What Is the Posterior Falx?

Mary McMahon
Mary McMahon

The posterior falx is the rear portion of the falx cerebri, an important part of the brain's anatomy. This structure runs between the two hemispheres of the brain to separate them from each other and provide support and stability. It is possible to visualize the falx cerebri with a medical imaging study or in a procedure where the patient's brain is exposed, although much of it is buried deep inside the brain, and it would be necessary to remove the brain to see it in its entirety.

Anatomical model of the human body
Anatomical model of the human body

The falx is a ridge of dura mater, the tough material that goes around the outside of the brain and appears in a set of folds, known as reflections, within the brain. Each reflection acts to separate different brain components. In the case of the falx cerebri, the structure runs the length of the skull between the hemispheres, and the posterior falx is the portion at the back of the head. The corresponding anterior falx is the section in the front of the skull.

At the rear of the skull, the falx is broader and thicker. Viewed from the side, the entire structure looks similar to a sickle, and the width increases at the posterior falx. The base of the structure floats freely in the skull cavity, while the ends connect with other portions of the dura mater. This material insulates and protects the brain, and provides a mechanism for draining fluids by allowing fluid to flow freely between its layers.

One potential disorder of the posterior falx is a meningioma, a tumor that arises in the dura mater and similar structures. The meningioma can push into the brain and may displace tissue. This will cause corresponding neurological symptoms in the patient. Symptoms can include headaches as well as cognitive decline caused by damage to brain cells. A medical imaging study will reveal a density in the brain, showing the location of the tumor. Sometimes densities are the result of shadowing or small anatomical anomalies, and the doctor may take images from several angles to avoid a false diagnosis.

Treatment for a malignancy in the posterior falx usually requires surgery to remove the tumor. The doctor will expose a small section of the falx to access the tumor with minimal disturbance to neighboring tissue. Once the procedure is over, the patient may receive targeted chemotherapy and radiation. Outcomes for patients with meningiomas in the posterior falx can be very favorable, especially when the growth is caught early.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


@Mammmood - I think that the definition of meningioma implies that it is benign by nature.

However, according to my doctor, any condition – even a benign one – can become dangerous if left untreated for a long period of time.

What really concerns me is that some symptoms, like seizures for example, do not necessarily raise alarm bells. Some people have learned to live with epilepsy through the use of medication.

Therefore it’s quite possible that they could be living with a potentially fatal tumor condition without knowing it, unless something serious forces them to get an MRI scan.


I think that nothing strikes fear in a patient as the prognosis of a brain tumor. Our pastor told the story of the day he heard such a prognosis for his son.

Immediately the pastor had the worst thoughts and fears assail him at that time. During such a time, you wish you had that prognosis, not your son.

Later, the doctors found out that it was a meningioma falx tumor, a benign condition. They were able to remove it and his son was healthy and whole again. Personally, I think that any tumor in the brain is cause for concern, benign or otherwise, but this condition never returned, for which we were all grateful.

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