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What Is Congenital Fourth Nerve Palsy?
This refers to a vertical misalignment of the eyes due to a weakness of one of the nerves to one of the eye muscles.
We all have a total of 12 cranial nerves that begin in the stem of the brain and travel to different areas of the head and neck. Each of these nerves has a specific function. The fourth cranial nerve gives impulses to one of the muscles on the surface of the eye. This muscle is called the "superior oblique" muscle.
The main function of the superior oblique muscle is to move the eye downward. As this muscle's function is weakened with a fourth nerve palsy, the eye tends to drift upwards. The resultant vertical strabismus is termed a "hypertropia".
This child has an obvious left hypertropia. Unbeknownst to her and her family, her doll has a right hypertropia.
The cause of congenital fourth nerve palsy is unknown.
What Are The Signs Of Congenital Fourth Nerve Palsy?
A noticeable vertical deviation of the eyes is not always the initial sign. Rather, the child with a fourth nerve palsy will often have a habitual head tilt to the side opposite the palsied eye.
This abnormal head position (a.k.a. torticollis) usually becomes noticeable after age three months. The torticollis is actually a natural compensation for the vertical strabismus. With the head tilted to the side opposite the palsy, the vertical misalignment of the eyes is least. The head tilt permits your child "binocular vision", or the ability to use both eyes together as a single unit.
Eye muscle surgery is generally recommended as the treatment for congenital fourth nerve palsy.
Before considering this surgery, your child must not have any evidence of "amblyopia". This refers to poor vision in one eye due to inadequate visual stimulation (a.k.a. "lazy eye").
Infants with congenital fourth nerve palsy (or any other type of strabismus) may favor one eye and habitually ignore the other eye. The ignored or deviated eye will likely have amblyopia.
Amblyopia is treated by patching the strong eye to stimulate normal visual development in the weak eye. The proper duration of patching therapy depends upon the degree of amblyopia.
Surgery is generally not recommended until the amblyopia is maximally treated!
Will My Child Outgrow This Problem?
Will Eye Exercises Help This Problem?
Why Is Good Ocular Alignment Important In Childhood?
Aside from the obvious improvement in your child's appearance when misaligned eyes are corrected, there are other functional benefits to consider.
When a significant ocular misalignment exists in childhood, the developing visual system may not acquire normal binocular vision. Aside from enjoying improved depth perception and fine motor skills, a person with binocular vision tends to maintain good ocular alignment throughout life. Additionally, a child with good ocular alignment is at decreased risk for developing amblyopia.
At What Age Should The Surgery Be Performed?
Most pediatric ophthalmologists will recommend surgical correction of a congenital fourth nerve palsy sometime after the first birthday. Some children will require more than one strabismus operation to eliminate the strabismus.
Following corrective eye muscle surgery for congenital fourth nerve palsy, the compensatory head tilt usually disappears.
The content of this Web site is for informational purposes only. If you suspect that you or your child has an ocular problem, please consult your pediatrician, family practitioner, or ophthalmologist to decide if a referral to a pediatric ophthalmologist is required.