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Comparative classification ofaphasic disordersJose M. Ferro a & Andrew Kertesza Hospital de St. Maria , Lisbon, Portugalb St. Joseph's Hospital , London, OntarioPublished online: 04 Jan 2008.

To cite this article: Jose M. Ferro & Andrew Kertesz (1987) Comparative classification ofaphasic disorders, Journal of Clinical and Experimental Neuropsychology, 9:4, 365-375,DOI: 10.1080/01688638708405057

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Journal of Clinical and Experimental Neuropsychology 0168-8634/87/W365 $3.00 1987, Vol. 9, No. 4, pp. 365-375 @ Swets & Zeitlinger

Comparative Classification of Aphasic Disorders*

Jose M. Ferro Hospital de St. Maria, Lisbon, Portugal

Andrew Kertesz* St. Joseph’s Hospital, London, Ontario

ABSTRACT

This study compares aphasia classification of 20 aphasics who were evaluated with the Western Aphasia Battery (WAB) and the Lisbon Aphasia Examination Battery (LAEB). High correlations were found between tests evaluating the same functions in both batteries. Aphasia types derived from these two batteries showed only a partial overlap. This was due to the use of different numerical diagnostic criteria. When these criteria were used to specify aphasia types of 179 acute and 1 13 chronic aphasics grouped by cluster analysis, similar discrepancies were noted. Two major differences were found: some LAEB global aphasics turned out to be WAB Broca’s and some LAEB anomics were classified as WAB conduction aphasics. These disagreements reflect difficulties in delimiting Broca’s and conduction aphasia. The importance of the numerical approach to aphasia classification is stressed, as it is a reliable method to classify aphasic patients in order to allow comparison of data from different centers.

Classification is one of the important tools in biological sciences. Since aphasia has been examined scientifically, most aphasiologists have found that it is not a unitary phenomenon. This led to the several classification systems that have been published since Broca’s (1861) report on aphasia (cf. Kertesz, 1979 for review). The different aphasic types derived from such classifications reflect different theoretical concepts of language disturbances and the different meth- odologies used in patient evaluation. Clinicians also found aphasia types to be a reliable tool in the localization of hemispheric lesions. The regular association between specific sites of lesion and particular types of aphasias described by late- 1800 and early- 1900 neurologists has been confirmed in the last decade in large series of patients whose lesions were located by isotope or CT scans.

* This work was supported by grants from the Instituto Nacional de Investigacao Cientifica and the Gulbenkian Foundation to Dr. Jose Ferro, and the Ontario Ministry of Health grant #PR-969 and the Medical Research Council grant #MT-7698 to Dr. Andrew Kertesz. Presented as a poster at the 6th INS Europe:n Conference, Lisboa, June 1983. Address for reprints: Andrew Kertesz, M.D., Department of Clinical Neurological Sciences, St. Joseph’s Hospital, London, Ont. Canada N6A 4V2.

Accepted for publication: May 28, 1986

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366 CLASSIFICATION OF APHASIA

Despite this evidence, some aphasiologists continue to consider aphasia as an unitary disorder and to rank their patients accordingly only with respect to the severity of their deficits. They claim that classification of aphasia is an oversim- plification, and that most patients do not fit any category or that they can change their aphasia type as they get worse or improve. The discrepancy between the several classification systems and the disagreement between observ- ers are continuing arguments pointed out by those opposing classification.

Most modern investigators accept the classification based on the Wernicke (1874)-Lichtheim (1885) model and defined further recently by Goodglass and Kaplan (1972). Although the latter authors illustrated each aphasic type with a typical case and provided Z scores to which individual scores could be com- pared, they did not establish limits of test scores for each aphasia group. Other comprehensive aphasia batteries, such as the Neurosensory Center Comprehen- sive Examination for Aphasia (Spreen & Benton, 1968) or the Multilingual Aphasic Examination (Benton, 1969), provide centile scores for subtests but do not define aphasia types. Therefore, examiners using these batteries (Damasio & Damasio, 1980) base their classification on somewhat subjective clinical grounds.

Only a few centers define aphasia type according to numerical limits of test scores (Ferro, Santos, CastroCaldas, & Mariano, 1980; Kertesz & Poole, 1974; Reinvang, 1985; Vignolo, 1964; Willmes, Poeck, Wenigar, & Huber, 1980). Beyond these intuitive numerical classifications, numerical taxonomy based on cluster analysis of aphasic scores has also been recently used (Crockett, 1977; Kertesz & Phipps, 1977,1980).

This paper deals with some of these issues by comparing aphasia types derived from two aphasic populations through the use of two of these batteries: the Lisbon Aphasia Examination Battery (LAEB) (CastroCaldas, 1979; Ferro et al., 1980) and the Western Aphasia Battery (WAB) (Kertesz, 1982; Kertesz & Poole, 1974).

METHODS

Study 1. In order to compare the aphasia classification derived from the LAEB and the WAB, 20 adult aphasics were tested with all the language subtests ofboth batteries.* Examinations were conducted at the Language Research Laboratory, Lisbon, by the same examiner, in a single testing session, and tests were given in the same order to all patients. Patients were all right-handed; 15 were male and 5 were female. Age ranged from 26 to 69 years. Etiology was ischemic CVA in 17 patients, hypertensive intracerebral hemorrhage in 1 patient, traumatic intracerebral hemorrhage in another, and left hemispheric glioma in 1 patient.

* A Portuguese version of the WAB was used.

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JOSE M. FERRO A N D ANDREW KERTESZ 367

The LAEB uses four principal tests, each of them designed to evaluate a specific function: Fluency (F), naming (N), repetition (R), and aural Comprehension (C). The aphasia quotient (quociente de afasia - QA) is calculated by adding the scores of these 4

tests (in percentages) and dividing the sum by 4 (QA = F + N + R + c)). This objective

measure of the overall severity of aphasia showed a strong correlation with a subjective Aphasia Severity Rating Scale. The fluency test grades the spontaneous speech displayed by the patient duringan introductory conversation with the examiner; it has 10 different categories. On the naming test 16 common objects are shown to the patient who has to name them. On the repetition test the patient is asked to repeat 30 words (10 disyllabic, 10 trisyllabic, and 10 polysyllabic), while on the aural comprehension test he has to follow four 1-step and four 2-step oral commands. On all these tests a correct response is scored one point. Two subtests comprising the Portuguese version of the Multilingual Aphasia Examination (Benton, 1969) are also included in the LAEB: a sentence repetition test and an abbreviated form (22 items) of the Token Test. However, these tests were not used for calculating the QA or in the classification criteria.

The WAB and the rationale for the Aphasic Quotient (AQ) have been described in detail elsewhere (Kertesz, 1979; Kertesz & Poole, 1974); only the major differences compared to the LAEB are stressed here. The WAB and LAEB use the same four functions to calculate the QA and the AQ and to classify aphasic patients. In the WAB, the fluency test also categorizes the spontaneous speech of patients into 10 categories. Although there are some minor differences between the WAB and LAEB fluency categories, they largely overlap. The WAB comprehension test includes yes/no ques- tions, a pointing test of auditory recognition, and a series ofsequential commands, some of which are more than two steps. The repetition task utilizes single common words, numbers, and sentences of increasing length as well as increasing grarnmatica and phonemic complexity. The naming section of the WAB includes object naming, word- fluency, sentence completion, and responsive speech subtests. Both batteries use nume- rical criteria to classify all aphasics unequivocally into the same eight aphasic types (Table 1). However, classification criteria are not set a t the same level in both batteries. Moreover, while the LAEB uses the same criteria for all patients, the WAB criteria on comprehension, repetition, and naming vary accordingly to the types of aphasia they separate, adjusting to the level of the other test scores.

Study 2. In an attempt to compare the validity of the LAEB and WAB diagnostic criteria, we modified the original WAB comprehension and repetition numerical criteria in order to meet LAEB criteria. These new scores, called WAB/LAEB transformed criteria, were calculated on 2 scores obtained by the 20 aphasics described in Study 1 on WAB and LAEB subtests that evaluate the same functions. For example, on the comprehension test, the LAEB criterion score of 7 corresponds to a 2 score of +.73, while on the repetition test the criterion score of 23 corresponds to a 2 score of +.58. On the WAB these 2 scores corresponded to raw scores of 7.8 and 5.8, respectively. When these new WABILAEB transformed criteria were applied to the 20 aphasics described in Study 1, agreement with LAEB-derived aphasia types was achieved in 19 patients. The exception was due to a minor difference in the determination of fluency by both batteries. This patient was classified as a transcortical motor aphasic on the LAEB and as an anomic on the WAB.

4

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Tabl

e 1

Cri

teri

a for

Cla

ssifi

catio

n

Tran

scor

tical

Tr

ansc

ortic

al

Glo

bal

Broc

a’s

Mix

ed

Mot

or

Wer

nick

e’s

Sens

ory

Con

duct

ion

Ano

mic

Fl

uenc

y LA

EB

NF/

O-

5 N

F/O

- 5

NF/

O-

5 N

F/O

- 5

F/O

- 5

F/O

- 5

F/O

- 5

FA

- 5

5-10

W

AB

0-4

0-

4

0- 4

0

-4

5-10

5-

10

5-10

5-

10

- C

ompr

ehen

sion

.r L R

epet

ition

tl

m

WA

B/LA

EB

0- 4

0-

4

0- 4

0

-4

5-10

5-

10

5-10

LAEB

0-

6

7- 8

0-

6

7- 8

0-

6

0- 6

7-

8

7- 8

W

AB

0- 3

.9

4-10

0- 3

.9

4-10

0- 6

.9

0- 6

.9

7-10

7-

10

WA

B/LA

EB

0- 7

.7

7.8-

10

0- 7

.7

7.8-

10

0- 7

.7

0- 7

.7

7.8-

10

7.8-

10

LAEB

0-

22

0-22

23

-30

23-3

0 0-

22

23-3

0 0-

22

23-3

0 *

WA

B 0-

4.9

0- 7

.9

5-10

8-

10

0- 7

.9

8-10

0- 6

.9

7-10

3

WA

B/LA

EB

0- 5

.7

0- 5

.7

5.8-

10

5.8-

10

0- 5

.7

5.8-

10

0- 5

.7

5.8-

10

2 LA

EB

0-15

0-

15

0-15

0-

15

0-15

0-

15

0-15

0-

15

8 W

AB/

LAEB

0-

9

0-9

0

-9

0- 9

0

-9

0-9

0

-9

0-9

Nam

ing

7c

WA

B 0-

6

0-8

0

-6

0- 8

0-

7

0-9

0-9

0-9

g

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CLASSIFICATION OF APHASIA 369

The WAB/LAEB transformed criteria as displayed in Table 1 were used to classify 179 acute (tested within 45 days from onset) and 113 chronic (tested beyond 330 days) aphasics who were studied by numerical taxonomy and were clustered on the basis of their WAB scores (Kertesz & Phipps, 1980). A minimum variance clustering algorithm, called the sum of squares agglomeration on the Euclidean distance matrix of dissimilari- ties, was used. The clusters were determined on dendrograms at the level of 2.1% of the total variance, obtaining 10 distinct groups in the acute and 11 in the chronic population. The algorithm selects individuals who are more similar to each other according to their language scores (10 subtests from the WAB). The distinctiveness of clusters was mea- sured by determining the intercentroid distances and the dispersion of each pair of clusters by a nearest neighbour network analysis (Kertesz & Phipps, 1980).

RESULTS

Study 1. LAEB and WAB performances of an aphasic population.

Although the two batteries are composed by different tests, in tas: 20 a+asics who were administered both batteries, high correlations were found between tests evaluating the same function (Table 2). QA and AQ correlated extremely well (I = .85).

However, discrepant results were obtained when classifying aphasia types on the basis of the respective numerical criteria by the LAEB and WAB. Table 3 shows that discrepancies in classification were due mainly to differences in comprehension and repetition criteria e.g. The higher range for comprehen- sion on the LAEB classifies the same patient as global aphasic who is classified as Broca’s aphasic on the WAB. Agreement was found in 10 patients. These were diagnosed as 2 Globals, 5 Wernicke’s and one of each Transcortical Sensory, Conduction, and Anomic aphasics.

Table 2

Correlation between LAEB and WAB tests designed to evaluate the same functions

Fluency Fluency Fluency Aural Comprehension Token Test Repetition Sentence Repetition Naming

vs. Fluency (Total) vs. Spontaneous Speech vs. Information Content vs. Comprehension (Total) vs. Comprehension vs. Repetition vs. Repetition vs. Naming

r = .93 r = .80 r = . 5 9 r = .96 r = .41 r = .84 r = .82 r = . 9 6

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370 JOSE M. FERRO AND ANDREW KERTESZ

Table 3

Discrepant LAEB and WAB Classification

LAEB Diagnosis WAB diagnosis n patients Global Broca’s Mixed Transcortical Broca’s Transcortical motor Anornic Transcortical sensory Wernicke’s Anomic Conduction

Study 2. The results of the second study are summarized in Tables 4 and 5 which show the composition of acute and chronic clusters according to WAB and WAB/LAEB transformed criteria. The clusters are displayed for the acute (Table 4) and chronic (Table 5 ) aphasics on the left sides of the tables. The clinical groups are represented by the columns and the clusters obtained by numerical taxonomy are represented by the rows. The composition of these clusters according to the predetermined WAB and transformed WAB/LAEB criteria is shown in the Tables. The composition of clusters based on these two criteria showed consid- erable overlap. Agreement in classification was higher in the chronic (91.3%) than in the acute clusters (79.8%). The disagreements between the transformed criteria and the original WAB criteria are summarized at the bottom of Tables 4 and 5 for each column of clinical groupings. The major disagreements were “WAB global” aphasics being classified as Broca’s and “WAB conduction” aphasics being classified as anomic under WAB/LAEB-modified criteria. Among acute aphasics, clusters I, 11, V, and VII to X showed similar composi- tion of aphasic types under both criteria. Cluster 111, equivalent to Broca’s aphasics on WAB criteria, was mainly composed of global aphasics under WAB/LAEB modified ones. Cluster IVY which included mainly WAB Broca’s and Transcortical motor aphasia, became mainly a mixed transcortical group. The “WAB conduction” aphasics included in cluster VI were reclassified as anomic under WAB/LAEB-modified criteria, so that the majority of conduc- tion aphasics were grouped in only one cluster (VII). Among chronic aphasics, differences were found only in clusters I1 and IV: WABILAEB modified criteria reclassified Broca’s aphasics included in those two clusters as global and mixed transcortical aphasics.

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CLASSIFICATION OF APHASIA 37 1

- N

C I - - 3

m a .

2 2 \ a. 4

- 3 E 3

m - -

3 l n m W r - M O O - - C I C I

mCI 3

m-. m w - - -

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372 JOSE M. FERRO AND ANDREW KERTESZ

d

M M - m m

+ m

m -

y = b c Q - - 3 hl

woo

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CLASSIFICATION OF APHASIA 373

DISCUSSION

Although the tests evaluating the same functions in the two batteries that we compared showed a high correlation, aphasia types derived from these two batteries showed only a partial overlap. This was due to the use of different numerical diagnostic criteria. When these criteria were used to specify aphasia types of aphasic populations studied by cluster analysis, the same differences were noted. Nevertheless, agreement in the identification of clusters was achiev- ed in the majority of them, especially chronic ones.

Differences in criteria led to two major discrepant classifications. Some LAEB globals turned out to be WAB Broca’s, while some WAB conduction aphasics were anomic under LAEB criteria. These disagreements reflect con- troversial issues about the definition of these two syndromes, namely, the extent of the comprehension deficit in Broca’s aphasia and whether the repetition defect of conduction aphasics must be considered at the word or at the sentence level. An important question in Broca’s aphasia is how much of a deficit in comprehension of speech is allowed before a patient is considered a global aphasic. Levine and Sweet (1983) propose that Broca’s aphasics should be able to follow two-step commands. This corresponds to LAEB criteria, while WABs criteria are more liberal, as 2/3 of the score on comprehension is based on performance on yes/no questions and auditory recognition subtests. Yet, while able to follow two-step commands, “LAEB’s Broca’s” showed impaired audi- tory comprehension of complex sentences, as demonstrated by their low Token Test scores (Study 1).

Concerning conduction aphasics, LAEB criteria emphasize the word repeti- tion defect, while on WAB criteria, a conduction aphasic may be able to repeat single words and short sentences. It is interesting to note that LAEB’s conduc- tion aphasics were almost all included in the same cluster while WAB’s conduc- tion aphasics were grouped in two distinct clusters. These two varieties of conduction aphasia - the efferent and the afferent - have different lesion loca- tion, more anterior in the efferent group and more posterior in the afferent group (Kertesz, 1979). The second group, with relatively fluent speech fits the classical picture of conduction aphasia and corresponds to the LAEB’s conduc- tion aphasia. They are also comparable to those described by Benson, Shere- mata, Bourchard, Segarra, Price and Geschwind (1973) and Green and Howes ( 1977). The efferent conduction aphasics were classified as anomic on LAEB criteria; they could repeat single words, but failed to repeat long and complex sentences. Their defect may be caused by an impairment of phonological encoding (Dubois, Htcaen, Angelergues, Chatelier, & Marcie, 1974), but it may also reflect syntactic incompetence.

The opinion of those who oppose aphasia classification may seem bo be reinforced by the disagreements in classification found in this study. These disagreements were identified as the consequence of slightly different classifica- tion criteria. Nevertheless, there was a large overlap between the two classifica-

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374 JOSE M. FERRO AND ANDREW KERTESZ

tion systems. Once testing procedures and criteria for classification are objec- tively stated, differences are easily explained and patients from different centers can be compared. This is a basic need in neurobehavioural research. Conflicting evidence on neuroanatomical correlates on certain types of aphasia, such as Broca's aphasia (Broca, 1861; Htcaen & Consoli, 1973; Marie, 1906; Moutier, 1908; Mohr et al., 1978) and conduction aphasia (Benson et al., 1973; Damasio & Damasio, 1980; Green & Howes, 1972) are in part due to different defmitions of these syndromes by different authors. Studies on the recovery of aphasia showed that aphasic syndromes have different evolution and prognosis (Kertesz & McCabe, 1977). Generalization of these data is possible only if aphasia types are objectively defined, and classification criteria used in different centers are objectively compared.

Placing cases into predetermined categories may consider the discrepancies between two classification systems caused by borderline cases that are included in one category under one set of criteria, but in a neighbouring category under the other criteria. This is hardly a significant disadvantage once the reason for the disagreement is realized. The alternative to numerical criteria in the clas- sification of aphasia is a large number of unclassifiable cases that is much less acceptable. Only when the basis of classification systems is clearly explained, and classification criteria unequivocally established on a numerical basls, can aphasia types derived from different criteria be objectively compared. Clas- sifications based on subjective clinical criteria or typical profiles do not allow that kind of comparison. The numerical approach to the classification of aphasia appears at present to be the more reliable method to classify aphasic patients, and thus to allow for comparison of data from different investigators.

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CastroCaldas, A. (1979). Diagnos:ip?e evoluqlio das afasias de causa vascular. Lisboa: Faculdade de Medicina de Lisboa.

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