brain, spinal cord, and nerve disorders
Sixth Cranial Nerve (Abducens Nerve) Palsy
Introduction
A palsy of the 6th cranial nerve impairs the ability to turn the eye outward. Sixth cranial nerve palsy has many causes, including damage to small blood vessels by diabetes, but the cause is often unidentified. The affected eye cannot turn fully outward and may turn inward when people look straight ahead. Doctors can identify 6th cranial nerve palsy based on the symptoms, but tests, including brain imaging, are done to try to identify the cause. Sixth cranial nerve palsy usually resolves whether the cause is identified or not. (See also Overview of the Cranial Nerves .) Palsy refers to paralysis, which can range from partial to complete. Many disorders can cause this palsy: Causes of Diabetes Complications and high blood pressure when they damage small blood vessels around the 6th cranial nerve Overview of Head Injuries None Tumors Multiple Sclerosis (MS) None A bulge ( Aneurysms of Arteries in the Arms, Legs, and Heart ) in an artery in the skull Overview of Brain Infections , such as meningitis, a brain abscess, or a chronic fungal infection Complications of an ear or eye infection Overview of Hemorrhagic Stroke None Blockage of an artery supplying parts of the brain stem, as can result from a Ischemic Stroke , a Wernicke Encephalopathy (commonly due to chronic alcoholism) Idiopathic Intracranial Hypertension (pseudotumor cerebri) Rarely, upper respiratory infections (in children) Some of these disorders, such as tumors and brain abscesses, increase pressure within the skull and put pressure on (compress) the nerve. Disorders, such as a blocked artery in the brain stem (for example, due to a stroke), interfere with blood flow to the parts of the brain that control 6th cranial nerve function. Disorders that affect very small blood vessels in the nerve (such as diabetes and high blood pressure) interfere with blood flow in the nerve. If 6th cranial nerve palsy occurs alone (without other cranial nerve palsies), its cause is often never identified. 