One auditory comprehension disorder that I have found particularly fascinating is pure word deafness/word sound deafness. It is quite a rare condition, and, according to Papathanasiou et al. (2013), this is because of two reasons. First of all, for it to occur, the temporal lobes must suffer bilateral damage, which does not happen very often. Secondly, when people have the condition in its pure form, they tend to recover from it spontaneously and quite well, therefore, it can only be perceptible in the acute phase. The factor of bilateral damage, however, is somewhat controversial: researchers are not certain whether word deafness always accompanies auditory agnosia (that is, the inability to recognize familiar non-speech sounds). Granted, most of the time pure word deafness comes with both bilateral damage and auditory agnosia; still, there is some evidence of pure word deafness occurring alone and being connected to left temporal lobe damage.
With the speech sound level of auditory comprehension, a deficit, whether the symptom or the syndrome, manifests itself in the same way. As per Papathanasiou et al. (2013), someone appears to be deaf upon hearing speech although they are normally perceptive to any kind of sound occurring around them. This is experimentally demonstrated by the normal performance of such individuals on audio-metric testing. They invariably face barriers when it comes to repetition and tests requiring specific sound recognition. Practically, comprehension is especially
challenging when a word sounds deaf Patients cannot use context to facilitate comprehension, for instance, when a subject change takes place (Papathanasiou et al., 2013). However, word sound deafness is almost always improved by a person being allowed to read lips.
It is interesting to note that some might argue that pure word deafness, just like pure alexia (inability to read) is not truly aphasia, since the language formulation is not impacted. Kirshner and Wilson (2022) state that, from a physiopathological point of view, both conditions are reflective of the verbal information’s inability to reach the structures that process it into meaning. Inner language workings and exteriorization of a well-defined language are still intact. However, Kirshner and Wilson (2022) provide reasons why these two conditions are to be associated with aphasias. First, they bear resemblance to aphasias in terms of the communication impairment they create. Secondly, the knowledge – both anatomical and physiological – gained from the study of these two disorders has made an important contribution to understanding what aphasias are.
It was especially interesting for me to learn that patients with right hemisphere disorders (RHD) might exhibit prosodic. Aprosodia is defined as an inability/reduced ability to produce or interpret linguistic/affective information transmitted by variations in intensity, fundamental frequency, or duration of cues in speech. Papathanasiou et al. (2013) report that RHD patients use fewer prosodic cues to convey emphasis in emotional utterances, which is associated with one’s prosodic encoding, not with their emotional processing. Additionally, adults with RHD might not effectively use prosody to signal changes in discourse structure. Clinically, expressive prosodic patients are likely to have monotonous voices or sound hyper-melodic (Papathanasiou et al., 2013). ‘Hypermelodic’ in this case means unpleasant to one’s ear and disturbing.
RHD patients might also have significant problems with the evaluation of emotions from the speech or the interpretation of linguistic information communicated by prosody (that is, syntactic markers). In many cases, the difficulties are connected to a prosodic decoding perception impairment, not to the utterance’s emotional or linguistic character. Jones and Jorge (2019) inform that they test for this condition by evaluating an individual’s ability to correctly understand, repeat, and convey three variants of the same sentence. These are: “He’s going to sing?” (surprise); “He’s going to sing?!” (anger); “He’s going to sing!” (happiness) (Jones and Jorge, 2019). What might be some other variants of this test to use when screening for aprosodia?
When it comes to dysarthria, there are eight clinically recognized types of it. For example, as per Papathanasiou et al. (2013), spastic dysarthria is a term that describes the speech disturbance observed concerning damage to the upper motor neurons. Upper motor neurons are the neurons that transmit nerve impulses from the cerebral cortex’s motor areas to the lower motor neurons. ‘Spastic’ in the ‘spastic dysarthria’ is reflective of the clinical signs of damage to the upper motor neurons in patients’ bulbar musculature. These signs of damage include spastic paralysis or involved muscles’ paresis; little to no muscle atrophy; the presence of pathological reflexes and hyperreflexia.
In a way, the treatment of speech disorders is very similar to the treatment of limb weakness. Jankovic et al. (2022) note that speech therapy improves aphasia by reinforcing contralateral speech and non-speech brain areas to compensate for the damaged speech center effects. If the damage is insubstantial, some language function aspects can be retained and thus insert an immediate communication mechanism. For example, a patient with aphasia might be able to communicate by writing. In terms of dysarthric patients, they can learn to improve their delivery and accentuate words, thus enhancing the clarity of their speech.
References
Jankovic, J., Mazziotta, J. C., Pomeroy, S. L., & Newman, N. J. (Eds.). (2022). Bradley and Daroff’s neurology in clinical practice (8th ed.). Elsevier Health Sciences.
Jones, M., & Jorge, R. E. (2019). Depression and other neuropsychiatric issues following stroke. In R. Wilson & Raghavan, P., Stroke rehabilitation (pp. 155-168). Elsevier Health Sciences.
Kirshner, H. S., & Wilson, S.M. (2022). Aphasia and aphasic syndromes. In J. Jankovic, J. C. Mazziotta, S.L. Pomeroy, & N. J. Newman (Eds.), Bradley and Daroff’s neurology in clinical practice (8th ed., pp. 133-148). Elsevier Health Sciences.
Papathanasiou, I., Coppens, P., & Potagas, C. (2013). Aphasia and related neurogenic communication disorders. Jones & Bartlett Learning.