Metastatic carcinomas.

These cancers arise elsewhere in the body and behave very much like glioblastoma except that 80 percent of patients are known to have a cancer elsewhere. The clinical picture depends upon whether the widespread manifestations of the disease are more evident than the neurological problem. In most patients the discovery of a brain metastasis does not meaningfully affect the treatment or outcome of the ' primary malignancy. Meningeal carcinomatosis, the spread of a meta-static cancer over the surfaces of the brain, results in confusion and a variety of neurological symptoms. It is not easily diagnosed unless abnormal cells are found during analysis of spinal fluid.

A few anomalous neurological syndromes can occur in the presence of carcinomas without actual invasion of the nervous system. These distant manifestations of cancer, thought to operate on a chemical basis, can appear as brain degeneration leading to dementia, diffuse damage to the cerebellum with movement disorders, and problems in muscular strength that vaguely resemble multiple sclerosis or myasthenia gravis. The incidence of spread to the central nervous system is highest in melanoma, occurring in 75 percent of all patients with this skin cancer. Cancers of the lung, breast, kidney, mouth, thyroid, intestines, and gynecologic system metastasize to the brain, in order of declining frequency, in 25 to 50 percent of patients. Surgical removal of single metastases may be best in a few patients. For most, however, radiation and corticosteroids remain the best course.

Acoustic neuroma.
These are by far the most common of several tumors that originate in the specialized cells that form the protective sheaths of nerve fibers. Acoustic neuroma is benign, but its steady growth puts pressure on and deforms adjacent brain structures, affecting walking, movement, and balance. Because it involves the nerve leading from the inner part to the brain, deafness, ringing in the ear, dizziness, and vertigo occur, if only to a mild degree, in almost every case.

Typically, acoustic neuroma is seen most often in middle-aged women. Testing of hearing and CT scanning confirm the diagnosis, although sometimes an acoustic neuroma is strongly suspected but cannot be proved. Repeated testing and close observation are in order for such patients. A spinal tap may be safely performed if there are no signs of increased intracranial pressure. Increased protein in the fluid may help confirm the diagnosis. Surgery is the sole method of treatment and may be performed by a specialist in ear surgery if studies indicate that growth has not extended beyond the acoustic nerve. A neurosurgeon may be more appropriate for larger tumors. The operative incision and areas of bone removed are quite small. Over 75 percent of patients are cured, especially those with tumors under one inch in diameter with no evidence of neurological damage to nearby brain tissue. Recurrence can be treated by repeat surgery in some patients.