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Re: Reply from Authors

We thank Dr. Abe for his interest and relevant suggestions. The aim of our study was to characterize the natural history of primary progressive aphasia (PPA) based on clinical data, not on imaging. We looked back to the imaging data available in the files of the cohort patients. Although all patients underwent CT or MRI and most had SPECT scans, we could find only 22 SPECT, 21 CT and 16 MRI scans, since patients kept imaging performed outside the center. Scans were read by two independent raters, blinded to clinical data, using a semi-quantitative 0-2 scale.

As suggested by Dr. Abe, we distinguished two groups of patients: those with atrophy or uptake decreased most severe in frontal regions (F-PPA, n=12), and those with most severe perisylvian impairment (P-PPA, n=11). Results were concordant for structural and functional imaging. All patients had a left hemisphere predominance of the lesions except one right-handed woman with a right atrophy and uptake decrease (crossed-aphasia). The more recent imaging displayed more symmetrical lesions.

In the F-PPA group, eight patients were non-fluent and four were fluent, mean age at onset was 61.7 (5.9) years, and mean delay between onset and first visit was 3.0 (1.8) years. In the P-PPA group, six patients were fluent, four were non-fluent (it could not be determined in one patient), mean age at onset was 62.6 (6.0) years, and mean delay between onset and first visit was 3.6 (2.7) years. The two groups did not differ on these characteristics.

The difference was not statistically significant for progression to one syndrome or another (frontotemporal dementia: F-PPA: 10/12, P-PPA: 6/11; dementia with Lewy bodies: F-PPA: 1/12, P-PPA: 3/11; corticobasal degeneration: F-PPA: 1/12, P-PPA: 2/11), for entry an institution, survival, and for loss of autonomy.

Thus, PPA patients who initially had more frontal atrophy or uptake decrease tended to be more non-fluent at first visit than those with initially more perisylvian impairment, but did not differ significantly for survival and loss of autonomy. As shown previously [1], patients with a fluent form of aphasia tended to have a better prognosis, especially concerning survival and swallowing difficulties and to a lesser extent, entry an institution, mutism, walking, toilette and dressing, urinary incontinence, and eating.

According to these results, we cannot assert that there are different natural histories of PPA based on the initial location of the degeneration, frontal or perisylvian.

Acknowledgements: We thank Drs JY Gauvrit, X. Leclerc, A. Emptaz, M. Steinling and for assessing CT, MRI and SPECT scans.

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Re: Natural history of primary progressive aphasia

Le Rhun et al [1] report on the controversy surrounding the natural history of primary progressive aphasia (PPA). In 1997, we investigated patients with PPA and divided them into two groups--fluent PPA and nonfluent PPA. These two groups showed different patterns of isotope uptake on SPECT images [2]. Le Rhun et al reported that seventy-five percent of patients met clinical criteria for frontotemporal dementia (FTD) and final diagnoses of PPA patients were mainly FTD. However, they did not further describe neuroimaging findings. We question whether most of their patients showed predominant atrophies and low isotope uptakes in the frontal part of the cerebrum.

Mesulam [3] reported many patients with PPA had atrophy and decreased blood flow in the perisylvian portions of the inferior frontal and temporoparietal regions as well as surrounding regions of the frontal, parietal, and temporal cortex. Since these two regions are known as Broca's and Wernicke's areas, I believe that PPA can be divided clinically as well as pathologically into two groups. If so, recruited patients in Le Rhun's study included two different groups of PPA and constituents of them deviated to nonfluent PPA.

Fluent and nonfluent PPA develop into different disease courses. Further comments on this may be helpful to understand natural history of PPA.

References

1. Le Rhun E, Richard F, Pasquier F. Natural history of primary progressive aphasia. Neurol 2005; 65:887-891.

2. Abe K, Ukita H, Yanagihara T. Imaging in primary progressive aphasia. Neuroradiology 1997; 39:556-559.

3. Mesulam M-M. Primary progressive aphasia-A language based dementia. N Engl J Med 2003; 349:1535-1542.