Chapter 105 The deaf-blind child
Background
A Danish study estimated the prevalence of deaf-blind children at 1 : 15 000 and congenital deaf-blindness at 1 : 19 000.1 Visual problems of all severities are found in 40−60% of deaf children.2 Although profound deaf-blindness is uncommon, it was found in 21.4% of intellectually disabled residents in an Austrian institute and is under-recognized in this setting.3 Conversely, deaf-blind people may be misdiagnosed as having learning difficulty particularly as behavioral and psychiatric problems are more common.4 Using a functional definition of deaf-blindness, the US National Deaf-Blind Child Count identified 66% also had cognitive disability, 57% physical disability, and 9% behavioral challenges.5
Communication with dual sensory impaired
Communication is often idiosyncratic and depends on several factors:
1. The onset of the disability relative to speech and reading development.
2. Associated neurodevelopmental problems.
3. The absolute and relative severity of each form of impairment.
When communicating with hearing impaired it is best to speak clearly, not too fast, and reduce background noise. Face the child and have good lighting so she/he can lip-read. Follow the child’s lead and make use of gestures where appropriate. Dark clothes can help the child to see hand movement when signing. Various methods including fingerspelling (Print on palm) and tactile lip-reading (Tadoma)* are used. Makaton** uses printed symbols that are helpful with learning difficulties. Tablet computers or Braille displays are available.
Neuroadaptation
Like vision, hearing has a sensitive period of cortical development. Cochlear implantation in the congenitally deaf after the period of auditory plasticity has a worse outcome. Early implantation promotes cortical maturation and speech development.6
Functional neuroimaging and behavioral studies show that deaf-blindness allows recruitment of the sensory cortex by, for example, tactile stimuli and language processing.7 Braille alexia in a congenitally blind person following a visual cortex stroke illustrates this cross modal mechanism.8 Cross adaptation allows behavioral gains, but may prevent rehabilitation of the primary sensory function.
