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Originally published in See/Hear Newsletter, Summer 2007
Versión Español de este artículo (Spanish Version)seis

Chris Montgomery, TSBVI Outreach, Deafblind Education Consultant

Abstract: A former classroom teacher, now Outreach deafblind consultant, shares the observations and educational intervention strategies he compiled when working with one student a few years ago. Natasha had cortical visual impairment, central auditory processing disorder, seizure disorder, and additional sensory integration problems.

Keywords: visually impaired, cortical visual impairment, central auditory processing disorder, deafblind.

Natasha is a seven-year-old girl who has been labeled deafblind. She has a severe bilateral hearing loss, a cortical visual impairment, and a long history of severe seizure disorder that began at four months of age. To restrict and lateralize her seizures, by age three she needed a corpus callosotomy to separate the anterior two-thirds of the corpus callosum. After surgery Natasha made significant improvements in her general health, sleep, growth, development, midline control, and sustained visual gaze. Her seizures continued, and at age six she received a Vagus Nerve Stimulator (VNS). The VNS is a device that sends an electric signal to the Vagus nerve at consistent intervals so regular brain waves can be established, thus minimizing seizure activity.

It has been approximately three years since Natasha's neural surgery. Research suggests that the first three to four years of a child's life is the most critical for the development of neural pathways. Early identification of Natasha's neurological conditions, including CVI provide the best opportunity to take advantage of the brain's plasticity. I feel we are just in time in this regard, and I am noticing improvement in her use of vision weekly.

Observations

In Natasha's case, her CVI had a more profound effect on her vision before her corpus callosotomy. According to her mother her depth perception problems have improved. Her ability to stay on task and recognize people and calendar symbols is also improving. Natasha still exhibits a strong preference for bright primary colors, and usually attends better when her environment is kept visually uncluttered. She does not demonstrate fluctuations in her vision.

Natasha is starting to respond to my voice during familiar activities such as eating breakfast. She will lean her ear toward my mouth to listen to familiar phrases that I say to her. I try to keep these vocalizations as consistent as possible during the routines so they will in effect be paired with the routine we are doing. I am hoping the next step will be her hearing these vocalizations from a further distance, and associating my vocalizations with the particular activity by signal or gesture when we are away from the activity. Natasha is motivated by her near senses including:

  • Vestibular: swinging, being flipped, rocking, swaying, and extreme extension in a inverted position.
  • Oral/Tactile: oral exploration, smelling, tasting, textures (e.g. pegboard, carpet, familiar blanket), water, vibration.
  • Touch/Proprioceptive: deep pressure, physical rough house play, tapping, stomping feet.

Cortical Visual Impairment

Cortical visual impairment (CVI) is a temporary or permanent visual impairment caused by the disturbance of the posterior visual pathways and/or the occipital lobes of the brain. The degree of neurological damage and visual impairment varies with the time of the onset, as well as the location and intensity of the injury. It is a condition in which the visual systems of the brain do not consistently understand or interpret what the eyes see. CVI can have wide-ranging effects. Individuals can have multiple disabilities, and other cognitive disorders, as well as motor impairments that compound their CVI.

The major causes of CVI are asphyxia, developmental brain defects, head injury, hydrocephalus, and infections to the central nervous system, such as meningitis and encephalitis. (Jan & Groenveld, 1993) The damage may be localized to a

specific area of the brain or generalized to different cerebral regions. Additionally the severity of the visual impairment is related to both the gestational age at the time of insult and neonatal seizures. Other causes for cortical visual impairment include toxoplasmosis, cytomegalovirus, and such cerebral degenerative conditions as Tay-Sachs disease, and galactosemia. (Cogan, 1966) Similar injuries to an adult's nervous system may have very different outcomes than those effecting children.

Individuals with CVI may exhibit any of the following characteristics:

  • Their visual acuities may range from light perception to print reading ability.
  • There is almost always a field deficit present.
  • Nystagmus is absent unless there is an additional ocular disorder.
  • The eyes show no apparent abnormality.
  • A high percentage demonstrate light gazing, even though about the same percentage are light sensitive.
  • Visual functioning fluctuates.
  • Color perception is generally intact and many students seem to perceive red or yellow more easily.
  • Difficulties with depth perception are frequently present, particularly with foreground/background perception.
  • Suppressing unnecessary visual information may be difficult. Close viewing may be preferred even though visual acuities are normal.
  • Perception of objects is difficult when they are spaced close together.
  • Avoiding obstacles during travel is easier than using vision for close work. (Smith & Levack, 1997)

While Natasha uses the distance senses of vision and audition, these senses are less reliable. The information gained through them seems to be more difficult for her to process. Natasha sometimes exhibits signs of auditory overload. She may have a difficult time filtering out environmental noises. Sensitivity reactions observed in the past have included withdrawal, covering her ears, vocalizations indicating stress, and shut-down behavior. Extraneous objects in the environment tend to distract her if they are brightly colored or if they have a desirable texture for touching or mouthing. People walking past or about the room also distract Natasha.

Central Auditory Processing Disorder and Auditory Neuropathy

Central auditory processing disorder (CAPD) is a term that refers to some type of problem in the auditory system, which occurs neurologically instead of in the ear itself. A person may have one or more auditory processing problems for a variety of reasons. Differences in auditory nerve (auditory neuropathy) might cause some of these problems, however there is more to the neurology of the auditory system than the auditory nerve.

As the nerve fibers enter the brainstem at the base of the skull they split and cross (similar to the optic nerve at the optic chiasm). Then the fibers go to various parts of the cortex of the brain. Most of the fibers go to the temporal lobe. Differences in neurology, anywhere along the line, might result in the symptoms of CAPD. (Durkel, 2001)

CAPD is similar to CVI in that it results from neurological causes instead of damage to the sensory system itself. Children with cortical visual impairments are at a greater risk of having CAPD, because the damage to their neurological systems which caused the visual impairment may also have caused damage to the auditory system.

CAPD is defined as a disorder with problems in one or more of the following six areas:

  • Sound localization and lateralization (knowing where in space a sound is located).
  • Auditory discrimination (usually with reference to speech, but the ability to tell one sound is different from another).
  • Auditory pattern recognition (musical rhythms are one example of an auditory pattern).
  • Temporal aspects of audition (auditory processing relies on making fine discriminations of timing changes in auditory input, especially in differences in the way the input comes through one ear as opposed to the other).
  • Auditory performance decrements with competing signals (listening in noise).
  • Auditory performance decrements with degraded acoustic signals (listening to sounds that are muffled, missing information or for some reason are unclear, e.g. trying to listen to speech from the other side of a wall. The wall filters or blocks out certain parts of speech, but a typical listener can often understand the conversations.).

Both at home and at school Natasha associates specific locations with specific actions. She travels to various locations in the classroom to perform these actions, leaving and returning to a given activity repeatedly. Natasha seems to process information by interacting with a person or object for several minutes then withdrawing to a calming activity for several minutes. She has recently begun to associate her calming activities with familiar people, and is attaching her calming activities to places or objects in the room with less and less frequency.

Natasha shows significant signs of sensory disorganization. It is not easy for her to attach meaning to what she sees, hears, or how her body feels within a movement or activity. This means it requires a lot of effort on her part to combine her skills. Natasha's sensory processing skills vary throughout the day, and from day to day. There are occasions when it appears she is using her vision to actively explore and search within her environment. There are other situations in which she is less actively attending to her vision, but seems more aware of her own body through movement, sound, or oral/tactile involvement. The appropriate educational strategies and methods are modified according to her responses.

Body position is a strong contributor to functional use of vision. Natasha is able to hold her head steady to scan the environment and make visual contact with adults. However, there are long periods of time in which her head position is constantly changing and the ability for her to combine her vision and midline control is limited. Movements that promote controlled head and neck extension are helpful.

Epilepsy Surgery and Corpus Callosotomy

Most seizures can be controlled with medicine. When medications are unable to eliminate seizures, other therapies are considered, including surgery. When a part of the brain can be identified as the source of seizures, surgical removal of that source will often eliminate the seizures all together. Several different types of surgery can be offered. The temporal lobe is the most common part of the brain involved in seizures and these patients undergo lobectomy. Extratemporal lobectomy, hemispherotomy, and corpus callosotomy are also used in patients with seizure sources in different parts of the brain. In patients who are not candidates for brain surgery, the Vagus nerve stimulator can be used to reduce seizure frequency.

The surgical procedure corpus callosotomy is resection of the anterior two thirds of the corpus callosum. In many cases, limiting the resection provides significant seizure reduction and may avoid some of the cognitive complications that may arise from complete corpus callosotomy. Anterior corpus callosotomy is less likely to lead to significant cognitive difficulties, so-called split-brain phenomenon, than larger resections. More extensive corpus callosum resections can disrupt the cross-hemispheric communication of visual information and may lead to more noticeable neuropsychological problems. All divisions likely cause some deficit and acute, transient problems are common, especially in total resections.

Nevertheless, when anterior corpus callosotomy fails to provide significant seizure reduction, some patients may benefit from a secondary procedure to resect the remaining posterior one third of the corpus callosum.

The goal of these procedures is seizure reduction, not cure. Accordingly, reduction in seizures to a certain percentage is used as a measure of success. Overall outcome has been reported as 8% seizure free, 61% improved, and 31% not improved. In children who undergo corpus callosotomy, quality of life measures improved with seizure reduction, even in the absence of seizure-free status. (Beach, 1998)

A Vagus Nerve Stimulator is used with patients who have medically intractable epilepsy, and are not candidates for resective surgery. The stimulator is placed on the left Vagus nerve, in the neck. A battery is placed under the skin in the chest, like a pacemaker. By using the stimulator, a significant reduction in seizure frequency can be achieved. Although complete seizure freedom is unlikely, the effect of the stimulator seems to improve with continued use. Seizure reduction is greater the longer the device is used.

Learning Implications

In order to address Natasha's unique learning style, the educational team has adopted the following educational strategies.

  • Provide opportunities for a variety of vestibular and tactile stimuli. Allow Natasha to swing for at least 20 minutes prior to a structured activity. This type of vestibular input has great impact on increasing her eye contact and focus on objects and people. Vibration and deep touch are also calming to her nervous system.
  • For sensory motor participation and play, Natasha should direct her own movements as much as possible. Sensory motor play is a chance for Natasha to experience comfort within her own body. The caregiver's role should be to establish trust, offer options, and make themselves available for interaction.
  • Use the near senses (tactile, oral, vestibular, proprioceptive) to gain Natasha's attention and motivate her to attend to visual and auditory information.
  • To promote self-initiation, provide opportunities for Natasha to build a sense of anticipation. The layout and organization of the classroom and calendar systems must be predictable. A quiet uncluttered environment with a limited number of people will help her focus. Combining object symbols, voice, and gesture (e.g. pointing, gestural sign) will help to direct Natasha's attention. Adding rhythmic sounds and singing while Natasha is engaged in an activity helps her to focus her attention as well.

Conclusion

Research indicates that the ear and the eyes neurologically function and develop in much the same way. I feel Natasha still has time to establish neuro-pathways that will facilitate her use of both vision and hearing in meaningful ways. Through the use of consistent activities and communication strategies we are already seeing Natasha make more sense of her world and use her vision and hearing in more functional ways. I feel the future is very bright for Natasha.

Bibliography

Beach, S. (1998). Washington University Neurosurgery (retrieved 2001) (neurosurgery.wustl.edu).

Cogan, D. (1966). "Neurology of the visual system". Springfield, Ill: C.C. Thomas.

Durkel, J. (2001). "Central Auditory Processing Disorder and Auditory Neuropathy." See/Hear, 6 (1).

Jan, J., & Groenveld, M. (1993). Visual behaviors and adaptations associated with cortical and ocular impairment in children. Journal of visual impairment and blindness (JVIB), 87, 101-105.

Jan J., Wong P., Groenwell M., Flodmark O., & Hoyt CS. (1986) Travel vision Collicular visual system? Pediatr. Neurol. 2 (6) 359-62.

Morse, M. (1990). Cortical visual impairment in young children with multiple disabilities. Journal of Visual Impairment & Blindness, 84, 200-203.

Smith and Levack, (1997). Teaching students with visual and multiple impairments. Austin, TX: Texas School for the Blind and Visually Impaired.