Diabetes Insipidus in Children with Septo-Optic Dysplasia
By Sandra D Stirnweis, MA, COMS

In an orientation and mobility program at the Foundation for Blind Children in Phoenix, AZ, I work with children who have septo optic dysplasia (SOD) and optic nerve hypoplasia (ONH). The majority of children with SOD that I have encountered also have hypothyroidism and central (neurogenic) diabetes insipidus (DI). I first began working with children with SOD in 1986. However, it’s only in the last two years, when I had two preschoolers in side-by-side classrooms, an older student in a private placement, and three others of various ages in public school settings, that I realized the effect central DI and medication breakthroughs or "escapes" have on these children’s behavior.

SOD and ONH are often used interchangeably. However, although SOD has ONH as a component, the two conditions are very different. A child with ONH has underdeveloped optic nerves. The restricted nerve causes restricted visual fields and reduced clarity of vision. This is a stable condition, evidenced at birth or soon thereafter by small optic disks with a halo around them.

Children with ONH alone usually have quite a bit of residual vision, with acuities of 20/1000 or better. A child with ONH can see large objects, people at a close distance, and some detail at extremely close distance. They probably will not drive a car but they have good vision for mobility purposes and may be braille or large print readers. If a child with ONH has only or no light perception, the child should be checked for SOD since most, but not all, severe forms of ONH are in children with SOD because of damage to the optic chiasm. Children who have SOD may also have this degree of vision, but their vision is usually 20/1000 at best, and often limited to light and shadow or worse.

SOD is so named because of the lack of a septum pellucidum. The septum pellucidum is a thin layer of nervous tissue that separates the two lateral ventricles of the brain. It is attached to the corpus callosum at the top and the cerebral lobes at the bottom. To visualize this, think of the heart’s ventricles. In the brain, the lateral ventricles are cavities in each cerebral hemisphere that communicate with the third ventricle. The third ventricle is the cavity in the brain surrounded by the thalamus, the hypothalamus, the optic chiasm, and the tubercinereum (the connection to the pituitary gland). Without the septum pellucidum, communication between these areas of the mid brain is impaired. It is also possible for some of these components to be damaged as well. The thalamus receives all sensory information (except olfactory) and is the area of the brain that appreciates pain, crude touch, and temperature. The corpus callosum processes sensory information and relays it to other parts of the brain. The optic chiasm is where visual information from each optic nerve comes together and then separates on it’s way to the occipital lobe in the back of the brain. The hypothalamus controls maintenance of water balance, regulation of body temperature, and secretion of releasing and inhibiting hormones. It is also responsible for integration of sympathetic and parasympathetic activities. A child with SOD experiences vision loss, sensory motor delays, hormonal deficiencies (primarily growth), spatial orientation problems, and endocrine deficiencies. In addition, a child with SOD is unable to regulate body temperature, has a malfunctioning thirst center, and has language delays and other difficulties.

Like ONH, SOD is also congenital. However, it is typical to have different reports on the same child from different doctors with differing opinions. A child who has been diagnosed with ONH but is demonstrating some of the symptoms mentioned above probably has SOD. The only way to know for sure is to have an MRI to confirm the presence of the septum pellucidum, although there are cases where the MRI has indicated the septum pellucidum when it is not there. Recently, for example, a four year old entered our program who’s endocrinologist labeled the condition as SOD but the pediatrician labeled it as ONH. Her MRI showed the septum pellucidum but the endocrinologist felt that because of her DI, ONH, and pituitary problems she really was SOD. We have asked this mother to ask all the physicians working with her child to come to consensus. Because of the underlying difficulties and the importance of early treatment, especially in regard to hormonal replacement therapies, it is important to make a definite diagnosis.

Currently there is no known cause for ONH or SOD. What is known is that it is not genetic or hereditary. In nearly all cases the child with ONH or SOD has no other family members with the condition. Sometime during the development of the child in the womb, the optic nerves do not fully develop, which is true for most types of congenital vision impairments.

There is no treatment for ONH. In fact, there are very few treatable vision impairments at all. For a child who has SOD, hormone replacement therapy can sometimes improve metabolism or encourage more normal growth. Most children diagnosed with SOD can live full, long lives. Their productivity level depends on the extent of neurological damage, but one of my students will be going to college and plans to be an interpreter for the UN. The other end of that spectrum is the child with moderate mental delays, motor planning difficulties, language delays, and growth deficiencies who may or may not be able to work in a sheltered workshop setting and will always need to be looked after. But even these children can expect to live out normal life expectancies.

Many of the children with SOD and diabetes insipidus also have motor planning difficulties and language delays. Most of these children are on DDAVP to control the DI, mostly given once a day in the nasal spray form, with additional doses as needed. Their vision ranges from severe field loss to light perception. Although they are fairly slow movers, they have a good sense of orientation and kinesthetic awareness (the ability to remember how much the muscles have to move to perform a specific task). Among most of these students, obvious behavioral changes occur at or near the time of a medication breakthrough.

An SOD/DI student near breakthrough will exhibit irritability, severe mood swings, breakdown of the language center, and inconsolability, which is soon accompanied by high urine output. Once the DDAVP is given the child will soon return to his or her normal personality. Sometimes she will be fatigued and require a nap. Unfortunately, there is no clinical evidence to support these observations. In fact, there is very little research at all among children with SOD and DI. Understanding the effects DI has on children with SOD is complicated because many of these children, if there is damage to the thalamus and hypothalamus, also have difficulty regulating their thirst centers. In addition, DI is such a rare disorder it is overlooked as the cause of poor fluid and urine regulation. Whatever the reason for the lack of clinical data on this phenomenon, it is real and it can be observed, studied, and perhaps, used as a preventative assistance against breakthroughs. If an additional dose of DDAVP could be given at the onset of these changes, it might prevent the breakthrough, and as a result, keep the body in better balance.

Interpreting these behavioral changes can only be done by careful observation of the SOD/DI child. In many cases, the child may have language or behavior problems that make this difficult. They may not be able to express their thirst, or understand neurological changes that are a precursor to the breakthrough. And sometimes their behavior is simply misinterpreted, especially if they are throwing a tantrum or showing non-compliance to given directions. However, if behavior modification and re-direction techniques that are usually successful do not work, it probably indicates a breakthrough in progress. Among my students, we can use this technique to warn us of the breakthrough, although we never administer additional doses of DDAVP until the breakthrough has evidenced itself through the child’s urine output. However, we can help the child by modifying our expectations until the breakthrough has passed and they are, again, able to perform at their optimum level.

Sandra Stirnweis is a certified orientation and mobility specialist who has been teaching since 1986. Her areas of expertise are preschool children, multiple-handicapped children, and low-vision children. She may be contacted through the Foundation for Blind Children, 1235 E. Harmont, Phoenix, AZ 85020.