IONM in Cranial Surgery - Revision history

Wdoyon: /* Cranial nerve monitoring */

2022-01-18T17:17:24Z

Cranial nerve monitoring

← Older revision		Revision as of 12:17, 18 January 2022
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	==Cranial nerve monitoring==		==Cranial nerve monitoring==
	~~The cranial nerves are monitored with for a~~ variety of surgical procedures. ~~The modalities that are monitored~~ typically ~~include~~ spontaneous and triggered EMG ~~recordings~~ and motor evoked potentials.		A variety of surgical procedures require cranial nerve IONM. Cranial nerve monitoring typically includes recordings of spontaneous and triggered EMG activity and motor evoked potentials.

	1. The recurrent laryngeal nerve, a branch of the vagus nerve (CN X), is monitored for thyroidectomies. The recurrent laryngeal nerve, one of approximately 11 branches of CN X, innervates the intrinsic muscles of the larynx. This nerve is monitored using an endotracheal tube that is lined with recording electrodes.		1. The recurrent laryngeal nerve, a branch of the vagus nerve (CN X), is monitored for thyroidectomies. The recurrent laryngeal nerve, one of approximately 11 branches of CN X, innervates the intrinsic muscles of the larynx. This nerve is monitored using an endotracheal tube that is lined with recording electrodes.

Wdoyon: /* Cortical mapping */

2021-12-16T03:05:11Z

Cortical mapping

← Older revision		Revision as of 22:05, 15 December 2021
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	==Cortical mapping==		==Cortical mapping==
	The resection of tumors located within or near the eloquent cortex can result in postoperative sensory, motor and language deficits. Cortical brain mapping techniques have been used for many years to help the neurosurgeon identify and avoid these important brain structures. For tumors that impact the primary motor cortex, the main concern includes loss of motor ~~functions~~ in the contralateral face and upper and lower extremities. Two techniques have been developed for intraoperative cortical and subcortical mapping of the corticospinal tracts - the Penfield and Taniguchi techniques. Sufficient stimulation of the motor cortex along the homunculus elicits compound muscle action potentials in lower motor neurons that innervate contralateral muscle tissue. Electromyography is used to record these electrical responses. The Penfield technique uses low frequency stimulation. The current is delivered between the two points of the probe with trains of monophasic cathodal pulses. In contrast, the Taniguchi technique uses high frequency stimulation. The current is delivered between the probe and ~~a reference~~ electrode placed on the skull close to the motor strip with trains of monophasic anodal pulses. In either case, it is essential to determine the motor response threshold - the lowest intensity required to elicit a motor response in muscle tissue. Determination of the motor response threshold provides information on (1) the level of excitation of the motor cortex and (2) the distance between the stimulation site and the motor cortex.		The resection of tumors located within or near the eloquent cortex can result in postoperative sensory, motor and language deficits. Cortical brain mapping techniques have been used for many years to help the neurosurgeon identify and avoid these important brain structures. For tumors that impact the primary motor cortex, the main concern includes loss of motor function in the contralateral face and upper and lower extremities. Two techniques have been developed for intraoperative cortical and subcortical mapping of the corticospinal tracts - the Penfield and Taniguchi techniques. Sufficient stimulation of the motor cortex along the homunculus elicits compound muscle action potentials in lower motor neurons that innervate contralateral muscle tissue. Electromyography is used to record these electrical responses. The Penfield technique uses low frequency/long duration stimulation. The current is delivered between the two points of the probe with trains of monophasic cathodal pulses. In contrast, the Taniguchi technique uses high frequency/short duration stimulation. The current is delivered between the probe and an electrode placed on the skull close to the motor strip with trains of monophasic anodal pulses. In either case, it is essential to determine the motor response threshold - the lowest intensity required to elicit a motor response in muscle tissue. Determination of the motor response threshold provides information on (1) the level of excitation of the motor cortex and (2) the distance between the stimulation site and the motor cortex.

	The following are stimulation parameters and information for the Penfield and Taniguchi techniques:		The following are stimulation parameters and information for the Penfield and Taniguchi techniques:

Wdoyon: /* Subcortical mapping */

2021-09-06T03:42:02Z

Subcortical mapping

← Older revision		Revision as of 22:42, 5 September 2021
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	==Subcortical mapping==		==Subcortical mapping==
	Subcortical mapping is used for tumors that are located within or near the descending subcortical motor pathways. A monopolar stimulating electrode is used to determine the motor threshold, indicating the relative distance from the electrode tip to the motor pathways. Every 1 mA change is approximately 1 mm distance change from the motor pathways. It is recommended that the surgeon not proceed further if a motor threshold of 7 mA is reached. ~~Resection past this point~~ may result in postoperative motor deficits.		Subcortical mapping is used for tumors that are located within or near the descending subcortical motor pathways. A monopolar stimulating electrode is used to determine the motor threshold, indicating the relative distance from the electrode tip to the motor pathways. Every 1 mA change is approximately 1 mm distance change from the motor pathways. It is recommended that the surgeon not proceed further if a motor threshold of 7 mA is reached. Continued resection may result in postoperative motor deficits.

	The following are stimulation parameters and information for subcortical mapping:		The following are stimulation parameters and information for subcortical mapping:

Wdoyon: /* Subcortical mapping */

2021-09-06T03:40:36Z

Subcortical mapping

← Older revision		Revision as of 22:40, 5 September 2021
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	The following are stimulation parameters and information for subcortical mapping:		The following are stimulation parameters and information for subcortical mapping:
	Intensity: 2-20 mA, Stimulation type: monopolar cathodal stimulation, pulse duration: 0.5-1.0 ms, Frequency: 250-500 Hz, Pulse number: 4-5, Interstimulus interval: 3-4 ms.		(1) Intensity: 2-20 mA (2) Stimulation type: monopolar cathodal stimulation (3) pulse duration: 0.5-1.0 ms (4) Frequency: 250-500 Hz (5) Pulse number: 4-5 (6) Interstimulus interval: 3-4 ms.

	Monopolar cathodal stimulation has been shown to be more effective than bipolar stimulation for eliciting subcortical MEPs (Szelenyi et al., 2011).		Monopolar cathodal stimulation has been shown to be more effective than bipolar stimulation for eliciting subcortical MEPs (Szelenyi et al., 2011).

Wdoyon: /* Subcortical mapping */

2021-09-06T03:39:30Z

Subcortical mapping

← Older revision		Revision as of 22:39, 5 September 2021
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	Subcortical mapping is used for tumors that are located within or near the descending subcortical motor pathways. A monopolar stimulating electrode is used to determine the motor threshold, indicating the relative distance from the electrode tip to the motor pathways. Every 1 mA change is approximately 1 mm distance change from the motor pathways. It is recommended that the surgeon not proceed further if a motor threshold of 7 mA is reached. Resection past this point may result in postoperative motor deficits.		Subcortical mapping is used for tumors that are located within or near the descending subcortical motor pathways. A monopolar stimulating electrode is used to determine the motor threshold, indicating the relative distance from the electrode tip to the motor pathways. Every 1 mA change is approximately 1 mm distance change from the motor pathways. It is recommended that the surgeon not proceed further if a motor threshold of 7 mA is reached. Resection past this point may result in postoperative motor deficits.

	Stimulation ~~parameters~~:		The following are stimulation parameters and information for subcortical mapping:
	Monopolar cathodal stimulation is more effective than		Intensity: 2-20 mA, Stimulation type: monopolar cathodal stimulation, pulse duration: 0.5-1.0 ms, Frequency: 250-500 Hz, Pulse number: 4-5, Interstimulus interval: 3-4 ms.

			Monopolar cathodal stimulation has been shown to be more effective than bipolar stimulation for eliciting subcortical MEPs (Szelenyi et al., 2011).

	==Skull base or CP angle tumors==		==Skull base or CP angle tumors==

Wdoyon: /* Subcortical mapping */

2021-09-06T03:33:50Z

Subcortical mapping

← Older revision		Revision as of 22:33, 5 September 2021
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	==Subcortical mapping==		==Subcortical mapping==
	Subcortical mapping is used for tumors that are located within or near the descending subcortical motor pathways.		Subcortical mapping is used for tumors that are located within or near the descending subcortical motor pathways. A monopolar stimulating electrode is used to determine the motor threshold, indicating the relative distance from the electrode tip to the motor pathways. Every 1 mA change is approximately 1 mm distance change from the motor pathways. It is recommended that the surgeon not proceed further if a motor threshold of 7 mA is reached. Resection past this point may result in postoperative motor deficits.

			Stimulation parameters:
			Monopolar cathodal stimulation is more effective than

	==Skull base or CP angle tumors==		==Skull base or CP angle tumors==

Wdoyon: /* Subcortical mapping */

2021-09-06T01:19:49Z

Subcortical mapping

← Older revision		Revision as of 20:19, 5 September 2021
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	==Subcortical mapping==		==Subcortical mapping==
	~~Some~~ tumors are ~~Subcortical mapping~~		Subcortical mapping is used for tumors that are located within or near the descending subcortical motor pathways.

	==Skull base or CP angle tumors==		==Skull base or CP angle tumors==

Wdoyon at 00:24, 6 September 2021

2021-09-06T00:24:25Z

← Older revision		Revision as of 19:24, 5 September 2021
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	Alternatively, some have suggested using a bipolar probe with the Taniguchi technique to increase the spatial resolution of stimulation. This method may be useful for cases involving the primary motor cortex or supplementary motor cortex (Rossi et al., 2021).		Alternatively, some have suggested using a bipolar probe with the Taniguchi technique to increase the spatial resolution of stimulation. This method may be useful for cases involving the primary motor cortex or supplementary motor cortex (Rossi et al., 2021).

			==Subcortical mapping==
			Some tumors are Subcortical mapping

	==Skull base or CP angle tumors==		==Skull base or CP angle tumors==

Wdoyon: /* Cortical mapping */

2021-08-21T03:19:21Z

Cortical mapping

← Older revision		Revision as of 22:19, 20 August 2021
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	(7) Duration: 20 microsec		(7) Duration: 20 microsec

	Some difficult cases may require adjustment of these parameters, such as increasing the number of pulses to 7-9 or increasing the pulse up to 800 ms).		Some difficult cases may require adjustment of these parameters, such as increasing the number of pulses to 7-9 or increasing the pulse width up to 800 microsec).

	Alternatively, some have suggested using a bipolar probe with the Taniguchi technique to increase the spatial resolution of stimulation. This method may be useful for cases involving the primary motor cortex or supplementary motor cortex (Rossi et al., 2021).		Alternatively, some have suggested using a bipolar probe with the Taniguchi technique to increase the spatial resolution of stimulation. This method may be useful for cases involving the primary motor cortex or supplementary motor cortex (Rossi et al., 2021).

Wdoyon: /* Cortical mapping */

2021-08-21T03:17:46Z

Cortical mapping

← Older revision		Revision as of 22:17, 20 August 2021
Line 25:		Line 25:
	(3) Frequency: 250-500 Hz		(3) Frequency: 250-500 Hz
	(4) Pulse width: 500 microsec		(4) Pulse width: 500 microsec
	(5) Pulse number 5-9		(5) Pulse number 5
	(6) Intensity: 2-20 mA		(6) Intensity: 2-20 mA
	(7) Duration: 20 microsec		(7) Duration: 20 microsec

			Some difficult cases may require adjustment of these parameters, such as increasing the number of pulses to 7-9 or increasing the pulse up to 800 ms).

	Alternatively, some have suggested using a bipolar probe with the Taniguchi technique to increase the spatial resolution of stimulation. This method may be useful for cases involving the primary motor cortex or supplementary motor cortex (Rossi et al., 2021).		Alternatively, some have suggested using a bipolar probe with the Taniguchi technique to increase the spatial resolution of stimulation. This method may be useful for cases involving the primary motor cortex or supplementary motor cortex (Rossi et al., 2021).