Pure word deafness
Psychiatric disorders Right hemisphere disorders Dementing diseases lips and impairs enunciation of labial consonants (B, M, P). Neurological examination may reveal atrophy and fasciculations of the tongue and weakness of the palate and the facial muscles. When a history of variable dysarthria or dysphonia, with prominent fatigability is elicited, a neuromuscular junction disorder such as myasthenia gravis may be present.
Spastic dysarthria is also called upper motor neuron dysarthria. It is a motor speech problem characterized by a harsh, low-pitched, slow, monotonous verbal output that sounds strained or strangled. This is the speech that characterizes pseudobulbar palsy (bilateral involvement of corticobulbar tracts) and, to a lesser degree, may be present following significant unilateral upper motor neuron disturbance. Spastic dysarthria may occur with nonfluent aphasia, particularly Broca's aphasia. MUTISM
Mutism is the total loss of speech and is discussed here because the underlying pathology most often involves the upper motor neurons. Several diseases and various sites of pathology can produce mutism. Peripheral disorders such as laryngitis or vocal cord paralysis occasionally can cause a mute state. Patients with aphemia (described later), global aphasia, transcortical motor aphasia, and aphasia with subcortical lesions frequently present with initial mutism. Persistent mutism is associated with bihemispheric involvement, particularly of the frontal lobes. y , y Tissue destruction or dysfunction affecting the upper brain stem or the frontal septal area bilaterally, or both, can interfere with the initiation of both behavior and verbal output. When it is severe, this state is called akinetic mutism. y Mutism can also be of psychogenic origin.
Ataxic dysarthria is manifested by slowness of speech, altered rhythm, irregular breakdowns, and improper stress, producing an uneven, jumpy, and unpredictable output. Coordination of speech and of respiration is disturbed. There may not be enough breath to utter certain words or syllables, and others are expressed with greater strength than intended (explosive speech). This speech disorder is most commonly encountered with acute and chronic cerebellar disease.
Scanning speech is part of Charcot's triad (ataxia, nystagmus, scanning speech), which is historically considered to be pathognomonic for multiple sclerosis, but it is more common with head injuries. Scanning speech is characterized as a slow, deliberate, segmented, and monotonous output, presented as individual words or major segments of words. The output retains both grammatical and semantic competence, and articulation remains relatively normal. It is the prosodic quality, particularly of the rhythm and inflection, that are disrupted. The major pathology underlying
this disorder is located at the level of the decussation of the brachium conjunctivum in the mesencephalon affecting crossed efferent cerebellar pathways and motor fibers in the cerebral peduncles, which lie in close proximity. y Although scanning speech is easily misinterpreted as a nonfluent aphasia, careful evaluation reveals that there is no true language impairment.
Extrapyramidal disease is often associated with either hypokinetic or hyperkinetic dysarthria. Hypokinetic dysarthria occurs in Parkinson's disease and other rigid types of extrapyramidal disorders. This speech abnormality is characterized by rapid utterances, slurring of words, and decrescendo volume at the ends of sentences. The voice is low pitched and monotonous, lacking both inflection and volume (hypokinetic and hypophonic). In advanced states only whispering is possible.
Two varieties of speech disorders can be classified as hyperkinetic. The first, choreiform dysarthria, features prolonged phoneme and sentence segments, intermixed with silences and showing variable, often improper, stress (phoneme inflections). This gives speech a bursting quality. This speech output occurs in choreiform disorders such as Huntington's disease and in myoclonic disorders. The second type, dystonic dysarthria, produces a slower speaking rate, with prolongation of the individual phonemes and segments and with abnormal, unexpected appearances of stress or of silence. Dystonic dysarthria occurs in dystonia musculorum deformans. Spastic dysphonia is one type of dystonic dysarthria.
In clinical practice, a mixed dysarthria syndrome that has characteristics of several types of motor speech disorders is commonly seen. Several classic neurological disorders, such as multiple sclerosis, Wilson's disease, and advanced amyotrophic lateral sclerosis, produce several variations of dysarthria concurrently including spastic, flaccid, ataxic, and hypokinetic and hyperkinetic dysarthrias.
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