Amyotrophic lateral sclerosis: Toward evidence-based management of dysarthria

1
Amyotrophic lateral sclerosis Toward
evidence-based management of dysarthria

• Kathryn M. Yorkston, PhD, BC-NCD
• Laura Ball, PhD
• David R. Beukelman, PhD
• Pamela Mathy, PhD

2
Website
http//www.ticeinfo.com http//aac.unl.edu
3
Amyotrophic Lateral Sclerosis (ALS)

• Degenerative motor neuron disease
• Muscle atrophy and spasticity
• In the limbs and bulbar muscles
• Dysarthria and dysphagia are common
• Decisions for SLP re types timing of
• speech intervention
• AAC intervention

4
Overview

• An introduction to evidence-based decision
  making
• Yorkston - University of Washington
• Question 1 How can early bulbar symptoms be
  identified?
• Ball - University of Nebraska, Omaha
• Question 2 What techniques are appropriate for
  maintenance of natural speech in progressive
  dysarthria?
• Beukelman, University of Nebraska, Lincoln
• Question 3 Are AAC techniques effective in
  maintaining communication in ALS?
• Mathy, Arizona State University

5
Introduction of Terms

• Evidence-based practice
• Practice guidelines
• Staging of intervention

6
Toward Evidence-Based Practice

• Medical students do the wrong things in a
  clinical setting not because of a deficiency in
  knowledge, but because they dont make good
  decisions. They know a lot, but they dont think
  systematically.

(Arthur Elstein, Ph.D, University of Illinois,
presenting a lecture at University of
Washington, April 27, 1999).
7
Evidence-Based Practice

• . . is a commitment to a constant reexamination
  of practices through research and outcomes
  analyses.

- Enhancing our knowledge-base - Enhancing our
decision making
Sackett et al., (1997)
8
Evidence-Based Practice

• . . an approach to decision making in which the
  clinician uses the best evidence available, in
  consultation with the patient, to decide upon the
  option which suits that patient best.

Muir Gray, 1997
9
Evidence-based practice is of interest to

• Practitioners
• Policymakers
• Payers
• Purchasers
• Patients
• Public

10
Definition Practice Guidelines

• Clinical practice guidelines are explicit
  descriptions of how patients should be evaluated
  and treated. The explicit purpose of guidelines
  is to improve the quality of care and to assure
  it by reducing variation in care provided.

- review of evidence - consensus of experts
11
Practice GuidelinesExamples from ALS

• breaking the news to patients and families,
• nutrition and PEG placements,
• respiratory insufficiency and mechanical
  ventilation,
• management of emotional lability,
• and palliative care.

American Academy of Neurology Miller et al, 1999
12
ANCDS - Practice Guidelines

• Velopharyngeal Management
• Behavioral Tx of Respiration/Phonation
• Surgical/Pharm. Tx of Phonation
• Speech Supplementation
• Tx of Speech Rate Naturalness

• Technical Report due Nov. 2000
• Ready for expert review Jan. 2001
• Ready for expert review Jan. 2001
• Ready for expert review Dec. 2000
• To be drafted, 2001

13
Definition Staging

• . . . the sequencing of management so that
  current problems are addressed and future
  problems anticipated.

14
ALS Stage 1

No Detectable Speech Disorder
. . Diagnosis has been made, but often speakers
do not yet exhibit speech symptoms in those with
spinal presentation.
15
ALS Stage 2

Obvious Speech Disorder with Intelligible Speech
. . both the speaker and listener notice changes
in speech - speakers may perceive extra effort
needed for speech.
16
ALS Stage 3

Reduction in Speech Intelligibility
. . . changes in speaking rate, articulation, and
resonance are all evident.
17
ALS Stage 4

Natural Speech - Supplemented
. . . natural speech is no longer a functional
means of communication in all situations.
18
ALS Stage 5

No Functional Speech
. . . speakers with advance bulbar ALS have lost
functional speech due to profound weakness.
19
Staging

• Question 1 How can early bulbar symptoms be
  identified?
• Stages 1 and 2 - Early intervention
  
• Question 2 What techniques are appropriate for
  maintenance of natural speech in progressive
  dysarthria?
• Stages 3 and 4 - Moderate to severe dysarthria
• Question 3 Are AAC techniques effective in
  maintaining communication in ALS?
• Stage 4 and 5 Severe to profound dysarthria

20
How can early bulbar symptoms be identified?

• Laura J. Ball, Ph.D.

21
Rationale

• With the advent of new drug interventions for
  ALS, early diagnosis identification of bulbar
  symptoms has become critical.
• (Quality Standard Subcommittee of the American
  Academy of Neurology, 1997)

22

• Diagnostic techniques that may be implemented to
  facilitate early identification of bulbar ALS
  symptoms have become essential for pharmaceutical
  communication interventions.

23
Review of literature

• In the 1990s, treatments were tested to slow ALS
  progression. Decision-making regarding these
  interventions requires
• information to place these treatments in the
  context of other treatments and
• to understand the significance of the efficacy
  these treatments may show.
• Many drug trials target addressing the earliest
  possible signs of ALS.

24
Bulbar Characteristics

• Speech swallowing symptoms usually parallel --
  71 of 200 consecutive visits(Yorkston, Miller
  Strand, 1995)
• First symptoms involve
• swallowing difficulties
• dysarthric speech
• possible nasal resonance changes
• laryngeal changes

25
Focus on Bulbar Characteristics of Dysarthria

• Neurological or neuromuscular damage causing
  paralysis, paresis, or incoordination in the
  bulbar or spinal sensorimotor systems can affect
  the range, velocity, force, or timing of speech
  movements as well as the respiratory processes
  that support speech production. (Warren,
  Rochet, Hinton, 1997, p. 81)

26
ALS Dysarthria Database

• N 218 visits of persons with ALS documented
• Protocol measurement includes numerous factors
  including intelligibility, speaking rate,
  aerodynamic measures of oral pressure nasal air
  flow, VP descriptor from aerodynamic measures,
  communication effectiveness ratings (self
  listener), ALS Severity Rating Scale

27
ALS Database Questions

• Who is going to need AAC?
• How soon do we know they will need AAC?
• What will predict loss of intelligible speech
  with sufficient time to implement functional
  interventions?
• Assess
• Acquire Device
• Training

28
Question 1

• Who is going to need AAC?
• How do we identify bulbar characteristics of
  dysarthria?
• How do we assess speech characteristics?

29
Speech Assessment Strategies

• Intelligibility
• Speaking Rate
• Aerodynamic Measurements
• Pattern of Velopharyngeal Closure
• ALS Speech Severity Scale
• Communication Effectiveness

30
Intelligibility

• Sentence Intelligibility Test
• (Yorkston, Beukelman Tice, 1991)
• Measures intelligibility in sentences
• Scored by unfamiliar (to speaker content)
  listener
• Obtain intelligibility

31
Speaking Rate

• Sentence Intelligibility Test
• Speaking rate in sentences
• Obtain rate in words per minute

32
Rate Intelligibility

• Changes in speech rate and oral diadokokinetic
  rates may be precursors of changes in speech
  intelligibility.
• (Yorkston,Strand, Miller, Hillel Smith, 1993)

33
Rate Intelligibility

• Information obtained from the UNMC database is
  consistent with previous research, in that when
  rate decreases to half of normal (or
  approximately 100 wpm) for an individual with
  ALS, a precipitous decline in intelligibility may
  be expected.
• R2 .828, p .000

34

35
Garys Progression

• A 40 year old male with bulbar onset of
  symptoms.
• 09/1999 97 intelligible, rate 90wpm
• 11/1999 75 intelligible, rate 68wpm
• 02/2000 33 intelligible, rate 52wpm
• 05/2000 6.8 intelligible, rate 36wpm

36
Aerodynamic Measurement Rationale

• Accurate description of speech deficits
• Develop new treatment approaches
• Demonstrate quantifiable changes in physiologic
  responses
• (Warren, Rochet, Hinton, 1997)

37
Aerodynamic Measurement of Speech Productions

• Air Flow Meter
• (pneumotachograph with nasal mask)
• Normally no flow unless /m, n, ?/
• Air Pressure Transducer
• (flexible tube placed laterally on tongue)
• Normal between 3-8cm H2O)

38
Pattern of VP Closure

• Obtained from Aeros printouts.
• 1. VP closure on pressure consonants
• 2. Initial VP insufficiency, eventually closes
• 3. VP insufficiency on some consonants,
  approximates but never closes
• 4. Initial VP closure, insufficient by end of
  utterance
• 5. Excessive VP insufficiency on all pressure
  consonants

39
VP Closure Intelligibility

• Consistent with Intelligibility and Speaking Rate
  measures, VP closure and Intelligibility
  measures remain fairly steady until the person
  with ALS completely and consistently loses
  velopharyngeal closure.
• R2 -.393, p.005

40
VP Closure Speaking Rate

• Examination of data assessing VP closure and
  Speaking Rate indicate a pattern similar to that
  identified with Speaking Rate and
  Intelligibility.
• When Speaking Rate approximates 100wpm,
  Intelligibility takes a rapid precipitous
  decline.

41
VP Closure Rate

• Likewise, when Speaking Rate approximates 120wpm,
  the Pattern of VP closure changes to demonstrate
  progressively more consistent VP incompetence.
  Another decline is observed at the 100wpm mark.
• These data indicate that VP Closure Pattern/Rate
  changes precede Intelligibility/ Rate changes in
  persons with ALS.

42
VP Closure ALS Speech Rating

• Pearson Product-Moment Correlation
• (R2 -.417 p .002)
• With increase in VP rating, observe lower ALS
  Speech Ratings

43
Question 2

• How soon do we know about the loss of natural
  speech?

44
Communication Effectiveness

• Modified Index (Lomas, 1989)
• Measure societal limitation perceived when
  communicating
• Likert-type scale
• 0 not at all able
• 6 very effective
• 10 contextual situations

45
I am effective at conversing with

• 1. familiar persons in a quiet environment.
• 2. strangers in a quiet environment.
• 3. a familiar person over the phone.
• 4. young children.
• 5. a stranger over the phone.
• 6. while traveling in a car.
• 7. someone at a distance.
• 8. someone in a noisy environment.
• 9. before a group.
• 10. someone in a long conversation (gt1 hour).

46
Intelligibility Communication Effectiveness

• Communication effectiveness scores followed a
  stair-step decline following a decline in
  intelligibility.

47
Communication effectiveness declines occurred
at...

• 1st at 95 gt intelligibility (m 5.5)!!
• 2nd at 90-95 intelligibility (m 4.7)
• 3rd at 80-90 intelligibility (m 3.7)
• 4th at 70-80 intelligibility (m 2.3)
• Final at lt 70 intelligibility (m 1.5)

48
Intelligibility Communication Effectiveness

49
Intelligibility Communication Effectiveness

• With some slight (nonsignificant) differences,
  speakers with ALS and their frequent
  communication partners (spouses, children,
  caregivers) demonstrate similar descriptions of
  communication effectiveness.

50
Recommendations

• It is recommended that evidence-based speech
  assessment strategies be implemented into a
  protocol to facilitate early identification of
  bulbar ALS symptoms.
• Early identification may promote earlier
  diagnosis of ALS provide a more reasonable
  timeline to physicians wishing to implement drug
  trials patients wishing to take advantage of
  them.

51
Maintaining the Use of Natural Speech (David
Beukelman)

• Behavioral Interventions
• Environmental Interventions
• Prosthodontic Interventions
• Supplemented Speech Interventions

52
Behavioral Interventions

• Speaking rate modification
• Speakers usually reduce rate with
  intervention--especially with cognitive changes.
• Maintain coordinated respiratory patterns
• Coordinated thoracic and abdominal breath
  (speech grammatical structure)
• Reduce fatigue
• Conserve energy for communication
• Eliminate oral or non-speech exercises

53
Prosthodontic Interventions

• Palatal lift
• Palatal augmentation (drop-down)
• Voice amplification

54
Palatal Lift Evidence

• Gonzalez Aronson (1970).
• Aten, et al. (1984).
• Esposito et al. (2000) retrospective study
• 21 of 25 speakers with ALS decreased
• hypernasality
• 2 of 25 refused to wear the lift
• 4 of 25 received no benefit
• Progression of tongue and lip weakness almost
  always cause for lack of benefit.

55
Palatal Augmentation

• Esposito et al (2000).

56
Environmental Interventions

• Optimize hearing of frequent listeners
• Optimize adverse speaking situations
• Reduce background noise
• Mute TV
• Amplify speaker in meetings, groups, noise
• Private conference room

57
Supplemented Speech Interventions

• Alphabet Supplementation
• Topic Supplementation
• Mixed Topic Alphabet Supplementation
• Gestural Supplementation

58
Mutuality Model (Lindbolm, 1990)
Rich

• Information
• from
• Speech
• Signal
• (Speech
• Intelligibility)

Understanding
Poor
Poor
Rich
Information from Non-speech Sources
59
Intelligibility
Speech Impairment Compensatory Strategies

• Acoustic
• Signal

Listener Processing
Speech Intelligibility
Language Knowledge World Knowledge Disability
Knowledge
60
Comprehensibility
Speech Signal Information Speech Impairment
Compensatory Strategies
Signal-Independent Information Semantic
Context Syntactic Context Alphabet
Gestures
Acoustic Signal
Listener Processing
Speech Comprehensibility
Language Knowledge World Knowledge Disability
Knowledge
61
Alphabet Semantic Topic Board
Small Talk
Church
Food
Health
Schedule

• Family

Family
Yes
Wait
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
Personal
No
Not done
Transportation

Please stop
Trips
Start over
Not finished
Weather
Forget it
Sports
Please repeat words
Will spell words
Maybe
Shopping
Point to first letter
Dont know
62
Alphabet Supplementation

• Beukelman Yorkston (1977)
• 42 47 improvement in intelligibility (TBI
  BS Stroke)
• Schumacher Rosenbek (1986)
• 57 improvement in intelligibility (PD)
• Hustad (1999) (Pilot for Dissertation)
• 42.5 Improvement in Intelligibility (CP)
• Crow Enderby (1989)
• 15 Mean improvement in intelligibility (speech
  signal only) (mixed group of speakers)
• Hustad Beukelman (Submitted)
• 19 Mean improvement in intelligibility (Alphabet
  information with habitual speech) (CP)

63
Topic Supplementation

• (Dongilli, 1994)

64
Topic Supplementation (Cont)

• Carter et al. (1996).
• 9 Mean improvement in intelligibility
• Hustad Beukelman (1998)
• 10 Improvement in intelligibility
• Hustad Beukelman (Submitted)
• 10 mean improvement in intelligibility (Topic
  information with habitual speech (CP).

65
Semantic Supplemented Speech (Hammen, Yorkston,
Dowden, 1991)

• Speaker Group Sentence Intell() Sentence
  Intell()
• No Context Semantic
  Context
• Profound 2 20
• Severe 27 67
• Moderate 64 96

66
Mixed (Topic Alphabet) Supplementation

• Hunter, Pring, and Martin (1991)
• 15 relative to topic cues only.
• Hustad Beukelman (Submitted)
• 34 Mean improvement for mixed compared to no
  cues (Mixed cues with habitual speech) (CP)

67
Gestural Cues

• Garcia Cannito (1996).
• 25 Improvement in low predictive context
• 22.5 Improvement in high predictive context

68
Techniques for Improving Comprehensibility
(Speaker-1)

• Provide listener with context
• Dont shift topics abruptly
• Use turn-taking signals
• Get your listeners attention
• Use complete sentences
• Use predictable types of sentences
• Use predictable wording
• Rephrase you message

Yorkston, Beukelman, Strand, Bell, 1999
69
Techniques for Improving Comprehensibility
(Speaker--2)

• Accompany speech with simple gestures
• Take advantage of situational cues
• Make environment as friendly as possible
• Avoid communication over long distances
• Use alphabet board supplementation
• Have a handy backup system

Yorkston, Beukelman, Strand, Bell, 1999
70
Techniques for Improving Comprehensibility
(Listener-1)

• Know topic of conversation
• Watch for turn-taking signals
• Give your undivided attention
• Choose time and place to talk
• Watch the speaker
• Piecing together the cues
• Make the environment work for you
• Avoid communicating over long distances

Yorkston, Beukelman, Strand, Bell, 1999
71
Techniques for Improving Comprehensibility
(Listener-2)

• Make sure
• your hearing is as good as possible
• Decide on and incorporate strategies for
  resolving communication breakdowns
• Establish some rules of the game
• Facilitate communication with others

Yorkston, Beukelman, Strand, Bell, 1999
72
AAC ALS Pam Mathy
73
AAC Methods Used By Individuals Who Have ALS
(Pam Mathy)

• Unassisted methods--these methods do not involve
  any form of chart or electronic device
• Low tech methods--these methods use some form of
  chart (e.g., alphabet board) and some means to
  access it (e.g., finger, light pointer, partner
  scan). Also included here is handwriting (e.g.,
  paper, pencil, dry-erase boards, magic slate)

74
Laser Pointer With Alphabet Board
75
Partner Assisted Manual Scan Board
76
Partner Assisted Manual Scanning
77
Handwriting Using White Board
78
AAC Methods Used By Individuals Who Have ALS

• High tech methods--these methods involve use of
  an electronic device
• Uni-Access Devices Synthesized Speech Devices
  Accessed Primarily Using Manual Direct Selection
  (e.g., LightWriter, Link, IMPACT)
• Multi-Access Devices Synthesized Speech Devices
  Designed To Support Multiple Access Methods
  (e.g., Freedom 2000, DynaVox)

79
Uni-Access Devices LightWriter Series--Zygo
Dual display, direct select scanning, DECtalk,
custom-keyboard arrangement, very portable,
letter-coding, phrase storage.
80
Uni-Access Devices LinkAssistive Technology
Inc.
Direct-selection access only, Letter-coding, Phras
e storage, DECtalk, Standard size
keyboard, Relatively low- cost.
81
Uni-Access Devices IMPACTENKIDU Research
Handheld Portable IMPACT combines a large
keyboard (80 of full size) with a touchscreen to
provide additional methods of message production.
The expanded touchscreen means that you can have
more (or larger) onscreen buttons, allowing for
more varied augmentative interfaces. With its
nylon carrying case, the Handheld can be used
effectively while standing or sitting.
InputsTouchscreen, keyboard, scanning.
82
Multi-Access Devices E Z Keys for WindowsWords

83
Multi-Access Devices DynaVox Sunrise Medical
84
Switches and Mounts
Jellybean switch (Ablenet)
Slimarmstrong (Ablenet)
85
Decision Parameters in AAC Intervention

• Disease Progression
• Employment Status
• Age
• Motivation to Communicate
• Support (family, friend, employer)

86
Disease Progression

• Using ALS severity scale (ALSSS) (Hillel, Miller,
  Yorkston, McDonald, Norris Konikow, 1989
• Yorkston, et. al. (1993) followed
• 101 individuals
• Fifty eight men
• Fifty two women
• Across 303 clinic visits
• Six profiles were identified based on Speech,
  Upper Extremity and Lower Extremity Functioning

87
Functioning Cutoffs on ALSSS Used to Identify
Groupings

• Adequate speech 5 or greater (Stages 1 3).
• Poor speech 4 or less (Stages 4 and 5)
• Adequate UE 5 or greater (partial complete
  use of UE)
• Poor UE 4 or less (needs assistance in
  self-care, cant use pencil/pen)
• Adequate LE 7 or greater (noticeable gait
  changes normal ambulation)
• Poor LE 6 or less (impaired mobility--requires
  cane, walker, wheelchair)

88
Disease Progression Groupings Identified by
Yorkston, et. al.

• Group 1 (46.5)--adequate speech, adequate UE
• Group 2 (20)--adequate speech, poor UE
• Group 3 (16)--poor speech, adequate UE and LE
• Group 4 (8)--poor speech, adequate UE, poor LE
• Group 5 (2.5)--poor speech, poor UE, adequate LE
• Group 6 (7)--poor speech, UE and LE

89
AAC Interventions Used by Disease Progression
Group

• Group 1 (46.5)--adequate speech, adequate UE
• None
• Portable amplifiers
• Alphabet Supplementation

90
AAC Interventions Used by Disease Progression
Group

• Group 2 (20)--adequate speech, poor UE
• None
• Portable amplifiers
• Alphabet Supplementation
• Assess for writing augmentation (computer access)
  if desired--writing now--speech later

91
AAC Interventions Used by Disease Progression
Group

• Group 3 (16)--poor speech, adequate UE and LE
• Low tech alphabet boards/supplementation
• Handwriting
• Magic slate
• White boards
• High tech devices depending on needs
• Community, work, car
• Portable, keyboard-based
• Phone
• Talking word processors, email for home computer
• TTD, FAX

92
AAC Methods Used by Patients With Bulbar
Presentation (Groups 3 4)
93
Category of AAC Method(s) Used Most of the Time
by Communicative Activity
Bulbar Presentation Patients
No Tech
Stories
Handwriting
Written Comm
Other Low Tech
In depth Info.
High Tech
Phone
Doesn't Participate
Detailed Needs
Quick Needs
Conversation
0
2
4
6
8
10
12
Number of Patients (Total N12)
94
AAC Interventions Used by Disease Progression
Group

• Group 4 (8)--poor speech, adequate UE, poor LE
• Most issues similar to group 3
• Portable AAC devices can be mounted on wheelchair
• Attention getting devices

95
AAC Interventions Used by Disease Progression
Group

• Group 5 (2.5)--poor speech, poor UE, adequate LE
• No tech partner dependent auditory scanning
• Low tech partner dependent visual scanning
• Low tech optical pointing
• Portability needs
• High tech dedicated and/or multipurpose systems
• Light weight, portable
• Adaptations to home computer
• Attention getting devices

96
AAC Interventions Used by Disease Progression
Group

• Group 6 (7)--poor speech, UE and LE
• No tech partner dependent auditory scanning
• Low tech partner dependent visual scanning
• Low tech optical pointing
• High tech dedicated and/or multipurpose systems
• Check needs for portability--wheelchair mounting
• Adaptations to home computer
• Attention getting devices

97
AAC Methods Used by Patients With Spinal
Presentation (Groups 5 and 6)
Coded Eye- Blink
Dep. Aud. Scanning
Yes/No Hier.
Alphabet Board (S or D)
Call Buzzer
Multipurpose Device
Facial Expr.
Yes/No Questions
x
x
x
S
x
x
J,P
x
x
x
x
S
x
x
D,D
x
x
x
x
x
I,G
x
x
x
S
x
x
C,A
x
x
S
x
x
J,M
x
x
x
x
x
x
O,O
x
x
x
x
x
P,M
x
x
x
S
x
x
P,W
x
x
D (optical pointer)
x
x
L,L
x
x
x
S
x
x
L,J-1
x
x
x
S
x
x
L,J-2
x
v
S
x
x
E,V
98
Category of AAC Method(s) Used Most of the Time
by Communicative Activity
Spinal Presentation Patients
No Tech
Stories
Low Tech
Written Comm
High Tech
In depth Info.
Doesn't Participate
Phone
Detailed Needs
Quick Needs
Conversation
0
2
4
6
8
10
12
Number of Patients (Total N12)
99
Overall AAC Method Use Breakdown by Communicative
Activity (N6)
100
No Tech
90
Low Tech
80
High Tech
70
60
Mean Percentage
50
40
30
20
10
0
Stories
Basic Needs
Conversation
Detailed Needs
Detailed Information
100
Use of AAC Methods by Partner Familiarity (N6)
100
No Tech
90
Low Tech
80
High Tech
70
60
Mean Percentage
50
40
30
20
10
0
Basic Needs With Very Familiar Partner
Conversation With Very Familiar Partner
Conversation With Stranger
Basic Needs With Stranger
101
Satisfaction With AAC Methods by Communicative
Activity (N6)
6
7 (Very Satisfied )
6
5
5
4
4 (Neutral)
3
Subjects N6
3
2
2
1 (Very Dissatisfied)
1
0
Stories
Conversation
Detailed Needs
Quick Basic Needs
Detailed Information
Written Communication
102
Related References

• Yorkston, Miller, Strand (1995). Management of
  speech and swallowing in degenerative diseases.
  Tuscon, AZ Communication Skill Builders.
• Warren, Rochet, Hinton. (1997). Aerodynamics. In
  (M. McNeil, Ed.) Clinical management of
  sensorimotor speech disorders. NY Thieme.
• Lomas, Pickard, Bester, Elbard, Finlayson,
  Zoghaib (1989). The communication effectiveness
  index Development and psychometric evaluation of
  a functional communication measure for adult
  aphasia. JSHD, 54 (1), 113-124.

103
More references

• Mathy, P., Yorkston, K. M., Gutmann, M. (2000).
  Augmentative communication for individuals with
  amyotrophic lateral sclerosis. In D. R.
  Beukelman, K. M. Yorkston, J. Reichle (Eds.),
  Augmentative communication in adults . Baltimore,
  MD Paul H. Brookes.
• Yorkston, K. M., Beukelman, D. R., Strand, E. A.,
  Bell, K. R. (1999). Management of motor speech
  disorders in children and adults. Austin, TX
  Pro-Ed.

104
More references

• Miller, R. G., et al. (1999). Practice parameter
  The care of the patient with amyotrophic lateral
  sclerosis (an evidence-based review) Report of
  the Quality Standards Subcommittee of the
  American Academy of Neurology. Neurology, 52,
  1311-1323.
• Sackett, D. L., Richardson, W. S., Rosenberg, W.,
  Haynes, R. B. (1997). Evidence-based medicine.
  New York Churchill Livingstone.
• Yorkston, Beukelman, Tice. (1991) Sentence
  Intelligibility Test. Lincoln, NE Tice
  Technologies.