Pseudo-Foster Kennedy Syndrome due to unilateral optic nerve hypoplasia: a case report
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Pseudo-Foster Kennedy Syndrome is described as unilateral optic disc swelling with contralateral optic atrophy in the absence of an intracranial mass causing compression of the optic nerve. This occurs typically due to bilateral sequential optic neuritis or ischaemic optic neuropathy.
We describe a case of pseudo-Foster Kennedy Syndrome in a two year old boy with unilateral papilloedema due to a congenital optic disc anomaly in one eye preventing transmission of raised intracranial pressure to the optic nerve.
From our findings we conclude that congenital optic nerve hypoplasia is a cause of pseudo-Foster Kennedy Syndrome.
KeywordsOptic Nerve Optic Disc Optic Nerve Head Optic Atrophy Intracranial Mass
Foster Kennedy Syndrome is unilateral optic disc swelling with contralateral optic atrophy, usually due to a frontal lobe tumour compressing the optic nerve on one side and resulting in papilloedema contralaterally. In the absence of an intracranial mass these findings may be labelled as pseudo-Foster Kennedy Syndrome.
Hypoplastic optic disc is a congenital abnormality which may be unilateral or bilateral and is a characterised by a reduced diameter of the optic nerve head. Although clinically distinct from optic atrophy, it has been suggested that it is merely a type of non progressive optic atrophy acquired before the full development of the eye .
The appearance of unilateral optic disc swelling with contralateral optic disc atrophy has been described as the Foster Kennedy Syndrome. In "true" Foster-Kennedy Syndrome unilateral disc swelling is caused by a tumour on the inferior surface of the frontal lobe, compressing the optic nerve on one side with papilloedema contralaterally . In the absence of an intracranial mass these findings may be labelled as pseudo-Foster Kennedy Syndrome, typically due to bilateral sequential optic neuritis or ischaemic optic neuropathy [3, 4].
Explanations for the unilateral disc swelling in Foster Kennedy syndrome include failure of transmission of the intracranial pressure to the optic disc secondary to pressure on the vaginal sheath; or closure of the vascular bed of the optic disc . Our case demonstrates that this finding may be observed in patients with unilateral optic disc hypoplasia and is thus another differential cause of pseudo-Foster Kennedy Syndrome.
In this case the finding of unilateral papilloedema was due to a congenital abnormality of the left optic disc, preventing transmission of the raised intracranial pressure to the optic nerve head. This is important to bear in mind when examining children with optic nerve hypoplasia.
The authors obtained written informed consent from the parents of this patient for the publication of this case report along with images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.