Chapter 11: Disorders of Speech
Author's Commentary
The ability to make and understand language is uniquely human. Although great strides have been made in the basic understanding of speech mechanisms, localization of speech deficits is a critical component of our understanding of speech.
Dysarthria refers to the articulation of the spoken word. Mutism is considered when a patient makes no attempt to speak or utter a sound. An abulic patient produces no speech and may only respond with a yes or no answer to intense stimulation. Aphonia refers to patients who are able to speak but are unable to produce words or have a diminished volume of speech.
Aphasia
Aphasia is the loss or impairment of language function due in most instances to structural brain damage.
There are deficits in:
- The prosody (the rhythm of speech)
- Timbre (speech modulation)
- Confrontation naming (small parts of common objects)
- The ability to follow commands off the midline
- Repetition of individual words or a sentence
- Reading and writing
- Color naming
Excerpts From Chapter 11
The ability to make and understand language is uniquely human, and defects are categorized as aphasia. These extend to reading and writing. Although advances have been made with magnetic resonance imaging (MRI), functional MRI, single-photon emission computed tomography (SPECT) and positron emission tomography (PET) scanning, all we can currently accomplish is to localize speech deficits. Until we can understand how inanimate material, lipids, membranes, sodium-potassium ATPase, and the structure of the brain can become sensate, we will not understand behavioral neurology (Aristotle’s “mind–brain barrier").
Dysarthria refers to articulation of the spoken word. It requires excellent tongue movement against the teeth (glottals), precise movement of the mouth and lips (labials), closing of the nasopharynx (tensor veli palatini), and the coordination of speech and breathing.
A conscious patient who makes no attempt to speak or make a sound is mute. An akinetic mute patient does not speak, is paralyzed, but may reflexly follow the examiner with the eyes. An abulic patient proffers nothing and may only respond with a yes or no answer to intense stimulation. This is often the result of a subfrontal lesion. Amazingly, if handed a toy telephone, the patient may speak into it. Mutism, in general, is caused by lesions of the anterior wall of the third ventricle and bilateral lesions of the posterior medial frontal lobes, as well as subfrontal lesions (anterior communicating aneurysm or head trauma; rarely a tumor). Total mutism may occur from a stem middle cerebral artery (MCA) embolus or supplementary motor area lesion (SMA supplementary area of the frontal lobe). Most often under these conditions the patient appears stunned, but occasionally gives the impression of trying to speak, but is unable to produce words. An aphonic patient is able to speak, but cannot produce any words or has a greatly diminished volume. This type of aphonia is caused by disease of the larynx or vocal cords. If the patient has a normal cough, this is hysterical. Disorders of voice volume from central lesions most often are secondary to disease of the basal ganglia (Parkinson’s disease or of the cortex, cerebral hypophonia).