Intraoperative monitoring for tethered cord surgery: an update

Object Intraoperative neurophysiological recording techniques have found increasing use in neurosurgical practice. The development of new recording techniques feasible while the patient receives a general anesthetic have improved their practical use in a similar way to the use of digital recording, documentation, and video technology. This review intends to provide an update on the techniques used and their validity. Methods Two principal methods are used for intraoperative neurophysiological testing during tethered cord release. Mapping identifies functional neural structures, namely nerve roots, and monitoring provides continuous information on the functional integrity of motor and sensory pathways as well as reflex circuitry. Mapping is performed mostly by using direct electrical stimulation of a structure within the surgical field and recording at a distant site, usually a muscle. Sensory mapping can also be performed with peripheral stimulation and recording within the surgical site. Monitoring of the motor system is achieved with motor evoked potentials. These are evoked by transcranial electrical stimulation and recorded from limb muscles and the external anal sphincter. The presence or absence of muscle responses are the parameters monitored. Sensory potentials evoked by tibial or pudendal nerve stimulation and recorded from the dorsal columns via an epidurally inserted electrode and/or from the scalp as cortical responses are used to access the integrity of sensory pathways. Amplitudes and latencies of these responses are then interpreted. The bulbocavernosus reflex, with stimulation of the pudendal nerve and recording of muscle responses in the external anal sphincter, is used for continuous monitoring of the reflex circuitry. Presence or absence of this response is the pertinent parameter that is monitored. Conclusions Intraoperative neurophysiology provides a wide and reliable set of techniques for intraoperative identification of neural structures and continuous monitoring of their functional integrity.

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Electrical Stimulation of Anal Sphincter or Pudendal Nerve Improves Anal Sphincter Pressure

Diseases of the Colon & Rectum ◽

10.1097/dcr.0b013e31826ae2f8 ◽

2012 ◽

Vol 55 (12) ◽

pp. 1284-1294 ◽

Cited By ~ 1

Author(s):

Margot S. Damaser ◽

Levilester Salcedo ◽

Guangjian Wang ◽

Paul Zaszczurynski ◽

Michelle A. Cruz ◽

...

Keyword(s):

Electrical Stimulation ◽

Anal Sphincter ◽

Pudendal Nerve ◽

Sphincter Pressure ◽

Anal Sphincter Pressure ◽

Stimulation Of

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Selective block of external anal sphincter activation during electrical stimulation of the sacral anterior roots in a canine model

Neurogastroenterology & Motility ◽

10.1111/j.1365-2982.2005.00678.x ◽

2005 ◽

Vol 17 (5) ◽

pp. 721-726 ◽

Cited By ~ 3

Author(s):

n. bhadra ◽

j. t. mortimer

Keyword(s):

Electrical Stimulation ◽

Anal Sphincter ◽

External Anal Sphincter ◽

Canine Model ◽

Stimulation Of

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Activation of thalamic ventroposteriolateral neurons by phrenic nerve afferents in cats and rats

Journal of Applied Physiology ◽

10.1152/japplphysiol.00334.2002 ◽

2003 ◽

Vol 94 (1) ◽

pp. 220-226 ◽

Cited By ~ 12

Author(s):

Weirong Zhang ◽

Paul W. Davenport

Keyword(s):

Electrical Stimulation ◽

Somatosensory Cortex ◽

Phrenic Nerve ◽

Proprioceptive Information ◽

Neural Responses ◽

Afferent Stimulation ◽

Physiological Conditions ◽

Sensory Pathways ◽

Increased Activity ◽

Stimulation Of

It has been demonstrated that phrenic nerve afferents project to somatosensory cortex, yet the sensory pathways are still poorly understood. This study investigated the neural responses in the thalamic ventroposteriolateral (VPL) nucleus after phrenic afferent stimulation in cats and rats. Activation of VPL neurons was observed after electrical stimulation of the contralateral phrenic nerve. Direct mechanical stimulation of the diaphragm also elicited increased activity in the same VPL neurons that were activated by electrical stimulation of the phrenic nerve. Some VPL neurons responded to both phrenic afferent stimulation and shoulder probing. In rats, VPL neurons activated by inspiratory occlusion also responded to stimulation on phrenic afferents. These results demonstrate that phrenic afferents can reach the VPL thalamus under physiological conditions and support the hypothesis that the thalamic VPL nucleus functions as a relay for the conduction of proprioceptive information from the diaphragm to the contralateral somatosensory cortex.

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Giant fiber activation of an intrinsic muscle in the mesothoracic leg of Drosophila melanogaster

Journal of Experimental Biology ◽

10.1242/jeb.177.1.149 ◽

1993 ◽

Vol 177 (1) ◽

pp. 149-167 ◽

Cited By ~ 6

Author(s):

J. R. Trimarchi ◽

A. M. Schneiderman

Keyword(s):

Drosophila Melanogaster ◽

Electrical Stimulation ◽

Motor Neuron ◽

Cell Body ◽

Escape Response ◽

Large Cell ◽

Giant Fiber ◽

Leg Muscle ◽

Muscle Responses ◽

Stimulation Of

Cinematographic analysis reveals that an important component of the light-elicited escape response of Drosophila melanogaster is the extension of the femur-tibia joint of the mesothoracic leg. During the jumping phase of the response, this extension works synergistically with extension of the femur. Femur extension is generated by contraction of the tergotrochanteral muscle (TTM), one of four previously described escape response muscles. Femur-tibia joint extension in the mesothoracic leg has been thought to be controlled by contraction of the tibial levator (TLM), an intrinsic leg muscle. We investigated the activation of the TLM during the escape response. Electrical stimulation of the giant fiber interneuron that mediates the escape response results in activation of the TLM with a latency of 1.46 +/− 0.02 ms. The TLM is innervated by a motor neuron (TLMn) with a large cell body in the mesothoracic ganglion. The TLMn has extensive arborizations in the lateral mesothoracic leg neuromere and has a prominent medially directed neurite. To investigate possible presynaptic inputs activating the TLMn during the escape response, we analyzed the muscle responses of two mutants, giant fiber A1 and bendless. Our analysis suggests that the TLMn is activated by a novel pathway.

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Magnetically Evoked Facial Nerve Potential

Otolaryngology ◽

10.1177/019459988910000417 ◽

1989 ◽

Vol 100 (4) ◽

pp. 345-347 ◽

Cited By ~ 7

Author(s):

Ian M. Windmill ◽

Serge A. Martinez ◽

Christopher B. Shields ◽

Markku Paloheimo

Keyword(s):

Electrical Stimulation ◽

Facial Nerve ◽

Nerve Stimulation ◽

Magnetic Stimulation ◽

Electrical Current ◽

Facial Muscle ◽

Facial Nerve Stimulation ◽

Muscle Responses ◽

Stimulation Of

Facial nerve stimulation by electrical current is painful and tends to discourage serial studies. Transcutaneous magnetic stimulation of the facial nerve is painless, easily reproducible, and elicits facial muscle responses identical to electrical stimulation.

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Cerebral-evoked potential responses following direct vagal and esophageal electrical stimulation in humans

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1993.264.3.g486 ◽

1993 ◽

Vol 264 (3) ◽

pp. G486-G491 ◽

Cited By ~ 10

Author(s):

G. Tougas ◽

P. Hudoba ◽

D. Fitzpatrick ◽

R. H. Hunt ◽

A. R. Upton

Keyword(s):

Electrical Stimulation ◽

Evoked Potential ◽

Vagal Stimulation ◽

Direct Electrical Stimulation ◽

Sensory Pathways ◽

Afferent Fibers ◽

Health And Disease ◽

Esophageal Sphincter ◽

Afferent Response ◽

Stimulation Of

Cerebral evoked responses following direct electrical stimulation of the vagus and esophagus were compared in 8 epileptic subjects and with those recorded after esophageal stimulation in 12 healthy nonepileptic controls. Direct vagal stimulation was performed using a left cervical vagal pacemaker, which is used in the treatment of epilepsy. Esophageal stimulation was obtained with the use of an esophageal assembly incorporating two electrodes positioned 5 and 20 cm orad to the lower esophageal sphincter. Evoked potential responses were recorded with the use of 20 scalp electrodes. The evoked potential responses consisted of three distinct negative peaks and were similar with the use of either vagal or esophageal stimulation. The measured conduction velocity of the afferent response was 7.5 m/s in epileptic subjects and 10 m/s in healthy controls, suggesting that afferent conduction is through A delta-fibers rather than slower C afferent fibers. We conclude that the cortical-evoked potential responses following esophageal electrical stimulation are comparable to direct electrical stimulation of the vagus nerve and involve mostly A delta-fibers. This approach provides a method for the assessment of vagal afferent gastrointestinal sensory pathways in health and disease.

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Spinal and pudendal nerve modulation of human corticoanal motor pathways

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1998.274.2.g419 ◽

1998 ◽

Vol 274 (2) ◽

pp. G419-G423 ◽

Cited By ~ 3

Author(s):

Shaheen Hamdy ◽

Paul Enck ◽

Qasim Aziz ◽

John C. Rothwell ◽

Samet Uengoergil ◽

...

Keyword(s):

Anal Sphincter ◽

Nerve Stimulation ◽

External Anal Sphincter ◽

Neural Control ◽

Pudendal Nerve ◽

Cortical Stimulation ◽

Evoked Responses ◽

Pudendal Nerve Stimulation ◽

Sphincter Function ◽

Sensorimotor Interactions

We investigated the effects of lumbosacral and pudendal nerve stimulation on the corticofugal pathways to the human external anal sphincter. In 11 healthy subjects, anal sphincter electromyographic responses, evoked to transcranial magnetic stimulation of the motor cortex, were recorded 5–500 ms after lumbosacral root or pudendal nerve stimulation. Lumbosacral and pudendal nerve stimulation alone evoked responses with amplitudes of 293 ± 73 and 401 ± 153 μV and latencies of 3.2 ± 0.2 and 2.2 ± 0.2 ms, respectively. Cortical stimulation also evoked responses with amplitudes of 351 ± 104 μV and latencies of 20.9 ± 1.1 ms. When lumbosacral or pudendal nerve stimulation preceded cortical stimulation, the cortically evoked responses were facilitated ( P < 0.01), with the effect appearing greatest at 5–20 ms after both lumbosacral and pudendal excitation and at 50–100 ms after lumbosacral excitation alone. Our results demonstrate that cortical pathways to the external anal sphincter are facilitated by prior lumbosacral and pudendal nerve stimulation, indicating that sensorimotor interactions are important in the central neural control of sphincter function.

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