Paralysis of the cerebral nerve: Eye movement disorder

Eye muscles are needed to make eye movements. A certain eye muscle, the musculus rectus lateralis, causes the movement of the eye outwards, away from the nose. This eye muscle is driven by the sixth cranial nerve (abducens nerve), which travels a long way from the brainstem to the rectus lateralis musculus. In some patients, the sixth cranial nerve is damaged or malfunctions, causing paralysis. When the patient presents only with the paralysis of the sixth cranial nerve, strabismus, double vision and amblyopia (a lazy eye) are the most important symptoms, although many additional (neurological) symptoms are possible, depending on the underlying condition. The prognosis is good when the patient has no other condition. Many treatment methods are available.

Synonyms paralysis sixth cranial nerve

A 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 disorder

2.5 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 nerve

The 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 form

In 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 form

A 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.

Unknown

Sometimes 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) symptoms

The 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 nerve

When 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 nerve

When 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 examination

The 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).

Differential diagnosis

Temporal arthritis, an eye socket fracture (broken eye socket), myasthenia gravis (chronic autoimmune disorder with muscle weakness in the face, limbs and eyes), Graves' eye disease and eye spasms are possible differential diagnoses.

Treatment eye abnormality

Underlying condition

The doctor first examines the cause of the disorder, and then coordinates targeted treatment. Antibiotics are useful with a bacterial infection. In the case of inflammation, the doctor prescribes corticosteroids. Surgery or chemotherapy are needed when the condition presents itself as a result of a tumor. It also happens that the doctor has no effectively proven treatment for the underlying cause of the paralysis of the sixth cranial nerve.

No treatment

In some cases, treatment starts immediately, but the doctor may also decide to wait a few months before starting additional treatment, as the symptoms sometimes resolve spontaneously within six months. For example, this is often the case with paralysis of the sixth cranial nerve after a viral disease or with a trauma, although the symptoms often do not disappear completely with trauma. The symptoms usually also disappear when the patient has isolated paralysis of the sixth cranial nerve.

A treatment

Possible methods of treatment in patients whose symptoms persist for more than six months include wearing an eye patch that alternates with each eye to treat double vision. With amblyopia (a lazy eye) the patient wears the eye patch on the strong eye. Special prism glasses also sometimes relieve symptoms. In addition, a botulinum toxin injection (botox injection) into the eye is required. An eye muscle correction and / or stray eye surgery are also possible if the other treatments have not been successful.

Prognosis damage to the brain nerve

For most patients, the symptoms disappear within six months, but sometimes additional treatment is required. The eye movement disorder itself does not involve any life-threatening symptoms, but these are of course possible with an underlying disease.

Complications eye problem

The most favorable prognosis occurs with isolated paralysis of the sixth cranial nerve, in which usually no complications occur. But other underlying conditions may cause complications. An operation also always entails the necessary risks and side effects.

Video: Neuro - Cranial Nerve 3 Palsy (February 2020).

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