• INCLUSION CRITERIA:

Healthy research volunteers and patients with SD, MTD, and VT from 21 years of age will be eligible for the study.

SD PATIENTS:

• A diagnosis of adductor or abductor SD will be based on voice testing and fiberoptic nasolaryngoscopy conducted during the initial interview by an otolaryngologist and speech-language pathologist according to following criteria:

  1. Intermittent strained hoarseness, uncontrolled voice breaks or changes in pitch during vowels, liquids (r & l), semivowels (w & y), during speech are present in adductor SD, or
  2. Prolonged voiceless consonants producing breathy breaks are present in abductor SD,
  3. Less prominent symptoms during whisper, singing or falsetto,
  4. Normal voice and vocal fold movement for protective and emotional laryngeal function, such as cough, laugh or cry.
• Postmortem brain and larynx tissue from SD patients deceased from other than neurological, psychiatric, laryngological causes which would not affect our study as determined by medical history.

MTD PATIENTS:

• Increased phonatory muscle tension in the paralaryngeal and suprahyoid muscles on palpation;
• A consistent hypertonic laryngeal posture for phonation, such as either an anterior-posterior squeeze (pin-hole posture) or ventricular hyperadduction and an absence of SD or vocal tremor as determined by a Speech-Language Pathologist and the staff otolaryngologist;
• Exclusion of other laryngeal pathologies based on a fiberoptic nasolaryngoscopic examination conducted during the initial interview by the staff otolaryngologist.

VT PATIENTS:

• Vocal tremor during vocalization that primarily involves laryngeal structures;
• Exclusion of other laryngeal pathologies based on a fiberoptic nasolaryngoscopic examination conducted during the initial interview by the staff otolaryngologist.

CONTROLS:

• Normal vocal function refers to normal voice quality with a negative history of voice or laryngeal disorders.
• Research volunteers without neurological, psychiatric, otolaryngological problems as determined by medical history and examination by a physician.

EXCLUSION CRITERIA:

• Pregnant women will be excluded from the study until a time when they are no longer pregnant.
• Any individual with a medical history or postmortem diagnoses of one or more of the following contraindications will be excluded from the study:

SD, MTD, AND VT PATIENTS:

• Other laryngeal pathologies as determined by medical history and fiberoptic nasolaryngoscopic examination conducted during the initial screening by the otolaryngologist and speech-language pathologist, such as:

  1. Vocal fold paralysis, paresis, joint abnormality, or neoplasm;
  2. Vocal fold nodules, polyps, carcinoma, cysts, contact ulcers, or chronic laryngitis;
  3. Swallowing problems; airway obstruction
• Speech problems as determined by medical history and examination by the otolaryngologist and speech-language pathologist.
• Neurological diseases and disorders such as stroke affecting the brain regions of interest, movement disorders (e.g., Huntington disease, chorea, myoclonus, Gilles de la Tourette syndrome, Parkinson's disease, progressive supranuclear palsy, and neuroleptic-induced syndromes), brain tumors, traumatic brain injury with loss of consciousness, genetic diseases of the CNS, chronic infections of the nervous system, ataxias, myopathies, myasthenia gravis, demyelinating diseases, epilepsy, alcoholism, and drug dependence.
• Psychiatric diseases and disorders such as schizophrenia, major and/or bipolar depression, and obsessive-compulsive disorder.

CONTROLS:

• Laryngeal pathologies as determined by medical history and fiberoptic nasolaryngoscopic examination conducted during the initial screening by the otolaryngologist and speech-language pathologist, such as:

  1. Spasmodic dysphonia, muscular tension dysphonia, voice tremor;
  2. Vocal fold paralysis, paresis, joint abnormality, or neoplasm;
  3. Vocal fold nodules, polyps, carcinoma, cysts, contact ulcers, or chronic laryngitis;
  4. Swallowing problems;
• Speech problems as determined by medical history and examination by the otolaryngologist and a speech-language pathologist.
• Neurological diseases and disorders such as stroke affecting the brain regions of interest, movement disorders (e.g., Huntington disease, chorea, myoclonus, Gilles de la Tourette syndrome, essential tremor, Parkinson's disease, progressive supranuclear palsy, and neuroleptic-induced syndromes), tumors involving the brain region of interest, genetic diseases of the CNS, traumatic brain injury with loss of consciousness chronic infections of the nervous system, ataxias, myopathies, myasthenia gravis, demyelinating diseases, epilepsy, alcoholism, and drug dependence.
• Psychiatric diseases and disorders such as schizophrenia, major and/or bipolar depression, and obsessive-compulsive disorder.