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Types of Voice Disorders
Dysarthria
Dysarthria is a speech disorder resulting from neurological
injury including amyotrophic lateral sclerosis (ALS or Lou
Gehrig’s disease),
cerebral
palsy, Parkinson’s disease, locked-in syndrome, multiple sclerosis and
traumatic brain injury. It may also
arise from
other
diseases with neurological sequelae, including tumor, postoperative
complications, inflammatory and metabolic diseases, and other sporadic,
degenerative neurological conditions.
After a
stroke or other brain injury, the muscles of the mouth, face, and
respiratory
system may become weak, move slowly, or not move at all, resulting in
dysarthria. An individual with severe
dysarthria is
able to
formulate intent to communicate (i.e., to formulate a thought,
linguistically
encode it appropriately as a message, and program the motor sequence
necessary
to produce the message as speech). However, that individual’s body is
unable,
because of the disability, to execute those commands that control
speech
production.
The type and severity of
dysarthria
depends on
which area of the nervous system is affected. The complete loss of
speech is called "anarthria". Dysarthric speech is
characterized by
problems with articulation (i.e., production of speech sounds), voicing
(i.e.,
volume and quality of speech) and prosody (i.e., speech rate, rhythm
and
naturalness). The symptoms include: "slurred" speech, slow rate of
speech, rapid rate of speech with a "mumbling" quality, speaking softly
or barely able to whisper, limited tongue, lip, and jaw movement,
abnormal intonation, changes in vocal quality ("nasal" speech or
sounding
"stuffy"), hoarseness, breathiness, drooling or poor control of
saliva, chewing and swallowing difficulty.
Vocal
Cord Impairments
Vocal fold motion impairment is of two major types:
unilateral (more common) and bilateral. These types differ in their
seriousness, symptoms, and treatment.
Patients with unilateral paralysis may exhibit
a weak and "breathy" voice, and speaking may require considerable
effort. Because the vocal folds are unable to close completely during
swallowing, patients may also experience coughing and choking while
eating or drinking. Patients with bilateral paralysis may experience
these symptoms, but the possibility of a compromised airway is a more
serious threat. The muscles which normally abduct the folds and provide
for a patent airway are unable to function. Thus, the folds may remain
adducted in the airway and block normal respiration.
The most common cause of vocal fold motion impairment is injury to the
recurrent laryngeal nerve, the nerve responsible for controlling the
intrinsic muscles of the larynx. This may be due to trauma, surgery,
viral infection, a tumor pressing on the recurrent laryngeal nerve, or
other causes. Occasionally, injury or diseases of the brain, including
stroke, result in impaired motion. Mechanical obstruction can also
result in vocal fold motion impairment. The arytenoid cartilages can
become "locked" and restrict movement. Scar tissue may also accumulate
and inhibit vocal fold movement.
Spasmodic
dysphonia
What is
spasmodic
dysphonia?
Spasmodic dysphonia (SD), a focal
form of dystonia, is a neurological
voice disorder that involves involuntary "spasms" of the vocal cords
causing interruptions of speech and affecting the voice quality.
Types of
spasmodic
dysphonia
The two types of recognized spasmodic dysphonia are
adductor spasmodic
dysphonia and abductor spasmodic dysphonia. Adductor SD causes an
intermittent excessive closing of the vocal folds during vowel sounds
in speech; while in abductor SD, there is a prolonged vocal-fold
opening during voiceless consonants. The control problems of the vocal
cords result in different speech symptoms in the two types of disorder.
There are three subtypes of SD which have been identified by
clinicians. One is a combination of adductor and abductor symptoms in
which an individual may demonstrate both types of spasms as he/she
speaks. In a second subtype, SD symptoms are accompanied by a voice
tremor. A third subtype involves a primary voice tremor that is so
severe the patient experiences adductor voice stoppages during the
tremor.
What
causes
spasmodic dysphonia?
The cause of spasmodic dysphonia is unknown. The general
medical
consensus is that SD is a central nervous system disorder and a focal
form of dystonia. Dystonia is the general neurological term for a
variety of problems characterized by excessive contraction of muscles
with associated abnormal movements and postures. Dystonia disorders are
thought to originate in the area of the brain called the basal ganglia,
which are that help coordinate movements of the muscles throughout the
body.
Treatment for
spasmodic dysphonia
Botulinum
toxin injections
Local injections of botulinum toxin (BTX) into the vocal
cord muscles have
proven to be the most effective treatment for spasmodic dysphonia. The
treatment weakens the vocal muscles so that spasms are greatly
diminished and
speech is greatly improved. The treatment can also reduce the
breathiness and
help decrease the effort required to speak
Surgery
Surgery may be performed for people for whom botulinum toxin injections
are no
longer providing relief of symptoms.Selective Laryngeal Adductor
Denervation-Reinnervation surgery involves cutting the nerve to the
affected
vocal cord and re-innervating the muscle with another muscle to prevent
muscle
atrophy.
Speech Therapy
General voice relaxation techniques and speech therapy may play an
adjunct role
in the treatment of spasmodic dysphonia. These include reducing one's
vocal
effort, loudness, intonation, and rate of utterance while increasing
pause time
between phrases. These techniques can only be reinforced and adapted if
they do
not intrude on the vocal naturalness.
Aphonia
Aphonia
refers to an
inability to
produce
voice
naturally (i.e., due to physical impairment) and/or inability to
produce voice
by using a speech prosthesis (e.g., Passy-Muir valve, electrolarynx,
tracheoesophageal puncture) due to physical disability or absence of
larynx.
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