FINAL DIAGNOSIS: CRANIOPHARYNGIOMA
Craniopharyngiomas arise from remnants of Rathke's pouch, a part of the embryonic nasopharynx that migrates cephaldad and gives origin to the anterior lobe of the hypophysis. Derivations of this epithelium assume positions above the sella turcica, where they generate cystic and solid lesions, invading and compressing adjacent tissues (1). Two distinct clinicopathological variants of craniopharyngioma exist: the classic adamantinomatous type and a recently described papillary form that predominates in adults and behaves in a less aggressive manner (2). They are rare tumors of uncertain behavior that occur at a rate of 1.3 per million person years (3). They constitute 3 to 5 percent of all intracranial neoplasms. Although craniopharyngiomas are usually manifested in children (4), 45% are over age 20 and 20% are - as this patient - over age 40 at the time of diagnosis. A total of approximately 338 cases of this disease are expected to occur annually in the United States (3).
Children usually present with signs of increased intracranial pressure, including headache, vomiting and papilledema (80%). Visual abnormalities occur in 60%.
About 80% of adults present with visual complaints - as this patient. Headaches (40%), mental deterioration and personality changes (26%), as well as weight gain (15%) are frequent presenting signs (6) - as in this patient.
The tumors may cause anterior pituitary failure with hypopituitarism in 95% of cases (5) and hyperprolactinemia in 38% of cases (5) or involve the posterior pituitary inducing vasopressin (ADH) deficiency and central diabetes insipidus in 16.1% of patients (6) manifested by increased thirst (as in this patient) and/or dehydration.
Laboratory data most frequently show moderately increased prolactin levels, rarely exceeding 100 to 150 ng /dl (4) (as in this patient, who had a prolactin level of 67.4 ng/dl).
Many patients show hypopituitarism or panhypopituitarism with a decrease in some or all of the following: growth hormone, IGF-1, TSH, FSH, LH, and ACTH (4). This patient had growth hormone deficiency with low IGF-1 ( 36.4 ng/ml). She had very low postmenopausal levels of both FSH and LH (1.4mIU/ml and < 0.5 mIU/ml respectively). Her TSH was normal. She had low a.m. cortisol level with a normal response to the rapid ACTH stimulation test, showing normal adrenal function.
Some patients also have hypernatremia secondary to central diabetes insipidus (4). This patient had an increased serum sodium level of 150 mEq/l with decreased urine specific gravity and osmolality (this patient's urine specific gravity was 1,003 and urine osmolality was 179 mOsm/kg - both low ) and increased serum osmolality ( as in this patient who had a serum osmolarity of 321 mOsm/kg).
Therapy is often unsatisfactory. Total resection often results in major functional pituitary deficits. Generally partial resection followed by conventional radiation therapy - as a more conservative approach - is recommended. It has been shown that preserving the pituitary stalk and gland at surgery is the best approach because of the definite chance that intact anterior pituitary functions can be maintained. Postoperative diabetes insipidus must be accepted as a common sequela following attempts at complete removal of the craniopharyngioma (6). Tumors less than 3 cm have a better prognosis. This patient had craniotomy and resection of the tumor with subsequent diabetes insipidus, hypothyroidism, hypogonadotropism, and low cortisol levels - managed by hormone supplementation.
Contributed by Octavia Graur, MD, PhD and Mohamed A Virji, MD, PhD