This abnormality, characterized by interruptions of the normal rhythm of speech by involuntary repetition and prolongation or arrest of uttered letters or syllables, is a common developmental disorder, discussed in Chap. 27. But as pointed out by Rosenbek and colleagues and by Helm and colleagues, it may appear in patients who are recovering from aphasic disorders and who had never stuttered in childhood. This form of acquired stuttering in adults has some different features from the developmental type in that the repetitions, prolongations, and blocks are not restricted to the initial syllables of words, stuttering occurs at equal frequency for grammatical as for substantive words, there is little adaptation with continued speaking, and is generally unaccompanied by grimacing or associated movements, as happens in some developmental types. These features are discussed in the review by Lundgren and colleagues. Stuttering differs from palilalia, in which there is repetition of a word or phrase with increasing rapidity, and from echolalia, in which there is an obligate repetition of words or phrases.
In many instances, acquired stuttering is transitory; if it is permanent, according to Helm and associates, bilateral cerebral lesions are present. Nevertheless, we have observed some cases in which only a left-sided, predominantly motor aphasia provided the background for acquired stuttering, and others in which stuttering was an early sign of cerebral glioma originating in the left parietal region. Benson also cites patients in whom stuttering accompanied fluent aphasia. The causative lesion in acquired stuttering may be subcortical and even, as in an exceptional case described by Ciabarra and colleagues, located in the pons. The treatment of Parkinson disease with l-dopa and, occasionally, an acquired cerebral lesion may reactivate developmental stuttering. The latter may explain the emergence of stuttering with oddly situated lesions, such as the aforementioned pontine infarct.
A few points should be made concerning the fourth group of speech disorders, that is, those that are a result of disturbances of phonation. In adolescence, there may be a persistence of the unstable “change of voice” normally seen in boys during puberty. As though by habit, the patient speaks part of the time in falsetto, and the condition may persist into adult life. Its basis is unknown. Probably the larynx is not masculinized, that is, there is a failure in the spurt of growth (length) of the vocal cords that ordinarily occurs in pubertal boys. Voice training has been helpful.
Paresis of respiratory movements, as in myasthenia gravis, Guillain-Barré syndrome, and severe pulmonary disease, may affect the voice because insufficient air is provided for phonation. Also, disturbances in the rhythm of respiration may interfere with the fluency of speech. This is particularly noticeable in extrapyramidal diseases, where one may observe that the patient tries to talk during part of inspiration as noted earlier. Another common feature of the latter diseases is the reduction in volume of the voice (hypophonia) because of limited excursion of the breathing muscles—the patient is unable to shout or to speak above a whisper. Whispering speech is also a feature of advanced Parkinson disease, stupor, and occasionally concussive brain injury and frontal lobe lesions, but strong stimulation may make the voice audible.