Tumor size is the main factor in selecting the surgical route. The Hardy Classification (3; Table 1) is based on radiologic appearances and remains a satisfactory system, although alternatives have been suggested.
Microadenomas (Grades 0 and 1) should only be approached via the transsphenoidal route. It is impossible to perform the microdissection required to separate the tumor from the normal gland transcranially. Any attempt to do so runs a significant risk of damage, not only to the normal gland but also to the posterior lobe (Fig. 4).
Tumors occupying the whole sella (Grades II and III) are also best approached from below (Fig. 5).
Occasionally, in a significantly expanded fossa a reasonable decompression can be carried out from above. It is difficult to justify such an approach because significant tumor clearance and preservation of endocrine function is far less easy to achieve. Tumors that extend laterally into the cavernous sinus (Grade E) or further into the subtemporal area are always a difficult surgical problem, because it is difficult to reach this area by either route (Fig. 6).
Cavernous sinus surgery is now an established division of skull-base surgery, but it is questionable whether a formal extradural approach to the sella via the cavernous sinus is warranted in pituitary adenoma because of the benign nature of the tumor. The response to radiotherapy is usually favorable, although slow. In our view, however, this approach is never a first-line option. It is of historical interest that both Sir Victor Horsley and Harvey Cushing, the pioneers of pituitary surgery, began their attempts to approach the pituitary by using the subtemporal route and abandoned it because of unacceptable complications.
The Hardy Classification of Pituitary Adenomas
0 Intact with normal contour
1 Intact with bulging floor
II Intact, enlarged fossa Invasive adenoma
III Localized sellar destruction
A Suprasellar cistern only B Recesses of third ventricle C Whole anterior third ventricle D Intracranial extradural E Extracranial extradural (lateral cavernous)
Endoscopic pituitary surgery employing an angled endoscope may provide the most promising way to approach an adenoma extending into the cavernous sinus.
With suprasellar tumors (Grades A, B, C, and D) good results can also be achieved with transsphenoidal surgery for both chiasmal decompression and endocrine preservation. This is particularly true for those tumors of Grades A, B, and C. Increasing experience with the extended transsphenoidal approach (Couldwell and Weiss, 1998; Kaptain et al., 2001) means that most experienced pituitary surgeons have extended the range of suprasellar tumors for which they will consider an inferior approach as a first option. Even for multilobulated suprasellar tumors of higher grade, transsphenoidal surgery can still be effective if used as part of a staged procedure. The large tumor cavity often fails to collapse initially, appearing as a mass of saline with clot on early postoperative scans. These appearances can be misleading; it is important to rescan the patient before the second transcranial procedure, at which time the residual tumor has usually reduced markedly in size.
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