Foster Kennedy syndrome
Foster Kennedy syndrome describes the clinical syndrome of unilateral optic atrophy with contralateral papilledema caused by an ipsilateral compressive mass lesion.
The syndrome consists of two cardinal features :
Other common clinical features include :
- ipsilateral anosmia
- nausea and vomiting
Foster Kennedy syndrome, by definition, is caused by a compressive mass . This mass directly compresses one optic nerve, accounting for ipsilateral optic nerve atrophy, and causes chronic raised intracranial pressure resulting in the contralateral papilledema . 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 . The most commonly reported mass is a meningioma, although a number of other causes have been reported such as craniopharyngiomas, pituitary adenomas, neuroblastomas, and even aneurysms and frontal lobe abscesses .
The same syndrome 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 . Indeed, these are considered to be more common as the etiology for this constellation of clinical features . Some causes include :
- mass lesions that cause indirect unilateral optic nerve compression but do not directly compress that optic nerve
- bilateral sequential ischemic optic neuropathy: non-arteritic is more common with the new neuropathy developing in the eye with papilledema
- retrobulbar neuritis
- chronic unilateral optic atrophy
- hypertrophic pachymeningitis
- idiopathic intracranial hypertension: bilateral papilledema is far more common
- unilateral optic nerve hypoplasia
- vitamin B12 deficiency
Furthermore, the description pseudo-pseudo-Foster Kennedy syndrome has been employed in one case report . This report describes a case of Foster Kennedy syndrome alongside concurrent contralateral non-arteritic ischemic 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 ischemic optic neuropathy . 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 . However, this entity should properly fall under the definition of pseudo-Foster Kennedy syndrome.
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 papilledema 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 .
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 . This is an example of Stigler's law of eponymy.