1.Overview
Foreign accents syndrome (FAS) was first reported in 1907 by PierreMarie, a Parisian who developed a distinct London Alsatian accent after right-sided hemiparesis, and was described in detail by Pick in 1919, who found a Czech who developed a Polish accent after a stroke in the left hemisphere. Edwards et al. reported 35 cases of FAS, mostly involving the premotor cortex (Brodmann area 4, BA4) or the motor-related cortex (BA6, BA44), such as the frontal lobe, basal ganglia, parietal lobe, corpus callosum, with more subcortical damage. Coelho et al. reviewed the literature on 16 cases of FAS and found that 40% were subcortical and 33% involved both cortex and subcortex. Coelho et al. found that 63% of FAS cases had concomitant language disorders, such as aphasia, dysarthria, and apraxia of speech (AOS).
In general, patients with FAS do not interfere with the phonological rules of the language, but rather produce certain phonological manifestations that result in changes in intonation, word endings, stress and vocalization that are different from their native language. The patient does not speak a foreign language, but makes the accent or dialect sound different. The difference in accent is apparent to the listener, who cannot determine its true origin. The same FAS patient can be judged to have an Asian, Swedish or German accent by different listeners. Common FAS accents involve German, Polish, Spanish, Chinese, Nordic, French, Slavic, Hungarian, Korean, Dutch, and Irish.
Different studies have pointed out that FAS is not a foreign accent that acquires a stereotype, but rather a general foreign accent without any language-specific foreign accent. It may be associated with language prolongation, such as vowel production, word duration, excessive pauses between words, or longer latency for language onset, slowing down language fluency and giving the listener the perception of a foreign accent.
2. Clinical manifestations
There is no simple motor impairment in FAS. In some patients, only mild facial and pharyngeal muscle weakness is seen, with normal voice volume. There is no facial disuse. Pronunciation disorders are rare. The patient is briefly silent, and once speech is restored, the patient shows FAS. about 50% of patients reported to date have aphasia, commonly transcortical motor aphasia or mild Broca’s aphasia. accent judgment in FAS varies from person to person. For example, in a 28-year-old Brazilian patient with frontal lobe hematoma, a North American accent developed during recovery from Broca’s aphasia. Ten people were asked to evaluate the patient’s video, and seven confirmed a foreign accent, while the other three described it as a “strange accent”. They did not consider the accent to be foreign, with five cases identified as Spanish, one as German, and one as southern Brazilian.
Abel et al. reported a 60-year-old woman with FAS, distal right upper extremity weakness, and dysarthria, who was examined for metastatic left parietal breast cancer. Preoperatively, she presented with FAS and dysarthria, and postoperatively, the dysarthria disappeared with residual FAS. luzzi et al. reported a case of a 64-year-old female right li italian with 8 years of education. Family and friends noticed that the patient developed a Spanish accent and the duration of the disease was about 3 years. The patient spoke only Italian before the onset of the disease, had not traveled abroad and had not learned a foreign language. At the 12-month follow-up after the disease, spontaneous speech hesitations were not perceived and occasional phonological mispronunciations were seen. Comprehension was normal. Spanish accent. Formal language testing revealed mild to moderate naming, reading, writing and repetition deficits. Grammatical deficits and phonological errors. Mild nonfluent aphasia was present, with a diagnosis of frontotemporal lobar degeneration variant.
Ryalls et al. reported a case of a 57-year-old female American with right-sided hemiparesis and speech loss. The hemiparesis and speech recovered significantly after 2 months. A foreign accent (British or Australian) was present. Patient had brief contact with Britons and Australians. Unresponsive when watching British or Australian TV programs. Had a New York accent before the stroke and had been living in New York. In contrast, multiple British people described the patient’s accent as Sussex, London or Yorkshire. Fridriksson et al. reported a case of a 45-year-old right-handed male with a left-sided subcortical ischemic stroke and severe ambiguity in speech output. Two hours after the illness, the speech disturbance and facial droop resolved. The diagnosis of FAS. later returned to work as a salesman. Many customers asked him what country he was from and were surprised that he had been living locally in South Carolina and spoke only English. The listener was unable to consistently determine where the patient’s accent originated and suspected French, Greek, or British English. On examination 6 weeks after stroke, the accent improved, mainly with inappropriate application of the “r”, seen in the absence of word endings and certain insertions; certain odd vowels, such as glide shift and diphthongization. After the disease, the senses of taste and smell are enhanced, and the enjoyment of music is enjoyed. The labial sounds are diminished and the horn cannot be blown.Takayama et al. reported a case of a 44-year-old female with speech disorder, muted state, mild facial palsy on the right side, and no hemiparesis. Speech resumed after a few hours and the right-sided facial palsy resolved after 24 hours. The language was similar to that of a Korean speaking Japanese, who did not have a Korean background. Neuropsychological examination: no word finding difficulty, speech confusion, and the only physical sign was a foreign accent detected by family, friends, and doctors. The person himself was aware of a language disorder. No abnormalities in listening comprehension, repetition, naming, reading, or writing, and normal Token test results. Language analysis: Fluent language output, normal grammar and semantics, sounds like a foreigner speaking Japanese. Japanese people use accents sparingly, but in this case they are used occasionally. There were long pauses between syllables, which affected the rhythm of the language.
Bakker et al. reported a case of a 52-year-old female with multiple sclerosis presenting with FAS. the duration of the disease was 20 years, and symptoms included memory loss, word finding difficulties, grammatical errors, and emotional dependence. The patient spoke only Canadian-accented English. Significant change in language compared to a telephone recording made months earlier. 4 significant language changes in 5 years. Some thought it was a Dutch accent. Symptoms all resolved on their own. Twelve to 24 hours before each episode, the patient’s speech was sharply slurred and intermittent, with a sluggish tongue and a tight jaw. There was bilateral optic papillae pallor, mild hemiparesis on the right side, bilateral extensor plantar reflexes, asymmetric hyperreflexia, and ataxia of both hands. Dexamethasone treatment was ineffective. Speech returned to normal after high-dose methylprednisolone treatment.
Avila et al. reported a case of a right-sided female with Spanish as her native language and proficiency in French, English and Catalan. FAS developed after right carotid occlusion, presenting with FAS involving her native language (Spanish), while the languages learned after the age of 12 years (French, English, Catalan) were not affected.
3. Clinical variants
Some patients with FAS do not present with a foreign accent, but with an accent from another region of the country, which is generally considered a variant of FAS, called foreign accent syndrome.Naidoo et al. reported a Canadian patient with left internal capsule, basal ganglia, and frontal lobe radiation crown infarction. Kwon and Kim reported a case of FAS in which the listener did not perceive a foreign accent but a regional accent, suggesting a variant of FAS. the first case of FAS reported by PierreMarie in 1907, only regional accent changes were seen, with French-speaking Parisians developing an Australian accent after the disease. critchley reported 3 cases of standard British English speakers developed a Welsh accent after the disease. Kwon et al. reported a case of a 71-year-old right-handed female with 6 years of education. History of stroke was 20 months. There were no neurological signs and the main presentation was aphasia. The patient and family found that the accent changed from Cholla-buk provincial accent (southwestern Korean peninsula) to Kangwon accent (northeastern). Speech output decreased after the disease, and accent change occurred 2 days after the disease when speech was relatively fluent. The patient was born in Sam-rye, Cholla-buk province, and both parents and husband used the Cholla-buk accent. The Korean accent has different rhythmic types, such as Seoul or Cholla-buk accent for fixed accent language and Kyongsang or Kangwon accent for voiced language. Auditory analysis showed that the patient had a large pitch shift in the second syllable and at the end of the sentence, a type seen in the Kangwon accent rather than the Cholla-buk accent. Post-stroke rhyme disorder is seen, which the listener perceives as a Kangwon accent.
4. Neuroimaging
Left frontal lobe damage is commonly seen near or involving Broca’s area, and deep subcortical areas (head of caudate nucleus, anterior part of internal capsule, and nucleus accumbens) are also seen without cortical damage.Takayama et al [10] reported that the patient showed cerebral infarction with abnormal linear damage in the posterior lateral aspect of the left precentral gyrus 4 weeks after the disease, suggesting patchy hemorrhage within the infarct; coronal view showed damage in the middle 1/5 of the central sulcus of the left precentral gyrus. MRIFLAIR imaging showed a small focal lesion in the left lateral shell nucleus and CT showed infarction in the left frontoparietal region. MRI at 2 weeks of stroke: cortical ischemic damage in the left middle cerebral artery region, mixed with discontinuous hemorrhagic transformation involving the inferior frontal gyrus (BA44, 45), precentral gyrus (BA4), and anterior insular cortex (BA52).
Rarely, Abel et al. reported FAS due to tumor, and cortical stimulation studies confirmed that the damage was in the somatosensory area, not in the motor cortex.Luzzi et al [9] reported FAS due to neurodegeneration, with mild atrophy around the left lateral fissure seen on MRI; SPECT showed hypoperfusion in the left frontotemporal lobe.Bakker et al [15] reported FAS due to multiple sclerosis, and MRI showed multiple T2 high signals in the white matter, 2 adjacent damages in the anterior horn of the left lateral ventricle (lower dorsolateral frontal lobe), 2 in the corpus callosum, and 1 in the left parietal lobe.
5. Neuropsychological
Verbal and operational IQs, short and long term memory, naming, reading and spelling abilities were in the normal range.
Many studies have reported slower speech in FAS. For example, Berthier et al. (1991) found that the duration of speech in FAS patients was 16-40% longer than in normal healthy Spaniards. Prolonged speech. The vowel “r” is converted to “a”. Song-like tones, dialect-related phonetic vowel substitution, vowel lengthening, and diphthong changes. Early reports of FAS cases show significant impairments in word and/or sentence rhythm. Other abnormalities include altered vowel quality and frequent relaxation of tense vowel targets (e.g., “u” is pronounced as “U”). Sporadic substitution of central vowels is also seen, with the exception of the high vowels “i” and “u”. Some listeners also point out unusual consonants that are not part of the patient’s accent. For example, liquids are strangely pronounced with a non-English accent. Voiceless-terminated consonants often have accent stops, and voiced-terminated consonants often become clear at the end of words.
Gurd et al. found three main features of FAS pronunciation: first, an unusual “syllabic” rhythm: each syllable has approximately equal duration, which is a French feature, while normal English syllables have unequal duration, mainly based on the distribution of sentence stress and the composition of syllabic vowels and consonants. This feature appeared earlier than the French accent and lasted up to 5 months. Second, a rare high tone is seen in syllables with distinct intonation. Third, the “h” sound is pronounced very hard, producing an unusually loud glottal fricative or avoidance of articulation. The latter combined with pitch control disorders indicates rhythm disorders and problems with glottal control. The syllable time-limited rhythm, the “h” shedding and the “h” over-pronunciation are all features of French pronunciation, while the tone aggravation leads to a foreign accent. The patient’s English diphthongs are actually unitary. Certain manifestations of speech disuse have been reported in patients with FAS, such as lack of labial sounds, prolonged production of vowels and consonants, rare lack of stress, and even words that are very familiar to the patient.
Laures-Gore et al [25] examined acoustic measurements, voice-onset time (VOT), vowel duration, 1st and 2nd resonance peak frequency analysis, fundamental frequency (FF), and consonant duration in two Americans with FAS and found vocal fold contraction timing errors in both. More tense or relaxed vowel production, vowel resonance peak variation, and restricted F1 range were noted. Consonant variation included errors in articulation site, manner, or sound. Rhythmic abnormalities included a variety of major phonological qualities, but certain quantitative features such as insertional tone contours, normal or reduced fundamental frequency contours, longer pauses in speech, broken speech rhythms, and end-of-sentence rising tone contours. Most notably, both individuals saw a reversal of VOT for voiced and voiceless sound onset in American English, whereas normally American speech has a long labial-alveolar VOT for voiced pauses and a short pause VOT for voiceless pauses.
6. Pathogenesis
The pathogenesis of FAS is not known, and there are two hypotheses. One is that the original neural circuitry is inhibited by release. The other is that stroke destroys the usual accent center, while the native accent center is intact, and the latter prevails, and as the disease recovers, the usual accent is restored. Abnormalities in rhythm, which includes pitch, stress, and rhythm, are classified by Monrad-Krohn as intrinsic rhythm, intellectual rhythm, emotional rhythm, and nonarticulatory rhythm. Intrinsic rhythm disorders can cause foreign accents. It was found that the rhyme system is mainly present in the right hemisphere and is mainly involved in intellectual and emotional rhythms.Mariën et al [13] proposed that FAS is a developmental disorder.
Abel et al. provided a study of intraoperative cortical stimulation in 1 case of FAS, confirming facial somatosensory cortex as the site of damage, associated with the previously thought impaired normal language programming and execution. Sound and somatosensory feedback play an important role in speech production. Recent evidence suggests that somatosensory feedback, independent of acoustic information, modifies jaw movements to maintain normal speech production. Based on this, it can be inferred that somatosensory feedback can independently generate instructions for language production.
Some scholars have hypothesized that mirror neurons regulate language by altering primary somatosensory cortical activity. Using magnetoencephalography, Mottonen et al. found that primary somatosensory cortical activity was enhanced during language activity, whereas listening to language activity had no effect on somatosensory activation, suggesting a role for mirror neurons in regulating language production. It is proposed that mirror neurons play a role in the execution of language vocalization to their own language vocalization, linking language perception to production.
Kurowski et al. (1996) proposed that the site of brain damage in FAS is the motor language network. It is thought that cortical excitatory activity in the nucleus accumbens has excitatory (via direct pathways) or inhibitory (via indirect pathways) effects on supplementary motor areas. Brain activation studies in healthy adults suggest a specific role for the nucleus accumbens in language. Selective involvement of the nucleus accumbens can affect the regulation of motor-verbal activity. Shell nucleus damage leads to loss of motor regulation and increased motor processing load, in other words, enhanced neural activation in the left motor area. It was proposed that FAS is not a mild disuse, but that impaired motor regulation in the basal ganglia leads to increased motor execution dependence in producing fluent speech [14].Berthier [23] suggested that FAS involves the middle precentral gyrus of the dominant hemisphere and the premotor areas of the dominant hemisphere, with lesions mainly in Brodmann areas 4 and 6 and/or their subcortical projection-specific areas.
It is controversial whether FAS is an AOS subtype, and Dronkers identifies the site of AOS as the language area of the insula of the dominant hemisphere, located anterior to the central auditory sulcus. Early proposals of ataxic aphasia and cortical dysarthria suggest that the symptoms of AOS are similar to those of ataxic dysarthria. Speech disorders due to cerebellar lesions are commonly slow, monotonous, intermittent, scanning, and unclear. Reflecting distorted processes of articulatory procedures and coordination, FAS, AOS, and ataxic dysarthria may share common pathophysiological mechanisms. Based on the recently recognized role of lateral cerebellar linguisticity in multiple speech and language processes and the close connection between the right cerebellum and the dominant hemisphere speech motor language centers, the right cerebellum, in addition to the lateral fissure language area, may play an important role in motor speech program disorders [12].
7. diagnosis differential diagnosis treatment
Diagnosis is mainly based on clinical manifestations.Whitaker proposed four basic features: first, a foreign accent as perceived by the patient himself, acquaintances and examiners. Second, it is different from the accent before the brain damage. Third, it is associated with CNS damage. Fourth, the patient does not have a foreign language speaking background.
FAS needs to be differentiated from dysarthria, dysarthria, and aphasia [2].Coelho et al [8] found that 63% of FAS cases had concomitant language disorders such as aphasia, dysarthria, and dysarthria. Dysarthria and apraxia of speech were not associated with a foreign accent. Hemiplegic-like dysarthria was seen with ambiguous articulatory sequences and erroneous pauses. Impractical speech substitution, discontinuous omission and additional sounds are common. Both dysarthria and speech aphasia have significant distortions of normal speech, whereas FAS has normal speech components [8,10].FAS and Broca’s aphasia differ in type and severity.FAS is characterized by rhythmic and segmental impairment, with features that approximate normal speech but differ from the native language. The mechanisms of language production are complex and accents are important markers of personality, place of birth, culture, class and identity. A distinct German accent was reported early on in 1 deported Norwegian female just after the end of the German occupation. Speech therapy helped to improve FAS [26].