Sixth nerve palsy

Sixth nerve palsy
Synonyms	Lateral rectus palsy, VIth cranial nerve palsy, abducens nerve palsy
Pronounce
Field	Neurology, Ophthalmology
Symptoms	Diplopia (double vision), inability to move the eye outward (abduction), eye deviation inward (esotropia), head tilt to compensate
Complications	Persistent double vision, impaired vision, compensatory head posture
Onset	Sudden or gradual, depending on cause
Duration	Variable (weeks to permanent)
Types	Congenital, acquired (isolated or part of a syndrome)
Causes	Microvascular ischemia (e.g., due to diabetes or hypertension), trauma, increased intracranial pressure, tumors, infections, multiple sclerosis, meningitis
Risks	Older age, diabetes, hypertension, head trauma, neoplastic diseases
Diagnosis	Neurological examination, MRI, CT scan, lumbar puncture (if infection or pressure is suspected)
Differential diagnosis	Myasthenia gravis, thyroid eye disease, orbital trauma, internuclear ophthalmoplegia, third nerve palsy
Prevention	Control of vascular risk factors; protective measures during head trauma
Treatment	Depends on cause; may include observation, prism glasses, eye patching, botulinum toxin injections, or surgery
Medication	Based on underlying etiology (e.g., steroids for inflammation, antivirals for infections)
Prognosis	Good for microvascular causes (usually resolves in 2–3 months); varies with other causes
Frequency	Rare in general population; more common in individuals with vascular risk factors
Deaths	Not directly, but underlying cause may be serious

Limitation of abduction of the right eye. This individual tries to look to his right, but the right eye fails to turn to the side

Sixth nerve palsy, also known as abducens nerve palsy, is a neurological disorder that affects the sixth cranial nerve, known as the abducens nerve. This nerve is responsible for controlling the lateral rectus muscle, which is responsible for moving the eye outward, away from the nose. When this nerve is impaired, it results in a condition where the affected eye cannot move outward properly, leading to strabismus and diplopia (double vision).

Signs and Symptoms

The primary symptom of sixth nerve palsy is the inability to move the affected eye outward. This results in:

• Diplopia: Double vision, particularly when looking in the direction of the affected eye.
• Strabismus: Misalignment of the eyes, where the affected eye may turn inward.
• Head turn: Patients may turn their head to compensate for the misalignment and reduce double vision.

Causes

Sixth nerve palsy can be caused by a variety of factors, including:

• Trauma: Injury to the head or orbit can damage the abducens nerve.
• Vascular disorders: Conditions such as diabetes mellitus or hypertension can lead to microvascular ischemia affecting the nerve.
• Infections: Infections such as meningitis can cause inflammation and damage to the nerve.
• Tumors: Masses in the brain or near the nerve can compress it, leading to dysfunction.
• Idiopathic: In some cases, the cause of sixth nerve palsy is unknown.

Diagnosis

Diagnosis of sixth nerve palsy involves a thorough clinical examination and may include:

• Ophthalmologic examination: To assess eye movement and alignment.
• Neuroimaging: MRI or CT scan to identify any structural causes such as tumors or trauma.
• Blood tests: To check for underlying conditions like diabetes or infections.

Treatment

Treatment of sixth nerve palsy depends on the underlying cause:

• Observation: In cases where the cause is idiopathic or due to microvascular ischemia, the condition may resolve spontaneously over time.
• Prism glasses: To help alleviate double vision.
• Botulinum toxin injections: To temporarily paralyze the opposing muscle and improve alignment.
• Surgery: In cases where the palsy does not resolve, surgical intervention may be necessary to correct the eye alignment.

Prognosis

The prognosis for sixth nerve palsy varies depending on the cause. In cases related to microvascular issues, recovery is often complete within a few months. However, if the palsy is due to a tumor or significant trauma, the outcome may depend on the success of treating the underlying condition.

Related Pages

• Cranial nerves
• Oculomotor nerve
• Trochlear nerve
• Strabismus
• Diplopia