Prosodic preservation in Landau-Kleffner syndrome: a case report

Landau-Kleffner syndrome (LKS) is a rare acquired condition of auditory verbal agnosia and convulsive disorder in children. It has been proposed that there is a functional relationship between electrical disturbance and the speech defect. Prosody or the melody of language, as described by Monrad-Krohn (1947), is one aspect of non-verbal communication which is distributed bilaterally in the brain. Prosodic parameters of expression and perception in one 7.5-year-old child were tested to see if they were preserved as a means of communication. The child was observed during video-electroencephalogram (EEG) monitoring over a 48-hour period. All utterances were recorded and subject to analysis for the salience and variation of acoustic correlates of prosody. Prosodic comprehension was measured using specific perceptual tasks previously presented to normal children between the ages of 5.5 and 8.5. Despite being unable to meaningfully use or perceive phonemes, the child was able to use variations in fundamental frequency, duration and intensity of utterances, to convey both emotional and propositional intent. Similarly, the child was able to discriminate prosodic contours of a male adult voice to an age equivalent to 5.5 to 6.5 years. This argues in favour of the notion for educating such children not only through the visual channel but also through the auditory channel.