Lesser Known Disorders
Each issue of this series contains at least three lesser known disorders. Some of these disorders may contain subtypes which will also be presented. You will also notice that each disorder has a code. These codes represent the coding system for all disabilities and disorders listed in the Educator’s Diagnostic Manual(EDM) Wiley Publications.
Disorders in this issue:
VI 8.02-Hemianopsia (Hemianopia)
Disability Category- Visual Impairments
Definition
A homonymous hemianopsia is the loss of half of the field of view on the same side in both eyes (Windsor & Windsor, 2005).
Explanation
Common causes of Hemianopsia causes include stroke, trauma (injury) or tumors. A stroke occurs when there is a sudden disturbance in the blood supply to the brain and in 75% of cases this will be due to the effects of a blocked blood vessel. The other major cause of stroke is a leaking blood vessel. The majority of people who experience stroke will be over retirement age.
People with high blood pressure are at higher risk of stroke and heart-related illnesses. People with an abnormal heart rhythm may be at risk. Where there is identifiable change, Hemianopsia will affect both eyes and sight loss can be severe or so slight that many people do not notice the changes (Royal National Institute of the Blind, 2004).
There are several types of field loss in this condition:
VI 8.02a-Absolute Hemianopsia
In Absolute Hemianopsia, the affected part of the retina is totally blind to light, form and color.
VI 8.02b-Bitemporal Hemianopsia
In Bitemporal Hemianopsia, the visual the field loss consists of both temporal (outside edge) halves of visual field—this is typical of pituitary tumors
VI 8.02c-Congruous Hemianopsia
In Congruous Hemianopsia, there are identical defects in the visual fields of each eye
VI 8.02d-Homonymous Hemianopsia
In Homonymous Hemianopsia, the visual the field loss consists of the nasal half of one eye and temporal (or outer) half of the other—this is typical of stroke patients
VI 8.02e-Incongruous Hemianopsia
In Incongruous Hemianopsia, both visual fields are differently affected in one or more ways.
VI 8.02f-Relative Hemianopsia
In Relative Hemianopsia, there is a loss of form and color but not of light.
HI 6.00 Syndromic Hearing Losses
Disability Category – Hearing Impairment
Definition
Syndromic hearing impairment is associated with malformations of the external ear or other organs or with medical problems involving other organ systems (Smith, Green & Van Camp, 2005).
Diagnostic Symptoms
The symptoms for Syndromic Hearing Loss will vary by disorder and as a result no general symptoms can be reported.
Further Key Points
Genetic causes of hearing loss can be “syndromic” or “nonsyndromic”. Syndromic means that a person has other related symptoms besides hearing loss. For example, some people with hearing loss are also blind. Usher’s Syndrome is one example. There are many different syndromes that have hearing loss as one of the symptoms. “Nonsyndromic” means that the person does not have any other symptoms related to the hearing loss. Whatever caused the hearing loss does not cause any other symptoms. The more common type of genetic hearing loss is “nonsyndromic” which includes 2/3 of all genetic hearing losses. A very common “nonsyndromic” hearing loss is caused by one gene known as Connexin 26 (abbreviated CX26). CX26 alone is the cause in about 1/3 of all children with a non-syndromic genetic hearing loss (National Center on Birth Defects and Developmental Disabilities, 2005).
Types of Syndromic Hearing Losses
HI 6.01-Aplasia
Definition
An aplasia is an abnormal development of either the bony or membranous portion of the inner ear (cochlea) (League for the Hard of Hearing, 2005; MedicineNet.com (2005).
Explanation
The disorders discussed in this section have a variety of symptoms. Therefore no generalized list of diagnostic symptoms can be made.
HI 6.01a-Michel aplasia
A type of Aplasia characterized by the complete absence of the inner ear and auditory nerve, resulting in total absence of hearing. It may appear in one ear (unilaterally) or both ears (bilaterally). Patients cannot be helped by either a hearing aid or a cochlear implant if the hearing nerve is absent. They may be assisted by a vibrotactile device (a device that augments remote voice communication with touch, by converting hand pressure into vibrational intensity between users in real-time).
HI 6.01b-Mondini aplasia
A type of Aplasia characterized by an abnormal development of the cochlea. The normal cochlea has two and one half turns. In Mondini Aplasia the turns may range from one to four. The most severe form results in a common cavity (no turns). It may occur unilaterally or bilaterally. Hearing loss can range from moderate to profound and is often progressive in cases where residual hearing is present. In less severe cases, hearing aids are beneficial. If the loss is too profound to be helped by hearing aids, cochlear implants are an option.
HI 6.01c-Scheibe aplasia
A type of Aplasia characterized by an abnormal formation of the cochlear membrane. The defect may be unilateral or bilateral. There may be residual low frequency hearing that is aidable. If not, a cochlear implant is an option.
LD 12.10-Visual Pursuit and Tracking Disorder
Disability Category – Specific Learning Disability
Definition
A type of visual processing disorder specifically associated with difficulties in tracking moving objects while seated or standing, and the ability to keep a stable visual image when the head or eyes are in motion (Behavioral Neurotherapy Clinic, 2006).
Explanation
To function comfortably and safely in the world, our eyes must be able to smoothly follow a moving object, make continuous adjustments in the positions of our eyes as we move about, shift our gaze quickly and accurately from one object to another. An individual with Visual Pursuit and Tracking Disorder will be unable to track one’s eyes from left to right in an efficient manner (Behavioral Neurotherapy Clinic, 2006).
For success in school, children must have other equally important visual skills besides their sharpness of sight, or visual acuity. They must also be able to coordinate their eye movements as a team. They must be able to follow a line of print without losing their place. They must be able to maintain clear focus as they read or make quick focusing changes when looking up to the board and back to their desks (Terry, 2001). And they must be able to interpret and accurately process what they are seeing. If children have inadequate visual skills in any of these areas, they can experience great difficulty in school, especially in reading (Children’s Vision Information Network, 2005).
It should be noted that medical problems associated with this child’s vision have been ruled out as a primary cause of the child’s difficulties. The difficulties are in the internal processing of information, not due to a visual impairment.
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