Functional speech disorder
Functional speech disorders are a subtype of functional neurological disorder and mimic the symptoms of organic speech disorders. Although any aspect of speech production can be affected, they most commonly manifest as dysphonia, stuttering or prosodic abnormalities (Duffy et al., 2016; Espay et al., 2018). In addition to functional speech disorders, it is also important to mention motor speech disorders, which include several types of dysarthria and apraxia of speech.
Motor speech disorders are thought to be caused by organic abnormalities in the brain regions and neurological networks responsible for planning, programming, controlling and executing speech.
Both types of speech disorders can co-occur, and in some cases a functional speech disorder may be an maladaptive psychological or physiological response to an organic neurological disorder. On the other hand, both types of disorder may manifest as relatively independent entities (Duffy et al., 2016).
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Abnormal speech pattern not compatible with any form of motor speech disorder (e.g. dysarthria and apraxia of speech)
Abnormal speech pattern not explained by organic cause, injury or other speech neurological disorder
Inconsistencies during the examination or in the patient's history
e.g. speech deteriorates dramatically when the centre of the task is,
The severity of symptoms varies depending on the type of task (e.g. reading, repetition, conversation, etc.),
irregularity and slowness of speech varies according to the speech task; speech varies according to external stimuli (e.g. smell, hearing), the type of listener or the environment).
Suggestibility - symptoms worsen when the investigator tells him that the next task will be challenging
Distractibility - speech improves (severity of symptoms, fewer grimaces) when the patient talks about a favourite topic or during a relaxed conversation
Paradoxical fatigue - speech impairment is not due to increasing weakness but to muscle fatigue
Indifference or denial of a speech disorder, even though it is easily noticed by others
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Variability of stuttering (long episodes of fluent speech with episodes of stuttering or vice versa)
Excessive consistency (stuttering on every syllable, word or sound)
Exaggerated stuttering behaviours (e.g. grimaces or stretching the neck)
Absence of dysarthria, apraxia or aphasia
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The ability to create a second accent with relative ease on demand.
No history or current aphasia, dysarthria or apraxia of speech.
Infantile/childish prosody, especially if accompanied by infantile affective facial expressions and gestures.
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Weakness of the tongue, jaw or face in non-speaking tasks that is disproportionate to articulatory imprecision.
If hemiparesis is present - tongue deviation to the wrong side.
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The incoherence of hypernasality.
Consistent hypernasality or nasal emission of only one or a small number of consonants.
Stuttering
Patients who have never stuttered may develop what is known as an acquired stutter. So-called functional stuttering is characterised by exaggerated variability in symptom expression, where patients may have long episodes of fluent speech interrupted by stuttering and/or vice versa. There may also be exaggerated symptom expression, where patients stutter on every syllable, sound or word, and there may be exaggerated facial grimaces or neck stretching.
Foreign accent syndrome
Foreign accent syndrome( FAS) is a speech disorder that causes a sudden change in speech so that a natural speaker appears to speak with a foreign accent. Speech is intelligible and not necessarily confusing, but it varies according to time, intonation and grammatical layout, making it perceived as foreign by others. Functional foreign accent syndrome is diagnosed when there are changes in the history, symptoms or signs of the syndrome and/or when the accent varies on examination. One of the good diagnostic indicators is that the patient can speak with a different accent (preferably he/she may have spoken with the accent in question in the past). Patients with organic FAS cannot do this at all, whereas some patients with functional FAS can. This is because the voluntary production of an accent requires considerable motor control of speech, and is therefore a strong indication of the functionality of the syndrome. As is true for any functional speech disorder, rapid resolution of the accent with symptomatic therapy is also a strong indicator.
Questions to ask before diagnosing a functional speech disorder
Does the abnormal speech pattern have a neurological cause?
As with all functional neurological disorders, the possibility of a functional speech impairment should be considered when the results of investigations do not point to neurogenic or other structural causes of the speech deficit. In patients diagnosed with a neurological disease or locus of injury, the discrepancy between an abnormal speech pattern or lesion and a speech disorder increases the possibility of a diagnosis of functional speech disorder.
Is the speech deficit consistent?
Unlike functional speech disorders, organic speech abnormalities (there are exceptions such as: flaccid dysarthria, paroxysmal ataxic dysarthria and canalopathy) are consistent during the examination. In the case of functional speech disorders, there is considerable inconsistency between the examination or the reporting of symptoms by the patient and the patient's family.
Is the speech disorder suggestible or subject to distraction?
The speech of patients with functional speech disorders may deteriorate or improve under certain conditions that do not occur in organic speech disorders.
Is speech fatigue happening the right way?
The "fatigue" that occurs in some people with functional speech disorders, whose main complaint is weakness or tiredness, is often due to increased muscle contraction (e.g. the appearance of a strained voice or exaggerated facial expressions during speech).
Is the speech disorder reversible?
Although motor speech disorders can improve after therapy, this improvement is rarely as rapid and dramatic as in functional speech disorders, where improvement can occur after just a few sessions with an experienced speech therapist.
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Baker, J., Barnett, C., Cavalli, L., Dietrich, M., Dixon, L., Duffy, J. R., ... and McWhirter, L. (2021). Management of functional communication, swallowing, cough and related disorders: consensus recommendations for speech and language therapy. Journal of Neurology, Neurosurgery & Psychiatry, 92(10), 1112-1125.
Duffy, J. R. (2016). Functional speech disorders: clinical manifestations, diagnosis, and management. Handbook of clinical neurology, 139, 379-388.
Chung, D. S., Wettroth, C., Hallett, M., in Maurer, C. W. (2018). Functional speech and voice disorders: case series and literature review. Movement disorders clinical practice, 5(3), 312-316.
Espay, A. J., Aybek, S., Carson, A., Edwards, M. J., Goldstein, L. H., Hallett, M., ... in Morgante, F. (2018). Current concepts in diagnosis and treatment of functional neurological disorders. JAMA Neurology, 75(9), 1132-1141.