The most common transcranial approaches that are used are the frontal craniotomy and the subfrontal approach. These types of operations are used for dealing with large tumours that have suprasellar extensions. A trans-sphenoidal approach would not allow adequate access to the tumour and would not produce satisfactory results.
The transcranial approach was developed over 100 years ago and has the advantage of providing a good view of the tumour. The development of the operating microscope has made the trans-sphenoidal approach the treatment of choice for the removal of pituitary adenomas.
Victor Horsley performed the first subfrontal approach in 1889. The incision takes the form of a bicoronal scalp flap or a two-thirds coronal incision. Fashioning of the osteoplastic flap is important as every effort should be made to make it as low as possible in the frontal region in order to have ready access to the floor of the anterior fossa. The frontal sinuses play an important role in the making of the osteoplastic flap.
A dural incision is made anteriorly so that the brain can be retracted and access gained to the pituitary. Careful removal of CSF by suction allows retraction of the undersurface of the frontal lobe and allows the visualisation of the olfactory nerve and the optic nerves. The tumour can then be identified and work can start on removing it.
Specimens of the tumour are then taken for peri-operative smear to confirm the diagnosis. The decompression is usually carried out with rongeurs, and the central bulk is gradually removed. If the tumour is adherent, the greatest skill is required to dissect it free. If the tumour cannot be removed safely then it is safer to leave the tumour intact.
If the frontal sinuses have been opened in the operation they must be stripped of mucosa and packed, then covered in a layer of temporalis fascia, tensor fascia lata or Iyodura, which is then fixed in position to prevent the leakage of CSF. The bone flap is then replaced and the flap resutured over a drain.
If the tumour has expanded laterally, then this approach is inadequate and a more lateral approach is required. The best lateral approaches are the frontozygomatic, pterional and the lateral subtemporal approach.