Conducted somatosensory evoked potentials during spinal surgery

1982 ◽  
Vol 57 (3) ◽  
pp. 354-359 ◽  
Author(s):  
James B. Macon ◽  
Charles E. Poletti ◽  
William H. Sweet ◽  
Robert G. Ojemann ◽  
Nicholas T. Zervas
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Conduction Velocity ◽  
Somatosensory Evoked Potentials ◽  
Spinal Surgery ◽  
Dorsal Column ◽  
Operative Field ◽  
Content Type ◽  
Spinal Lesions ◽  
Spinal Cord Function

✓ In 27 patients undergoing laminectomy, spinal cord function was monitored by epidural bipolar recordings of conducted spinal somatosensory evoked potentials (SEP's) across the laminectomy site, with calculation of spinal conduction velocity (CV). In control cases without myelopathy, the CV remained relatively constant (± 3%) even during prolonged operations, despite markedly changing levels of anesthesia. Acute CV changes were detected intraoperatively in three cases: these patients displayed improvement after extramedullary (Case 1) and intramedullary decompression (Case 2), and deterioration after direct unilateral dorsal column injury (Case 3). These intraoperative CV alterations correlated postoperatively with changes in the neurological examination. Although a unilateral lesion confined to the dorsal column abolished the ipsilateral SEP in Case 3, complete anterior quadrant lesions did not consistently change the CV (Case 4). This further suggests that the SEP is generated entirely by ipsilateral dorsal column activation. Accurate measurement of this dorsal column conduction velocity across the operative field provides a very sensitive means of monitoring spinal cord function during operations for neurosurgical spinal lesions.

Recording of spinal somatosensory evoked potentials for intraoperative spinal cord monitoring

1986 ◽  
Vol 64 (4) ◽  
pp. 601-612 ◽  
Author(s):  
Ian R. Whittle ◽  
Ian H. Johnston ◽  
Michael Besser
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
Spinal Surgery ◽  
Neurological Deficits ◽  
Spinal Cord Monitoring ◽  
Intramedullary Tumors ◽  
Content Type ◽  
Profound Hypotension ◽  
Spinal Segments

✓ The authors' experience with intradural and epidural recording of spinal somatosensory evoked potentials (SSEP's) during 26 cases of spinal surgery is described. The techniques of monitoring spinal cord function provided good quality SSEP waveforms in patients both with and without neurological deficits. The SSEP configuration and peak latencies remained stable for up to 5 hours during anesthesia with nitrous oxide, halothane, and fentanyl. Patterns of baseline SSEP's were characteristic of different spinal segments. Distortion and asymmetry of these baseline patterns were seen in several patients with spinal neoplasms. Loss of waveform components during surgery occurred with profound hypotension, overdistraction of the vertebral axis, dorsal midline myelotomy, and removal of intramedullary tumors. Persistent loss of waveform components was associated with an acquired neurological deficit. Fluctuations in the amplitude of the SSEP's were common but were not associated with postoperative neurological deficits. Spinal cord monitoring by means of SSEP recording would appear to be useful during extradural spinal surgery, but there are limitations associated with this technique during some types of intradural surgery.

Conducted somatosensory evoked potentials during spinal surgery

1982 ◽  
Vol 57 (3) ◽  
pp. 349-353 ◽  
Author(s):  
James B. Macon ◽  
Charles E. Poletti
Keyword(s):  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
Spinal Surgery ◽  
Peroneal Nerve ◽  
Common Peroneal Nerve ◽  
Content Type ◽  
Spinal Lesions ◽  
Conduction Velocities ◽  
A Site ◽  
Peroneal Nerve Stimulation

✓ Intraoperative recordings of conducted bipolar epidural somatosensory evoked potentials (SEP's) generated by unilateral common peroneal nerve stimulation have been obtained in 27 patients. The SEP's were multiphasic, 0.3 to 1.5 µV in amplitude, and recorded in 100% of patients with normal cords or in patients with spinal lesions, at a site caudal to the lesions. Control spinal conduction velocities (CV's), measured in the midthoracic to lower cervical regions, were in the range of 65 to 85 m/sec. Control lumbar and lower thoracic CV's were in the range of 30 to 45 m/sec. The CV values were obtained periodically throughout the course of surgery and were plotted as a function of time. In control patients with extradural lesions and neuroleptic anesthesia, the CV's remained constant (± 3%). The consistency, sensitivity, and safety of SEP recordings obtained by this technique make precise monitoring readily available during spinal operations.

Spinal cord pathways mediating somatosensory evoked potentials

1982 ◽  
Vol 57 (4) ◽  
pp. 472-482 ◽  
Author(s):  
Stephen K. Powers ◽  
Catherine A. Bolger ◽  
Michael S. B. Edwards
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
High Intensity ◽  
Dorsal Column ◽  
Motor Threshold ◽  
Spinal Cord Lesions ◽  
Content Type ◽  
Spinocerebellar Tract ◽  
Fine Print

✓ Using a CO2 laser, discrete thoracic spinal cord lesions were made in cats anesthetized with ketamine and xylazine (Rompun). Differences in cortical somatosensory evoked potentials (SEP's) produced with high-intensity stimulation (20 times the motor threshold) of each posterior tibial nerve were determined for nine different combinations of unilateral spinal cord lesions. The results of these studies show that nerve fibers in the ipsilateral dorsal column, the ipsilateral dorsal spinocerebellar tract, and the contralateral ventrolateral tracts with respect to the side of leg stimulation, contribute to cortical SEP's. A lesion of the dorsal spinocerebellar tract affected only the early waves (< 30 msec) of the SEP from leg stimulation ipsilateral to the side of the lesion, whereas a solitary lesion of the ventrolateral tract caused changes primarily in the amplitude of later waves (> 30 msec) of the SEP produced by contralateral leg stimulation. Lesions involving one-half of the dorsal column caused changes in the amplitude of both the early and late waves produced by stimulation ipsilateral to the side of the lesion. The effects of various combinations of lesions on the cortical SEP's were not additive, which indicates significant interaction between afferent pathways. These findings suggest that high-intensity peripheral nerve stimulation, which activates both C and A fibers, could be used intraoperatively to assess spinal cord function with more accuracy than the current practice of using a stimulus strength of twice the motor threshold. The importance of using anesthetic agents that do not depress cortical activity (which may affect the later components of the SEP) is also emphasized.

Percutaneous flexible bipolar epidural neuroelectrode for spinal cord stimulation

1984 ◽  
Vol 60 (6) ◽  
pp. 1317-1319 ◽  
Author(s):  
Alfred G. Kaschner ◽  
Wilhelm Sandmann ◽  
Heinz Larkamp
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Epidural Space ◽  
Somatosensory Evoked Potentials ◽  
Spinal Cord Stimulation ◽  
Spinal Cord Ischemia ◽  
Aortic Occlusion ◽  
Content Type ◽  
Fine Print

✓ This article describes a new flexible bipolar neuroelectrode which is inserted percutaneously into the epidural space for segmental spinal cord stimulation. This electrode was used in experiments with dogs and monkeys for recording cortical somatosensory evoked potentials in order to identify intraoperative spinal cord ischemia during periods of aortic occlusion.

Spinal evoked potentials from the motor tracts

1983 ◽  
Vol 58 (1) ◽  
pp. 38-44 ◽  
Author(s):  
Walter J. Levy
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Motor System ◽  
Evoked Potential ◽  
Motor Evoked Potential ◽  
Dorsal Column ◽  
Content Type ◽  
Dorsal Columns ◽  
Evoked Potential Monitoring ◽  
Potential Monitoring

✓ There is a need to monitor the motor system, but it has a different blood supply and a different location in the spinal cord from those measured by traditional somatosensory evoked potential monitoring. This paper reports a motor evoked potential monitoring system that uses direct spinal cord stimulation overlying the areas of the motor tract in the cord. In nine cats, evoked potentials were recorded from the dura, which gave a much faster main signal component than the traditional dorsal column evoked potentials, which were also recorded. This 100-m/sec signal was not affected by sectioning of the dorsal columns, which was verified histologically. This mode of monitoring the motor system can be used during surgery. It may also provide a better evaluation of patients after spinal cord trauma.

Somatosensory Evoked Potentials

2016 ◽  
pp. 539-566 ◽  
Author(s):  
James C. Watson ◽  
Jonathan L. Carter
Keyword(s):  
Spinal Cord ◽  
Nervous System ◽  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
Dorsal Column ◽  
Medial Lemniscus ◽  
Prognostic Information ◽  
Technical Aspects ◽  
Non Invasive ◽  
Anoxic Coma

Somatosensory evoked potentials (SEPs) provide a non-invasive, sensitive, and quantitative way of assessing the functional integrity of the peripheral and central proprioceptive, dorsal column–medial lemniscus somatosensory conduction pathways. SEPs can be used to localize lesions in the nervous system, to identify objectively abnormalities in patients with few sensory manifestations or none at all, to determine whether a process potentially affecting the spinal cord is functionally impairing, and to provide prognostic information in the context of post-anoxic coma. This chapter discusses the technical aspects, limitations, and roles of SEPs in the evaluation of neurologic symptoms, and provides examples of SEPs in different diseases.

Reversible spinal cord trauma: a model for electrical monitoring of spinal cord function

1972 ◽  
Vol 36 (4) ◽  
pp. 402-406 ◽  
Author(s):  
Thomas J. Croft ◽  
Jerald S. Brodkey ◽  
Frank E. Nulsen
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Sensitive Indicator ◽  
Spinal Cord Trauma ◽  
Content Type ◽  
Cortical Evoked Potentials ◽  
Spinal Cord Damage ◽  
Sensory Transmission ◽  
Spinal Cord Function ◽  
Fine Print

✓ Cortical evoked potentials in anesthetized cats were recorded by a noninvasive averaging technique as a means of estimating spinal cord damage. Graded pressure on the spinal cord produced reversible blocking of these potentials. With this type of trauma, block of motor transmission through the cord paralleled the block of sensory transmission, and each seemed to be a sensitive indicator of spinal cord function. The possible use of such monitoring in anesthetized patients undergoing spinal operations is discussed.

Dorsal Column Mapping via Phase Reversal Method

Neurosurgery ◽  
2014 ◽  
Vol 74 (4) ◽  
pp. 437-446 ◽  
Author(s):  
Dinesh Nair ◽  
Vishakhadatta M. Kumaraswamy ◽  
Diana Braver ◽  
Ronan D. Kilbride ◽  
Lawrence F. Borges ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
Spinal Cord Tumor ◽  
Tumor Resection ◽  
Dorsal Column ◽  
Neurological Deficits ◽  
Reliable Technique ◽  
Intramedullary Spinal Cord ◽  
Phase Reversal

ABSTRACT BACKGROUND: Safe resection of intramedullary spinal cord tumors can be challenging, because they often alter the cord anatomy. Identification of neurophysiologically viable dorsal columns (DCs) and of neurophysiologically inert tissue, eg, median raphe (MR), as a safe incision site is crucial for avoiding postoperative neurological deficits. We present our experience with and improvements made to our previously described technique of DC mapping, successfully applied in a series of 12 cases. OBJECTIVE: To describe a new, safe, and reliable technique for intraoperative DC mapping. METHODS: The right and left DCs were stimulated by using a bipolar electric stimulator and the triggered somatosensory evoked potentials recorded from the scalp. Phase reversal and amplitude changes of somatosensory evoked potentials were used to neurophysiologically identify the laterality of DCs, the inert MR, as well as other safe incision sites. RESULTS: The MR location was neurophysiologically confirmed in all patients in whom this structure was first visually identified as well as in those in whom it was not, with 1 exception. DCs were identified in all patients, regardless of whether they could be visually identified. In 3 cases, negative mapping with the use of this method enabled the surgeon to reliably identify additional inert tissue for incision. None of the patients had postoperative worsening of the DC function. CONCLUSION: Our revised technique is safe and reliable, and it can be easily incorporated into routine intramedullary spinal cord tumor resection. It provides crucial information to the neurosurgeon to prevent postoperative neurological deficits.

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