The foramen magnum is the largest foramen of the skull. It is located in the most inferior portion of the cranial fossa as a part of the occipital bone.

Occipital bone. It has an opening that allows your spinal cord to connect to your brain.

: the opening in the skull through which the spinal cord passes to become the medulla oblongata.

The foramen lacerum (plural: foramina lacera) is a triangular opening located in the middle cranial fossa formed by the continuation of the petrosphenoidal and petroclival fissures. Thus, it is a gap between bones, alternatively termed the sphenopetroclival synchondrosis, rather than a true foramen within a bone 2.

Foramen magnum decompression involves removing a small part of the base of the skull and sometimes parts of the top of the spine to take the pressure off the cerebellum. Before the surgery, your surgeon will take a look at your medical history and walk you through the surgery and the associated risks.

In most cases, syringomyelia improves on its own after surgery to correct a Chiari malformation because the normal flow of cerebrospinal fluid is restored. An acquired Chiari malformation requires treatment of the underlying condition.

Sleep disorders — People with Chiari malformations often experience sleep apnea and chronic fatigue.

An acquired Chiari malformation type I happens to a person after birth. It is caused by excess leaking of spinal fluid from the lower back (lumbar) or chest (thoracic) areas of the spine. This can happen because of an injury, contact with harmful substances, or an infection.

Not everyone with a Chiari malformation requires surgery, but when a patient’s individual circumstances warrant it, a neurosurgeon may recommend “decompression” surgery (known as a “decompressive suboccipital craniectomy and cervical laminectomy”).

Chiari malformations will not recur following surgery. This is because they formed during your development before birth, and your brain and skull have generally completed growth by this point. However, patients will experience differing levels of relief following surgery, and sometimes, symptoms may return.

A dull headache is common, and most patients experience significant neck pain and stiffness after a Chiari decompression. The neck pain is due to the surgical elevation of the muscles from the back of the spine, and may take a number of weeks (or even longer) to settle. Pain medication will be ordered.

Syringomyelia can recur after surgery. You’ll need regular examinations with your doctor, including periodic MRI s, to assess the outcome of surgery. The syrinx can grow over time, requiring additional treatment.