Olfactory Groove Meningioma
A meningioma arising along the floor of the frontal skull base near the nerves responsible for smell, where growth can affect smell, vision, personality, and frontal-lobe function.
Quick Answer
An olfactory groove meningioma arises at the front of the skull base, from the bone that separates the brain from the nasal cavity, directly beneath the frontal lobes and the nerves for smell. Loss of smell is usually the earliest sign, and because it develops gradually on both sides it is very often not noticed — which is why these tumors are frequently large by the time they are found. As they enlarge they press on the frontal lobes, causing changes in motivation, attention, and personality that families notice before the patient does, and eventually on the optic nerves, causing visual loss. Surgery is the main treatment, and can be performed either through the skull or through the nose depending on the tumor.
Key Takeaways
- These tumors arise at the front of the skull base, beneath the frontal lobes and the nerves for smell.
- Loss of smell is usually the first sign and is very often unnoticed, which is why these tumors are commonly large at diagnosis.
- Changes in motivation, attention, and personality are common and are frequently attributed to something else.
- Visual loss occurs later, when the tumor reaches the optic nerves.
- Surgery can be performed through the skull or through the nose, and the choice depends on the tumor’s size, its extension, and whether any sense of smell remains.
- Smell that has already been lost does not usually return after surgery.
At a Glance
| Where it arises | From the bone at the front of the skull base, between the brain and the nasal cavity |
|---|---|
| Typical first symptom | Loss of smell, usually unnoticed; later, personality or attention change |
| Key structures at risk | The nerves for smell, the frontal lobes, and the optic nerves |
| Imaging emphasis | MRI with contrast; CT for bone involvement and extension into the sinuses |
| Usual approach | Through the skull from above, or endoscopically through the nose |
| Extent of removal | Complete removal including involved bone is the goal and is usually achievable |
| Role of radiation | Reserved for residual or recurrent tumor and for higher-grade tumors |
| Outlook | Good, with frontal symptoms commonly improving; smell rarely recovers |
This page focuses specifically on Olfactory Groove Meningioma. For a broader look at meningiomas—including grades, symptoms, diagnosis and treatment options—visit our Meningioma overview
Symptoms
These tumors grow in a part of the brain that tolerates pressure quietly, which is why they often become large before anything obvious happens. The symptoms fall into three groups, appearing roughly in order as the tumor enlarges.
Loss of smell
The nerves for smell run directly along the surface these tumors grow from. Smell fades gradually, usually on both sides, and because it is lost slowly and symmetrically most people do not register it. Patients frequently confirm it only when asked directly, or realise in retrospect that food had become uninteresting.
Frontal lobe symptoms
As the tumor presses upward on the frontal lobes, it produces changes that are easy to attribute to age, stress, or depression: reduced motivation, difficulty initiating things, poorer attention and organization, apathy, or uncharacteristic bluntness. Families very often notice these before the patient does, and they are frequently the reason a scan is finally obtained.
Vision
Visual loss occurs when the tumor extends far enough back to reach the optic nerves. It is usually gradual and painless. Occasionally the pattern involves loss of vision in one eye combined with swelling of the other optic nerve, which is a specific and long-recognized sign of a large tumor at this location.
Headache is common. Very large tumors can cause a change in gait or in bladder control, and rarely, if the tumor erodes into the nasal cavity, clear fluid drainage from the nose.
Common Reasons for Evaluation
- Gradual loss or change in the sense of smell
- Changes in motivation, attention, organization, or personality
- Progressive headaches
- Gradual visual changes or loss of part of the visual field
- New seizures
Symptoms That Need Prompt Evaluation
- A first-time seizure or a seizure lasting several minutes
- Sudden or rapidly worsening vision loss
- New severe confusion or a major change in alertness
- A sudden severe headache with vomiting or new neurologic symptoms
Diagnosis
MRI with contrast shows a midline tumor at the front of the skull base with a broad attachment. CT adds two things: whether the underlying bone is thickened or eroded, and whether the tumor extends downward into the nasal cavity or sinuses — both of which affect the choice of approach and what the operation must include.
Formal visual field testing is performed whenever the tumor approaches the optic nerves, and establishes a baseline for judging recovery. Formal smell testing is worth doing before surgery, because it changes the discussion: a patient with no remaining smell has nothing further to lose, which widens the surgical options.
These tumors draw blood supply from vessels at the front of the skull base, and larger ones may be assessed with angiography. In selected cases the feeding vessels are embolized shortly before surgery to reduce bleeding.
WHY LOCATION MATTERS
Why Location Matters in Olfactory Groove Meningioma
Olfactory groove meningiomas grow at the front of the skull base, where they can quietly affect smell and frontal-lobe function before eventually reaching the optic nerves.
Where it sits
At the midline anterior skull base, beneath the frontal lobes and along the nerves responsible for smell.
What it can affect
Smell, motivation, attention, personality, and—when larger—the optic nerves and vision.
Why it matters for treatment
Tumor size, bone involvement, sinus extension, and proximity to the optic nerves help determine whether a transcranial or endoscopic route is most appropriate.
Treatment
The aim is complete removal of the tumor together with the involved covering of the brain and the involved bone at the skull base, since leaving abnormal bone behind is a recognized source of recurrence. The frontal lobes usually recover well once decompressed, and the changes in motivation and attention frequently improve substantially.
Frontal symptoms often improve markedly, sometimes within weeks. Vision improves in many patients whose loss was recent. Smell that was already lost seldom returns, and this is discussed clearly beforehand. Follow-up imaging continues for years, particularly where bone involvement was extensive.
At Atlantic Brain and Spine, these cases are reviewed by a multidisciplinary skull base and brain tumor team to determine the approach that offers the best balance of tumor control and preservation of neurological function. Our Skull Base Surgery Center has been designated a Multidisciplinary Team of Distinction by the North American Skull Base Society, recognizing an established multidisciplinary approach to skull base care.
TREATMENT PLANNING
How Treatment Is Planned for Olfactory Groove Meningioma
The safest strategy depends on the tumor’s exact anatomy, the structures it involves, and the goals of treatment.
01
Transcranial Routes
Several routes reach these tumors with a craniotomy. A subfrontal or bifrontal approach comes across the front of the skull base and is well suited to large tumors extending on both sides. A pterional approach comes from the side, behind the hairline at the temple. A supraorbital eyebrow approach uses a small opening within the eyebrow and suits smaller, more contained tumors. Each is chosen according to the tumor’s size, how far back it extends toward the optic nerves, and how much bone is involved.
02
Endoscopic Endonasal Surgery
Endoscopic endonasal surgery reaches these tumors from below, along the direction they grew. Its advantages are that the tumor’s blood supply at the skull base is interrupted early, the involved bone is directly accessible, and the frontal lobes are not retracted at all. Its costs are that any remaining sense of smell is lost, that the skull base must then be reconstructed to separate the nose from the fluid space around the brain, and that tumors extending widely to either side or wrapping around the optic nerves cannot be reached this way. For a patient who has already lost their sense of smell and whose tumor is midline and not too large, it is an excellent option.
03
Choosing the Approach
The decision turns on tumor size, lateral extension, involvement of the optic nerves, extension into the sinuses, and whether smell is preserved. Both approaches are used at Atlantic Brain and Spine, and for some tumors they are combined. Having both available is what allows the choice to be made on the tumor rather than on the available technique.
The Diagnosis-to-Treatment Pathway
1. Define the skull-base tumor
MRI with contrast shows the tumor at the anterior skull base and its relationship to the frontal lobes and optic nerves.
2. Assess bone and sinus extension
CT shows thickened or eroded skull-base bone and whether the tumor extends into the nasal cavity or paranasal sinuses.
3. Measure vision and smell
Formal visual-field and smell testing establish the functional baseline before treatment planning.
4. Evaluate blood supply when needed
Larger tumors may be studied with angiography, and selected feeding vessels may be embolized before surgery.
5. Choose the surgical route
Tumor size, bone involvement, sinus extension, and optic-nerve anatomy help determine whether a transcranial or endoscopic endonasal approach is best.
6. Follow recovery over time
Vision and frontal-lobe symptoms are reassessed after treatment, with MRI surveillance continuing for years.
Frequently Asked Questions
An olfactory groove meningioma arises along the floor of the frontal skull base near the nerves responsible for smell and can grow upward beneath the frontal lobes.
Loss or reduction of smell is common, and larger tumors can affect vision, judgment, personality, memory, or other frontal-lobe functions. Because these tumors can grow slowly, symptoms may develop gradually.
MRI defines the tumor and its relationship to the frontal lobes and optic nerves. CT can show skull-base bone involvement or extension toward the sinuses, and formal vision and smell testing can establish a functional baseline.
Depending on tumor size, anatomy, bone involvement, sinus extension, and optic-nerve relationships, surgery may be performed through a transcranial approach or, in selected cases, an endoscopic endonasal approach.
Recovery depends on whether the olfactory nerves remain functional and how much they have been compressed or involved by the tumor. When smell has been absent for a long time, recovery may be limited.
Specialists Who Treat Olfactory Groove Meningiomas
Meningioma care at Atlantic Brain and Spine is provided by neurosurgeons with specialized expertise in brain and skull base tumors, with treatment tailored to the tumor’s location and nearby neurological structures.
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