When I first heard of this malady a couple of days ago, I must admit, it appealed to my macabre sense of humor, especially when Wikipedia described Americans afflicted with strokes speaking with English accents after recovery, a Norwegian shrapnel victim in 1941 suddenly speaking with a German accent, and so on. It was just like something from Woody Allen’s movie Zelig. The headlines referenced in the Wikipedia article reinforced how weird this phenomenon is: “Woman’s migraine gave her French accent“. The Guardian (London) Steven Morris, (2010-09-14); “Severe Migraine Leaves English Woman with Chinese Accent” Fox News. 19 April 2010. Retrieved 20 April 2010 ; “Woman Gets Oral Surgery, Wakes Up with Irish Accent” Huffingtonpost.com. 2011-06-05. Retrieved 2011-06-16. 
Many of the cases mentioned in Wikipedia noted that stroke was frequently a precursor to FAS. Damage to the speech centers, involvement of the cerebellum (a part of the brain involved with motor activities) are thought to be responsible for FAS. Perhaps motor impairment does not allow musculature involved in speech to enunciate certain sounds. If, for example, a person was unable to pronounce an “R” for some reason, one might think that he or she was from Boston. In fact, the ‘accent’ that a person develops depends on large part, who is listening: while some may note a Slovakian accent for example, others may hear a Russian accent.
Some researchers think that brain damage is not involved with this syndrome. Peter Mariën, a neurolinguist studying FAS stated, “There is no such thing as one simple recipe that explains what happens to a person who has foreign accent syndrome,”
To be taken seriously
In another case, reported by ABC news, a 16 year old girl who developed an accent after seizures following a Lyme disease infection.
What struck me about this article was not the strangeness of the phenomenon, but rather the humane and understanding response by her doctor: “Dr. Lynn Durand, says that while he can’t explain [the girl’s foreign accent], he doesn’t doubt it either. ‘Lyme can have some very strange symptoms,’ he said. ‘And I think what’s so important about Lyme disease is that patients will present with strange symptoms and, we, the medical community, will not know what to make of it, and unfortunately we think, ‘If the diagnosis isn’t in my head, it must be in the patient’s head, so they must be making this up.’ My feeling is that it’s very, very important to take the patients at their word and hear what they have and really try to explore what the causes are.’ ” 
Bravo, Dr. Durand.
 Mariën P., Verhoeven J. (2007). Cerebellar involvement in motor speech planning: some further evidence from foreign accent syndrome. Folia Phoniatrica et Logopaedica, 59:4, 210-217.