Paralysis of the cerebral nerve: Eye movement disorder
Synonyms paralysis sixth cranial nerveA paralysis of the sixth cranial nerve is also known by these synonyms
- nerve abducens parese
- paralysis outer eye muscle nerve
- sixth (brain) nerve palsy
Epidemiology eye movement disorder2.5 out of 100,000 patients worldwide are affected with this eye movement disorder. The paralysis of the sixth cranial nerve occurs at any age. In children, a tumor is more common that leads to the eye problem, while in the elderly a stroke is more likely. Men and women are finally affected in equal numbers in the paralysis of the sixth cranial nerve.
Anatomy eye muscle and sixth cranial nerveThe eye has six eye muscles, each with its own effect. A muscle is attached to the outside of the eye, the so-called musculus rectus lateralis (outer straight eye muscle). The sixth cranial nerve sends signals to this little muscle. The eye then moves away from the nose as this muscle contracts. Each eye has its own musculus rectus lateralis that is controlled by its own brain nerve. The sixth cerebral nerve is located in the lower part of the brain and then goes through a long way to the lateral musculus. Sometimes damage occurs during that long way, as a result of which the nerve no longer works or works poorly. Because the rectus lateralis musculus no longer tightens properly, the eye rotates inwards towards the nose when the patient moves his eye.
Causes: Congenital or acquired form
Innate formIn some newborn patients, the paralysis of the sixth cranial nerve is already present at birth. This is sometimes due to an injury during delivery. Moreover, the sixth cranial nerve may be missing at birth. This occurs with the Duane syndrome.
Acquired formA number of patients develop paralysis of the sixth nerve later in life. Possible causes of this acquired form are a stroke (insufficient blood supply to the brain with mental and physical symptoms), a brain tumor, an infection (for example due to Lyme disease or a virus), migraine (attacks of an aura and / or unilateral headache) ), an inflammation of the nerves (for example due to an inflammatory disease such as multiple sclerosis (chronic neurological autoimmune disorder)), a trauma (especially with a skull fracture) and increased pressure in the brain, for example due to meningitis (meningitis with headache, fever and a stiff neck). Especially in children, trauma often results in an acquired paralysis of the sixth cranial nerve. Adults, on the other hand, often have a stroke that involves the paralysis of the sixth cranial nerve.
UnknownSometimes the cause of the paralysis of the sixth cranial nerve is unknown. This is known in medical terms as "idiopathic".
Symptoms: Double vision, strabismus, amblyopia (lazy eye) and other (neurological) symptomsThe symptoms occur at birth or later in life. The patient sometimes only has paralysis of the sixth nerve and no other symptoms, which is known as "isolated paralysis of the sixth nerve". In addition, neurological or other symptoms may occur, known as "non-isolated paralysis of the sixth cranial nerve". Depending on the underlying cause, one or both eyes are affected.
Isolated paralysis of the sixth cranial nerveWhen the paralysis of the sixth cranial nerve occurs without additional symptoms, this is usually the result of a congenital form, high blood pressure (hypertension), an injury, a viral disease and diabetes (diabetes mellitus). The patient may suffer but not always double vision (known as “diplopia” in medical terms) when both eyes are open. Double vision occurs when the patient's eyes are looking for an object far away from the eye and when the patient is looking for something in the direction of the affected eye. Strabismus (strabism) and amblyopia (a lazy eye) are other common eye problems.
Non-isolated paralysis of the sixth cranial nerveWhen the patient suffers from uninsulated paralysis of the sixth cranial nerve, additional symptoms are present such as a drooping eyelid (ptosis), a decreased feeling in the face, wobble (nystagmus), hearing loss, visual weakness, headache, fever and nausea and vomiting. These symptoms depend on the type of structure that is affected, and the location of the damage.
Diagnosis of the eye problem and examinations by the neurologist and eye doctor
Ophthalmological and physical examinationThe doctor or neurologist performs a thorough neurological examination of the patient. He tries to identify the cause of the paralysis of the sixth cranial nerve. In addition, an extensive eye examination in combination with an eye muscle function test is required in which the eye doctor examines the six eye muscles. Furthermore, it is important that the doctor has sufficient medical background of the patient, for example diabetes mellitus, cancer, thyroid disease and hypertension (increased blood pressure).
Dorsal injection / Source: Brainhell, Wikimedia Commons (CC BY-SA-3.0)Diagnostic research
Some imaging tests are needed to confirm the diagnosis such as a CT scan and an MRI scan. Blood tests for lumbar puncture (epidural: examination of cerebrospinal fluid) are sometimes required to detect the cause of the paralysis of the sixth cranial nerve. In children with hearing loss, an otoscopy is useful (internal viewing of the outer ear).