Craniopharyngiomas which derive from remnants of Rathke's pouch account for about 1% of all intracranial tumors in adults. They are more frequent in children were they represent about 10% of all intracranial tumors (24). Though craniopharyngiomas are benign, and grow rather slowly, they frequently infiltrate surrounding structures.

Histology shows adamantinous epithelial pallisades frequently with cyst formation and calcification. In adults about one third of the craniopharyngiomas show a squamous papillary pattern without calcification and without local infiltration. Adult patients with craniopharyngiomas usually have a better prognosis in respect to endocrine, visual and other neurological deficits than children with these tumors (25).

Craniopharyngiomas can be differentiated from epidermoid and dermoid cysts, which are much rarer than craniopharyngiomas, and Rathke's cleft cysts, though they are related embryologically. Fifteen percent of the epidermoids are located around the pituitary fossa in adults, whereas dermoid cysts are more frequently found in children.

The clinical presentation of craniopharyngiomas in adults depends on the location of the tumor. Intrasellar craniopharyngiomas cause mainly endocrine symptoms similar to those seen in patients with NFPAs. Patients with suprasellar invasive craniopharyngiomas may present with endocrine abnormalities, visual problems from visual field defects up to loss of vision, and neurological defects such as cranial nerve palsy, ataxia, and convulsions. Raised intracranial pressure can lead to headache, somnolence, and a comatous state (table 4). However, such severe craniopharyngioma induced symptoms are mainly seen in children, less often in adults.

The diagnosis, which is often suspected on clinical grounds in growth retarded children, is made on account of plane radiographs of the skull showing often an enlarged pituitary fossa and suprasellar calcification. The imaging technique of choice is the MRI or CT which shows the extension of the usually cystic space occupying lesion. The fluid in these cysts have been shown to contain high concentrations of immunoreactive b -hCG. The latter can also be found in the CSF. This brings up the differential diagnosis of germinomas, in which measurable b -hCG levels are often found in the CSF and occasionally also in the general circulation Some cells in the epithelial wall of the cyst can be positively immunostained for b-hCG(26).

The treatment of craniopharyngiomas is with surgery, though particularly in children it is difficult to obtain radical removal of the tumor. Postoperative external radiation, interstitial irradiation with radioactive isotope instilled into the cyst fluid, and shunting to relieve the hydrocephalus are therapeutic options to alleviate the symptoms (25).

Endocrine management is not different from those of other hypothalamic pituitary deficiencies. However, non-endocrine hypothalamic disturbances of fluid balance due to disturbances of thirst- and osmotic control, hyperphagia, hyperthermia and somnolence, may be life threatening and extremely difficult to control.

Germ cell tumors are differentiated into germinomas, which represent 65% of intracranial germ cell neoplasms, and non-germinomatous germ cell tumors (NGGCT) such as terratomas, embryonal carcinomas and chorioncarcinomas. The incidence of these neoplasms is rather low in western countries but is much higher in Japan (27).

Germinomas and non-germinomatous germ cell tumors (NGGCT) differ with regard to their age of onset, location and prognosis. Germ cell tumors may secrete b -hCG and alpha -fetoprotein which can be found in the CSF and the peripheral circulation (28).

NGGCTs occur in children whereas germinomas are more frequently observed in adult males. Germ cell tumors are usually found in the region of third ventricle between the suprasellar space (mainly germinomas) and the pineal gland (mainly NGGCTs). The clinical presentation in younger patients includes precocious puberty which may occur due to pressure on the median eminence or as a consequence of the elevated hCG levels which may directly stimulate Leydig cells of the testes.

The clinical features of these tumors, which may spread by direct invasion or via the CSF into the ventricles or suparachnoid pathways down to the spinal cord, are anterior pituitary failure, diabetes insipidus, visual disturbances, and other neurological deficits.

Radiotherapy is the treatment of choice after tumor extension has been delineated carefully by appropriate imaging techniques. Germinomas have a better prognosis than NGGCTs of which chorioncarcinomas have the worst prognosis. Chemotherapy is also used, particularly in patients with wide spread disease whereas surgery is only reserved for those patients with radiotherapy resistant tumors (29). The efficacy of therapy can be monitored by measuring ? -hCG or ? -fetoprotein in the circulation when they are produced and secreted by these tumors (28).

Chordomas are very rare neoplasms representing less than 0,5 % of primary intracranial tumors. First described by Rudolf Virchow 1856, it was believed that they were of cartilaginous origin. At present it is thought that the chordoma derives from remnants of the embryonic notocord, the precursor of the intraspinal nucleus pulposus which extends up to the sphenooccipital suture (30). They can present any time in life with symptoms of headaches, diplopia and palsies of the 6th, the 9th, the 10th and the 11th nerves. In addition, when the tumor mass is located in sellar area near the clivus, endocrine symptoms with hypogonadism, hypothyroidism and adrenal failure, hyperprolactinemia and diabetes insipidus may occur. Chordomas do not only occur intracranially. If they occur in the spinal cord they are more likely to give rise to distant metastases, which occur rarely when they are located in the pituitary hypothalamic area.

The diagnosis is made by MRI. A chordoma is suspected whenever the clivus is involved. However, the diagnosis of an isolated intrasellar chordoma is usually made only on account of the histology after surgery has been performed (31).Surgery is the established treatment. Whereas surgery can be performed in purely intrasellar chordomas and in extra cranial sacral chordoma, larger skull base chordomas are subjected to radiotherapy which has been shown to extend survival. Without treatment intracranial chordomas have an unfavourable prognosis (30).

Hypothalamic hamartomas (HH) are hyperplastic formations consisting of foci, of neurons and glia. HH are rare tumors which have profound influence on endocrine function since they may secret gonadotropin releasing hormone (GnRH) or growth hormone releasing hormone (GHRH). Since they occur exclusively in children they can cause precocious puberty and gigantism in addition to neurological complications such as intractable seizures. Diagnosis and treatment will be discussed in the chapter Pituitary - Hypothalamic Tumor Syndromes: Children.

Hodgin's disease, lymphomas, leukaemic infiltration, Langerhan's cell histiocytosis (histiocystosis X), eosinophilic granuloma and giant cell tumors can occur in the suprasellar area. They lead to the classical triad of anterior pituitary failure, diabetes insipidus and visual disturbances, which can be accompanied with other neurological deficits and symptoms due to the original disease (32, 33, 34, 35). Treatment depends on the diagnosis, the extent of endocrine dysfunction, the space occupying lesion and staging of the disease. The reversibility of endocrine dysfunctions, i. e. hyperprolactinemia or diabetes insipidus can be used as an indicator for the effectiveness of the respective therapy.

Sarcoidosis of the nervous system can lead to peripheral and central manifestations (32, 34). When granulomatous disease in the CNS leads to local infiltration of brain substance and impedes the flow of CSF giving rise to increased intracranial pressure, diabetes insipidus, hyperprolactinemia and anterior pituitary failure as well as other hypothalamic disturbances like somnolence, disturbance of water balance, food intake, and temperature regulation are observed (36). Hypothalamic involvement is the most common feature of neurosarcoidosis though other neurological symptoms like seizures and psychiatric disturbances are also encountered. The diagnosis can not be made by MRI or CT alone. Determination of angiotensin converting enzyme is usual not helpful though analysis of the CSF may reveal an elevated protein content or an increase of CSF lymphocytes. Lymph node enlargement and pulmonary sarcoid disease are seldom present. Often the diagnosis is made only after a pituitary biopsy reveals the classical granulomas. Treatment of choice is prednisone (1,5 mg/kg body weight) which usually rapidly normalizes endocrine disturbances. However, other diseases should be excluded, before steroid treatment is considered (34).

Other rare differential diagnoses include hypophysitis (see above), infectious diseases at the base of the skull like tuberculosis, syphilis, fungal infections, and cysticercosis, and Wegner's granulomatosis which may all lead to endocrine and ophthalmological symptoms. In patients with HIV, manifestations of opportunistic infections may occur in the pituitary-hypothalamic area (37). CSF-examination may be helpful in making the differential diagnosis.