Pituitary tumour

 Upto 15% of brain tumours occur in the cellar and parasellar region, commonest of which is pituitary tumour. Normal size of pituitary is less than 15 mm and its weight is less than 1gram. it is attached to the infundibulum or pituitary stalk. Pituitary gland is housed in the Sella Turcica or pituitary fossa of the body of the sphenoid bone. The pituitary fossa is delineated anteriorly by the tubercular sella & schismatic sulcus and posterior by the dorsal sella & posterior clinoid process. Diaphragma sella is a fold of dura mater which forms the roof of the pituitary fossa. It has a central opening for pituitary stalk or infundibulam. Just beneath the sella turcica, inside the body of the sphenoid there are sphenoid sinuses which are paired cavities separated by a septum.

The distance between intracavernous parts of two carotid arteries are about 12 mm to 14 mm. 

Optic chiasm lies just above the pituitary gland (8-13 mm) , in the sucus chiasmaticus in 5%, over diaphragm sella in 12% and in 79% over the dorm sella ( post-fixed location of optic chiasm). 

The symptoms and signs of pituitary tumours vary according to the size and type of tumour. Visual symptoms occur due to compression of the optic chiasm. Visual field defects are very common. Bitemporal hemianopia is very common in pituitary tumours. Headache is also very common. Endocrine symptoms are very common. Prolactinomas are the most common pituitary tumours and account for up to 40% of such lesions. The is history of milk production ( galactorrhoea) in females. There is history of amenorrhoea. The endocrinopathy produced in women is the galactorrhea- amenorrhoea syndrome ( Forbes-Albright syndrome). The various menstrual disorders are amenorrhea, oligomenorrhoea & irregular periods. About 30% of women complain of galactorrhea. There is also associated infertility. 

The normal level of serum Prolactin is less than 25 ng/ml. Elevation of the fasting prolactin above 150 ng/ml is strongly suggestive of a prolactinoma.

Hormonal assay of the hormones is part of the detailed work up of the pituitary tumours. Most of the functioning pituitary tumours are associated with decreased thyroid function, increased growth hormone level, increased serum cortisol level, derranged FSH and LH. 

Ophthalmolocal examination is part of the investigation for diagnosis and prognosis of treatment of pituitary tumours. Visual field, visual acuity and funds examination must be done in all patients with pituitary tumours. Most of the time patients and sometimes doctors are not aware about the extent of visual defects in the patient. There may be mono-ocular visual loss before the surgery and it is noticed only after surgery. So, preoperative visual field chart ( bitemporal hemianopia) and visual acuity ( like finger counting upto 1 meter distance) are very much necessary.

CT scan of the brain show shows a lesion in the cellar region. MRI brain with contrast demonstrates the extent of the lesion, location of optic chiasm, any enhancement of the tumour inside pituitary, size of the pituitary tumor (micro adenoma or macro adenoma). MRI brain also shows the location of the carotid arteries in relation to the tumour. Pituitary tumour of size more than 10mm is known as pituitary macroadenoma. If tumour size is less than 10 mm, it is known as pituitary micro adenoma. Sometimes , haemorrhage occurs in pituitary tumor which is known as pituitary apoplexy. 

Drugs available for treatment are: bromocriptine, pergolide, cabergoline, quinagolide ( CV 205-502 ). Bromocriptine is an ergot alkaloid and dopamine agonist. The usual dose of Bromocriptine is 2.5 mg three times a day, which can be increased.

Surgery is done either through transcranial route or through transsphenoid route. If sphenoid bone is pneumatized and tumour is located in the mideline and without any para seller extension, the transnasal trans-sphenoidal surgery is the ideal mode of surgical intervention. After surgery, if any part of the tumour could not be excised, then Gamma knife radiosurgery is also an option to treat it.

Growth hormone secreting pituitary tumours present gigantism in children and acromegaly in adults. Hypertension, coronary artery disease, valvular heart disease, are common in these patients.