Strabismus
Conditions
Keywords
Extraocular muscle, Electromyogram, Monopolar, Needle guidance, Botulinum toxin, Strabismus
Brief summary
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.
Interventions
None listed
Sponsors
Manchester University NHS Foundation Trust
Liverpool University Hospitals NHS Foundation Trust
Study design
Observational model
CASE_ONLY
Time perspective
CROSS_SECTIONAL
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| α (Slope) Parameter of the Electromyogram (EMG) Signal Power Spectral Density (PSD) Plot as Needle Approaches Then Enters Muscle. | Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal | 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. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Clinical Score of EMG Change | Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal | 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. |
| Clinical Score of Needle Placement Accuracy | Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal | 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. |
| Clinical Score of EMG Quality. | Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal | 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. |
| Post-treatment Angle of Deviation | 2 weeks | Change in participant's angle of deviation following treatment, measured in prism dioptres. |
Countries
United Kingdom
Participant flow
Participants by arm
| Arm | Count |
|---|---|
| Observation Participants who were recruited and had their data recorded for this observational study. | 25 |
| Total | 25 |
Baseline characteristics
| Characteristic | Observation | — |
|---|---|---|
| Age, Continuous | 55 years | — |
| Electrode distance | 13 mm | — |
| Race and Ethnicity Not Collected | — | — Participants |
| Rectus muscle Lateral rectus | 17 Participants | — |
| Rectus muscle Medial rectus | 8 Participants | — |
| Sex/Gender, Customized Not recorded | — | — Participants |
Adverse events
| Event type | EG000 affected / at risk |
|---|---|
| deaths Total, all-cause mortality | 0 / 25 |
| other Total, other adverse events | 0 / 25 |
| serious Total, serious adverse events | 0 / 25 |
Outcome results
Primary
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.
Time frame: Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal
| Arm | Measure | Group | Value (NUMBER) |
|---|---|---|---|
| Observation | α (Slope) Parameter of the Electromyogram (EMG) Signal Power Spectral Density (PSD) Plot as Needle Approaches Then Enters Muscle. | Off-target | 1.49 log (mV^2 / Hz) / log (Hz) |
| Observation | α (Slope) Parameter of the Electromyogram (EMG) Signal Power Spectral Density (PSD) Plot as Needle Approaches Then Enters Muscle. | Approaching-target | 2.86 log (mV^2 / Hz) / log (Hz) |
| Observation | α (Slope) Parameter of the Electromyogram (EMG) Signal Power Spectral Density (PSD) Plot as Needle Approaches Then Enters Muscle. | On-target | 3.56 log (mV^2 / Hz) / log (Hz) |
Comparison: The null hypothesis was that α (the slope of the Power Spectral Density (PSD) plot) is not related to signal segment (off-, approaching- and on-target).p-value: <0.0001Linear mixed-effects model
Secondary
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.
Time frame: Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal
| Arm | Measure | Value (MEAN) |
|---|---|---|
| Observation | Clinical Score of EMG Change | 4.6 score on a scale |
Secondary
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.
Time frame: Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal
| Arm | Measure | Value (MEAN) |
|---|---|---|
| Observation | Clinical Score of EMG Quality. | 4.5 score on a scale |
Secondary
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.
Time frame: Approximately 5 minutes, i.e. immediately prior to needle insertion until Botulinum toxin (BTX) delivery and needle withdrawal
| Arm | Measure | Value (MEAN) |
|---|---|---|
| Observation | Clinical Score of Needle Placement Accuracy | 87.6 percentage of confidence |
Secondary
Post-treatment Angle of Deviation
Change in participant's angle of deviation following treatment, measured in prism dioptres.
Time frame: 2 weeks
Population: Data was not collected; it was determined before recruitment began that the value of this data did not merit the significant inconvenience to participants of returning for follow-up measurements.