MANIFESTATIONS OF SUPRASELLAR DISEASE
Suprasellar lesions that may lead to hypothalamic dysfunction include craniopharyngioma, dysgerminoma, granulomatous diseases (e.g., sarcoidosis, tuberculosis, Langerhans cell histiocytosis), lymphocytic hypophysitis, metastatic neoplasm, suprasellar extension of a pituitary tumor, glioma (e.g., hypothalamic, third ventricle, optic nerve), sellar chordoma, meningioma, hamartoma, gangliocytoma, suprasellar arachnoid cyst, and ependymoma.
Endocrine and nonendocrine sequelae are related to hypothalamic mass lesions. Because of the proximity to the optic chiasm, hypothalamic lesions are frequently associated with vision loss. An enlarging hypothalamic mass may also cause headaches and recurrent emesis. The hypothalamus is responsible for many homeostatic functions such as appetite control, the sleep–wake cycle, water metabolism, temperature regulation, anterior pituitary function, circadian rhythms, and inputs to the parasympathetic and sympathetic nervous systems. The clinical presentation is more dependent on the location within the hypothalamus than on the pathologic process. Mass lesions may affect only one or all of the four regions of the hypothalamus (from anterior to posterior: preoptic, supraoptic, tuberal, and mammary regions) or one or all of the three zones (from midline to lateral: periventricular, medial, and lateral zones). For example, hypersomnolence is a symptom associated with damage to the posterior hypothalamus (mammary region) where the rostral portion of the ascending reticular activating system is located. Patients with lesions in the anterior (preoptic) hypothalamus may present with hyperactivity and insomnia, alterations in the sleep–wake cycle (e.g., nighttime hyperactivity and daytime sleepiness), or dysthermia (acute hyperthermia or chronic hypothermia).
The appetite center is located in the ventromedial hypothalamus, and the satiety center is localized to the medial hypothalamus. Destructive lesions involving the more centrally located satiety center lead to hyperphagia and obesity, a relatively common presentation for patients with a hypothalamic mass. Destructive lesions of both of the more laterally located feeding centers may lead to hypophagia, weight loss, and cachexia.
Destruction of the vasopressin-producing magnocellular neurons in the supraoptic and paraventricular nuclei in the tuberal region of the hypothalamus results in central diabetes insipidus (DI) (see Plate 1-27). In addition, DI may be caused by lesions (e.g., high pituitary stalk lesions) that interrupt the transport of vasopressin through the magnocellular axons that terminate in the pituitary stalk and posterior pituitary. Polydipsia and hypodipsia are associated with damage to central osmoreceptors located in anterior medial and anterior lateral preoptic regions. The impaired thirst mechanism results in dehydration and hypernatremia.
Anterior pituitary function control emanates primarily from the arcuate nucleus in the tuberal region of the hypothalamus. Thus, lesions that involve the ﬂoor of the third ventricle and median eminence frequently result in varying degrees of anterior pituitary dysfunction (e.g., secondary hypothyroidism, secondary adrenal insufﬁciency, secondary hypogonadism, and growth hormone deﬁciency).
Hypothalamic hamartomas, gangliocytomas, and germ cell tumors may produce peptides normally secreted by the hypothalamus. Thus, patients may present with endocrine hyperfunction syndromes such as precocious puberty with gonadotropin-releasing hormone expression by hamartomas; acromegaly or Cushing syndrome with growth hormone–releasing hormone expression or corticotropin-releasing hormone expression, respectively, by hypothalamic gangliocytomas; and precocious puberty with -human chorionic gonadotropin (-hCG) expression by suprasellar germ cell tumors.
Because of the close microanatomic continuity of the hypothalamic regions and zones, patients with suprasellar disease typically present with not ne but many of the dysfunction syndromes discussed.