Sorayouth Chumnanvej

Linear model of peripheral nerve after surgical manipulation: Preliminary report in animal study and model shift

Generally, the neurophysiologic intra-operative monitoring (NIOM) is acknowledged to correlate with reducing the risk of perioperative neurological deficits. This electrophysiological method is commonly used and neurosurgeons could aware where the nervous system is at risk of being permanently injured while doing the operation under NIOM. However, this monitoring is quite a qualitative evaluation. Neurosurgeons have to use their own experiences to consider and made the estimation. Traditionally, the peripheral nerve function can be preserved by continuous electromyography (EMG) and compound muscle action potential response (CMAP) monitoring. The spike and burst EMG occur when the nerve trunk is irritated or damaged. Decreased amplitude of CMAP response is also considered as nerve damage even it might cause from a severe irritation. By using this information, the peripheral nerve function is qualitatively evaluated by the surgeons. This present study proposed a new predictive nerve model for peripheral nerve function prediction. This input and output data were used for nerve modeling in each condition. The results showed that parameters of the linear nerve model had significantly differences and tendency changes in each nerve condition. Therefore, the proposed method for predicting the nerve function by the shifted linearly nerve model might be a promising approach for peripheral nerve function estimation in the human nerve model.

Electrical stimulation-based nerve location prediction for cranial nerve VII localization in acoustic neuroma surgery

Cranial nerve (CN) VII localization is a critical step during acoustic neuroma surgery because the nerve is generally hidden due to the tumor mass. The patient can suffer from Bells palsy if the nerve is accidentally damaged during tumor removal. Surgeons localize CN VII by exploring the target area with a stimulus probe. Compound muscle action potentials (CMAPs) are elicited when the probe locates the nerve. However, false positives and false negatives are possible due to unpredictable tissue impedance in the operative area. Moreover, a single CMAP amplitude is not correlated with probe‐to‐nerve distance.

Visualization of Needle-Tip Localization by Ultrasound Guidance with Contrast Bubble in Lumbar Selective Nerve Root Block: Clinical Pilot Study

BACKGROUND Epidural steroid injection for low back and leg pain has been shown to result in a positive clinical outcome. Lumbosacral selective nerve root block (SNRB) via a transforaminal approach is commonly performed under fluoroscopic guidance. However, ultrasound guidance is an alternative to overcome the radiologic disadvantages. This study examined the accuracy of needle-tip localization under ultrasound guidance with a contrast bubble, compared with fluoroscopic guidance. OBJECTIVE The primary objectives were to envisage the needle-tip localization with an air bubble by ultrasound and also to determine the accuracy of needle-tip location in transforaminal lumbar SNRB for low back and leg pain patients who were not surgical candidates. METHODS A prospective study of 30 SNRBs was conducted. An air bubble was produced and was used to envisage the needle-tip location under ultrasound guidance. Finally, the needle tip was confirmed by fluoroscopy. The accuracy of needle-tip location was statistically analyzed. RESULTS Twenty-four SNRBs were performed at L4-5 and 6 SNRBs at L3-4. The accuracy of needle-tip localization was 80%. CONCLUSION In order to avoid radiation exposure during the SNRB procedure, ultrasound guidance might be an alternative. Despite being accepted practice, there is a steep learning curve involved in the use of ultrasound guidance for lumbar SNRB, and proper training is crucial. A contrast bubble is a prospective enhancement for better visualization of ultrasound guidance.

Peripheral nerve function estimation by linear model of multi‐CMAP responses for surgical intervention in acoustic neuroma surgery

Nerve function assessments are crucial for surgical intervention during acoustic neuroma surgery. Cranial nerves such as acoustic and facial nerves, can be possibly damaged during tumor dissection. Proper surgical intervention should prevent neurological deficit and achieve total tumor removal. Conventionally, nerve function is qualitatively evaluated by surgeon and neurologist. Facial nerves can be preserved by monitoring the compound muscle action potential (CMAP) response. The differences in the amplitude and latency of CMAP are used as indicators during surgical interventions. However, baseline CMAPs cannot be recorded in the presence of large acoustic tumors. This paper presents a new way of estimating nerve function. Instead of a single CMAP examination, multi‐CMAP responses are obtained from a train of varied stimulus intensities and these are applied a mathematical model. Shifts in the mathematical model parameters reflect changes in facial nerve function. In this study, experiments conducted in frog revealed that shifts in the linear model parameters were related to the level of induced nerve injury. Significant differences in the slope parameter of the linear model were found between each nerve condition. The identification of healthy and severed nerves via a support vector machine (SVM) corresponded to 94% accuracy. This classification criterion could be used with surgical intervention to prevent severed facial nerve palsy in acoustic neuroma surgery. The proposed method could be used to estimate nerve outcomes without prior information of a CMAP baseline.

Physical and Mechanical Characterizations of Oxidized Regenerated Cellulose/Polycaprolactone Composite for Use as a Synthetic Dura Mater

An inadequate dural closure is one of the most challenging problems for neurosurgeons during the surgical procedures. A repair of the dura mater by natural or synthetic materials is often needed. This should satisfy fundamental criteria for example preventing cerebrospinal fluid leakage, exhibiting similar mechanical properties to the natural dura mater and not inducing foreign body reaction or inflammation. Oxidized regenerated cellulose (ORC) and polycaprolactone (PCL) have been extensively used as hemostatic agent and implant in many biomedical applications due to their long term proven safety, biodegradability and biocompatibility. This study investigated the potential of using a combination of ORC and PCL as a novel dural substitute. ORC/PCL composites were prepared by solution infiltration of ORC sheet with PCL solution (Mw ≈ 80,000) at various concentrations ranging 10-50 g/100 ml. Characterizations including density, tensile properties and microstructure were then performed. It was found that the density of all formulations did not differ and were in the range of 0.5-0.6 kg m-3. Microstructure of the samples typically comprised a bilayer structure having a PCL layer on one side and the ORC/PCL mixed layer on another side. Tensile modulus and strength initially decreased with increasing PCL concentration for up to 20% and re-increased again with further increasing PCL concentration. Elongation at break of all formulations was not significantly different. Both physical and mechanical properties of the samples were found to be similar to those of natural human dura mater.

ANN-based nerve damage preservation system for neurosurgical operation

The neurophysiologic intraoperative monitoring system (NIOM) is used for assessing the nerve function during operation. The free running electromyography (EMG) and the compound muscle action potential (CMAP) are monitored by the neurophysiologist for surgical intervention to avoid neurophysiologic deficit. However, there is a variation of surgical intervention in different neurophysiologist. 50% decrease in amplitude of CMAP response is considered as nerve damage compared with the baseline which may vary in particular case. These would make the nerve function estimation qualitative evaluated by neurophysiologist. This study aimed to investigate the quantitative method of nerve function prediction. Instead of applying one pulse stimulus, the varied current amplitude pulse train was applied to the nerve to obtain the variation of the CMAP responses. The varied CMAP responses were used as an input of artificial neuron network (ANN) for estimating the remaining nerve function. The results revealed that the estimated nerve damage level was linearly correlated with the measured nerve damage.

Peripheral Nerve Localization by Frequency-Based Electrical Stimulation

During surgery, the nervous system is at risk if surgeon could not localize nerve’s location. In case of tumor blocked, the surgeon can completely not visualize the nerve due to the tumor. Hence, nerve localization is very important during to operation. Generally, the neurophysiologic intra-operative monitoring (NIOM) has alarming feature, when the surgeon irritated the nerve, they could pre-localize the nerve. However, this alarming is quite sensitive since it sometime alarms even when the surgeon hints other area expected the nerve. This would makes the surgeon qualitative evaluates location of the nerve. This study proposed the new modality of nerve localization. The nature of compound muscle action potential (CMAP) was used in this study. Given a frequency-based electrical stimulation to a targeted area, the CMAP would response if and only if the stimulating electrode was placed directly to the nerve. The results from preliminary study in animal revealed that applying the stimulation at 30Hz and 0.3Volt with 1.5 millimeters width of a bipolar electrode gave highest CMAP detection accuracy (97.5%).