I saw a patient who had had a stroke (described in a previous post) on Friday again. Their family noted that they were talking to the patient predominantly in his first language, as they had been told that aphasic patients often regain competency in their first language, even if it is non-dominant.
Bilingualism is a hotly contested subject in Speech Pathology (just see my brief discussions on stuttering and child language development for a taster), and the field of aphasia has its fair share of bilingual theories.
Since I don’t have sufficient time or energy for full comprehensive reviews of a topic, I thought I’d share a few findings from the last ten years:
There are at least two theories of bilingual brains:
- “Procedural/Declarative” (aka “divergent” aka “distinct representation”) – the languages (especially their grammars) “are served by distinct neural circuits” 
- If this is true, prognostic models built on lesion analyses of monolingual patients will not be accurate for bilinguals
- “Neural convergence” – “identical regions mediate monolingual and bilingual language” (lexically and syntactically) 
- If this is true, prognostic models built on lesion analyses of monolingual patients will be accurate, and perhaps the same lesion would lead to more severe outcomes in bilingual clients, because the region affected is “doing more with less”.
For bilinguals at least, there appear to be two possibilities for stroke recovery in terms of language dominance:
- Pitres’s Law (1895) – “In acquired aphasia with a multilingual patient, recovery comes first and most completely in the language most used just before the injury, whether or not it is the patient’s mother tongue” [Quoted in 2]
- Ribot’s Law (1882) – “‘In a multilingual patient with aphasia, recovery comes first in the person’s mother tongue …” [Quoted in 2]
- A very recent paper  has found support for the neural convergence theory, and concluded that bilinguals are probably more sensitive to brain lesions than monolinguals. The study was based on a previously-devised prognostic/statistical model derived from brain scans. The researchers applied the monolingual model to bilingual people who had had strokes, and saw that similar lesions produced similar defects, but they tended to be more severe in bilinguals.
- The researchers believe these differences could not be attributed to pre-morbid language proficiency, or English-only testing (they were tested in both of their languages).
- Note that the researchers call for more controlled testing, noting their mismatched control group and diverse language histories in the bilinguals.
- Recovery in bilinguals has been reported to take one of many patterns:
|Parallel||Recovery is proportional to premorbid ability|
|Differential||One language recovers disproportionally more than the other|
|Antagonistic||One language is available, but is replaced by the other after some time|
|Alternating||Languages alternate in availability|
|Blending||Mixing of words and grammatical constructions|
|Selective||Loss in one language while the other remains at premorbid levels|
|Successive||One language recovers before the other|
[Adapted from 3, itself adapted from Paradis (2004) and Fabbro (2001)]
There are few clear prognostic indicators about which pattern will occur.
Implications for Practice
- Assessors should not assume clients had equal proficiency in languages premorbidly, or that a language deficit is necessarily due to the injury 
- Before a comprehensive assessment in the chronic phase, a detailed language history should be taken.
- Tests should be done in both of the client’s languages, but not by simply translating monolingual tests. An example is the Bilingual Aphasia Test, which is available for FREE.
- Research regarding treatment efficacy in bilingual aphasia is a notable gap in the literature.
I think my recommendation would be for the family to continue to converse with the patient in the same way they did premorbidly – in a mix of English and their home language.
- Hope, T. M. H., Parker Jones, Ō., Grogan, A., Crinion, J., Rae, J., Ruffle, L., . . . Green, D. W. (2015). Comparing language outcomes in monolingual and bilingual stroke patients. Brain, 138(4), 1070-1083.
- Pearce, J. M. S. (2005). A Note on Aphasia in Bilingual Patients: Pitres’ and Ribot’s Laws. European Neurology, 54(3), 127-131.
- Lorenzen, B., & Murray, L. L. (2008). Bilingual Aphasia: A Theoretical and Clinical Review. American Journal of Speech-Language Pathology, 17(3), 299-317. doi: 10.1044/1058-0360(2008/026)