Pseudo-Pseudo Foster Kennedy Syndrome (PPFKS) is an extremely rare condition that presents with the same fundus findings as FKS (optic atrophy on one side and papilledema on the opposite side), but its cause is a coincidental combination of two independent pathologies.
To understand this condition, it is necessary to first clarify the definitions of three related syndromes.
FKS
Foster Kennedy syndrome: A classic syndrome in which an intracranial mass in the frontal lobe or sellar region directly compresses the ipsilateral optic nerve causing atrophy, and increased intracranial pressure causes papilledema on the contralateral side. Type 1 (direct compression injury) is the most well-known.
Causes: Frontal lobe tumors, meningiomas, craniopharyngiomas, pituitary adenomas, etc.
PFKS
Pseudo-Foster Kennedy syndrome: A condition in which there is no intracranial mass, but sequential nonarteritic anterior ischemic optic neuropathy in both eyes leads to optic atrophy in the first affected eye and papilledema in the later affected eye, observed simultaneously.
Features: A history of sudden vision loss due to nonarteritic anterior ischemic optic neuropathy in one eye is important for differential diagnosis.
PPFKS
Pseudo-pseudo Foster Kennedy syndrome: A rare syndrome in which optic atrophy due to an intracranial mass and papilledema due to unrelated contralateral nonarteritic anterior ischemic optic neuropathy (ischemic optic neuropathy) coincidentally coexist.
Features: It is a combination of two independent conditions, distinct from FKS and PFKS.
The first report of PPFKS was by Gelwan et al. (1988) [¹]. In an 80-year-old woman, left eye nonarteritic anterior ischemic optic neuropathy and right eye optic atrophy due to tuberculum sellae meningioma were confirmed. Subsequently, Limaye et al. reported a PFKS-like case with papilledema due to contralateral non-basal glioma in an eye with a history of anterior ischemic optic neuropathy [²].
QHow are FKS, PFKS, and PPFKS different?
A
In FKS, an intracranial mass is the sole cause, and ipsilateral compressive optic atrophy and contralateral papilledema due to increased intracranial pressure arise from a single pathological process. PFKS presents similar findings due to bilateral sequential ischemic optic neuropathy (typically nonarteritic anterior ischemic optic neuropathy) without an intracranial mass. PPFKS differs from these two, arising from the coincidental coexistence of two independent conditions: an intracranial mass (optic nerve compression) and nonarteritic anterior ischemic optic neuropathy.
The symptoms of PPFKS are a combination of two conditions: intracranial mass and ischemic optic neuropathy.
Acute vision loss in one eye: Occurs on the side of non-arteritic anterior ischemic optic neuropathy. Many patients (over 70%) notice vision loss upon waking.
Headache: Associated with increased intracranial pressure.
Nausea and vomiting: Secondary to increased intracranial pressure.
Diplopia: May occur due to tumor invasion of cranial nerves.
Transient visual disturbance: Intermittent fluctuations in vision caused by increased intracranial pressure.
Fundoscopic findings are characterized by asymmetric optic disc appearance: “optic atrophy on one side + papilledema on the contralateral side.”
Optic atrophy side (tumor compression side): Pallor and thinning of the optic disc. Visual loss often progresses slowly.
Papilledema side (non-arteritic anterior ischemic optic neuropathy side): Disc redness and swelling, flame-shaped hemorrhages at the disc margin. Acute visual loss precedes on the non-arteritic anterior ischemic optic neuropathy side.
Visual field defects: Scotoma formation and enlargement of the physiological blind spot are observed.
Disk at risk: Presence of a small, crowded optic disc (small disc) that increases the risk of developing non-arteritic anterior ischemic optic neuropathy.
Diplopia: May occur secondary to cranial nerve involvement by the tumor.
Visual acuity on the side affected by non-arteritic anterior ischemic optic neuropathy varies from 10/10 to light perception. At initial presentation, 20–33% have 10/10, over 50% have 5/10 or better, and 20–33% have 1/10 or worse.
QDoes PPFKS cause vision loss in both eyes?
A
Not necessarily both eyes are affected. On the side with non-arteritic anterior ischemic optic neuropathy, rapid vision loss occurs, while on the side with tumor compression, progression is slow and vision may be preserved at initial presentation. The visual prognosis depends on the nature and progression of the underlying disease.
“Disk at risk”: A small optic disc (crowded optic disc) is the greatest structural risk factor for optic disc ischemia.
Optic disc drusen: In young patients under 50 years of age with non-arteritic anterior ischemic optic neuropathy, an association with drusen has been reported.
Vascular risk factors: Hypertension, diabetes, dyslipidemia, ischemic heart disease, and sleep apnea syndrome have been confirmed as risk factors for non-arteritic anterior ischemic optic neuropathy in large meta-analyses [⁵].
Neuroimaging (CT/MRI): Identification of an intracranial mass compressing the optic nerve is essential. Perform contrast and non-contrast head/orbital CT and MRI. Meningiomas show homogeneous enhancement on contrast imaging.
Orbital CT: Used to rule out intraorbital lesions and assess compression of the optic nerve.
Complete neurological examination: Evaluation for cranial nerve deficits and pyramidal tract signs.
Blood tests (to rule out GCA): In patients aged 50 years or older, measure ESR, CRP, and platelet count to differentiate arteritic ischemic optic neuropathy (AAION) from non-arteritic anterior ischemic optic neuropathy.
The following table shows the main differences in laboratory values between non-arteritic anterior ischemic optic neuropathy and AAION.
Test item
Non-arteritic anterior ischemic optic neuropathy
AAION (giant cell arteritis)
ESR
Normal
Elevated
CRP
Normal
Elevated
Platelet count
Normal
Elevated
Temporal artery biopsy: Performed in patients aged 50 years or older when giant cell arteritis is suspected. Due to skip lesions, approximately 5% of biopsies may yield false-negative results.
To confirm the diagnosis of PPFKS, differentiation from the following conditions is necessary.
FKS: Caused solely by intracranial mass. Contralateral papilledema is due to increased intracranial pressure and is not accompanied by ischemic optic neuropathy. The clinical subtypes, imaging evaluation, and treatment strategies for FKS are systematically summarized in a StatPearls review [⁴].
PFKS: No intracranial mass. Appears as sequential non-arteritic anterior ischemic optic neuropathy in both eyes. History of sudden vision loss is important. Patil et al. reported in an observational study of 7 PFKS cases that the average interval between bilateral onset was approximately 12.7 months (range 2–30 months) [³].
Optic neuritis: Differentiating features include young age, female sex, good initial visual acuity, pain with eye movement, hyperemic disc edema, and central scotoma.
Pseudopapilledema: Optic disc drusen (often bilateral, asymmetric, usually normal visual function), high hyperopia, high myopia, tilted disc, and myelinated retinal nerve fibers. These are distinguished from non-arteritic anterior ischemic optic neuropathy by preserved visual function.
QWhy is a blood test for giant cell arteritis necessary?
A
In patients aged 50 years or older, arteritic anterior ischemic optic neuropathy (AAION) may present with clinical findings similar to non-arteritic anterior ischemic optic neuropathy. AAION due to giant cell arteritis has a high risk of progression to the contralateral eye, and prompt steroid treatment is essential to prevent blindness. ESR, CRP, and platelet counts should be measured to actively rule out giant cell arteritis.
Systemic steroids: Initiate immediately when giant cell arteritis is suspected.
Temporal artery biopsy: Performed for definitive diagnosis. Due to skip lesions, false negatives occur in about 5% of cases, so a negative result does not rule out giant cell arteritis.
Treatment for Intracranial Mass (e.g., Meningioma)
Surgical resection: Main treatment for meningioma. Removes the tumor to relieve compression on the optic nerve.
Corticosteroids: Used preoperatively to reduce peritumoral edema and intracranial pressure.
Stereotactic radiotherapy/radiosurgery: Considered as a non-surgical option for elderly patients, those who do not wish to undergo surgery, or when surgical risk is high.
Resection of space-occupying lesions: Removal of the tumor to relieve increased intracranial pressure is the basic approach.
Ventriculoperitoneal (VP) shunt: Considered when hydrocephalus is present.
Acetazolamide (Diamox): Used for idiopathic intracranial hypertension.
Mannitol: Used for acute increased intracranial pressure.
QIf a meningioma is the cause, are there options other than surgery?
A
Stereotactic radiotherapy (such as Gamma Knife, CyberKnife, etc.) and conventional radiotherapy are available as non-surgical options. They are considered particularly in elderly patients, those with poor general condition and high surgical risk, or when the patient does not wish to undergo surgery. Radiotherapy aims to suppress tumor growth, but its tumor shrinkage effect is often inferior to surgical resection.
Nonarteritic anterior ischemic optic neuropathy is a disease primarily caused by ischemia of the optic disc. In patients with structural risk factors such as “disc at risk” (a small, crowded optic disc), blood vessels within the optic nerve are more easily compressed, leading to ischemia. In patients with optic disc drusen, an association with nonarteritic anterior ischemic optic neuropathy has been noted, particularly in those under 50 years of age.
Meningiomas arise from meningothelial cells. There are 15 subtypes, most of which are benign, non-invasive, slow-growing tumors. When they occur in areas adjacent to the dura and arachnoid mater surrounding the optic nerve (such as the sphenoid ridge, tuberculum sellae, or olfactory groove), they can directly compress the optic nerve, causing a unilateral component of FKS or PPFKS.
Prognosis depends on the underlying disease. AAION is considered to have a worse visual prognosis compared to non-arteritic anterior ischemic optic neuropathy. Optic atrophy due to tumor compression may partially improve with early decompression, but complete recovery is often difficult.
Patil A, Takkar A, Goyal M, Singh R, Lal V. Sequential NAION presenting as pseudo Foster Kennedy syndrome.J Neurol Sci. 2017;376:49-51. doi:10.1016/j.jns.2017.02.002. PMID: 28431627
Liu B, Yu Y, Liu W, Deng T, Xiang D. Risk Factors for Non-arteritic Anterior Ischemic Optic Neuropathy: A Large Scale Meta-Analysis.Front Med (Lausanne). 2021;8:618353. doi:10.3389/fmed.2021.618353. PMID: 34671609
Copy the article text and paste it into your preferred AI assistant.
Article copied to clipboard
Open an AI assistant below and paste the copied text into the chat box.
