Saturday, June 15, 2024

Craniotomy

Background

The term “craniotomy” refers broadly to the surgical removal of a section of the skull in order to access the intracranial compartment. The portion of skull temporarily removed is called a bone flap, and it is placed back in its original position after the operation is completed, typically fastened into place with low-profile titanium plates and screws. “Craniectomy” refers to an operation wherein the bone flap is removed but not replaced.

A craniotomy is named for the specific region of the skull where the bone is removed. For example, if the craniotomy is opened in the frontal bone, it is called a frontal craniotomy. Among the more common craniotomies in addition to the frontal include the parietal, temporal, occipital, and suboccipital. One of, if not the most common craniotomy site is referred to as “pterional.” The pterional craniotomy is named for the pterion, the junctional point of 4 bones within the skull (frontal, temporal, greater wing of sphenoid, parietal).

If a craniotomy involves 2 contiguous regions of the skull, it is named for both regions (eg, frontotemporal craniotomy, also rendered as fronto-temporal craniotomy); if 3 regions are involved, all names are included in the description (eg, a frontotemporoparietal craniotomy).

Craniotomies that involve the use of MRI-based navigational software, which has become standard in nearly all planned craniotomy operations, are referred to as “stereotactic” craniotomies. “Stereotactic” is a generic term and does not specify the location of the craniotomy site.

Smaller craniotomies are often referred to as “keyhole” craniotomies and are used in situations that require less bone removal. As the accuracy of navigational software has improved, along with advances in surgical technique and visualization, these keyhole craniotomy approaches have become more commonplace.
An example of such a minimally invasive craniotomy is the supraorbital craniotomy, also more coloquially known as an “eyebrow” craniotomy, in which the incision and bone flap are placed in the region of the patient’s eyebrow.  

The smallest type of craniotomy is technically a “burr hole,” also known as trephination. This is less regarded as a true craniotomy and more so as its own category of surgical approach, since it provides an extremely limited view of the underlying brain. However, with the advent of the endoscope, a long and thin high-definition camera, the burr hole serves as the entry port for the endoscope in a variety of intracranial approaches. Creating a burr hole involves drilling a small hole into the skull, revealing the underlying dura mater, the outermost of the 3 meninges covering the brain. The dura can then be opened to allow further exploration of the underlying brain.

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