What is Foster Kennedy Syndrome?
Foster Kennedy syndrome (FKS) is a neurological condition that often causes loss of smell and vision. These symptoms can affect only one side or both sides of the body, depending on the disease’s progression. The syndrome occurs when pressure builds up inside the brain due to a tumor or similar problem, causing damage to the optic nerve (the nerve that connects the eyes to the brain) in one eye and swelling of the optic disc in the other eye.
It’s essential that doctors distinguish “true” FKS from what’s known as pseudo-FKS because they have the same symptoms but different causes. This makes it crucial that doctors use the right tests and examination techniques to provide an accurate diagnosis.
There are typically three types of FKS. Type 1 often results in optic nerve damage in one eye and swollen optic disc in the other eye. Type 2 involves swelling of the optic disc on both sides and optic nerve damage on one side. Type 3 is characterized by swelling of the optic disc that eventually turns into optic nerve damage on both sides. These three types correspond to different stages of brain tumors spread.
Pseudo-FKS also presents with nerve damage in one eye and a swollen disc in the other eye, just like Type 1 FKS. However, in pseudo-FKS, there is no tumor or similar issue causing pressure inside the brain. Causes of pseudo-FKS include pressure on the optic nerve due to the brain’s physical structure, damage to the optic disc caused by diabetes, and incomplete development of one optic nerve.
Meningiomas are tumors that arise from the brain’s protective layers. These tumors can be either cancerous or non-cancerous and are most commonly found in the brain’s sphenoid wing, olfactory groove, and frontal lobe.
Meningiomas often grow slowly and subtly, leading to minor changes that might go unnoticed as the disease progresses. They can stretch into the spaces beneath the brain’s protective layers and sinuses, causing high pressure within the brain. Eventually, they may also press on nearby blood vessels and brain areas, causing a variety of symptoms and tissue damage.
Pituitary gland’s tumors, located at the base of the brain, have also been reported to potentially cause FKS and are the second most common cause of brain tumors. This risk becomes higher in patients who had surgery to remove pituitary adenomas (a type of tumor) and underwent radiation therapy, as they may develop complications, including meningiomas.
What Causes Foster Kennedy Syndrome?
Brain tumors are responsible for approximately 12% of cases involving swelling in the optic disc, which is the area where the optic nerve enters the eye. The most common cause is a type of tumor known as an anterior cranial fossa meningioma. However, tumors in other parts of the brain, such as the frontal lobe, olfactory groove (near the nose), sphenoid wing and pituitary gland can also result in this condition.
Meningiomas, a type of tumor, generally occur due to inherited factors, influence of female hormones, or if a person has been exposed to radiation before. These tumors press against the optic nerve on the same side of the brain where they develop, resulting in a gradual decline in the sense of sight. As they grow larger, they may spread to the other side of the brain, obstructing the flow of cerebrospinal fluid – the fluid in and around the brain and spinal cord – and causing more swelling in that eye. Some patients may experience complete loss of sight in one eye, and loss of peripheral (side) vision in the other eye.
Risk Factors and Frequency for Foster Kennedy Syndrome
Research indicates that central nervous system tumors occur at a rate of 23.41 per 100,000 people when adjusted for age. The rates are slightly higher in women. On the other hand, FKS accounts for 1 to 2.5% of all intracranial tumors.
Signs and Symptoms of Foster Kennedy Syndrome
When talking about symptoms and medical history with patients, it’s key to pay attention to certain signs. These can include complaints of headaches, diminished vision in one or both eyes, and a loss of sense of smell in some cases (particularly later stages of the condition). Doctors often look out for a swollen optic nerve, known in medical terms as “papilledema”. Identifying early-stage papilledema can be tough, especially at stage 1. This might appear as a ‘C’-shaped halo preserving the edge of the optic disc.
Spotting papilledema in the later stages becomes easier because the optic disc is noticeably elevated and blood vessels are hidden. These advanced stages of papilledema may show signs of a tumor in the frontal part of the brain, including emotional instability, coordination problems, and speech impairments. A condition called ICSOL (intracranial space-occupying lesion) of the frontal part of the brain can extend beyond the anterior cranial fossa – the space in the skull that houses the brain, possibly leading to tumors affecting other parts of the brain.
Testing for Foster Kennedy Syndrome
If your doctor suspects you have Foster Kennedy Syndrome, an initial examination typically begins with a test called a funduscopy. This test lets the doctor look at the back of your eye and see if any damage has been done to your optic nerve or the surrounding area. They might use a special filter to get an even clearer view. The swelling of the optic disk, a part of your eye, is a common symptom in people with Foster Kennedy Syndrome and can be seen during this test.
Alongside looking at your eyes, your doctor might also recommend imaging tests, like standard X-rays, although these are not typically effective in identifying brain tumors. This is because the skull absorbs the radiation from the X-ray, making it hard to see any deeper tissues.
Studies have shown that when the pressure inside the skull increases, the pressure inside your eye might also rise. This pressure can be measured using a method known as tonometry.
A CT (Computerized Tomography) scan is another test that could be helpful. This scan uses X-rays to create 3D images of your body. The better you stay still during the test, the clearer the images will be. You might also have to remove any metal objects or clothing from your head before the imaging is done. Sometimes, doctors inject a special dye into your veins to make the images even clearer. It’s important to have your kidney function checked before this dye is used, to confirm that your body can safely remove it.
Likewise, an MRI (Magnetic Resonance Imaging) scan could provide an even better view. Instead of using radiation like a CT scan, an MRI uses a magnetic field and radio waves to create detailed images. The machine uses a complex process to disrupt the natural arrangement of atoms in your body and then rearrange them again. This process lets the machine pick up signals from the atoms which are then put together to form a 2D image. This makes the MRI a preferred choice when it comes to monitoring brain tumors. But keep in mind, MRI scans tend to take longer than CT scans and might not be available during emergency situations at some hospitals.
Treatment Options for Foster Kennedy Syndrome
Foster Kennedy syndrome tumors are typically treated using the following methods:
- Surgery to remove the tumor
- Chemotherapy, which uses medications to fight the cancer
- Radiotherapy, which uses high-energy radiation to destroy the cancer cells
- Medical therapy, a broad term for treating disease with drugs or other therapies
In general, the most common way to manage Foster Kennedy syndrome is through surgical removal of the tumor. However, chemotherapy and radiotherapy are also options. These methods are often used for older patients who may face higher risks from surgery.
As part of medical therapy, doctors often first prescribe corticosteroids. These are drugs that help reduce swelling around the tumor and lower pressure inside the skull. Keep in mind, however, that this treatment usually doesn’t get rid of the symptoms, but rather eases some of the discomfort caused by the tumor.
For older patients, doctors often prefer non-surgical procedures like stereotactic radiotherapy and radiosurgery, which are more targeted forms of radiation treatment. There have also been some cases where hydroxyurea, a type of medication, has been helpful, particularly for tumors that can’t be removed completely through surgery or are large in size.
What else can Foster Kennedy Syndrome be?
When diagnosing Foster Kennedy Syndrome (FKS), doctors need to consider several other conditions that could potentially cause similar symptoms. These include:
- frontal lobe brain tumors
- meningioma – a kind of tumor in different areas of the brain, like the olfactory or sphenoid wing
- Non-arteritic anterior ischemic optic neuropathy (NAION), a condition that leads to loss of blood flow to the optic nerve
- Optic nerve hypoplasia, a congenital condition where the optic nerve does not fully develop
- Optic neuritis, an inflammation of the optic nerve
- Vitamin B12 deficiency which, if not treated, could cause progressive optic neuropathy
For example, tumors in the brain that affect the frontal lobe are often related to FKS. Also worth considering are the meningiomas, tumors that develop in the brain’s protective linings and can affect different parts of the brain.
Another condition that could be mistaken for FKS is pseudo-FKS. In simple terms, this is FKS without a tumor. It mimics FKS quite closely but exhibits different clinical characteristics.
NAION is a key condition to consider. This condition is about a significant drop in blood flow to the optic nerve resulting in vision loss. It’s primarily caused by blood clotting and low blood pressure while sleeping.
Test results might also suggest optic nerve hypoplasia, a condition present from birth where the optic nerve does not develop completely. Some studies suggest this might be associated to fetal alcohol syndrome or a mom’s intake of certain meds during pregnancy.
Optic neuritis, inflammation of the optic nerve, may also appear similar to FKS. This can affect just the optic nerve or a broader region involving both the optic nerve and the macula.
Last but not least, we have Vitamin B12 deficiency. This deficiency could result in progressive optic neuropathy that’s similar to FKS, but luckily, it can be reversed with the appropriate dietary supplements.
Surgical Treatment of Foster Kennedy Syndrome
The decision to have a surgery for Foster Kennedy syndrome is based on careful assessment of the possible benefits and risks, as recommended by your doctors. It’s important to understand that brain surgery is a complex procedure that requires input and coordination from various medical fields. Typically, when dealing with tumors, the best course of action is to completely remove the cancer through surgery. Afterwards, samples of the removed tissue are sent to a lab for a detailed examination, which helps get a clearer picture of the disease and its stage. Following the surgery, additional treatment using medications to destroy cancer cells, known as chemotherapy, might be suggested.
What to expect with Foster Kennedy Syndrome
The outcome for individuals with Foster Kennedy syndrome is primarily influenced by the location, size, and progression of the underlying cause, known as intracranial space-occupying lesion (ICSOL).
Possible Complications When Diagnosed with Foster Kennedy Syndrome
Foster Kennedy syndrome can lead to a number of complications that can affect both your eyes and your overall health.
Eye complications from Foster Kennedy syndrome can include:
- Swollen optic disc (disc edema)
- Issues with the pupils not responding to light as usual (relative afferent pupillary defects)
- Limited eye movement
- Reduced sharpness of vision (decreased visual acuity)
- Swelling of the optic nerve due to increased pressure in the skull (papilledema)
- Damage to the optic nerve leading to vision loss (optic atrophy)
System-wide complications can arise from the inability to perceive smell (anosmia) and any other symptoms that come about from a tumor pressing on specific areas of the brain.
Preventing Foster Kennedy Syndrome
Foster Kennedy syndrome can sometimes be the first hint that something is wrong, leading to more tests and exams which could reveal a brain tumor. It’s crucial to tell the patient that managing this condition requires a team effort from different kinds of doctors. This helps in properly handling the disease and ensuring that aspects such as quality of life, treatment, and overall outlook are taken care of properly.
