LETTER TO EDITOR
|Year : 2006 | Volume
| Issue : 2 | Page : 126
Primary progressive aphasia
Kamakshi Shanbhogu, Bijoy K Menon, CT Suresh
Institute of Neurology, Chennai, India
Institute of Neurology, Chennai
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Shanbhogu K, Menon BK, Suresh C T. Primary progressive aphasia. Ann Indian Acad Neurol 2006;9:126
We read with interest, the report on progressive nonfluent aphasia (PNA) by Mathuranath et al. In 1987, Mesulam introduced the term 'Primary progressive aphasia' (PPA) for a syndrome of progressive worsening of language with preservation of the activities of daily living and evidence of normal nonverbal abilities on neuropsychological testing for at least 2 years after onset. Subsequently, PPA was further classified into progressive non-fluent aphasia and semantic dementia. Other workers proposed additional subtypes of PPA such as, PPA with comprehension deficits characterised by fluent speech and anomic, but not the multimodal semantic deficits of semantic dementia and Logopenic progressive aphasia with slow rate of speech output and word- finding pauses, but without agrammatism and articulation deficits.
These various descriptions of PPA has led to a more general discussion on whether a stage model or a subgroup model might be appropriate to explain the neuropsychological consequences of these degenerative diseases, as the various types mentioned above seemed to provide support for a subgroup model. Subgroup models assume that the differences in presentation of these different subtypes are due to impairment of different cognitive modules in a qualititative manner. In contrast, stage models assume a global progression of deficits of all cognitive performances and the observed performances between different patients groups are due to differing severity of disease.
However, follow up studies have not provided concrete evidence for subgroup models, as we find that the syndrome of PPA does progress to a more general neuropsychological deficit. Mathuranath et al in their study, provide more evidence for the stage model by stating that early behavioral dysfunction within two years, can be seen in cases of PPA. They also highlight the type of language dysfunction seen in such cases and state that the extent of language impairment is a function of disease stage than disease duration. This argument is a very strong refutement of a subgroup model.
In their article, they differentiate PPA with early behavioural dysfunction from those without, by poor information content on WAB. What is not clear though, is whether they would like to explain the "poor information content" as a consequence of early behavioural dysfunction or as coexistent. This has an important bearing on whether PPA can be explained by a 'subgroup' model or a 'stage model'.
Answers to questions of this type, can only be obtained by rigorous follow up studies followed by post mortem examination of more and more patients. As such, studies are very few at present and not very conclusive and the best way to approach the problem is to combine the two models and assume that PPA can present with various language manifestations depending on the specific area involved in the language network and can be associated with behavioural dysfunction if the pathology involves neuro anatomical substrates for behaviour early in the disease.
At our institute, we have been able to see two cases of PPA since 2000. This does reflect on a lack of awareness amongst the referring physicians and the society in general, about this debilitating disease. More and more studies like Mathuranah's are needed to correct the discrepancy.
| References|| |
|1.||Mathuranath PS, George A, Mathew R, Cherian PJ. Profiles of language impairment in pregressive nonfluent aphasia. Ann Indian Acad Neurol 2006;9:24-31. |