked Potentials (SEPs) and H-reflex are here used in a combined neuromonitoring method: both signals monitor the spinal cord status, though involving different nervous pathways.

However, SEPs express a trial-to-trial variability that is difficult to track because of the intrinsic low signal-to-noise ratio. For this reason single trial techniques are needed to extract SEPs from the background EEG.