Spastic dysphonia (SD) is an uncommon,
sometimes debilitating, disorder of unknown
aetiology, probably a form of focal dystonia,
originally described as nervous hoarseness by
Traube in 1871.
In 1973 a subdivision of the entity was
suggested by Aronson who distinguished between
abductor SD, where there is a widening of the
glottis causing intermittent aphonia with
breathy phonation and adductor SD, associated
with adduction of the true and/or false vocal
cords, with speech characterised by a strained,
low-pitch, harsh, monotonous, staccato,
effortful voice with intermittent voice
stoppages.
Over a 6-year period 20 patients (7 male and
13 female) with the characteristics of adductor
SD were seen at St Vincent's Hosptial, Sydney.
All underwent a routine medical and neurological
examination, voice analysis and review by an ear
nose and throat surgeon (the latter two reported
elsewhere). The clinical notes of these patients
were reviewed and combined with the results of a
mail survey (response 17 of 20 subjects).
Clinical Features : Nine of the
patients experienced a voice tremor associated
with an essential tremor (SD+ET), variably
involving the head, trunk and limbs (one patient
had a family history of tremor). Seven patients'
employment required the active use of their
voices (e.g. teachers, a telephonist).
The patients were divided into those with
essential tremor (SD+ET) and those without
essential tremor (SD alone).
Onset : Ten patients experienced a
gradual onset of dysphonia, with the remaining
10 noting an abrupt onset, in 3 related to an
upper respiratory tract infection and in 7 to
psychosocial stress. The mean age of onset in
patients with SD alone was 45 years (range 30 to
54 years) and for SD+ET 52 years (range 15 to 67
years).
Course and Duration : The mean
duration of the speech disorder prior to review
was 8.8 years for SD alone, and 14 years for
SD+ET. Of the 17 patients responding to the
later postal survey, 8 noted no change, 4 a
worsening and 5 an improvement in their speech
since the onset of SD (equally divided between
patients with or without ET).
Factors Affecting the Quality of Speech :
Patients with or without ET were equally
divided with respect to factors that worsened
speech, but no patients with SD+ ET noted an
improvement with strong emotional statements,
waking in the morning, use of a loud voice or on
being woken from sleep. Only 1 or 2 patients
with SD+ET reported improving with yawning,
swallowing, speaking in a low or high pitch,
laughing, making spontaneous statements or
singing. Two patients with SD alone noted
that inspiratory speech was more effective than
expiratory speech.
Abnormalities on Physical Examination :
The following abnormalities were noted on
physical examination: a brisk jaw or facial jerk
(2/20 subjects); mild cogwheel rigidity of the
upper limbs (1/20); hypertensive retinopathy
grade 2 (3/20) and dysphagia (pharyngeal web)
(1/20). No structural abnormalities were noted
on ENT examination in any subject.
Therapy : Only a small number of
patients received pharmacological therapies
including alcohol (SD+ET 2/2 excellent
responses, SD alone, 2/4 slight to good
response), propranolol (SD+ET 3/5 slight to good
response), benzhexol (SD+ET 1/2 slight response;
SD alone, 3/3 slight response) and doxepin
(SD+ET 1/2 slight response; SD alone, 2/2 slight
response). Two patients were intolerant of the
side effects of benzhexol. Other therapies given
in 1 or 2 patients only with no or only a slight
response included phenobarbitone, clonazepam,
clobazam, diazeparn, benzhexol, carbamazepine
and intravenous lignocaine/mexiletine.
Speech therapy yielded a slight to good
response in 7 of 13 patients. Relaxation therapy
resulted in a slight to good response in 6 of 8
patients. Patients with SD+ET and SD alone
responded equally to speech and relaxation
therapy.
Two patients with SD alone underwent
recurrent laryngeal nerve sectioning, one with a
good response and the other with a temporary
improvement (although the speech remained better
than prior to operation).
Discussion : The patient group
described is similar to other published series
although showing a female predominance. The
onset was mainly in middle age (slightly later
for patients with SD+ET), and was in half
related to an upper respiratory tract infection
or psychosocial stress, probably fortuitous.
The over all course showed little tendency
for spontaneous improvement, with a number of
factors such as stress, public speaking,
tiredness, strong emotions, upper respiratory
tract infections and prolonged use of the voice
temporarily worsening speech in patients with
both SD+ET and SD alone. Patients with SD alone
experienced a temporary improvement in speech
related to laughing, yawning, slow
speech, use of a quiet voice, making spontaneous
statements,employing high and low pitch,
chewing, swallowing and on first waking in the
morning. Little improvement in speech was noted
by patients with SD+ET.
To date, SD has proven to be a distinct
nosological entity. The presence of any other
neurological abnormality should alert the
clinician to the existence of another disease
process. Dysphagia, present in one patient in
this series, was due to a pharyngeal web.
The number of patients given pharmacological
therapy was small, with SD+ET patients
responding to alcohol or propranolol, whereas
patients with SD alone responded less frequently
and less well to alcohol or benzhexol or
doxepin. Speech therapy offered slight to good
improvement and relaxation therapy slight
improvement in both patient groups.
Of 2 patients undergoing recurrent laryngeal
nerve sectioning (RLNS) one experienced a good
outcome, whereas the other noted only temporary
good improvement, although speech remained
better than prior to surgery. Dedo et al in a
review of 121 patients undergoing RLNS for SD
found a 92% satisfactory reduction in spasticity
in the first 1 to 3 years. In a slightly
different patient group (including more patients
with voice tremor) Aronson et al. recorded only
a 36% improvement at 3 years.
Botulinum toxin injection has recently been
shown to bc of benefit, but awaits further
detailed investigation.
An association between essential tremor and
the characteristic features of SD bas been noted
frequently. Aronson et al. noted the regular
occurrence of voice stoppages at the point of
highest pitch on each tremor cycle (tremor
median frequency of 5.5 Hz) and a constant
strained-strangled dysphonia in patients with
SD+ET. In contrast, patients with SD alone
tended to experience irregular voice stoppages
and an intermittent strained-strangled
dysphonia. Aronson therefore postulated that
patients with SD+ET represent an extreme variant
of essential tremor. Alternatively this variant
may represent an association between essential
tremor and a focal dystonia, as has been noted
with other disorders (e.g. spasmodic torticollis
and essential tremor)
.
