Defects will sometimes be deliberately left following emergency neurosurgery. The repair of such defects serves to improve cosmetic appearance as well as to provide protection to the exposed brain. Occasionally corrective surgery may be desirable to improve appearances as a result of bone flap shrinkage following craniotomy.
Cranioplasty
Repair of a defect in the cranial vault is termed cranioplasty. Autologous cranioplasty utilises a persons one bone that may have been stored following the initial procedure. Bone flaps stored under the skin or externally can shrink meaning the cosmetic result is poor and the margins of the bony door may be visible. This is usually only an issue with craniotomies on the cranial convexities and defects in the sub-occipital bone, over the cerebellum, are well covered by the thick muscles of the neck. Autologous cranioplasty may also be associated with an elevated risk of infection after implantation.
Repair of a defect in the cranial vault is termed cranioplasty. Autologous cranioplasty utilises a persons one bone that may have been stored following the initial procedure. Bone flaps stored under the skin or externally can shrink meaning the cosmetic result is poor and the margins of the bony door may be visible. This is usually only an issue with craniotomies on the cranial convexities and defects in the sub-occipital bone, over the cerebellum, are well covered by the thick muscles of the neck. Autologous cranioplasty may also be associated with an elevated risk of infection after implantation.
Decompressive craniectomy is a procedure where a large door is raised in the cranial vault to allow an injured brain to swell with pressing on adjacent uninjured brain. It is usually carried out as an emergency in order to save life. The commonest indications are follwoing traumatic brain injury or after a large stroke (Malignant middle cerebral artery stroke). Occasionally a defect in the cranium result from having to remove infected bone or a piece of bone which has been involved by a tumour. The image above is constructed from a CT scan and shows there has been a hemicraniectomy awaiting reconstruction.
A 3D printed plated designed on a template created from CT imaging of the skull defect can provide a perfect reconstruction and excellent cosmetic result. The materials we currently favour produce very little distortion on MR imaging subsequently and minimise the redundant space beneath the plate where blood may collect. It is possible to create complex plates to reconstruct the bones of the skull and the facial skeleton.
Syndrome of the Trephined
A rare consequences of any sizeable defect in the cranial vault is the development of motor impairment, cognitive and/or language disability that is directly related to the presence of the defect and imports when it is repaired. While probably underdiagnosed it is likely with earlier repair of a defect and is most associated with large craniectomies as shown above. It may result from the altered transcranial pressure and is frequently characterised by a very sunken wound.
