Pathogenesis and Pathophysiology. Craniopharyngiomas are thought to be congenitally derived and to arise from remnants of Rathke's pouch. Embryonic collections of epithelial cells remain after absorption of the hypophysealpharyngeal duct, from which the infundibulum/tuber cinereum is derived ( Fig ,..4.6.:8 ). The squamous cells are found to be metaplastic and may be present for a significant period before transformation occurs. Alternative proposals suggest that these tumors are derived from a malformation of the embryonic cells that can linger in the area and are not absorbed during fetal life for a significant period of time, leading to abnormal growth. There are two main histological types, one seen in children and the other in adults, suggesting the possibility of two different explanations for their origin.

These tumors range in size from very small round nodules to large loculated cysts. Two main histological types are found. In the majority of children, an adamantinomatous form that appears to resemble tooth-forming material is composed of interspersed fibrous and necrotic tissue as well as many multiloculated cysts. Cholesterol and an oily, thick cystic fluid may also be present, and this fluid can spill from the sack into the subarachnoid space, causing a chemical meningitis. These types of craniopharyngiomas are more often found to have calcium deposits that can be

Figure 46-8 MRI picture of a craniopharyngioma, demonstrating a cystic contrast-enhancing mass in the suprasellar area extending upward, compressing the hypothalamus.

visualized on plain skull radiographs. In adults, a squamous papillary form occurs; although it has no adamantinomatous features, a less cystic stratified squamous epithelium is found histologically. Keratin deposition may also occur. In many cases it may be difficult to differentiate these two main forms, leading some to propose the presence of a third mixed form.

Epidemiology and Risk Factors. Craniopharyngioma is an epithelial tumor arising from the region of the sella and represents 3 percent of all primary intracranial neoplasms. It is the most common childhood tumor involving the sella area. Although it is the third most common tumor in childhood, about 50 percent of all cases occur in adults. There are no known risk factors.

Clinical Features and Associated Findings. Because this tumor is located near the pituitary, the resulting syndromes resemble those characteristic of pituitary adenomas. Symptoms can arise slowly over many months. The most common presenting complaints are compression of the chiasm, causing visual disturbances in the form of bitemporal visual field loss or obstruction of the cerebrospinal fluid pathways yielding papilledema, headache, nausea, or vomiting. Involvement of the hypothalamus or pituitary may lead to endocrinological disorders. With enlargement, pressure on the third ventricle in children can lead to a failure to attain developmental milestones or, in adults, a dementing process. In 90 percent of cases, endocrinological abnormalities are present, usually involving the anterior pituitary, yet most patients do not seek initial evaluation for problems related to endocrinological dysfunction. Notwithstanding, almost half of affected children are of short stature, and a quarter are obese at presentation. The primary endocrinological disturbance found is related to GH production; next in frequency are disturbances in LH/ FSH, ACTH, and TSH. In contrast to pituitary adenomas, abnormalities of prolactin are seen in only about a fifth of cases.

Differential Diagnosis. Craniopharyngiomas usually have a characteristic radiographic appearance that generally excludes other pathological processes. The differential diagnosis of these tumors includes pituitary adenomas, which have no calcifications, and separation of these two possibilities without surgery may be difficult in adults. Rathke's pouch cysts are usually single cysts and lack a solid component. Meningiomas often possess a "dural tag," and a cleavage plane can be visualized on imaging studies. In adults, metastatic tumors such as melanoma should also be considered.

Evaluation. Neuroradiographic studies should be designed to aid in surgical planning. Plain skull radiographs may show enlargement of the sella or calcium deposits, thereby giving a hint of potential diagnoses, especially in children. CT scans with and without contrast agent and paying attention to the sella in the coronal section may show bony alterations, whereas MRI with and without gadolinium can define the soft tissue extension of the tumor and the presence of cysts. Craniopharyngiomas tend to extend downward into the sella, whereas pituitary adenomas, in contrast, extend upward from the sella. Occasionally, angiography is required to define lateral displacement that can interfere with arterial blood supply, especially the internal carotid artery. Full endocrinological evaluation is mandatory before and after surgery (see Table 46-5).

Management. Surgical resection remains the mainstay of treatment to establish diagnosis and to relieve pressure from the surrounding structures. '59] Patients need cortisol at the time of surgery regardless of their preoperative status. All patients require assessment of fluid and electrolyte balance, which should be monitored closely in the operative period. Derangements in water and electrolyte balance caused by diabetes insipidus, the syndrome of inappropriate antidiuretic hormone secretion, or cerebral salt wastingW are common in the postoperative period. Following total removal of the tumor, further treatment is usually not required. With subtotal removal, patients can be evaluated with serial neuroradiological imaging, and reoperation at regrowth of the tumor can be considered. Alternatively, depending on the amount of residual tumor, radiotherapy is also an option. There is increasing controversy about the role of stereotactic radiation or gamma knife as the sole treatment modality. Follow-up periods for patients treated with radiosurgery have been relatively short, and further research in this area is required. Instillation of radioactive phosphorus may be considered in some patients with cystic lesions. [6i] Endocrinological evaluation and postoperative treatment are similar to the regimen followed for patients with pituitary adenomas. Children require close observation with careful monitoring of neurocognitive and hormonal status.

Prognosis and Future Perspectives. Even when these tumors are detected before any neurological deficits become apparent, the prognosis remains guarded. Recurrence approaches 30 percent within 5 years and is higher in children and in those who have undergone incomplete resection. A significant number of patients continue to require hormonal supplementation. Further work is needed to determine ways to identify more aggressive tumors for which the use of radiotherapy and chemotherapy at initial tumor diagnosis may prevent recurrence.

Goetz: Textbook of Clinical Neurology, 1st ed., Copyright © 1999 W. B. Saunders Company

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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