Experts’ opinion – Case 2

In addition to answering the questions posed to our members, our Experts were also asked How they would treat the Proptosis? & What according to them is the role of genetic studies in such cases?

 Arif O. Khan MD;

This approximately 10-month-old infant has left eye glaucoma related to neurofibromatosis type 1 and extreme buphthalmos in that eye. The father and paternal grandmother also have signs of neurofibromatosis type I. Prior imaging of the child showed a probable neurofibroma entering the left superior orbital fissure and thus there may be an element of left eye proptosis in addition to buphthalmos. A refraction is not provided, but left eye extreme myopia is expected. An assessment of vision is not provided but significant left eye amblyopia is expected. It seems there has not been amblyopia treatment to date. The intraocular pressure is controlled with a single topical beta-blocker and oral acetazolamide.Realistically, the prognosis for useful vision in the left eye is poor because of amblyopia related to severe anisometropia. Goals for this child are comfort and preservation of what vision there is in the left eye. I would control the glaucoma with topical medications if possible. If surgery were required to control the pressure, I would implant a valve. If exposure keratopathy is not an issue and spectacles can be fitted, amblyopia treatment is a priority.If the left buphthalmos / proptosis is causing an exposure keratopathy that is not manageable by conservative measures or a partial tarsorrhapy, I would encourage my neurosurgical / orbital colleagues to remove / debulk the left orbital tumor as much as possible. If despite such measures there is still exposure keratopathy that is causing pain or infection risk, removal of the globe would be a consideration.Genetic testing is not required to make the diagnosis or to manage this case. However, analysis of the NF1 gene could be performed if the family is interested in knowing the underlying mutation and using this information for the benefit of other family members who are not clearly affected. Knowing the specific mutation would allow specific testing for the mutation in family members at potential risk for harbouring the mutation. Such testing would identify those family members who should be carefully screened throughout their lifetime and are at risk of passing the mutation to their children (and those who do are not).

 

 Kimberley Tan
MBBS, FRANZCO;

In response to the specific questions as they have been asked, my answers are : management is surgical, a valve and when more information is known about the neurosurgical plans.However, one could argue that all the options given are not incorrect. Medical treatment is working for now, although I would not continue Diamox long-term given potential side effects. If other drops are available they could be used. Surgery is likely to be more “curative”, and a valve is more likely to be effective in a complex case like this infant. However, if time is required for the neurosurgeon to decide on treatment then a combined Trabeculotomy / Trabeculectomy may be a simple way to control glaucoma until a decision is made on the intracranial / orbital mass.It cannot be over-emphasized that the primary outcome of the left eye will very much depend on what happens with the SOF / orbital tumour. This then dictates the value of aggressive management of glaucoma, amblyopia and refractive errors. Any neurosurgery obviously runs a high risk of vision loss, and given the maxillary nerve origin, one would expect a degree of sensory deficit post-operatively. Thus, a higher risk of exposure keratopathy, ulceration, infection and loss of eye. On the other hand, there appears to have been growth and the child is only 10 months of age, so we would expect ongoing growth. If the neurosurgeon elects to observe, one would expect increasing proptosis, more difficult to control glaucoma and generally increasing disfigurement. Both pathways make the treatment of refractive error and amblyopia very challenging and there is a real chance of enucleation with either.I would not treat the proptosis separately, rather just protect the cornea from exposure, using lubricants/gels and if needed a small tarsorrhaphy. I certainly would not contemplate additional orbit surgery for the proptosis as the surgery needs to be directed by the plans of the neurosurgeon.The diagnosis here seems straight forward so genetic studies have more of a place for the family for future children. Regardless, genetic counselling for the entire extended family should be arranged.

 

Paolo Nucci
MD, FEBO;

NF1 is considered a neurocristhopathy affecting the neural crest derived structure of the eye. Angle underdevelopment is often present in NF1 patients with variable prevalence of glaucoma, but only few papers reported globe enlargement, glaucoma and NF1.Morales et al reported a significant series in 2009 in which glaucoma surgery was required in all patients.In this specific case the most important thing is to differentiate between a secondary glaucoma related to an occupying space orbital lesion or a primary congenital glaucoma.In the latter case, although medical therapy seems to be effective, I hardly believe that will work for long time. At the same time, systemic acetazolamide carries significant collateral effect such as drowsiness, growth retardation, bone marrow depression and calculosis.
Therefore, I would discontinue the diuretic and if the pressure is higher than 20mmHg I would opt to carry out an immediate surgical procedure.I would expect a meshwork permanently compromised in this situation, and my choice would be for a tube, since by-pass surgery is less likely to fail than trabeculectomy and also warrants longer term pressure control.Regarding proptosis, I must admit that my experience is limited to ptosis repair that carries almost invariably an unfavorable outcome, particularly in the presence of sphenoid dysplasia.The attitude of Neurosurgeon in NF1 is to explain parents the burden of repeated and very long surgery, and to delay surgery. Of course if we are dealing with a secondary glaucoma the indication needs to be weighed with the ophthalmologist according to the visual prognosis.Genetic studies do not have priority in such a well-defined case.

 

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