Nystagmus

In my research I have found that there is a lot of useful information out there on Infantile Nystagmus but there is also a lot that is like reading a foreign language for the first time. It can all be very confusing! Below is (as best as I can understand it) a breakdown of the most useful information I have found on Nystagmus. It’s been gathered from many sources and rewritten so that it is easier to explain and hopefully understand. It is centered on Early Onset Nystagmus or EON, as there are many possible causes if the Nystagmus is acquired later on in life usually from injury or illness/disease.


When I started to write all this information down I though about the first thing people usually as when they meet Liam and see his eyes begin to “wobble” or hear about his Nystagmus: “What is it?” So for starters….
Nystagmus: /nɪˈstæɡməs/ is a condition of involuntary eye movement, acquired in infancy or later in life, that may result in reduced or limited vision. (thank you Wiki!!!)

The Nystagmus can be vertical or horizontal (vertical usually indicating a neurological issue). If the Nystagmus presents before 6 months of age (usually appearing around the 6-8 week mark) it is called Early Onset Nystagmus (EON). EON is broken down into 3 categories to find it’s root cause (if there is one).

1. Sensory Defect Nystagmus (SDN) – sensory impairment

2. Congenital Idiopathic Nystagmus (CIN) – No reason, neurological or visual can be found

3. Neurological Nystagmus (NN) – neurological disease



The diagram below is what helped me to understand best and was found in the British Journal of Ophthalmology.

                                           Early Onset Nystagmus
                                           (before 6 months of age)

  Sensory Defect                Congenital Idiopathic                  Neurological
Cataracts                                                Typical        Atypical                                      vestibular
Corneal opacities                                                                                                             trauma
Chorloretinal colobomas                                                                                             malformation
Retinopathy of Prematurity                                                                                        lesions/tumors
Aniridia                                                                                                                      metabolic disease
Optic Nerve hypoplasia                                                                          Vestibular/neurological disorders
Albinism
Cone dysfunction
Achromatopsia
Night blindness
Lebers congenital amaurosis
Other eye abnormalities
Deficits of binocular vision

To determine which type of Nystagmus an infant has, you must first start with either SDN or NN since CIN (congenital idiopathic nystagmus) is only diagnosed after excluding of the other two. Starting with Neurological requires usually an MRI be performed to rule out any tumors, brain lesions, etc. If the nystagmus is asymmetrical (not identical on both sides) or unilateral (affecting only one eye) neurological disease is to be suspected. Usually if a infant has NN there are other neurological symptoms present such as vomiting, walking funny or crooked, and/or headaches. Disorders typically with this type of nystagmus other than trauma could be Down’s Syndrome, Pelizaeus-Merzbacher disease, hypothyroidism, the list goes on and on. (There is even one called Maple Syrup Urine Disease where your urine is dark and smells of maple syrup. I know I had to look it up too!) An MRI should be done to rule out or determine this type of Nystagmus. In infants with sensory defect nystagmus (SDN), you could expect to find (or your ophthalmologist would find) disorders such as Cateracts, Corneal opacities, chorioretinal colobomas, retinopathy of prematurity, aniridia, albinism, optic nerve hypoplasia, cone dysfunctions, night blindness, achromatopsia, Leber’s congenital amaurosis or other eye abnormalities. This type of nystagmus is most common and requires many tests and family history to determine a condition. Vestibuloocular Reflex Testing or VOR, may be done along with an Electronystagmogram (ENG) test to determine the condition causing the patients nystagmus. It’s very important that the child be followed closely by a pediatric ophthalmologist or a specialist as all patients with nystagmus will experience some visual difficulty. If sensory defect and neurological nystagmus are both ruled out as the cause for the child’s nystagmus then it will be labeled as CIN or congenital idiopathic nystagmus (no known cause). There are two types of CIN known as typical and atypical. In typical CIN the nystagmus “shake” or “wobble” may decrease when the lids are closed or the eyes converge on and object together. The shake can almost be invisible when the eyes are fixed on an object and often there is a spot that is known as the null point for the child (a null point is where the eyes shake the least giving the infant the best vision there often causing them to angle or turn their heads to see from that point giving them a awkward head posture). Surgery can pull the null point back to center if desired to get rid of the head tilt. Some studies show there may be a genetic link with typical CIN from a parent showing no signs of nystagmus and all family members should be tested for the hereditary component. Atypical CIN is determined by ruling out underlying defects and electrophysiological oculomotor. Basically meaning, if the MRI was normal (ruling out NN) but there was an abnormal response by being visually provoked, atypical CIN is sometimes assumed.

With any of these types of Nystagmus, the infant needs to be closely followed by a pediatrician and a pediatric ophthalmologist to make sure the child has the best sight available to him and that there are no developmental delays from the loss of sight. Many children may need the help of an occupational therapist to make sure their hand eye coordination fully develops and to assist them in other common areas of delays for children with nystagmus. There are several sites listed on my home page that give much more information on infantile nystagmus and I’m sure many more I have yet to find.

1 comment:

  1. Hi. Thank you for summarising what must be tons of hours spent into understanding the condition. My youngest daughter who was also born in 2011 has nystagmus, which is probably linked to her Down's Syndrome. We are just monitoring at this time and really still have no clue of it's severity. At least neurological has been ruled out for now. - From a fellow father in Singapore

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