Subcortical Motor Mapping Technique.

Introduction about subcortical mapping .

• Subcortical motor mapping is a technique used in neurosurgery to identify and preserve critical motor pathways located below the surface of the brain.

Stimulation Parameters of subcortical mapping .

• During subcortical motor mapping, train of pulse electrical stimulation is applied to the brain tissue to identify the location of motor pathways. The stimulation parameters include the frequency, intensity, and duration of the electrical pulses. These parameters are carefully selected to safely elicit motor responses without provoking seizure ,causing damage to the tissue or brain bulge.

To elicit Response while doing subcortical mapping.

• The response threshold refers to the minimum intensity of stimulation required to elicit a motor response. By gradually increasing the intensity of the electrical stimulation, surgeons can determine the near/on of the motor pathways and avoid damaging them during the surgical procedure.

Image of probe.

 Types of Mapping Techniques: 

• Subcortical motor mapping can be performed using various techniques, including direct cortical stimulation, subcortical stimulation via monopolar probe /suction monopolar electrodes can be continuously used while decompressing deeply seated brain tumors .

suction monopolar probe.

Motor Mapping Parameter 

• A train of pulse standardized motor mapping parameter is followed during the surgical procedure to ensure consistent and reliable results. This parameter includes mapping specific motor functions, such as electromyogram though needle electrode from different portion of the body like face ,hand, leg muscles .

EMG responses while near to functional fibers.

• Short  train with five  biphasic pulses with Inerstimulus  interval (ISI) at 2-3 or 3-4 millisecond and 500 microsecond pulse width .  Intensity of current can be  start from 10-12 milliampere  and stop  up to 6-5 milliamps  , Benefit of especially this train of five pulses parameter does not provoke seizure.

Picture of pulses.

Conclusion.

Real-time monitoring of motor responses is essential during subcortical motor mapping to guide the surgical decision-making process, intensity of current will also vary on grading of tumors like high grade glioma above parameter will allow up to 6 milliampere if any signal comes with low intensity of current those tissue has to preserve otherwise patient can reveal with new motor weakness.

Low grade glioma up to 5 milliampere of current accepted if patient reveal with new motor weakness this symptoms will be resolve within couple of days or weeks .

{Note – Quality of patient life is very important which should be our concern}.

Related this article..

Subcortical motor mapping in deep structure pathology.

https://neurointraoperative.com/wp-admin/post.php?post=21&action=edit

https://www.sciencedirect.com/science/article/pii/B9780128150009000095

Question.

• What exactly does subcortical motor mapping?.

• If tumor left side should we monitor same side?.

• What is train of pulse technique?.

• While stimulating seizure can occur?.

• What is the role of cold saline?.