If tumours are small and confined to the sella turcica (the space in which the pituitary stalk, hanging down from the hypothalamus in the brain, sits) then transsphenoidal pituitary microsurgery can be done.
This involves surgery through the nasal cavity to access the pituitary through the sphenoid bone (the bone of the skull that lies anterior to the pituitary). Under general anaesthesia an incision is made in the gum at the root of the upper lip. The first stage is to dissect through the nasal cavity and associated nasal sinuses. Then a route through the sphenoid to access the sella turcica is made using a fine drill. Throughout, the surgical field is visualised with image intensifiers and microscopy. Precise microdissection then allows removal of tumours as small as 2 mm.
This technique leaves a hidden incision and is now well established, making this the surgery of choice for small tumours. It is curative in up to 95% cases of Cushing's disease where tumours are small. This falls to 50-70% when the tumours are larger. It also reduces visual problems resulting from the pituitary tumour pressing on vital neural structures related to sight (e.g. the optic chiasm) in 80% cases.
There is a mortality rate of less than 1% associated with transsphenoidal surgery. Other complications such as CSF rhinorrhoea (leaking of cerebrospinal fluid through the nose), nerve damage and visual impairment occur in up to 5% of cases. Damage to unaffected parts of the pituitary resulting in clinical problems occurs in 0.1% of operations for small tumours and 1-2% of operations for large tumours.