From the Guidelines
Sixth nerve palsy should be thoroughly investigated, especially in younger patients or those without vascular risk factors, as it can sometimes indicate serious neurological conditions requiring urgent intervention. This condition is characterized by weakness or paralysis of the lateral rectus muscle, resulting in an inward deviation of the affected eye (esotropia) and inability to abduct the eye (look outward) 1. Patients typically present with horizontal diplopia (double vision) that worsens when looking toward the affected side and improves when looking in the opposite direction. Common causes include microvascular ischemia (especially in patients with diabetes or hypertension), trauma, increased intracranial pressure, tumors, aneurysms, multiple sclerosis, or infections 1.
Diagnosis and Treatment
Diagnosis involves a complete neurological and ophthalmological examination, often supplemented by imaging studies like MRI or CT scans 1. Treatment depends on the underlying cause but may include:
- Addressing the primary condition
- Using prism glasses to correct diplopia
- Patching one eye temporarily for symptom relief
- Neuroimaging should be considered in all young patients or in any patient manifesting other cranial neuropathies, other neurologic change or elevated IOP, or signs of elevated intracranial pressure, or if there is no compelling vasculopathic risk factor 1 In cases of microvascular origin, spontaneous recovery often occurs within 3-6 months 1. Persistent cases may require strabismus surgery.
Key Considerations
Key considerations in the management of sixth nerve palsy include:
- A detailed treatment directed to the primary cause
- Symptomatic intervention to reduce diplopia and torticollis and to restore binocular vision 1
- Evaluation for possible giant cell arteritis in patients with scalp tenderness, jaw claudication, or pain 1
- Thorough investigation, especially in younger patients or those without vascular risk factors, as sixth nerve palsy can sometimes indicate serious neurological conditions requiring urgent intervention 1
From the Research
Causes and Prognosis of Sixth Nerve Palsy
- The most common cause of sixth nerve palsy in patients over 50 years old is vascular disease 2.
- In young adults (20-50 years old), the most common cause is a central nervous system (CNS) mass lesion, while isolated sixth nerve palsy is most commonly caused by multiple sclerosis 3.
- Sixth nerve palsy can also be caused by unintentional dural puncture, leading to bilateral sixth nerve palsy 4.
Diagnosis and Treatment
- A lesion anywhere along the course of the sixth cranial nerve can cause paresis or palsy, resulting in esotropia and an ipsilateral abduction deficiency 2.
- Diagnosis involves ruling out trauma and non-neurological problems, and classifying cases into neurologically isolated or non-neurologically isolated cases 2.
- Treatment options depend on the function of the paretic muscle, the field of greatest symptoms, and the likelihood of inducing diplopia in additional fields by a given procedure 5.
- Surgical intervention may be necessary if the condition does not resolve within 6-10 months, with options including vertical rectus muscle transposition and modified Nishida procedure 6.
Management and Outcome
- A sixth nerve palsy of vascular or undetermined causes typically resolves within 6 to 8 weeks, but if resolution does not occur within 2 to 3 months, imaging studies are indicated 2.
- Patients with a CNS mass lesion responsible for their palsy have a higher rate of nonresolution requiring strabismus surgery 3.
- Epidural blood patch (EBP) may be a reasonable treatment for ocular nerve palsy, relieving postdural puncture headache and producing partial improvement of diplopia 4.
- A modified Nishida procedure with adjunct botulinum toxin A (BTA) injection can be an effective treatment for chronic complete sixth nerve palsy, resulting in improved ocular alignment and stability 6.