Foster Kennedy syndrome

Foster Kennedy syndrome describes the clinical syndrome of unilateral optic atrophy with contralateral papilloedema caused by an ipsilateral compressive mass lesion.

Clinical presentation

The syndrome consists of two cardinal features, in relation to a mass lesion ^1,2:

1. ipsilateral optic nerve atrophy presenting with central scotoma
2. contralateral papilloedema 

Other common clinical features include ^1,2:

• ipsilateral anosmia
• headache
• nausea and vomiting

Pathology

Foster Kennedy syndrome, by definition, is caused by a compressive mass ^1,2. This mass directly compresses one optic nerve, accounting for ipsilateral optic nerve atrophy, and causes chronic raised intracranial pressure resulting in contralateral papilloedema ^1,2. Thus, in order to cause such a constellation of symptoms, masses are usually located in the olfactory groove, falx cerebri, sphenoid wing, or subfrontal region ^1,2. The most commonly reported mass is a meningioma, although a number of other causes have been reported such as craniopharyngiomas, pituitary adenomas, neuroblastomas, and evenrarely aneurysms and frontal lobe abscesses ^1,2.

The same syndromesyndromic features has also been reported to occur due to non-mass lesions or mass lesions that do not directly compress an optic nerve, and these cases are referred to as causing pseudo-Foster Kennedy syndrome ^3-8. Indeed, these are considered to be more common as the etiologyaetiology for this constellation of clinical features ⁸. Some causes include ^3-8:

• mass lesions that cause indirect unilateral optic nerve compression but do not directly compress that optic nerve
• bilateral sequential ischemicischaemic optic neuropathy: non-arteritic is more common with the new neuropathy developing in the eye with papilloedema
• retrobulbar neuritis
• chronic unilateral optic atrophy
• hypertrophic pachymeningitis
• idiopathic intracranial hypertension: bilateral papilloedema is far more common
• unilateral optic nerve hypoplasia
• vitamin B₁₂ deficiency
• neurosyphilis

Furthermore, the description pseudo-pseudo-Foster Kennedy syndrome has been employed in one case report ⁸. This report describes a case of Foster Kennedy syndrome alongside concurrent contralateral non-arteritic ischemicischaemic optic neuropathy such that one nerve was atrophied due to the direct compression from a meningioma and the other nerve was swollen due to both raised intracranial pressure and the non-arteritic ischemicischaemic optic neuropathy ⁸. This is likely to be a very rare coincidental entity.

Somewhat comically, pseudo-pseudo-pseudo-Foster Kennedy syndrome has also been suggested as a descriptor for a mass lesion that causes indirect unilateral optic nerve compression ¹¹. However, this entity should properly fall under the definition of pseudo-Foster Kennedy syndrome.

Radiographic features

Radiographic features vary depending on the exact cause of Foster Kennedy syndrome, but will generally show a mass lesion compressing one optic nerve resulting in features of papilloedema contralaterally.

Treatment and prognosis

Treatment options vary depending on the exact cause but generally 'true' Foster Kennedy syndrome requires neurosurgical intervention as part of management ¹.

History and etymology

Although the condition is attributed to Robert Foster Kennedy (1884-1952), an Irish neurologist working in England and America, who published a case series describing this condition in 1911, it was actually first described two years earlier by Leslie Johnson Paton (1872-1943), an English neurologist and ophthalmologist ^9,10. This is an example of Stigler's law of eponymy.