Interorbital Hypertelorism is an increased distance between the medial orbital walls only. The lateral orbital wall positions are not affected, ie, are normal. It is most commonly found in patients with frontoethmoidal meningoencephaloceles.
Meningoencephaloceles is herniation of meninges (meningocele) through a congenital bone defect with or without brain tissue (encephalomeningocele). The bone defect is usually at the junction of the frontal and ethmoidal bones.
Characteristics are the following:
• External defect can vary: – Naso-frontal – Naso-ethmoidal – Naso-orbital • Rare but more common in Southern and South-east Asia (Thailand 1:3500 to 1:6000) • Associated findings are: telecanthus, epiphora, dacryocystitis, facial and ocular deformities
The diagnosis of interorbital hypertelorism is made by physical examination and radiographic analysis.
Physical examination includes measurement of the intercanthal distance as well as a complete ophthalmologic assessment (lid position, presence or absence of strabismus, lacrimal drainage system etc.). The size and position of the encephalocele is noted.
Genetic evaluation is helpful to establish the presence or absence of a syndrome and to delineate extracranial associated conditions.
CT-scans are used to document the interorbital space and the size and position of the orbits. They are also essential for complete evaluation of the brain. Neurosurgical input is invaluable.
A 3D-CT scan is also useful for the planning of the corrective surgery.