Glossary

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Acoustic Schwannoma (Neuroma): also called vestibular schwannoma, this benign primary intracranial neoplasm arises from the myelin-forming cells (Schwann cells) of the 8^th cranial nerve (vestibulo-cochlear nerve). Initially, these skull base tumors arise in the internal auditory canal near the brainstem and typically cause tinnitus (ringing in the ear) and hearing loss. As they enlarge into the cerebello-pontine angle, they can compress the brainstem, cerebellum and other cranial nerves, resulting in loss of balance and coordination, vertigo, facial numbness, facial weakness and difficulty swallowing. Primary treatment is surgical removal or radiosurgery. Learn more.
Acromegaly: a pituitary hormonal disorder caused by a growth hormone (GH) secreting pituitary adenoma. The problems associated with acromegaly include the effects of GH and IGF-1 over-secretion, and in some instances by the tumor compressing the normal pituitary gland, and optic nerves. Untreated acromegaly is a serious condition that can cause dramatic bone and soft tissue changes including frontal bossing, prognathism, enlargement of the hands and feet, sleep apnea, and carpal tunnel syndrome. More serious problems can include cardiovascular disease, hypertension, diabetes mellitus and an increased risk of colon cancer. Primary treatment is endonasal transsphenoidal surgical removal. Learn more.
Adenoma: a benign growth of cells arising from glandular tissue. All pituitary adenomas are benign although approximately 1 in 1000 tumor of pituitary gland origin are a pituitary carcinoma (malignant). Despite their benign histology, pituitary adenomas can still cause serious health conditions including hormonal loss (hypopituitarism), hormonal excess (acromegaly, Cushing’s disease, prolactinoma) visual loss and headaches. Learn more
Adrenal Glands: two paired triangular-shaped glands which sit atop the kidneys and consist of an outer adrenal cortex and an inner adrenal medulla. The adrenal cortex produces the stress hormone cortisol in response to the pituitary hormone ACTH (adreno-corticotropic hormone) and aldosterone which helps control water and sodium balance. The adrenal medulla produces the catecholamines epinephrine (adrenaline) and norepinephrine, both essential for the stress response and maintaining adequate blood pressure.
Adrenalectomy: surgical removal of the adrenal gland or glands. Bilateral adrenelectomy is used sometimes to treat persistent Cushing’s disease after failed or unsuccessful transsphenoidal surgery to remove the ACTH-secreting adenoma. One potential risk or bilateral adrenalectomy is the development of Nelson’s Syndrome – an aggressive ACTH-secreting pituitary adenoma. Learn more.
Adrenocorticotropic Hormone (ACTH): an essential pituitary hormone which causes the adrenal glands to release cortisol, the stress hormone. An ACTH-secreting pituitary adenoma is the cause of Cushing’s disease which is characterized by excess cortisol production. An ACTH deficiency may result in low cortisol levels and adrenal insufficiency which can be life threatening. Learn more.
Amenorrhea: absent or irregular menstrual periods in a woman of reproductive age. This condition can be caused by multiple conditions including problems with the ovaries, uterus, pituitary gland or hypothalamus. Hormonal disturbances from the pituitary gland and hypothalamus that can lead to amenorrhea include decreased luteinizing hormone (LH) and follicle stimulating hormone (FSH) production or excess prolactin production (hyperprolactinemia). These hormonal imbalances can result from pituitary tumors, brain tumors or other forms of damage to the pituitary gland such as radiation or head trauma. In women with a prolactinoma and high prolactin levels, amenorrhea is often associated with galactorrhea (abnormal breast milk production).
Aneurysm: a weakness on a wall of a blood vessel (artery) which may be congenital, developmental or traumatic in origin. Over time, the area of weakness may enlarge, balloon outward and eventually rupture. In the brain, a cerebral aneurysm rupture can cause abrupt severe symptoms of headache, stiff neck, nausea, photophopia and even coma or death. Unfortunately most aneurysms are not diagnosed until they rupture which leads to bleeding over the surface of the brain (subarachnoid hemorrhage) or into the brain itself. Urgent treatment of a ruptured cerebral aneurysm is indicated to prevent re-rupture which is typically fatal. Cerebral aneurysms are successfully treated by either clipping the aneurysm through a craniotomy or coiling the aneurysm through the artery itself using an endovascular technique. In recent years, endovascular treatment of aneursyms is becoming more safe and effective.
Arachnoid Cyst: cerebrospinal fluid filled cysts that arise from an abnormal development of the arachnoid membrane that covers the brain surface. They may occur over the surface of the brain around or around the skull base. Most arachnoid cysts are discovered incidentally because of a CT scan or MRI obtained for another reason and do not require treatment. On occasion however, some arachnoid cysts enlarge and put pressure on adjacent neural structures such as the optic nerves, brainstem or cerebral cortex and require surgical drainage. This treatment is usually quite effective.
Astrocytoma: a primary brain tumor arising from the glial cells of the nervous system, specifically the astrocytes. These tumors are graded on a 3 or 4-point scale based on their differentiation and aggressiveness. The World Health Organization uses a 4-point scale: Grade 1 — pilocytic or low grade astrocytomas; Grade 2 — diffuse astrocytomas; Grade 3 — anaplastic (malignant) astrocytomas; Grade 4 — glioblastoma multiforme (most common and most malignant). In addition to these four tumor grades, astrocytomas may combine with oligodendrocytes to produce oligoastrocytoma and other variants. They may arise in the cerebral hemispheres, in the cerebellum, brainstem, optic nerves or spinal cord. Tumor-related symptoms depend on their location; for cerebral astrocytomas, the most common symptoms are seizures and headache. Treatment of astrocytomas usually involves surgical debulking, radiotherapy and chemotherapy with temazolamide. Learn more.