116 Chapter 6
perceptual features of extrapyramidal disorders (Tosi, Tanner, & Supal, 1976). Laryngeal coordina-
tion and movement therapies for laryngeal disorders are provided during dynamic speech focusing
on the timing, speed, and integration of phonatory muscle movements.
Neuromuscular dysfunctions involving the velopharyngeal port result in phonation- resonance
disorders. To varying degrees, all of the dysarthrias— f laccid, spastic, ataxic, hyperkinetic, and
hypokinetic— can prevent the velum from approximating the posterior pharyngeal wall dur-
ing speech. Velopharyngeal incompetence in dysarthria results in hypernasality, audible nasal
emission, and reduced intraoral air pressure. Hypernasality, the excessive nasal resonance on
non-nasal sounds, occurs because the velum does not approximate the posterior pharyngeal wall.
Hypernasality also occurs during connected speech (assimilated hypernasality) because slow,
sluggish velopharyngeal closure allows nasal contamination of non-nasal sounds. In assimilated
hypernasality, because the velopharyngeal port does not close in a timely manner, non-nasal
sounds are produced with nasalization. Audible nasal emission is the escape of air through the
nasal port during the production of pressure phonemes. As discussed earlier, velopharyngeal
incompetence causes reduced intraoral air pressure on the production of obstruent phonemes. It
can reduce speech intelligibility, especially in weak patients.
In many patients with progressive neuromuscular disorders such as Parkinson’s disease, ALS,
and multiple sclerosis, reduction of hypernasality as a speech perceptual feature is secondary to
increasing intraoral air pressure to improve speech intelligibility. Several appliances are available
to force the velum to continually approximate the posterior pharyngeal wall. Although continual
closure of the velopharyngeal port results in denasality, it often raises the intraoral air pressure
necessary to increase speech intelligibility. For patients with milder resonance disorders, therapies
to reduce hypernasality and nasal emissions used in persons with cleft lip and palate are help-
ful. These include drills to maximize available velopharyngeal timing and closure. Lowering the
habitual fundamental frequency decreases the perception of hypernasality. Speaking with a wider
mouth opening can also reduce perceived hypernasality and reduce nasal emission because air,
like all gases and f luids, takes the path of least re sis tance, directing speech air and energy through
the mouth rather than through the nose.
Articulatory Valve
At the articulatory valve, the airstream and energy coming from the larynx are shaped into
speech sounds. The articulators create valves in the oral cavity where the airstream is shaped in
several ways. First, air and acoustic energy are brief ly and completely blocked in the production
of stop phonemes. Second, constrictions are created between articulatory sites in the production
of continuant phonemes. Third, the height, front- to- back position of the tongue, and lip rounding
create the acoustic characteristics of vowels. In dynamic speech, nearly 100 muscles and thousands
of neurological impulses per second are required to make the articulatory adjustments for intel-
ligible utterances.
The apraxia of speech discussed earlier often results in articulatory additions and substitu-
tions. The coordination and movement dysarthrias, such as those involving the cerebellum and
extrapyramidal systems, can also include the addition and substitution of speech sounds. Flaccid
and spastic dysarthrias often cause omissions and distortions. According to Duffy (1995), in
unilateral upper motor neuron dysarthria, “[t]he most common deviant speech characteristics
are imprecise articulation and irregular articulatory breakdowns, both of which may be apparent
during contextual speech and AMRs [alternate motion rates]” (p. 232).
Paralysis of the tongue primarily causes articulatory distortions and omissions. Spasticity, such
as seen in ce re bral palsy, as well as flaccidity of extrinsic and intrinsic tongue muscles, result in
reduced range of motion for shaping the airstream into speech sounds. Spasticity and f laccidity