Optic Nerve Hypoplasia (ONH),
Blindness, and Savant Syndrome
Questions and Answers
DISCLAIMER: THIS INFORMATION IS NOT
INTENDED FOR DIAGNOSTIC PURPOSES.
IF YOU SUSPECT YOUR CHILD HAS OPTIC NERVE HYPOPLASIA, SEE A PEDIATRIC
OPHTHALMOLOGIST OR OTHER QUALIFIED PHYSICIAN.
ALL CHILDREN WITH ONH REQUIRE A COMPREHENSIVE ENDOCRINE EVALUATION.
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What is Optic Nerve Hypoplasia (DeMorsier’s Syndrome)?
In Optic Nerve Hypoplasia (ONH), the optic nerve to one or both eyes has failed
to develop properly before birth. This causes a wide range of visual impairments,
from mild nearsightedness to complete blindness.
ONH blindness is caused by factors which are probably in place by the fifth or sixth
week of pregnancy. Most children with ONH have brain structural defects, including
the absence or malformation (‘dysplasia’) of the septum pellucidum and corpus
callosum. Many have non-functioning or absent pituitary glands, resulting in serious
endocrine disorders which require lifelong hormone replacement programs. In addition,
children with ONH are sometimes born with arachnoid cysts, requiring surgery or
permanent draining shunts. ONH has many variations and is considered a serious
disability in most cases.
What is Septo-Optic Dysplasia?
The term Septo-Optic Dysplasia (SOD) is widely used a synonym for Optic Nerve
Hypoplasia (ONH). The term Septo-Optic Dysplasia was coined in 1956 by a Swiss
neurologist, Georges de Morsier, who noted an association between optic nerve
underdevelopment and the absence of the septum pellucidum. However, the term
Septo-Optic Dysplasia is slowly losing favor with physicians and researchers
because the presence or absence of the septum pellucidum does not seem to be
a defining aspect of the diagnosis. ONH is now the preferred term. It is also
called DeMorsier’s Syndrome, in honor of its discoverer.
How common is ONH and ONH blindness?
ONH was very rare a generation ago, with only 35 cases noted in the English language
medical literature before 1970. ONH is on the increase, and is today considered the
most common single cause of congenital blindness in the industrialized world. A
Swedish study published in 1997 reported an incidence of 6.7 out of 100,000 births
(Blohme, J., Tornqvist K. Visual Impairment in Swedish Children. Acta Ophthalmologica
Scandinavica 75: 681-687, 1997), or about 1 in 15,000 births. ONH blindness is
more common today than blindness due to retinopathy of prematurity (ROP), and is
outdistancing many other birth defects which are currently more familiar to the
general public, including congenital muscular dystrophy and Williams Syndrome.
To date, there is no pre-natal screening to detect ONH blindness.
What causes ONH?
No one knows. An “ONH gene” has not been identified or verified in humans.
According to Dr. Mark Borchert of Children's Hospital in Los Angeles,
ONH does not appear to be inherited. Environmental factors may eventually be
implicated in its increase, but to date, there is no explanation for this new
epidemic. The first government-sponsored investigation into possible patterns
of ONH cases across the US will be undertaken soon by Children’s Hospital in
Los Angeles.
What sort of behaviors are seen in children with ONH?
ONH is so new, a comprehensive behavioral survey is yet to be conducted. However,
it seems clear that many commonalities exist within the ONH family. When young,
ONH children often have very low (or high) muscle tone. They may go limp without
warning and have to be carried. They may also show a very high degree of obsessive
behavior, including flapping, rocking, tapping, screaming, or chewing on a finger.
They often like to follow strict household routines and become agitated when the
routines are not followed precisely or carried out in a particular order. Their
language and conversation is often very delayed and scripted, and they may repeat
back what words or phrases that they hear (‘echolalia’). They may ask the same
questions over and over again, paying attention to subtle variations in responses.
Or they may memorize a dialogue and attempt to engage every new person they meet with it.
Children with ONH are often extremely sensitive to sound. They may cover their ears
and cry not only when sounds are loud, but because they find it difficult to adjust
to overlapping sounds or to sounds which shift in register. ONH behaviors are
sometimes puzzling, and parents are never quite sure what might set their child
off or to what the child is responding. Children with ONH often show tactile
defensiveness (a reluctance to touch objects or to explore different textures)
and oral defensiveness (not permitting new or varied foods, rejecting use of a
toothbrush, etc). Many of these traits diminish over time.
Some children with ONH have extraordinary memories, and can quickly memorize songs
and stories. They may recall these stories, word for word, months or years after
they have first heard them (and with accurate intonation and inflection). Though
not all respond to music, many parents of ONH children notice the value of music
as a way of stimulating conversation with their children, or in smoothing over
difficult social or environmental transitions.
Are children with ONH Autistic?
20% or more of children with ONH are believed to have some autistic-like symptoms.
“ONH autism” is a controversial area. Many parents of ONH children have recognized
that their children do not fit the classical definitions or models of autism, and
have adapted therapies to suit their specific educational and therapeutic needs.
Some ONH parents accept the “autistic” label, some accept it reluctantly
(in order to gain access to therapies which might not otherwise be available),
and still others reject it outright. All agree that ONH behaviors needs to be
understood on their own terms. Focus Families, the leading information clearinghouse
for parents and supporters of ONH, has published a
useful online chart [pdf] comparing milestones of children in the
visually-impaired autistic spectrum with their ‘typical’ sighted and
‘typical’ non-sighted peers.
Why does the ONH diagnosis dispose to musical interest or ability?
There are some intriguing guesses, but no one knows. Nor is there a clear answer
to the question of why other “midline defects” (notably Williams Syndrome) also
dispose toward perfect pitch and musical ability in general. It is an unsolved
neurological mystery.
What advice do you have for parents of children with ONH?
As with all children, observe the musicality of baby talk, and encourage early
“conversations” along these lines. Pay particular attention to a child who taps
out rhythms in his or her crib, who sings back nursery songs, or who mimics
computer sounds or environmental noises. Echolalia, or scripted conversation,
can be viewed as a gift to be developed, for in some cases may indicate hidden
memory abilities and deeper musical talents or aptitudes. Embrace all forms of
communication, however stilted they may seem, and learn to enjoy and mimic the
‘sing song’ musical speech habits so often seen in children with ONH.
Not every child with ONH responds to music, but when a child's natural
perseverance becomes attached to music and making music, great things can
develop. Future ONH savants need a lot of attention and encouragement to unlock
their talents. They clearly benefit from multiple musical influences. Above all,
encourage and praise your child, whatever his or her abilities. Every child with
ONH should be immersed in a rich musical bath for the first few years of his or
her life. By the age of two or three, purchase a cheap electronic keyboard. It
could change everything. And even if you think you can't do it and have never
done it before in your life, start singing along.
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