Diagnosis Of Sellar And Parasellar Lesions General Principles

The clinical features of sellar region pathology primarily represent the functional consequences of mass lesions, which, independently of histology, compress, distort, or otherwise compromise any of the parasellar structures. The optic apparatus, cranial nerves of the cavernous sinus, pituitary gland, hypothalamus, ventricular system, and brain are all vulnerable. Neurologic, neuro-ophthalmo-logic, endocrinologic, and neuroradiologic evaluations are all essential components of treatment. Each of these is fully discussed in the context of individual lesions throughout this and previous chapters.

Table 1

Differential Diagnoses of Neoplasms and Tumor-Like Lesions of the Sellar Region

Type

Example

Tumors of adenohypophyseal origin Tumors of neurohypophyseal origin

Tumors of nonpituitary origin

Cysts, hamartomas, and malformations

Metastatic tumors

Inflammatory conditions

Vascular lesions

Pituitary adenoma Pituitary carcinoma

Granular cell tumor Astrocytoma of posterior lobe and/or stalk (rare)

Craniopharyngioma Germ cell tumors Glioma (hypothalamic, optic nerve/chiasm, infundibulum) Meningioma Haemangiopericytoma Chordoma Haemangioblastoma Lipoma

Giant cell tumor of bone Chondroma Fibrous dysplasia Sarcoma (chondrosarcoma, osteosarcoma, fibrosarcoma) Postirradiation sarcomas Paraganglioma Schwannoma Glomangioma Esthesioneuroblastoma Primary lymphoma Melanoma Rathke's cleft cyst Arachnoid cyst Epidermoid cyst Dermoid cyst Gangliocytoma Empty sella syndrome

Carcinoma

Plasmacytoma

Lymphoma

Leukemia

Infection/abscess

Mucocele

Lymphocytic hypophysitis Sarcoidosis

Langerhans' cell histiocytosis Giant cell granuloma Internal carotid artery aneurysms Cavernous angioma

Sellar/parasellar lesions have specific endocrinologic effects that require special consideration. Moderate degrees of hyperprolactinemia (<6000 mU/L, <300 ng/mL) can occur with any of the mass lesions involving the sellar region. This phenomenon, frequently referred to as the "stalk effect" (see Chapter 2), is the result of compressive or destructive lesions involving the hypothalamus or pituitary stalk, particularly any structural, inflammatory, or neoplastic process occurring in the sella, and is fairly common.

It is, therefore, a nonspecific finding whose presence should not be routinely interpreted as being the result of a prolactin-secreting pituitary adenoma. Posterior pituitary failure in the form of diabetes insipidus (DI) is an occasional feature of sellar region pathology and is especially prominent among destructive lesions such as inflammatory processes, metastatic tumors, and primary tumors having an extra-adenohypophyseal origin. Unexplained, but of practical interest, is the fact that DI is rarely, if ever, a presenting feature of pituitary adenomas, and its preoperative presence strongly suggests an alternative diagnosis.

In all patients suspected of having sellar region pathology, a thorough laboratory evaluation of endocrine status is mandatory, being directed at identifying deficient hormone axes.

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