Introduction:
A tremor is an involuntary contraction of skeletal muscles that causes uncontrolled movements of the body parts. Vocal or laryngeal tremor is a neurological (nerve) disorder causing involuntary muscle movement of the throat, vocal folds, and larynx, leading to slurred speech/voice. Vocal cords are present above the windpipe. The vocal cords are surrounded by two bands of muscles called vocal folds. Normally, these bands remain closed while breathing and swallowing. While speaking, the air from the lungs passes and makes these vocal folds vibrate, producing the sound of the voice. These sound waves then pass through the nose, throat, and mouth, forming the sound of a speech. Vocal tremors affect females more than males.
What Is Vocal Tremor and Voice Tremor?
Vocal and voice tremors generally refer to the same condition—uncontrolled rhythmic movements affecting the laryngeal muscles, resulting in variations in voice quality, pitch, and volume. However, sometimes vocal tremors may denote tremors affecting the vocal cords. In contrast, voice tremors could encompass a broader range of tremors impacting overall voice production, including the larynx and other speech-related structures. These terms are often used interchangeably and may vary in usage within different medical contexts or by professionals in the field.
What Is the Prevalence of Laryngeal Tremors?
Vocal tremor affects 30-40 % of the general population. Laryngeal or vocal tremor is characterized by involuntary rhythmic movements or oscillations of the larynx, leading to variations in voice quality, pitch, and volume. It can affect both genders and typically occurs in adults. The prevalence of laryngeal tremors isn't precisely documented for various reasons, including misdiagnosis or underreporting. Studies suggest its occurrence in neurological conditions, such as essential tremor, Parkinson's disease, or dystonia, where it might manifest as a symptom.
Essential tremor, a common neurological disorder, can be associated with laryngeal tremor. It is often under-recognized as its impact on voice might only sometimes be the primary concern for individuals dealing with essential tremors. Given the challenges in accurately determining the prevalence of isolated laryngeal tremors, it's advisable for individuals experiencing voice tremors or related issues to seek evaluation from a speech-language pathologist or an otolaryngologist for proper diagnosis and management.
What Are the Types of Laryngeal Tremors?
Vocal tremor is caused by both extrinsic and intrinsic muscles of the larynx (voice box). These muscles cause movement of the larynx in different directions.
Based on these movements, vocal tremors are classified as:
Horizontal Vocal Tremor:
It is the movement of the larynx, mostly in the horizontal plane. It is mediated by thyroarytenoid and lateral cricoarytenoid muscles. Horizontal tremors are more common than vertical tremors.
Vertical Vocal Tremor:
It is the movement of the larynx in the vertical plane, which is mediated by extrinsic muscles of the larynx, including strap muscles.
What Is the Cause of Laryngeal Tremor?
Various factors that are supposed to cause vocal tremors are:
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Direct injury to the vocal cords.
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Presence of underlying neuromuscular diseases like Parkinson's disease (central nervous system disorder) and myasthenia gravis (weakness of muscles).
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Cancerous or non-cancerous laryngeal tumors damage the nerve supply (damage to the superior or recurrent laryngeal nerve).
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Damage to the nerves or vocal cords during surgery.
What Are the Signs and Symptoms of Vocal Tremor?
People with laryngeal tremors show:
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Increase effort while speaking.
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Breathlessness while speaking.
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Slurring of speech.
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Impaired or shaky voice.
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Change in pitch or loudness of the voice.
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Incomplete words while speaking.
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Hoarseness of voice.
How Can We Diagnose Laryngeal Tremors?
Various diagnostic criteria for laryngeal tremor are:
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Clinical Examination: A complete clinical examination of the vocal fold movements with breathing, throat muscles, and larynx is done by an ENT specialist. Clinical examination also helps to differentiate between spasmodic dysphonia and vocal tremor, as spasmodic dysphonia involves only vocal cords, but vocal tremor involves complete muscles of the throat, vocal folds, tongue, voice box, and jaw, causing upper airway muscles.
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Medical History: A thorough medical history of the patient is recorded for any neuromuscular diseases like Parkinson's disease, myasthenia gravis (muscular weakness), or multiple sclerosis (nerve disorder). A history of any operated surgery for laryngeal cancer, neurosurgery, or head or neck surgery should be recorded.
Voice Assessment:
Assessment of voice impairment, voice quality, and alteration in the voice pitch and volume is assessed by a speech-language pathologist.
Laryngoscopy:
A rigid or flexible laryngoscope (an apparatus with light and a camera) is used to completely evaluate the movement of vocal fold muscles, larynx, and throat with respiration and swallowing.
Videostroboscopy:
Videolaryngostroboscopy is one of the most reliable diagnostic techniques for evaluating vocal cords while they vibrate and produce sound. The endoscope with an attached camera is inserted through the nose to examine the larynx and vocal cords with slow-motion video of the movement of muscles of vocal cords and magnified camera clicks images.
Electromyography:
It is done to check for electrical impulses in the vocal cord muscle when it vibrates or moves. Investigations for laryngeal tumor
What Is the Treatment of Laryngeal Tremor?
Vocal cord tremor management is a multidisciplinary approach. Various treatment methods for laryngeal tremors are :
Botox Injections:
It is one of the gold-standard treatments for vocal tremors. Botox injections (Botulinum toxin) are given by an ENT specialist in the muscle of the vocal cords through the mouth or nose. It needs to be repeated every 8 to 12 weeks. Botulinum toxin relaxes the hyperactive vocal cord muscles, making the speech loud and clear. Botox injections can also be given through the neck for a more accurate location under the guidance of electromyography (electrical activity of vocal cord muscles recorded with their movements).
Botox injections are given every 4 to 6 months. According to modified treatment techniques, botulinum toxin can also be given based on the type of tremor. Thyroarytenoid muscle injections are given in cases of horizontal tremor, and strap muscle injections are given in cases of vertical tremor.
Voice Therapy:
The speech-language therapist does it by helping normalize the throat, teaching some vocal functioning exercises, conversation training therapy, and behavioral modification therapy to the patients.
Medicinal Therapy:
The doctor prescribes beta-blocker drugs like Propranolol (10 milligrams twice daily) to reduce the vocal tremor. Primidone is another drug that is given as an alternative to Propranolol in patients for whom Propranolol does not work. Combination therapy of Propranolol and Primidone is also preferred in some cases.
Treatment of Underlying Diseases:
The diagnosis of the main cause behind the vocal tremor is important to managing the condition. Underlying diseases like Parkinson’s disorder, myasthenia gravis, and multiple sclerosis should be treated by taking appropriate medications prescribed by the doctor.
Conclusion:
The human voice plays one of the most important social communication roles. Any problem in the voice disturbs the quality of life of a person. Vocal tremor is a neurological disorder that can affect anyone, either due to trauma or the presence of underlying diseases. There are various techniques to diagnose the vocal tremor, but early diagnosis of the cause is important for a good treatment outcome. Botox injections are one of the gold-standard treatments for vocal tremors, but they have to be repeated every six months. Although there are many treatment methods for reducing vocal tremors, research is ongoing to develop new treatments for their complete cure.
