Extraocularmotor dysfunction associated with tumors.

Intracranial and extracranial tumors can be the cause of extraocularmotor dysfunction. In approximately 19% of reported cases, paralysis of the third, fourth, or sixth cranial nerves is due to neoplastic growth; the sixth nerve is the most commonly affected. Tumors can produce extraocular muscle dysfunction by directly affecting the extraocular muscle; directly affecting the third, fourth, or sixth cranial nerves; directly affecting the supranuclear extraocular movement areas; indirectly affecting any of the above by metastasis from a tumor in another part of the body; and indirectly affecting the third, fourth, or sixth cranial nerves or their nuclei or the supranuclear extraocular movement areas through an increase in intracranial pressure. The ocular signs and symptoms of disease vary based on the mechanism involved.