Neuropathology of language

1. Neuropathology of language Language impairments during dementia: Speech, reading and writing Differential diagnosis Language impairments after head injury: Speech, reading and writing Pragmatics Rehabilitation Summary

2. Language impairments after traumatic brain injury • Patients with traumatic brain injury (TBI) have a variety of language disorders but usually have an expressiveaphasia (Broca's aphasia) and anomia (word production) and/or receptive aphasia(Wernicke’s aphasia). • Most TBI patients can understand speech after emerging from Post-Traumatic Amnesia (PTA) but speech production impairments last longer. • TBI patients can spontaneously recover basic comprehension abilities sooner than expressive abilities following head injury (Groher, 1990).

3. Most typical language impairments following TBI • Speech impairments • articulation problems dysarthria • sound substitutions phonemic paraphasias • or word substitutions semantic paraphasias • Word finding difficulties (anomia) • Acquired dyslexia • Acquired dysgraphia • Peripheral writing problems (allographia) • Dis-inhibition characterizing speech content • Impairment to the indirect use of language called Pragmatics.

4. Written language impairments • Acquired dyslexia • Surface e.g., bury read as “b∫ry” • Deep e.g., bury read as “grave” • Phonological e.g., jar (√) better than nar (x) • Acquired dysgraphia • Surface e.g., bury written as “berry” • Deep e.g., bury written as “grave” • Phonological e.g., jar vs nar • Other writing problems • These include letter case substitution errors (B for b); letter sequencing and graphic motor errors; and word finding errors.

5. Pragmatics of communication • McDonald (1995) found TBI patients impaired at using language indirectly (metaphors, proverbs). • The ways in which language is used socially such as social rules about conversations with another person or in groups, e.g., turn taking. • Understanding and using words that mean one thing but when they are accompanied by a tone of voice or inflection this conveys the opposite meaning (e.g., innuendo, sarcasm). • Use of indirect questions leads TBI patients to use the literal rather than the inferred meaning.

6. Inference making • In order to understand a sarcastic comment, the listener must process the literal meaning, compare this to information available from the context; reject the literal meaning as patently unfeasible; and replace it with a meaning that is more appropriate but is in fact the opposite. • The listener must therefore have the skills to recognise that there is more to the question than the literal meaning and be able to infer the intention behind the utterance (mental model). • Communication with patients can be difficult.

7. Dementia • Deterioration in cognitive skills always involve memory, loss of time and place disorientation, intellectual decline and impaired judgment. • A central feature of dementia is progressive deterioration of language processing skill as well as memory and visuo-spatial deficits. • Language problems in dementia always include a restricted vocabulary that is limited to a few words and stereotyped automatisms.

8. Dementia • Process of diagnosis is one of elimination: • Medical history (falls, LOC, epilepsy, family history) • Clinical exam (neurological signs, MMSE = <24) • Neuropsychological testing (WAIS, WMS, PALPA) • Neuroimaging (CT, PET, fMRI) • Clinical features include • problems learning new material (episodic memory) • remembering to do things (prospective memory) • using language correctly (semantic memory).

9. Semantic memory • The memory system used for language skills. • It is conceived of as a mental thesaurus or store of knowledge about the meaning of objects, words etc. (Tulving, 1972). • The organised knowledge that a person has about words and other verbal symbols their meanings and the relations among them. • Our knowledge about the rules, formulas and algorithms for the manipulation of symbols, concepts and their relations is necessary for linguistic and higher cognitive processing tasks.

10. General language features • Dementia can result in language disturbance to one or more of the following domains: • spoken word comprehension and production • written word comprehension and production • lexical-semantic ability (concept formation) • perseverative speech errors • word finding difficulties • object naming problems • semantic paraphasias • mutism

11. Mild stage of cortical dementia • The patient is disoriented for time and place and memory for recent events has begun to fail. • The patient relies on over-learned situations such as stereotypical utterances and often is unable to generate a sequence of related ideas. • Patient begins to exhibit semantic impairment • slightly reduced vocabulary • word finding difficulties • increased use of automatisms and clichés.

12. Mild stage of cortical dementia • Speech production • syntax and phonology are both intact. • Reading and writing • reading regular words (jump) and nonwords (finp) is spared although there are errors with irregular words (yacht) = surface dyslexia. • writing impaired with peripheral dysgraphias. • Pragmatic impairment • this is characterised by a loss of desire to communicate and disinhibitions in speech.

13. Moderate stage • Patient has a severe impairment of memory and orientation to time and place (MMSE <23). • Speech is perseverative, non-meaningful and errors are not self corrected (as in mild stage). • Patient shows further semantic impairment • significantly reduced vocabulary naming. • errors semantically and visually related. • verbal paraphasias evident in discourse. • utterances are usually very concrete.

14. Moderate stage of cortical dementia • Speech production • reduction in syntactic complexity of speech. • phonology is generally intact though repetition skills begin to deteriorate. • patient makes frequent circumlocutions. • Reading and writing • nonword and irregular word reading both impaired. • surface dysgraphia emerges (e.g., yacht --> yot). • Pragmatic impairment • declining sensitivity to context, diminished eye contact and egocentricity in speech content.

15. Advanced stage • Patients are now very disoriented for time, place and person and fail to recognise family and friends i.e. prosopagnosic (MMSE <17). • Patients require extensive personal care. • Further semantic impairment is observed. • very reduced vocabulary. • frequent use of unrelated meanings. • jargonaphasia and neologistic speech.

16. Advanced stage of cortical dememtia • Speech production • further syntactic and phonological impairment • many inappropriate word combinations • paraphasias and neologisms • Reading and writing • reading aloud and spelling and writing of regular words, irregular words and nonwords is impaired. • Pragmatic impairment • non adherence to conversational rules (turn taking) • poor eye contact • lack of social awareness (disinhibited speech)

17. Focal lobar atrophy (Picks Disease) • Progressive atrophy of the brain that is confined initially to either the frontal or temporal lobes. • Pick's disease was considered to be a rare cause of dementia, that was indistinguishable from Alzheimer's disease but improved diagnostic tests have lead to an increased recognition of cases of focal lobar atrophy. • It has been claimed that 10-20 percent of younger patients with dementia (i.e those below the age of 65) may have Pick's disease.

18. Frontal lobe atrophy • A frontal dementia (loss of either executive and social function) and progressive nonfluent aphasia (loss of output grammar and phonology). • Frontal dysfunctions such as adaptive behaviour; abstract conceptual ability; set-shifting/mental flexibility; problem-solving; planning; sequencing of behaviour; temporal order judgments; personality, drive, motivation and inhibition. • Often changes in personality and social conduct predominate over the loss of cognitive skills.

19. Progressive Non-fluent Aphasia • A gradual decline in language abilities affecting predominantly language output - disintegration of grammar and phonology - which in some progresses to a state of complete mutism. • The language disorder resembles a Broca’s type non-fluent aphasia with very frequent phonological errors in speech although use of simple syntax can be preserved in early stages. • The preservation of nonverbal skills, nonverbal visuo-spatial memory and right hemisphere functions separates this from a dementia.

20. Temporal lobe atrophy • The most common presentation is fluent progressive aphasia because speech output is grammatically correct. • The language impairment is restricted to the comprehension of single words together with some reduced vocabulary causing anomia. • Most of the features can be explained in terms of a breakdown in semantic memory leading to severe anomia; impaired performance on category fluency tests; defective word-picture matching; and a loss of general knowledge.

21. Semantic dementia • The term semantic dementia has been applied to this syndrome of fluent progressive aphasia. • Episodic memory, visuo-spatial and frontal executive abilites are preserved in the early stages which contrasts sharply with the typical presenting features of Alzheimer's disease. • As the disease progresses SD patients may develop Kluver-Bucy Syndrome (disturbance in eating behaviour with a tendency to consume inedible things) as a result of bilateral damage to the amygdala as well as visual agnosia.

22. DAT or Semantic dementia (SD)? • Episodic and semantic memory • DAT patients can remember events from early years but are poor at recall of recently acquired episodic knowledge i.e. there is a negative temporal gradient whereas SD have preserved memory for recent events. • Visuospatial and perceptual skills • DAT patients are impaired on tasks such copying the Rey Figure but visuo-perceptual skills are intact in SD. • Lesion Loci • DAT patients have bilateral lesions in the medial temporal lobes whereas semantic dementia patients have damage to the inferior temporal cortex that is often worse in the left hemisphere.

23. DAT, SD or Progressive Aphasia (PA)? • 1) Spontaneous speech • DAT present initially with normal speech; SD show fluent and grammatical speech but devoid of content. • Patients with PA have impaired spontaneous speech. • 2) Comprehension of single words • DAT present initially with normal comprehension of single words but SD patients are impaired early in the disease and generate frequent semantic paraphasias. • 3) Comprehension of syntax • DAT and SD patients present initially with normal comprehension of syntax but patients with PA make frequent phonological errors.

24. Summary • Aphasias and language impairments can be useful in the differential diagnosis of brain damage due to head injury and dementia. • Head injured patients tend to show aphasia in the recovery phase but this resolves leaving longer term pragmatic language impairments. • Patients with semantic dementia display early comprehension impairments whereas patients with dementia of the Alzheimer’s type tend to develop language difficulty later in the disease.