Name: screening of axonal degeneration in carpal tunnel syndrome using ultrasonography and nerve conduction studies
Uploaded: 2019-01-11T14:30:00
Description: Watch this Scientific Journal Video about Screening of Axonal Degeneration in Carpal Tunnel Syndrome Using Ultrasonography and Nerve Conduction Studies at JoVE.com

Mr. Xue Deng, Dr. Yong Hu, and Dr. Ip Wing-Yuk were dedicated to the concept of the study design, subject recruitment, and draft and revision of the manuscript. Ms. Lai-Heung Phoebe Chau and Ms. Suk-Yee Chiu were dedicated to subject liaison, data collection, and the manipulation of NCS. Dr. Kwok-Pui Leung was dedicated to the electrophysiological diagnosis, clinical guidance, and the manipulation of the ultrasounds.

All the procedures have been approved by the University of Hong Kong/Hospital authorities Hong Kong West Institutional Review Board (HKU/HA HKW IRB, Ref. Number: UW17-129).
This protocol is applicable to patients who demonstrated clinical symptoms such as numbness, tingling, or pain over the median nerve-innervated area of the hand, with a positive outcome in Tinel&#39;s sign and Phalen&#39;s test. Those subjects with comorbidities, such as diabetes mellitus, cancer, rheumatoid arthritis, and ...

<ol>
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S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sonographic+cross-sectional+area+measurement+in+carpal+tunnel+syndrome+patients:+can+delta+and+ratio+calculations+predict+severity+compared+to+nerve+conduction+studies.">Sonographic cross-sectional area measurement in carpal tunnel syndrome patients: can delta and ratio calculations predict severity compared to nerve conduction studies.</a> European Radiology. 25 (8), 2419-2427 (2015).</li><li>Deng, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exploratory+use+of+ultrasound+to+determine+whether+demyelination+following+carpal+tunnel+syndrome+co-exists+with+axonal+degeneration.">Exploratory use of ultrasound to determine whether demyelination following carpal tunnel syndrome co-exists with axonal degeneration.</a> Neural Regeneration Research. 13 (2), 317-323 (2018).</li><li>Moon, H. I., Kwon, H. K., Lee, A., Lee, S. K., Pyun, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sonography+of+Carpal+Tunnel+Syndrome+According+to+Pathophysiologic+Type:+Conduction+Block+Versus+Axonal+Degeneration.">Sonography of Carpal Tunnel Syndrome According to Pathophysiologic Type: Conduction Block Versus Axonal Degeneration.</a> Journal of Ultrasound in Medicine. 36 (5), 993-998 (2017).</li><li>Razek, A. A. K. A., Shabana, A. A. E., El Saied, T. O., Alrefey, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffusion+tensor+imaging+of+mild-moderate+carpal+tunnel+syndrome-+correlation+with+nerve+conduction+study+and+clinical+tests.">Diffusion tensor imaging of mild-moderate carpal tunnel syndrome- correlation with nerve conduction study and clinical tests.</a> Clinical Rheumatology. 36 (10), 2319-2324 (2017).</li><li>Weber, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conduction+block+and+abnormal+temporal+dispersion--diagnostic+criteria.">Conduction block and abnormal temporal dispersion--diagnostic criteria.</a> Electroencephalography and Clinical Neurophysiology. 37 (5), 305-309 (1997).</li><li>Kiernan, C. M., Mogyoros, I., Burke, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conduction+block+in+carpal+tunnel+syndrome.">Conduction block in carpal tunnel syndrome.</a> Brain. 122 (5), 933-941 (1999).</li><li>Fong, S. Y., Goh, K. J., Shahrizaila, N., Wong, K. T., Tan, C. 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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Discriminatory+sonographic+criteria+for+the+diagnosis+of+carpal+tunnel+syndrome.">Discriminatory sonographic criteria for the diagnosis of carpal tunnel syndrome.</a> Arthritis &amp; Rheumatology. 46 (7), 1914-1921 (2002).</li><li>Mondelli, M., Filippou, G., Gallo, A., Frediani, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnostic+utility+of+ultrasonography+versus.+nerve+conduction+studies+in+mild+carpal+tunnel+syndrome.">Diagnostic utility of ultrasonography versus. nerve conduction studies in mild carpal tunnel syndrome.</a> Arthritis &amp; Rheumatology. 59 (3), 357-366 (2008).</li><li>Wong, S. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carpal+tunnel+syndrome:+diagnostic+usefulness+of+sonography.">Carpal tunnel syndrome: diagnostic usefulness of sonography.</a> Radiology. 232 (1), 93-99 (2004).</li><li>Baiee, R. H., AL-Mukhtar, N. J., Al-Rubiae, S. J., Hammoodi, Z. H., Abass, F. 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It is challenging to set up a universal standard for the measurement of NCS due to the influence of demographic and physical factors such as age, gender, ethnicities, and body weight, etc.14. Regarding SNAP amplitude,&#160;there is a difference between the orthodromic (the direction of currency runs proximally toward the body) and antidromic (the direction of currency runs distally away from the body) technique, as the SNAP amplitude measured by the orthodromic method is smaller than the ...

CTS is pathologically&#160;a disorder with segmental demyelination, whereas secondary axonal degeneration, which is indicative of surgical decompression, may coexist as the disease progresses1. However, the current diagnostic and severity gradation scale (from mild to very severe grade) for CTS cannot clearly indicate any coexistence of axonal degeneration, resulting in confusion when choosing the appropriate treatment. Conventional methods for confirming axonal degeneration, such as needle EMG and nerve biopsy, can be sensitive and accurate, but they are both restricted in the clinical practice due to their invasiveness2.
To overcome these shortcomings, ultrasound has been introduced for assisting&#160;diagnosing3,4,5 and grading of the severity of CTS6,7,8. Also, previous study successfully identified its cut-off values for discriminating axonal degeneration associated with CTS, with overall satisfactory sensitivity and specificity9. This study aims at introducing this efficient and noninvasive protocol to the practice in the clinical context. The rationale of this protocol is to combine the neurophysiological and structural information provided by NCS and ultrasounds to indicate the pathological progress1,10. It is assumed to be more accurate to describe the pathological progress than the current severity gradation system, helping clinicians to better figure out a plan of care. Compared to other conventional neuroimaging techniques such as diffusion tensor imaging (DTI), this evidence-based approach can&#160;be more easily applied in clinical settings&#160;with lower costs11.

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screening of axonal degeneration in carpal tunnel syndrome using ultrasonography and nerve conduction studies

Axonal degeneration, indicative of surgical decompression, may coexist in carpal tunnel syndrome (CTS) as the disease progresses. However, the current diagnostic and severity gradation system cannot clearly indicate its coexistence, resulting in&#160;confusion of appropriate treatment prescription. There are also constraints in conventional methods for&#160;differentiation as well. This study aims at introducing an innovative, efficient, and quick screening protocol to differentiate axonal degeneration associated with CTS, using ultrasound and nerve conduction studies (NCS). It starts by using NCS to perform orthodromic stimulation at the wrist, to obtain the sensory conduction of the median and the ulnar nerves respectively. Meanwhile, the motor conduction&#160;of the median nerve is collected by stimulating the palm, wrist, and elbow, followed by the stimulation of the ulnar nerve at the wrist,&#160;below and above the elbow. Then, an ultrasound assessment is performed, using a linear array transducer, with cross-sectional area (CSA) and perimeter (P) at the wrist and at the one-third distal forearm calipered. Ratios (R-CSA, R-P) and changes from wrist to one-third distal forearm (&#916;CSA and &#916;P) are calculated according to a standard format. Potential axonal degeneration coexisting in CTS will be screened according to the criteria of NCS and cut-off values of ultrasound measurements established in a previous study. In terms of its noninvasiveness, low cost, convenience, and efficiency, it is easy to apply ultrasound complimentarily in clinical practice to prescreen patients with potential coexisting axonal degeneration. Nevertheless, the ultrasonographic imaging cannot directly reflect axonal degeneration. It still relies on conventional but invasive methods&#160;such as electromyography (EMG) and biopsy&#160;for confirmation if needed.

As was described in Table 1, associated axonal degeneration has been&#160;primarily screened out should the subject fulfill the criteria of NCS as follows: (1) the sensory conduction velocity of the median nerve is less than 42m/s and/or (2) the distal sensory latency is more than 4.6 ms or the distal motor latency is more than 3.2 ms; (3) the SNAP amplitude at the wrist is less than 10 &#181;V with the CMAP amplitude drop being no more than 20%. Those with temporal dispe...

Watch this Scientific Journal Video about Screening of Axonal Degeneration in Carpal Tunnel Syndrome Using Ultrasonography and Nerve Conduction Studies at JoVE.com

Screening of Axonal Degeneration in Carpal Tunnel Syndrome Using Ultrasonography and Nerve Conduction Studies

Here we present a protocol using nerve conduction studies and ultrasound to screen potential axonal degeneration associated with carpal tunnel syndrome. The criteria for differentiation are established. Compared to conventional approaches, this method is noninvasive, convenient, and efficient, with an overall satisfactory accuracy, sensitivity, and specificity.

Axonal degeneration, indicative of surgical decompression, may coexist in carpal tunnel syndrome (CTS) as the disease progresses. However, the current ...

This non invasive approach using nerve conduction studies and ultrasound is used to specifically and sensitively assess the axonal degeneration in carpal tunnel syndrome patients. This method can be used by clinicians to directly assess the pathological stage of the disease, and can be easily applied for better treatment region planning. Demonstrating the procedure will be Phoebe Chau, an enrolled nurse, and Kwok-Pui Leung, a physician, both from my laboratory.To measure the conduction in the median sensory nerve, first have the patient wash their hands with warm water. After drying, place the recording ring electrode at the proximal interphalangeal joint, and the reference ring electrode over the distal interphalangeal joint. Place the other recording electrodes at the wrist, between the tendons of the flexor carpal radialis, and the palmaris longus.12cm proximal to the recording ring electrode, and ideally proximal to the distal wrist crease. After making sure that the ground electrode is between the stimulation and recording sites, apply super maximal stimulus 10 times to the median nerve via the attached electrodes over the index finger. To measure the conduction in the ulnar sensory nerve, place the recording ring electrode halfway on the proximal phalanx of the 5th digit, and the reference ring electrode 4cm distal to the recording ring electrode.Place the other recording electrodes near the tendon of the flexor carpi ulnaris, 12cm proximal to the recording ring electrode, making sure the ground electrode is between the stimulation and recording sites. Then apply a super maximal stimulus 10 times to the ulnar nerve via attached electrodes over the 5th finger. To measure the conduction in the median motor nerve, place the recording ring's electrode in the most prominent eminence of the thenar area at the motor point of the abductor pollicis brevis, and place the reference ring electrode on the proximal phalanx of the thumb.Then use an electronic stimulator to stimulate at the mid-palm, three to four centimeters distal to the distal wrist crease, and 6.5 centimeters proximal to the recording ring electrode at the wrist, between the tendons of the flexor carpi radialis and the palmaris longus. In the medial aspect of the antecubital space of the elbow, just lateral to the brachial artery. To measure the conduction in the ulnar motor nerve, place the recording ring electrode over the belly of the abductor digiti minimi.The reference ring electrode to the distal phalanx of the 5th digit, and the ground electrode, between the stimulation and the recording sites. Then stimulate at the wrist, 7cm proximal to the recording ring electrode, just lateral or medial to the flexor carpi radialis tendon. Below and above the elbow, 5cm distal and proximal to the ulnar groove.For ultrasound measurements, seat the patient on a plinth with their hands resting in a horizontal supination position, and the fingers semi extended. Place some ultrasound gel over the probe of the transducer, the wrist site, and the distal 1/3 forearm. Next, use a 13 to 14 megahertz linear array transducer to perform a transverse scan at the inlet of the carpal tunnel.Freeze the real time imaging and continuously caliper the hyperechoic epineurium of the median nerve at the inlet of the carpal tunnel. Then scan proximally along the innervated area of the median nerve to the site of the 1/3 distal forearm. Freeze the real time imaging, and caliper the hyperechoic epineurium of the median nerve at the 1/3 distal forearm.After screening for associated axonal degeneration, those patients with any ultrasound parameter values above the corresponding cutoff values are considered as suffering from the potential coexistence of axonal degeneration. Alternatively, the ultrasound readings can be considered as indicators of potential axonal degeneration, should the subject not fulfill the nerve conduction studies criteria. For example, in this representative study, significant differences were found between patients with demyelination and associated axonal degeneration, indicating that this protocol can be an effective tool in screening axonal degeneration associated with carpal tunnel syndrome.Further, in this group of patients who did not fulfill the nerve conduction criteria and were enrolled with ultrasound measurements generated descriptively, the ultrasound measurement data suggested that all of these patients were potentially associated with coexisting axonal degeneration based on their ultrasound measurements alone. In nerve conduction study, sanitized chemical procedure, and side-to-side comparisons are both important as they can increase the reliability of the assessment. Although the tomography is the gold standard for confirming axonal degeneration, further validation study can be used to evaluate the reliability and validity between the tomography and our assessment package.During the ultrasound assessment, make sure the ultrasound parameters are consistent and select the appropriate frequency and probe size. This technique path is the way for researchers to explore innovative uses of ultrasound for diagnosing carpal tunnel syndrome, and may have the potential to be used for predicting treatment effectiveness.

screening-axonal-degeneration-carpal-tunnel-syndrome-using

Research

JoVE Journal

Neuroscience

Recording and Analysis of Circadian Rhythms in Running-wheel Activity in Rodents

When rodents have free access to a running wheel in their home cage, voluntary use of this wheel will depend on the time of day1-5. Nocturnal rodents, including rats, hamsters, and mice, are active during the night and relatively inactive during the day. Many other behavioral and physiological measures also exhibit daily rhythms, but in rodents, running-wheel activity serves as a particularly reliable and convenient measure of the output of the master circadian clock, the suprachiasmatic nucleus (SCN) of the hypothalamus. In general, through a process called entrainment, the daily pattern of running-wheel activity will naturally align with the environmental light-dark cycle (LD cycle; e.g. 12 hr-light:12 hr-dark). However circadian rhythms are endogenously generated patterns in behavior that exhibit a ~24 hr period, and persist in constant darkness. Thus, in the absence of an LD cycle, the recording and analysis of running-wheel activity can be used to determine the subjective time-of-day. Because these rhythms are directed by the circadian clock the subjective time-of-day is referred to as the circadian time (CT). In contrast, when an LD cycle is present, the time-of-day that is determined by the environmental LD cycle is called the zeitgeber time (ZT).
Although circadian rhythms in running-wheel activity are typically linked to the SCN clock6-8, circadian oscillators in many other regions of the brain and body9-14 could also be involved in the regulation of daily activity rhythms. For instance, daily rhythms in food-anticipatory activity do not require the SCN15,16 and instead, are correlated with changes in the activity of extra-SCN oscillators17-20. Thus, running-wheel activity recordings can provide important behavioral information not only about the output of the master SCN clock, but also on the activity of extra-SCN oscillators. Below we describe the equipment and methods used to record, analyze and display circadian locomotor activity rhythms in laboratory rodents.

Circadian rhythms in voluntary wheel-running activity in mammals are tightly coupled to the molecular oscillations of a master clock in the brain. As such, these daily rhythms in behavior can be used to study the influence of genetic, pharmacological, and environmental factors on the functioning of this circadian clock.

When rodents have free access to a running wheel in their home cage, voluntary use of this wheel will depend on the time of day1-5. Nocturnal rodents, ...

An Ex Vivo Laser-induced Spinal Cord Injury Model to Assess Mechanisms of Axonal Degeneration in Real-time

Injured CNS axons fail to regenerate and often retract away from the injury site. Axons spared from the initial injury may later undergo secondary axonal degeneration. Lack of growth cone formation, regeneration, and loss of additional myelinated axonal projections within the spinal cord greatly limits neurological recovery following injury. To assess how central myelinated axons of the spinal cord respond to injury, we developed an ex vivo living spinal cord model utilizing transgenic mice that express yellow fluorescent protein in axons and a focal and highly reproducible laser-induced spinal cord injury to document the fate of axons and myelin (lipophilic fluorescent dye Nile Red) over time using two-photon excitation time-lapse microscopy. Dynamic processes such as acute axonal injury, axonal retraction, and myelin degeneration are best studied in real-time. However, the non-focal nature of contusion-based injuries and movement artifacts encountered during in vivo spinal cord imaging make differentiating primary and secondary axonal injury responses using high resolution microscopy challenging. The ex vivo spinal cord model described here mimics several aspects of clinically relevant contusion/compression-induced axonal pathologies including axonal swelling, spheroid formation, axonal transection, and peri-axonal swelling providing a useful model to study these dynamic processes in real-time. Major advantages of this model are excellent spatiotemporal resolution that allows differentiation between the primary insult that directly injures axons and secondary injury mechanisms; controlled infusion of reagents directly to the perfusate bathing the cord; precise alterations of the environmental milieu (e.g., calcium, sodium ions, known contributors to axonal injury, but near impossible to manipulate in vivo); and murine models also offer an advantage as they provide an opportunity to visualize and manipulate genetically identified cell populations and subcellular structures. Here, we describe how to isolate and image the living spinal cord from mice to capture dynamics of acute axonal injury.

An Ex Vivo Laser-induced Spinal Cord Injury Model to Assess Mechanisms of Axonal Degeneration in Real-time

We present a protocol utilizing two-photon excitation time-lapse microscopy to simultaneously visualize the dynamics of axon and myelin injuries in real time. This proposed protocol permits studies of both intrinsic and extrinsic factors which can influence central myelinated axon fate after injury and contribute to permanent clinical disability.

Injured CNS axons fail to regenerate and often retract away from the injury site. Axons spared from the initial injury may later undergo secondary axonal ...

External Excitation of Neurons Using Electric and Magnetic Fields in One- and Two-dimensional Cultures

A neuron will fire an action potential when its membrane potential exceeds a certain threshold. In typical activity of the brain, this occurs as a result of chemical inputs to its synapses. However, neurons can also be excited by an imposed electric field. In particular, recent clinical applications activate neurons by creating an electric field externally. It is therefore of interest to investigate how the neuron responds to the external field and what causes the action potential. Fortunately, precise and controlled application of an external electric field is possible for embryonic neuronal cells that are excised, dissociated and grown in cultures. This allows the investigation of these questions in a highly reproducible system.
In this paper some of the techniques used for controlled application of external electric field on neuronal cultures are reviewed. The networks can be either one dimensional, i.e. patterned in linear forms or allowed to grow on the whole plane of the substrate, and thus two dimensional. Furthermore, the excitation can be created by the direct application of electric field via electrodes immersed in the fluid (bath electrodes) or by inducing the electric field using the remote creation of magnetic pulses.

Neuronal cultures are a good model for studying emerging brain stimulation techniques via their effect on single neurons or a population of neurons. Presented here are different methods for stimulation of patterned neuronal cultures by an electric field produced directly by bath electrodes or induced by a time-varying magnetic field.

A neuron will fire an action potential when its membrane potential exceeds a certain threshold. In typical activity of the brain, this occurs as a result ...

Modeling Neuronal Death and Degeneration in Mouse Primary Cerebellar Granule Neurons

Cerebellar granule neurons (CGNs) are a commonly used neuronal model, forming an abundant homogeneous population in the cerebellum. In light of their post-natal development, abundance, and accessibility, CGNs are an ideal model to study neuronal processes, including neuronal development, neuronal migration, and physiological neuronal activity stimulation. In addition, CGN cultures provide an excellent model for studying different modes of cell death including excitotoxicity and apoptosis. Within a week in culture, CGNs express N-methyl-D-aspartate (NMDA) receptors, a specific ionotropic glutamate receptor with many critical functions in neuronal health and disease. The addition of low concentrations of NMDA in conjunction with membrane depolarization to rodent primary CGN cultures has been used to model physiological neuronal activity stimulation while the addition of high concentrations of NMDA can be employed to model excitotoxic neuronal injury. Here, a method of isolation and culturing of CGNs from 6 day old pups as well as genetic manipulation of CGNs by adenoviruses and lentiviruses are described. We also present optimized protocols on how to stimulate NMDA-induced excitotoxicity, low-potassium-induced apoptosis, oxidative stress and DNA damage following transduction of these neurons.

This protocol describes a simple method for isolating and culturing primary mouse cerebral granule neurons (CGNs) from 6-7 day old pups, efficient transduction of CGNs for loss and gain of function studies, and modelling NMDA-induced neuronal excitotoxicity, low-potassium-induced cell death, DNA-damage, and oxidative stress using the same culture model.

Cerebellar granule neurons (CGNs) are a commonly used neuronal model, forming an abundant homogeneous population in the cerebellum. In light of their ...

In Vivo Electrophysiological Measurement of the Rat Ulnar Nerve with Axonal Excitability Testing

Electrophysiology enables the objective assessment of peripheral nerve function in vivo. Traditional nerve conduction measures such as amplitude and latency detect chronic axon loss and demyelination, respectively. Axonal excitability techniques &#34;by threshold tracking&#34; expand upon these measures by providing information regarding the activity of ion channels, pumps and exchangers that relate to acute function and may precede degenerative events. As such, the use of axonal excitability in animal models of neurological disorders may provide a useful in vivo measure to assess novel therapeutic interventions. Here we describe an experimental setup for multiple measures of motor axonal excitability techniques in the rat ulnar nerve.
The animals are anesthetized with isoflurane and carefully monitored to ensure constant and adequate depth of anesthesia. Body temperature, respiration rate, heart rate and saturation of oxygen in the blood are continuously monitored. Axonal excitability studies are performed using percutaneous stimulation of the ulnar nerve and recording from the hypothenar muscles of the forelimb paw. With correct electrode placement, a clear compound muscle action potential that increases in amplitude with increasing stimulus intensity is recorded. An automated program is then utilized to deliver a series of electrical pulses which generate 5 specific excitability measures in the following sequence: stimulus response behavior, strength duration time constant, threshold electrotonus, current-threshold relationship and the recovery cycle.
Data presented here indicate that these measures are repeatable and show similarity between left and right ulnar nerves when assessed on the same day. A limitation of these techniques in this setting is the effect of dose and time under anesthesia. Careful monitoring and recording of these variables should be undertaken for consideration at the time of analysis.

In Vivo Electrophysiological Measurement of the Rat Ulnar Nerve with Axonal Excitability Testing

Axonal excitability techniques provide a powerful tool to examine pathophysiology and biophysical changes that precede irreversible degenerative events. This manuscript demonstrates the use of these techniques on the ulnar nerve of anesthetized rats.

Electrophysiology enables the objective assessment of peripheral nerve function in vivo. Traditional nerve conduction measures such as amplitude and ...

Partial Optic Nerve Transection in Rats: A Model Established with a New Operative Approach to Assess Secondary Degeneration of Retinal Ganglion Cells

Previous studies have shown that the secondary degeneration of retinal ganglion cells (RGCs) occurs commonly in glaucoma. Partial optic nerve transection is considered a useful and reproducible model. Compared with other optic nerve injury models used commonly for assessing secondary degeneration, e.g. complete optic nerve transection and optic nerve crush models, the partial optic nerve transection model is superior as it distinguishes primary from secondary degeneration in situ. Therefore, it serves as an excellent tool for evaluating secondary degeneration. This study describes a novel operative approach of partial optic nerve transection by directly accessing the area of the retrobulbar optic nerve through the orbital lateral wall of the eyeball. Moreover, we present a newly designed, low cost surgical instrument to assist with transection. As demonstrated by the representative results in distinguishing the boundary of primary and secondary injury areas, the new approach and instrument ensures high efficiency and stability of the model by providing adequate space for surgical operation. This in turn makes it easy to separate the meningeal sheath and ophthalmic vessels from the optic nerve before transection. An additional benefit is that this space-saving operative approach improves the investigators&#39; ability to administer drugs, carriers, or selective RGC tracers to the stump of the partially transected optic nerve, allowing the exploration of mechanisms behind secondary injury in RGCs, in a new way.

Secondary degeneration of retinal ganglion cells (RGCs) occurs commonly in glaucoma. This study describes an innovative operative approach for partial optic nerve transection. The use of this space-saving operative approach extends the model's application range, and allows exploration of secondary injury mechanisms in RGCs in a new way.

Previous studies have shown that the secondary degeneration of retinal ganglion cells (RGCs) occurs commonly in glaucoma. Partial optic nerve transection ...

Ablation of a Neuronal Population Using a Two-photon Laser and Its Assessment Using Calcium Imaging and Behavioral Recording in Zebrafish Larvae

To identify the role of a subpopulation of neurons in behavior, it is essential to test the consequences of blocking its activity in living animals. Laser ablation of neurons is an effective method for this purpose when neurons are selectively labeled with fluorescent probes. In the present study, protocols for laser ablating a subpopulation of neurons using a two-photon microscope and testing of its functional and behavioral consequences are described. In this study, prey capture behavior in zebrafish larvae is used as a study model. The pretecto-hypothalamic circuit is known to underlie this visually-driven prey catching behavior. Zebrafish pretectum were laser-ablated, and neuronal activity in the inferior lobe of the hypothalamus (ILH; the target of the pretectal projection) was examined. Prey capture behavior after pretectal ablation was also tested.

Here, we present a protocol to ablate a genetically labeled subpopulation of neurons by a two-photon laser from Zebrafish larvae.

To identify the role of a subpopulation of neurons in behavior, it is essential to test the consequences of blocking its activity in living animals. Laser ...

Facial Nerve Surgery in the Rat Model to Study Axonal Inhibition and Regeneration

This protocol describes consistent and reproducible methods to study axonal regeneration and inhibition in a rat facial nerve injury model. The facial nerve can be manipulated along its entire length, from its intracranial segment to its extratemporal course. There are three primary types of nerve injury used for the experimental study of regenerative properties: nerve crush, transection, and nerve gap. The range of possible interventions is vast, including surgical manipulation of the nerve, delivery of neuroactive reagents or cells, and either central or end-organ manipulations. Advantages of this model for studying nerve regeneration include simplicity, reproducibility, interspecies consistency, reliable survival rates of the rat, and an increased anatomic size relative to murine models. Its limitations involve a more limited genetic manipulation versus the mouse model and the superlative regenerative capability of the rat, such that the facial nerve scientist must carefully assess time points for recovery and whether to translate results to higher animals and human studies. The rat model for facial nerve injury allows for functional, electrophysiological, and histomorphometric parameters for the interpretation and comparison of nerve regeneration. It thereby boasts tremendous potential toward furthering the understanding and treatment of the devastating consequences of facial nerve injury in human patients.

This protocol describes a reproducible approach to facial nerve surgery in the rat model, including descriptions of various inducible patterns of injury.

This protocol describes consistent and reproducible methods to study axonal regeneration and inhibition in a rat facial nerve injury model. The facial ...

Use of In Vivo Single-fiber Recording and Intact Dorsal Root Ganglion with Attached Sciatic Nerve to Examine the Mechanism of Conduction Failure

Single-fiber recording has been a classical and effective electrophysiological technique over the last few decades because of its specific application for nerve fibers in the central and peripheral nervous systems. This method is particularly applicable to dorsal root ganglia (DRG), which are primary sensory neurons that exhibit a pseudo-unipolar structure of nervous processes. The patterns and features of the action potentials passed along axons are recordable in these neurons. The present study uses in vivo single-fiber recordings to observe the conduction failure of sciatic nerves in complete Freund&#8217;s adjuvant (CFA)-treated rats. As the underlying mechanism cannot be studied using in vivo single-fiber recordings, patch-clamp-recordings of DRG neurons are performed on preparations of intact DRG with the attached sciatic nerve. These recordings reveal a positive correlation between conduction failure and the rising slope of the after-hyperpolarization potential (AHP) of DRG neurons in CFA-treated animals. The protocol for in vivo single fiber-recordings allows the classification of nerve fibers via the measurement of conduction velocity and monitoring of abnormal conditions in nerve fibers in certain diseases. Intact DRG with attached peripheral nerve allows observation of the activity of DRG neurons in most physiological conditions. Conclusively, single-fiber recording combined with electrophysiological recording of intact DRGs is an effective method to examine the role of conduction failure during the analgesic process.

Single-fiber recording is an effective electrophysiological technique that is applicable to the central and peripheral nervous systems. Along with the preparation of intact DRG with the attached sciatic nerve, the mechanism of conduction failure is examined. Both protocols improve the understanding of the peripheral nervous system&#39;s relationship with pain.

Single-fiber recording has been a classical and effective electrophysiological technique over the last few decades because of its specific application for ...

Portable Thermographic Screening for Detection of Acute Wallenberg's Syndrome

Wallenberg&#39;s syndrome (WS) is a type of brainstem infarction. WS patients often show Horner&#39;s syndrome, dissociated sensory disturbance, truncal ataxia, and hoarseness. However, they rarely show tactile sensory disturbance and paralysis of the extremities. Additionally, acute brainstem infarction is often not apparent in magnetic resonance images. These symptomatic and imaging characteristics sometimes lead to misdiagnosis of WS as a non-stroke disease, including auditory vertigo. Although careful neurological examination is necessary to prevent misdiagnosis of WS, this type of examination may be difficult for non-neurologists to whom affected patients initially present. Lateral differences in body surface temperature (BST) constitute a recognized and widespread symptom of WS. We previously reported that most acute WS patients exhibit lateral differences in BST at multiple locations and that these lateral differences in BST could easily be detected by thermographic measurement. Here, we present the method for use of portable thermography to detect acute WS, using a simple, rapid, noninvasive, and cost-effective approach. To assess lateral differences in BST among patients with suspected WS, BST was measured as soon as possible in the examination room or in the patient&#39;s bedroom. Measurements were performed bilaterally at four locations where images could easily be acquired (face, palm of the hand, abdomen, and dorsum of the foot) using a portable thermal camera. When lateral differences in BST are observed macroscopically, especially in multiple locations on the same side, a diagnosis of WS should be suspected. Macroscopic assessment of BST laterality can be made within 2 min of the acquisition of thermographic images. This method may be useful in preventing misdiagnosis of acute WS as a non-stroke disease, especially when such patients initially present to non-neurologists.

Portable Thermographic Screening for Detection of Acute Wallenberg&#039;s Syndrome

Acute Wallenberg&#39;s syndrome can be misdiagnosed as a non-stroke disease, such as auditory vertigo. Thus, careful neurological examination, which is sometimes difficult for non-neurologists, is necessary for precise diagnosis. Here, we present a simple, rapid, noninvasive, and cost-effective method for detection of acute Wallenberg&#39;s syndrome using portable thermography.

Wallenberg&#39;s syndrome (WS) is a type of brainstem infarction. WS patients often show Horner&#39;s syndrome, dissociated sensory disturbance, truncal ...