Organic voice tremor is a neurogenic voice disorder of adulthood that most often occurs as a component of essential or hereditofamilial tremor; it may occur by itself, however. Organic voice tremor must be distinguished from other conditions, which also present with voice disturbances in the early stages. These include Parkinsonism, cerebellar disease, thyrotoxicosis, and anxiety.
Description
Organic voice tremor is a disorder of voice production characterized by unsteadiness of pitch and loudness and quavering intonation. In some patients, it may result in rhythmic arrests of voicing that occur at a rate of four to six per second. Voice quality is characterized by harshness, vocal strain, abnormally low pitch, and voice stoppages. Laryngeal examination typically reveals vocal folds of normal appearance, with no evidence of aberrant innervation. The abnormal oscillations of the larynx occur as a result of vigorous up-and-down vertical movements that occurred synchronously with the oscillation of the tremor. The quavering speech quality that characterizes organic voice tremor has been thought to include extralaryngeal influences arising from tremors in the diaphragm, lips, and tongue (Critchley, 1949; Tomoda, et al., 1985).
The origin of organic voice tremors has not been conclusively determined, though aging and occlusive arterial disease are thought to contribute significantly to the effects. Critchley (1949) showed that essential tremor occurred in persons with confirmed lesions in the brain stem, basal ganglia (e.g., putamen and lentiform nuclei) and within neural connections joining the red nucleus, dentate nucleus, and inferior olive. Vocal tremors usually coexist with tremors in the head and limbs, but may be localized entirely within the larynx. Disturbed central innervation to the larynx is thought to disturb coordination between abductor and adductor groups of laryngeal muscles, which may affect the symmetry of vibration of the vocal folds, and result in excess force of approximation or abruptness of vocal fold separation during conversational speech. Symptoms may be difficult to fully appreciate in conversational speech but become quite evident in sustained vowel production (Brown and Simonson, 1963). This finding is significant for differential diagnosis of essential tremor from spasmodic dysphonia, a focal dystonia affecting voicing.
Demographics
Organic voice tremor is a condition that usually occurs in persons over age 50. Males and females appear to be affected equally. Specific incidence data are not available.
Causes and Symptoms
Organic voice tremor is thought to result from neural degeneration in one or more regions of the extrapyramidal system. It usually is part of a more general condition of tremor involving the head, neck, and limbs called essential tremor. For some individuals, these changes are inherited and may occur in several members of the same family, sometimes occurring in successive generations. These persons are said to have hereditofamilial tremor. When the onset of organic voice tremor is rapid, the etiology may result from occlusive vascular disease (Brown and Simonson, 1963). When it is gradual, the etiology is likely related to progressive changes in several locations in the brain stem or basal ganglia.
Persons with organic voice tremor usually experience changes in voice slowly. In addition to changes in voice quality and reduced stability in pitch, loudness, and vocal flexibility, some patients may experience tremor in the pharynx, lips, and jaw. Some patients experience difficulties in initiating or maintaining voicing or experience sudden loss of voice during conversation. In addition to vocal tremor, some patients experience spasms in the diaphragm and expiratory musculature (Tomoda, et al., 1987), which may contribute to instability within the vocal tract and add to the quavering property of the voice.
Diagnosis
Organic voice tremor is usually made by examination of a neurologist and speech-language pathologist. Detailed history and medical examination is essential to determine if disruptions in voice functioning are related to other neurological conditions such as Parkinsonism, cerebellar disease, and systemic conditions such as thyrotoxicosis. Differential diagnosis needs to be made between organic voice tremor and spasmodic dysphonia, which is a focal dystonia. A complete laryngeal examination should be obtained from an otolaryngologist and include endoscopic and videostroboscopic examinations of the larynx. A battery of objective tests to assess the aerodynamic and acoustic properties of voice production should be obtained from a speech pathologist, who usually works with the otolaryngologist. In addition, neuromotor intactness of the speech mechanism (the motor speech examination), should be undertaken. In this examination attention is given to assessment of muscle strength, speed of movement, range of motion, accuracy of movement, motor steadiness, and muscle tone in the speech articulators, larynx, and resonatory systems.
Treatment Team
The treatment team for organic voice tremor consists of a neurologist, otolaryngologist, and speech-language pathologist.
Treatment
There is no cure for organic voice tremor. Medications (Sinemat or Inderal) used to treat essential tremor have not emerged as a reliable treatment modality for organic voice tremor. Koller, et al. (1985) used propranolol to treat organic voice tremor and found that voice tremor was more resistant to drug treatment than tremor in the hand. Others (Massey and Paulson, 1982; Hartman and Vishwanat, 1984; Tomoda, et al., 1987) report effective treatment of voice and hand tremors with clonazepan, and diazepam. Botulinum Toxin A (BOTOX) may be useful in treating some patients with organic voice tremor, in which vocal fold spasticity is a coexisting feature. Speech therapy may be useful in reducing laryngeal hyperfunction and in establishing improved respiratory support.
Recovery and Rehabilitation
Patients with organic voice tremor do not recover from the condition. They must learn to adapt or compensate for speech and voice deficits. Speech therapy may be useful in this regard.
Prognosis
Prognosis is very poor for clinically significant improvement of voice in those with organic voice tremor.
PERIODICALS
Ardran, G., M. Kinsbourne, and G. Rushworth. "Dysphonia due to tremor." Journal. Neurology Neurosurgery and Psychiatry 29 (1966): 219–223.
Aronson, A. E., and D. E. Hartman. "Adductor spasmodic dysphonia as a sign of essential (voice) tremor." Journal of Speech and Hearing Disorders 46 (1981): 52–58.
Aronson, A. E., J. R. Brown, E. M. Litin, and J. S. Pearson. "Spastic dysphonia. II. Comparison with essential (voice) tremor and other neurologic and psychogenic dysphonias." Journal of Speech and Hearing Disorders 33, no. 3 (1969): 219–231.
Brown, J. R., and J. Simonson. "Organic voice tremor: a tremor of phonation." Neurology 13 (1963): 520–525.
Critchley, M. "Observations on essential (hereditofamilial) tremor." Brain 72 (1949): 113–139.
Hartman, D. E., and B. Vishwanat. "Spastic dysphonia and essential (voice) tremor treated with primidone." Archives of Otolaryngology 110 (1984): 394–397.
Hachinski, V. C. "Thomsen IV Buch NH The nature of primary vocal tremor." Canada Journal of Neurological Sciences 2 (1975): 195–197.
Koller, W. Graner, and D. A. Mlcoch. "Essential tremor: Treatment with propanolol." Neurology 35 (1985): 106–108.
Tomoda, H., H. Shibasaki, Y. Kuroda, and T. Shin. "Voice tremor: Dysregulation of voluntary expiratory muscles." Neurology 37: 117–122.
ORGANIZATIONS
American Speech-Language and Hearing Association. 10801 Rockville Pike, Rockville, MD 20852-3279. (301) 897-5700. <http://www.asha.org>.
National Spasmodic Dysphonia Association. One East Wacker Drive, Suite 2430, Chicago, IL 60601-1905. 800-795-6732. NSDA@dysphonia.org. <http://www.dysphonia.org>.
