Cortical Silent Period in Laryngeal Dystonia

Study Overview
=================
Brief Summary
-----------------
The goal of this observational study is to evaluate the cortical silent period (cSP) in cricothyroid muscle (CT) in laryngeal dystonia and control healthy subjects. The study will provide norms related to latency and amplitude of motor evoked potentials (MEPs) and duration of cSP in CT muscle in laryngeal dystonia and control healthy subjects. Findings may give a baseline in comparison to findings in laryngeal diseases and insight into maladaptive cortical control function during phonation in laryngeal diseases like laryngeal dystonia.

Detailed Description
-----------------
Transcranial magnetic stimulation (TMS)-induced cSP provide a noninvasive in vivo insight into how the human motor cortical inhibitory pathway function by generating electric current at a specific brain area through electromagnetic induction. The stimulator generates a changing electric current within the coil, which induces a magnetic field that then causes a second inductance of inverted electric charge within the brain itself. A single supra-threshold pulse of TMS over the human motor cortex elicits multiple descending volleys (I-waves) that generate a motor evoked potential (MEP) followed by a period of electromyographic silence in the tonically contracted target muscle (cSP). To date, methodologies for mapping the primary motor cortex (M1) with TMS and intraoperatively by electrical stimulation techniques have been previously developed to record corticobulbar motor evoked potentials (MEP) from laryngeal muscles. Except for estimating the amplitude and latency of MEPs recorded from laryngeal muscles, the cSP was investigated from thyroarytenoid muscle (TA) as a measure of M1 excitability in the TMS study. Previous work using TMS has indicated reduced inhibition to be characteristic of focal laryngeal dystonia. According to investigators' knowledge, cSP from other laryngeal muscles other than TA has not been investigated so far. The proposed study analyses neurophysiological CNS data, including motor evaluation of corticospinal and corticobulbar pathways by recording MEPs and cSP using TMS. Firstly, a questionnaire will be given to check for any previous neurological conditions, and subjects will provide signatures on participation in the study. The MRI of the subject's brain will be performed, and then 3D reconstructed for the use of TMS. The evaluation of the MRI will be done by radiologists at University Hospital Split. With the subject comfortably seated, the MRI is co-registered to the subject's head using the tracking system with TMS's unique forehead tracker. After TMS measurement of the MEP and cSP of CT muscle of individual subjects will be recorded. Data collected will be analyzed using MATLAB 2022a (MathWorks, USA). Measurements and data evaluation will be performed at the School of Medicine University in Split. An otorhinolaryngology specialist will be consulted for the correct placement of the recording electrodes (Hookwire IOM electrodes, disposable subdermal needle electrode, 0.4 x 13 mm, SGM d.o.o, G. Novaka 22 a, 21000 Split, Croatia) into the CT muscle.

Official Title
-----------------
Cortical Silent Period in Laryngeal Dystonia

Conditions
-----------------
Laryngeal Dystonia, Spasmodic Dysphonia

Intervention / Treatment
-----------------
* Other: Transcranial Magnetic Stimulation (TMS)


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: adults (18-65 years old), no implanted metals in the body (e.g. pacemaker, metal prosthesis in the skull and oral cavity). Exclusion Criteria: pregnancy, other neurological disorders (except laryngeal dystonia in the laryngeal dystonia group), psychiatric disorders, epilepsy or history of previous epilepsy attack, using of brain-affecting pharmaceuticals, traumatic, tumor, infectious, metabolic brain lesions, heart conditions. The composition of the group is represented is both gender, various age gap, and different height.
Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Laryngeal Dystonia<br>The study will be performed on 10-15 (maximal 20) subjects with diagnosed laryngeal dystonia who meet the exclusion/ inclusion criteria. Inclusion criteria: adults (18-65 years old) who have confirmed diagnosis of laryngeal dystonia, no implanted metals in body (e.g. pacemaker, metal prosthesis in skull and oral cavity). Exclusion criteria: pregnancy, other neurological disorders, psychiatric disorders, epilepsy or history of previous epilepsy attack, using of brain affecting pharmaceuticals, traumatic, tumor, infectious, metabolic brain lesions, heart conditions (15 ). The composition of the group is represented is both gender, various age gap, and different height. Before the beginning of testing, all subjects with a confirmed diagnosis of laryngeal dystonia will be once again evaluated by a specialist otorhinolaryngologist at the University Hospital of Split. Medical documentation of the examination will be available for further analysis. | Other: Transcranial Magnetic Stimulation (TMS)<br>* An anatomical T1 magnetic resonance image (MRI) with high resolution will be acquired on a separate day before the TMS experiment. The image will be imported into the neuronavigation system (Nexstim, Helsinki, Finland) to guide the localization of the primary motor cortex (M1) for laryngeal muscle representation. Prior to M1 mapping for laryngeal muscle representation, mapping of the representation for hand muscle representation will be performed. Hand region excitability (abductor pollicis brevis, APB) will be evaluated by using surface electrodes attached to the right-hand APB muscle. The cSP threshold is defined as the lowest TMS intensity that elicits a cSP in 5 out of 10 consecutive trials. Single-pulse cortical stimulations will be performed during the vocalization of sustained /i/ sound.<br>|
| Healthy subjects<br>The study will be performed on 20 healthy volunteering subjects who meet the exclusion/ inclusion criteria. Inclusion criteria: healthy adults (18-65 years old), no implanted metals in body (e.g. pacemaker, metal prosthesis in the skull and oral cavity) Exclusion criteria: pregnancy, neurological disorders, psychiatric disorders, epilepsy or history of previous epilepsy attack, using of the brain affecting pharmaceuticals, traumatic, tumor, infectious, metabolic brain lesions, heart conditions. The composition of the group is represented is both gender, various age gap, and different height. | Other: Transcranial Magnetic Stimulation (TMS)<br>* An anatomical T1 magnetic resonance image (MRI) with high resolution will be acquired on a separate day before the TMS experiment. The image will be imported into the neuronavigation system (Nexstim, Helsinki, Finland) to guide the localization of the primary motor cortex (M1) for laryngeal muscle representation. Prior to M1 mapping for laryngeal muscle representation, mapping of the representation for hand muscle representation will be performed. Hand region excitability (abductor pollicis brevis, APB) will be evaluated by using surface electrodes attached to the right-hand APB muscle. The cSP threshold is defined as the lowest TMS intensity that elicits a cSP in 5 out of 10 consecutive trials. Single-pulse cortical stimulations will be performed during the vocalization of sustained /i/ sound.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Motor evoked potential (MEP) latency | MEP latency is expressed in milliseconds | MEP latency evaluated on the first day of the arrival on TMS experiment | 
| Motor evoked potential (MEP) amplitude | MEP amplitude is expressed in microvolts | MEP amplitude evaluated on the first day of the arrival on TMS experiment | 
| Duration of cortical silent period (cSP) | cSP is expressed in milliseconds | cSP duration evaluated on the first day of the arrival on TMS experiment | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
laryngeal dystonia, cortical silent period, spasmodic dysphonia, transcranial magnetic stimulation