Eye Muscle Needle Electromyogram (EMu) Study

Study Overview
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Brief Summary
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In some cases, strabismus, or squint, is treated with injections of Botulinum toxin (BTX) to temporarily relax the eye muscle responsible for causing the eye to be pulled to one side. Due to the deep location of the muscles, electromyogram (EMG) needle guidance is used to help ensure the toxin is delivered accurately. EMG needle guidance involves listening to the EMG signal from the tip of the delivery needle - when the needle is in the right place a sound akin to rain on a tin roof is heard and the BTX can be injected. From previous research, clearly clinicians want to improve the technology of this procedure and increase the treatment efficacy and repeatability. After all, the current procedure is imprecise and subjective for what is a small target, with the eye muscles being around 2.5 mm to 4.7 mm in diameter. There may also be an increase in the likelihood of side effects such as droopy eyelids when the toxin spreads beyond the target muscle. There is a strong need for new knowledge to improve EMG needle guidance in this context. It is hypothesised that the EMG signal could be cleaned and mined for information in real time during the procedure, thus providing the clinician with better information to guide the positioning of the needle before injecting. This pilot study will deliver the knowledge essential to indicate the feasibility of doing this. If feasible, this study will inform a full study with the aim of benefitting patients by allowing new technology to be developed to improve the treatment of strabismus with BTX.

Official Title
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A Data Collection and Analysis Pilot Study to Indicate Preliminary Characterisation of the Electromyogram Signal in Relation to Needle Position With Respect to the Extraocular Muscles, as Observed During Electromyogram Needle Guided Treatment of Strabismus in Adults

Conditions
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Strabismus

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: i. Adults undergoing planned, routine EMG needle guided BTX injection into either lateral or medial rectus muscle for the treatment of strabismus. ii. Patients being treated by Mr Yagan. Exclusion Criteria: - Patients with Chronic progressive external ophthalmoplegia (CPEO) are excluded; a highly attenuated EMG signal is expected.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| α (Slope) Parameter of the Electromyogram (EMG) Signal Power Spectral Density (PSD) Plot as Needle Approaches Then Enters Muscle. | The continuous change in the EMG signal as the needle is (a) distal to, (b) approaches, and (c) enters, the target extraocular muscle. Welch's periodogram estimator (Hamming window, 256-point FFT, 50% overlap) was applied to each of the three signal segments described above to obtain an estimate of the PSD of the signal. A robust linear model was fit to estimate the α (slope) parameter of each PSD plot. | Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Clinical Score of EMG Change | Clinician's score of the step change from baseline EMG to 'active' EMG level heard immediately prior to delivery of Botulinum toxin (BTX) from 1-5. Value from 1 = no significant step change heard, to 5 = a very clear step change heard. | Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal | 
| Clinical Score of Needle Placement Accuracy | Clinician's score of their confidence in accurate needle placement with respect to the target muscle. Given as a percentage, a higher score indicates more confidence in accurate needle placement. | Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal | 
| Clinical Score of EMG Quality. | Clinician's score of overall quality of the EMG signal heard during the procedure. A higher score indicates better quality of EMG signal, and is quantified as 1 to 5, where: 1 indicates signal not present and 5 indicates excellent quality EMG signal. | Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal | 
| Post-treatment Angle of Deviation | Change in participant's angle of deviation following treatment, measured in prism dioptres. | 2 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Extraocular muscle, Electromyogram, Monopolar, Needle guidance, Botulinum toxin, Strabismus