[Unilateral isolated partial third nerve palsy and sphenoiditis in a child: A case report]

We report a case of unilateral mydriasis associated with sphenoid sinusitis and mucocele in a child. An 11-year-old girl with a history of unilateral mydriasis was referred for ophthalmologic examination. She complained of a mild headache over the past four days. The right pupil was dilated and nonreactive to light. The left pupil was normal and reactive. There was no ptosis or other focal neurological deficit. She was orthotropic. Visual acuity in both eyes, ocular motility and fundi were normal. Magnetic resonance imaging (MRI) showed a sphenoid sinus mucocele with sphenoiditis. The diagnosis was partial third nerve palsy without ophthalmoplegia. Treatment with antibiotics was initiated and led to complete resolution of the mydriasis. Sphenoid sinus mucoceles are relatively rare. Failure to diagnose and treat can lead to serious neurologic sequellae such as third nerve palsy, compressive optic neuropathy, cavernous sinus thrombosis, meningitis or brain abscess. Head imaging by reconstructed CT and MRI can lead to the diagnosis of mucocele. Isolated unilateral mydriasis as a sign of third nerve palsy may be caused by a slowly enlarging lesion. In a child with isolated unilateral mydriasis, head MRI should be performed to rule out a compressive lesion of the oculomotor nerve.