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IOM basics 2
Interoperative monitoring basics 2
| Question | Answer |
|---|---|
| In addition to mechanical irritation, two other potential sources for intense intra-op EMG activity | temperature, osmotic irritation |
| The degree of nerve / nerve root irritation correlates with MUP __ __ | firing rate |
| Asynchronous high rate trains of MUP are referred to as the __ __ | interference pattern |
| The shape of MUPs are largely determined by these factors | distance and orientation of MUPs |
| Monophasic MUPs are most likely __ (proximal/distal) to the recording electrode | distal |
| Removal of epineurium, perineurium and +/- myelin leads to __ (increased/decreased) axonal depolarization in response to irritants | increased |
| Once an axonal is disrupted, it will cease to produce an MUP in responses to __ (proximal/distal) irritation | proximal |
| Sharp transection of an axon is usually associated with (high/low/no) amounts of EMG activity | no (may have initial burst followed by silence) |
| Nerve ischemia / compression results in __ (increased/decreased/variable) EMG activity | variable |
| Lumbar pedicle testing uses __ (bipolar/monopolar) stimulation | monopolar |
| Lumbar pedicle testing uses __ (anodal/cathodal) stimulation | cathodal |
| If the hole for a pedicle screw is tested and has a value of < 5 mA, perforation is __ | probable |
| If the hole for a pedicle screw is tested and has a value of 5-7 mA, perforation is __ | possible |
| If the hole for a lumbar pedicle screw is tested and has a value of > 7 mA, perforation is __ | unlikely |
| If the hole for a pedicle screw is tested and has a value of < __ mA, performation is probable | 5 |
| If the hole for a pedicle screw is tested and has a value of > __ mA, perforation is unlikely | 7 |
| If the current required to activate adjacent nerves for a pedicle screw is tested and has a value of < 7 mA, perforation is __ | probable |
| If the current required to activate adjacent nerves for a pedicle screw is tested and has a value of > 10 mA, perforation is __ | unlikely |
| If the current required to activate adjacent nerves for a pedicle screw is tested and has a value of 7-10 mA, perforation is __ | possible |
| If the current required to activate adjacent nerves for a pedicle screw is tested and has a value of __ mA, perforation is probable | < 7 |
| If the current required to activate adjacent nerves for a pedicle screw is tested and has a value of ___ mA, perforation is unlikely | > 10 |
| When stimulating the "hole" for a lumbar pedicle surgery, you stimulate using a balled tipped electrode as the __ (cathode/anode) | cathode |
| In IOM with SEPs, global cortical loss with intact cortical signal suggests this | Anesthetic effect |
| In IOMs with SEPs, unilateral cortical loss with intact subcortical signals suggests this | Cerebral ischemia (for carotid surgery) |
| In IOMs, with SEPs, unilateral loss of Erb's point, subcortical and cortical signals suggests this | Limb malpositioning |
| In IOM with SEPs, loss of subcortical and cortical signals with Erb's point intact suggests this | Spinal cord dysfunction |
| The generator for N9 | Brachial plexus |
| The generator for N11 | Spinal nerve root |
| The generator for N13a | Dorsal horn interneurons |
| The generator for N13b | Dorsal column |
| The generator for P13 | Spinomedullary junction |
| The generator for P14 | Lemniscal pathway, cuneate nucleus |
| The generator for N18 | Brainstem / thalamus |
| The generator for N19 | Primary sensory cortex |
| The generator for P22 | Primary motor cortex |
| Common chnnel used for N9 | Epi-Epc |
| Common channel used for N11 | Crv-Fpz |
| Common channel used for N13a | Crv6-Fpz |
| Common channel used for N13b | Crv2-Fpz |
| Common channel used for P13 | Crv-Fpz, Mast-Fpz |
| Common channel used for P14 | Crv-Fpz, Mast-Fpz |
| Common channel used for N18 | Ci-noncephalic |
| Common channel used for N19 | Cc-Fz, Cc-Ci |
| Common channel used for P22 | Cc-Fz, Cc-Ci |
| Generator for N23 | Dorsal horn interneurons |
| Typical channel for N23 | T12-illiac crest |
| Typical channel for P31 | Crv-Fpz, Mast-Fpz |
| Generator for P31 | Medulla |
| Generator for N34 | Primary sensory cortex |
| Channel for N34 | Cc-Fpz |
| Generator for P38 | Primary sensory cortex |
| Common channels for P38 | Ci-Fpz, Cz-Fpz, Ci-Cc, Cz-Cc |
| Generator for N38 | Primary sensory cortex |
| Common channel for N38 | Cc-Fpz |
| For most IOM, at least __ muscles are used below the level of the surgery and __ above the level of thet surgery | two, one |
| ___ responses are averaged MEP signals that may be obtained from the spinal cord white matter tracts using an electrode in the subdural or epidural space | D-waves |
| Transcranial activation of subcortical tracts with MEPs is elicited best with __ (anode/cathode) stimulation | anode |
| For most intraoperative MEP setups, the __ (anode/cathode) is placed over the area of brain to be stimulated (C1 or C2) and the __ (anode/cathode) is placed contralaterally | anode, cathode |
| MEPs are usually given in trains of __ - __ stimuli with an interstimulus interval of __ - __ msec | 4-9, 2-4 |
| For intraoperative monitoring, many individuals say that a signal is abnormal if there is a complete loss of signal or an abrupt __% decrease in amplitude | 80 |
| Gradual decreases in intraoperative MEP amplitude usually reflect metabolic changes or __ | anesthesia |
| The contraindications to the use of MEPs in intraoperative monitoring | brain DBS, cochlear implants, plegia, recent craniotomy / skull fracture |
| Agents with high MEP inhibiting potential | volatile anesthetics, nitrous oxide |
| Agents with moderate MEP inhibiting potential | benzodiazepines, propofol |
| Agents with little or no MEP inhibiting potential | ketamine, etomidate, narcotics |
| White noise is introduced in the contralateral nonstimulated ear at ~ this level | 60 dB nHl |
| Wave __ in the BAEP is negative | I |
| A __ (rarefaction/condensation) click produces enhancement of wave I | rarefaction |
| A loss of wave V amplitude of > __ is considered significant | 50% |
| A __ msec prolongation in wave V latency is considered significant | 0.5 |
| Abrupt loss of wave I during surgery most likely reflects this | compromise of the internal auditory artery |
Created by:
schmittse
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