Abducens Nerve Palsy - Symptoms, Diagnosis, and Management

What Is Abducens Nerve Palsy?

The brain is connected to various regions of the head, neck, and body through cranial nerve pairs. There are twelve of them, and each one is named after its structure or function. They are typically classified as having sensory or motor functions. When the sixth cranial nerve is injured or malfunctions, abducens nerve palsy ensues. This disorder makes it difficult to move the eyes.

The lateral rectus muscle receives signals from the sixth cranial nerve, a tiny muscle that connects to the outside of the eye. The eye shifts away from the nose as this muscle contracts. Each lateral rectus muscle in each eye is supplied by a separate cranial nerve. The brain's bottom region is where the sixth cranial nerve leaves the body. Before arriving at the lateral rectus, it travels a great distance.

The nerve may function badly or not at all if it sustains damage at any juncture along its course. The eye rolls inward toward the nose because the lateral rectus muscle cannot contract properly. Sixth nerve palsy can occasionally occur without any additional symptoms and is known as isolated sixth nerve palsy in such scenarios. Sixth nerve palsy, when it has additional symptoms, is known as non-isolated sixth nerve palsy.

What Are the Causes of Abducens Nerve Palsy?

Sixth nerve palsy can occur due to a variety of causes. It could be a consequence of a medical condition, a birth defect, or be brought on by physical trauma. The cause may not always be known. Sixth nerve palsy-related traumatic injuries include:

• Head injuries.

• Coma.

• Broken cervical spines.

• Brain damage.

Following are a few ailments or conditions that might result in sixth nerve palsy:

• Brain cancer or brain tumors.

• Headaches from migraines.

• Multiple sclerosis.

• Inflammation.

• Stroke.

• Pregnancy.

• Viral infection.

• An increase in cerebral pressure.

• Meningitis.

• Diabetic neuropathy or small-vessel disease.

• Gradenigo's syndrome is defined by the triad of abducens nerve palsy, trigeminal nerve pain, and suppurative otitis media. The middle ear infection extends medially to the petrous part of the temporal bone, resulting in this condition.

• Injury sustained during a procedure, such as spinal anesthesia or post lumbar puncture.

• Cavernous sinus thrombosis is a condition brought on by a blood clot behind the eyes.

• Mastoiditis is an infection in the bone behind the ear.

• Temporal arteritis is an inflammation of the blood vessels around the scalp.

What Are the Symptoms Observed in Abducens Nerve Palsy?

Sixth nerve palsy can damage one or both eyes because each eye has its own sixth cranial nerve and the lateral rectus muscle. Whether one or both of the eyes are afflicted will determine the symptoms and the severity of the problem. The symptoms include:

• Dual Vision: The most typical sign of abducens nerve palsy is diplopia, or double vision when gazing from side to side. When staring at something far away or with both eyes open, one could become aware of this vision impairment. Double vision can occasionally be seen when staring with the injured eye. Additionally, an abducens nerve palsy without double vision is also possible.

• Strabismus or Poor Eye Alignment: Poor eye alignment, often known as crossed eyes, occurs when both eyes are not focusing in the same place at the same time.

• Head Movement to Keep the Vision Maintained: In order to lessen their double vision, patients with sixth nerve palsy occasionally tilt their heads continuously.

With sixth nerve palsy, strabismus, and double vision are frequent symptoms. Other symptoms, however, might be present. From the brainstem, the sixth cranial nerve passes to the lateral rectus muscle. This suggests that sixth nerve palsy can result from neurologic conditions. Other signs can include:

• Headache.

• Vomiting and nausea.

• Loss of vision and hearing.

• Edema of the optic nerve (papilledema).

How Is Abducens Nerve Palsy Diagnosed?

Sixth or abducens nerve palsy is diagnosed using a variety of procedures, including a neurological examination that includes several tests and questions to examine the nerves' operations. Using an ophthalmoscope, a doctor will perform an eye examination. With the aid of this tool, they may examine the eye, look for blood vessel issues, and determine whether the skull is experiencing increased pressure. Other testing consists of:

• Testing the blood for inflammation.

• Diabetes screening tests, such as an oral glucose tolerance examination.

• The brain may be imaged using magnetic resonance imaging (MRI) or computed tomography (CT). These examinations are performed to look for malignancies that might raise the pressure inside the head.

• A spinal tap or lumbar puncture can be performed to check for the presence of any infection or bleeding.

Even after undergoing all these different testing, some individuals' conditions may still not have a known etiology.

How to Manage Abducens Nerve Palsy?

In certain cases, there may be no need for therapy; the illness may go away on its own within two to four months. Individuals who do not recover on their own have a major underlying ailment.

• The sixth nerve palsy's cause will often determine the course of treatment. Once the source is remedied, the problem typically disappears. However, if the physician suspects that the sixth nerve may be irritated, they may advise corticosteroids.

• Prism eyewear can assist in realigning visuals; however, the eyes will be misaligned differently depending on which way the person is looking. This indicates that double vision cannot be eliminated by prism eyewear in all eye positions. The strength of the prism can be lowered as the sixth nerve palsy gets better. Additionally, the doctor might advise applying a patch to one eye to treat the double vision. The doctor may regularly watch the child if they need to wear an eye patch because children might otherwise develop a lazy eye.

• To determine whether the eye alignment improves after prism correction, one must wait around six months. The doctor might suggest strabismus surgery if it does not. In order to enhance eye alignment, this entails releasing or tightening the eye muscle.

• Injections of the Botulinum toxin (botox) may also be advised by doctors. The eye muscle may become temporarily less mobile as a result of this.

• If a virus or some unidentified cause is to blame for the disease, it will probably go away entirely. However, if trauma has been the cause of the sixth nerve palsy, one might never fully recover. Some individuals may experience long-term visual changes.

Conclusion:

The disease known as sixth nerve palsy has the potential to impair eye movement. Dysfunction of the abducens nerve is the root of the problem. This nerve is in charge of communicating with the muscle that turns the eye away from the nose. The etiology affects the prognosis. Vasculopathy cases typically have a full recovery. The prognosis for other sixth cranial nerve instances is guarded. Typically, patients are followed up for six months to look for spontaneous improvement.