Related Experiment Video
Updated: Aug 2, 2026
12:43
A Protocol for Comprehensive Assessment of Bulbar Dysfunction in Amyotrophic Lateral Sclerosis (ALS)
Published on: February 21, 2011
Adductor muscle activity abnormalities in abductor spasmodic dysphonia
C B Cyrus1, S Bielamowicz, F J Evans
1Laryngeal and Speech Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1416, USA.
Summary
Abnormalities in laryngeal muscle activation, particularly the thyroarytenoid muscle, were observed in individuals with abductor spasmodic dysphonia (ABSD). This asymmetry may explain speech difficulties and treatment outcomes.
Area of Science:
- Laryngology
- Speech Science
- Neurology
Background:
- Abductor spasmodic dysphonia (ABSD) is a voice disorder characterized by involuntary spasms of the vocal folds during speech.
- Understanding the underlying laryngeal muscle activation patterns is crucial for effective treatment.
Purpose of the Study:
- To investigate laryngeal muscle activation abnormalities in patients with abductor spasmodic dysphonia (ABSD).
- To correlate these abnormalities with specific speech symptoms experienced by ABSD patients.
Main Methods:
- Electromyography was used to record activity in bilateral laryngeal muscles: posterior cricoarytenoid, thyroarytenoid, and cricothyroid.
- Muscle activity was measured in 12 ABSD patients during speech breaks and continuous speech.
- Data from ABSD patients were compared to 10 healthy controls.
Main Results:
- Significant differences in thyroarytenoid muscle activity were found between ABSD patients and controls.
- Patients exhibited greater right-sided thyroarytenoid muscle activity during both speech breaks and continuous speech.
- Increased right-sided cricothyroid muscle activity was also observed in ABSD patients.
Conclusions:
- Asymmetrical adductor muscle tone between the left and right sides of the larynx may contribute to phonation and voice onset difficulties in ABSD.
- Observed muscle activation abnormalities could explain the differential effectiveness of treatments like BOTOX injections in ABSD versus adductor spasmodic dysphonia.
Related Concept Videos
01:31Skeletal Muscle Relaxants: Therapeutic Uses
Skeletal muscle relaxants are used to relax muscle tone and alleviate painful muscle contractions. However, the choice of skeletal muscle relaxants depends on the duration of the surgical procedure in order to minimize potential side effects. Skeletal muscle relaxants like neuromuscular blocking agents [NMBAs] are commonly employed as adjuvants alongside general anesthetics in clinical settings. NMBAs are also used to maintain controlled ventilation during surgery of the larynx or pharynx as...
01:24Muscle Coordination and Action
Muscle coordination is a complex and finely tuned process essential for smooth and purposeful movements like flexion, extension, adduction, abduction, and rotation. The human body orchestrates the actions of various muscles working in concert, each with a specific role. Four functional types describe how muscles work together: agonist, antagonist, synergist, and fixator.
Agonists
Agonist muscles, often called prime movers, are the primary muscles responsible for producing a specific movement.
Agonists
Agonist muscles, often called prime movers, are the primary muscles responsible for producing a specific movement.
01:23Muscles of the Shoulder
The muscles surrounding the shoulder girdle, including the clavicle and scapula, primarily stabilize the scapula. This stable base allows other muscles to move the humerus effectively. Scapular movements often mirror those of the humerus and extend its range of motion. For instance, raising the arm above the head would not be feasible without simultaneous upward rotation of the scapula.
Anterior Thoracic Muscles
The anterior thoracic muscles include the serratus anterior, subclavius, and...
Anterior Thoracic Muscles
The anterior thoracic muscles include the serratus anterior, subclavius, and...
01:31Respiratory System Abnormal Finding II: Palpation and Auscultation
In assessing respiratory abnormalities, palpation and auscultation are critical tools for detecting and interpreting various pathophysiological changes. These techniques provide insight into underlying disorders by evaluating tactile sensations and sounds produced by the respiratory system.
Palpation Findings
During a respiratory assessment, palpation can reveal several vital abnormalities:
Palpation Findings
During a respiratory assessment, palpation can reveal several vital abnormalities:
01:12Alterations in Muscle Tone ll
Alterations in muscle tone are common manifestations of neurological disorders and reflect dysfunction within different nervous system regions. Spasticity, paratonia, and dystonia represent distinct forms of hypertonia, each with unique mechanisms, clinical features, and diagnostic importance.CharacteristicsSpasticity happens from upper motor neuron lesions and is characterized by velocity-dependent resistance to passive movement. Clinical features include:Exaggerated deep tendon reflexesClonus...
01:11Alterations in Muscle Tone lll
Rigidity and myotonia are distinct abnormalities of muscle tone that affect resistance and relaxation during movement. Although both involve altered muscle contraction, they arise from different neurological and muscular mechanisms.CharacteristicsRigidity is characterized by uniform resistance to passive movement across the entire range, independent of speed, affecting flexors and extensors equally. It may appear as lead-pipe rigidity (smooth, constant resistance) or cogwheel rigidity...