eMedicine Specialties > Otolaryngology and Facial Plastic Surgery > Laryngology

Laryngeal Tremor

Author: Monika I Sidor, MD, Staff Physician, Department of Surgery, University of Michigan at Ann Arbor
Coauthor(s): Soly Baredes, MD, Associate Professor of Clinical Surgery, Chief, Section of Otolaryngology-Head and Neck Surgery, Director, Division of Head and Neck Surgery, University of Medicine and Dentistry of New Jersey, New Jersey Medical School; Brian E Benson, MD,, Attending Physician, Department of Otolaryngology, St Luke's-Roosevelt Hospital Center; Clinical Assistant Professor, Department of Otolaryngology, Hackensack University Medical Center; Director, The Voice Center, Hackensack University Medical Center
Contributor Information and Disclosures

Updated: Feb 5, 2010

Introduction

Background

Vocal tremor is a common symptom of several neurological disorders. Tremors are defined as rhythmic involuntary oscillating movements, which, when the muscles of phonation are involved, have a disabling effect because of fluctuations in the amplitude and fundamental frequency of the voice. Vocal tremors involve not only tremor of the intrinsic muscles of the larynx but also, on occasion, the extrinsic laryngeal, pharyngeal, and palatal muscles, as well as the muscles of the diaphragm, chest wall, and abdomen.

Neurological disorders characterized by vocal tremor include essential tremor, Parkinson disease, Parkinson-plus syndromes (including multisystem degeneration, Shy-Drager syndrome, basal ganglia degeneration, stroke, progressive supranuclear palsy), myasthenia gravis, ataxic disorders such as Friedreich ataxia, and laryngeal dystonias.

Functional voice disorders may also result in vocal tremor. The reader is referred to the eMedicine articles Functional Voice Disorders and Spasmodic Dysphonia for a more detailed discussion of these topics. Vocal tremor in the absence of other neurological disorders is called essential tremor of the voice (ETV).

An imaging depicting the cartilages of the larynx can be seen below.

Pathophysiology

The larynx is under extensive neural control, and the physiology of phonation is complex. Several mechanisms have been implicated in the pathophysiology of laryngeal tremor, including the interaction between a central oscillatory source with peripheral reflex loops.

As a rule, tremor results from a lesion that involves the extrapyramidal system or cerebellum. Electromyographic studies show that vocal tremor can arise from the involvement of muscles at any level of the speech production mechanism. In contrast to spasmodic dysphonia (SD), which typically affects only the intrinsic laryngeal musculature, ETV that arises from the cerebello-olivary systems often affects a greater portion of muscles of the upper aerodigestive tract.

Frequency

United States

Measuring the true incidence of essential tremor is difficult because symptoms may be mild and unnoticed in as many as 50% of affected people. Vocal tremor may be present in 25-30% of patients with essential tremor.

Mortality/Morbidity

The degree of disability caused by laryngeal tremor may range from mild to incapacitating vocal symptoms.

Sex

Laryngeal dystonias are more prevalent in women, with a male-to-female ratio of 1:3-8. Some reports describe vocal tremor in 66.7% of patients with adductor SD.

Age

Essential tremor is characterized by a bimodal age of onset, usually manifesting in the second and sixth decades of life.Parkinson disease is the most common movement disorder in patients older than 55 years, and dysphonia may be the initial symptom. Perez et al report vocal tremor in 55% of patients with Parkinson disease and 64% of patients with Parkinson-plus syndromes.¹

Clinical

History

Often, the voice disorder present is diagnosed based on history findings alone. Onset of voice tremor, aggravating and alleviating factors, associated neurological symptoms, medications, and family history are important components of the patient history. A history of multiple neurologic findings may suggest that the laryngeal tremor is secondary to another disease. The patient should be asked about specific vocal symptoms, such as vocal fatigue, pain with speaking, increased effort, hoarseness, and pitch breaks, as well as tremor.

Approximately 50% of cases of essential tremor are inherited in an autosomal dominant fashion. Essential tremor is characterized by postural or kinetic tremor of the upper extremities and head that improves dramatically with alcohol.

Patients with laryngeal dystonia may have symptoms of adductor or abductor spasmodic dysphonia (SD). Adductor dysphonia is characterized by phonatory breaks, hoarseness, monotonal pitch, and a strained voice quality. A breathy voice quality and trouble with voiceless consonants (/p/, /t/, /l/, /h/, /f/, /s/) are associated with abductor dysphonia.

Symptoms in patients with essential voice tremor slowly worsen over months and years. Voice tremor increases with anxiety and improves after alcohol ingestion. Patients with Parkinson disease may experience limb tremor, bradykinesia, rigidity, poor articulation, difficulty initiating speech, and a soft breathy voice.

Physical

A thorough physical examination, including both otolaryngologic and neurologic components, should be performed, with special attention paid to the neurologic examination of the mouth, pharynx, and larynx, as well as the evaluation of the voice. The assessment of vocal quality during conversational speech may enable the examiner to make a working diagnosis based only on the history and the sound of the voice.

A neurolaryngeal examination, both at rest and during phonation, is performed with a flexible laryngoscope. Spontaneous rhythmic muscular activity of the laryngeal, supraglottic, and pharyngeal muscles while at rest is characteristic of tremor. However, tremor may also occur during sustained phonation. Tremor should be differentiated from myoclonus, which is jerky and arrhythmic.

Full evaluation of the voice should include measures of fluidity, articulation, and voice quality (raspiness, breathlessness, strain). Phonatory tasks that isolate the abductor, adductor, and tensor muscle groups of the larynx allow the examiner to assess for paralysis, fatigability, and agility.

Recently, Bove et al developed a vocal tremor scoring system that standardized the evaluation and scaling of vocal tremor.² Furthermore, this system determined which patients were likely to benefit from botulinum toxin A (BTA) injection therapy.

Causes

See Background.

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