Sixth Nerve Palsy
Sudden onset suggests a vascular etiology, while slowly progressive onset suggests a compressive etiology. Subacute onset suggests a demyelinating process - EyeWiki
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HWN Suggests
Approach to the Patient with Diplopia in the Emergency Department
Based on the current literature, unenhanced plain CT of the head or orbits is largely not useful in the work-up of patients with isolated diplopia in an emergency setting, with the exception of trauma patients. MRI is the imaging modality of choice in the assessment of ocular motor nerve palsies, and due to limited resources in the ED setting, patients with isolated fourth and sixth nerve palsies with the absence of other associated signs should be referred to Neurology or Ophthalmology for further assessment.
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The Six Syndromes of the Sixth Cranial Nerve
The sixth cranial nerve runs a long course from the brainstem to the lateral rectus muscle. Based on the location of an abnormality, other neurologic structures may be involved with the pathology related to this nerve. Sixth nerve palsy is frequently due to a benign process with full recovery within weeks, yet caution is warranted as it may portend a serious neurologic process.
Isolated binocular diplopia – is this cranial nerve 3 or not?
Common Causes You Don’t Want to Miss - In elderly, consider microangiopathic disease. Cerebral Venous Thrombosis. Idiopathic Intracranial hypertension. Bilateral palsy = bad: consider intracranial or subdural bleeds, neoplasm at the clivus, brainstem infarction.
Articles of Interest
Isolated Bilateral Abducens Palsy as a Presenting Feature of Multi-Infarct State: A Case Report
Isolated bilateral sixth nerve palsy is an uncommon presentation in the emergency department. The common causes are acquired, located along its course (between its nuclei in pons to lateral rectus muscle in orbit). Due to its long extracerebral intracranial course, the abducens nerve is vulnerable to injury in various disorders.
Seeing double: toil and trouble?
The abducens nerve, or 6th cranial nerve, innervates the lateral rectus muscle. In a 6th nerve plasy, patients will complain of a horizontal diplopia. There is often inward deviation of the affected eye (esotropia) and symptoms are made worse with lateral gaze to the affected side. This nerve palsy is often idiopathic in etiology, with diabetes mellitus as a risk factor. Be careful to assess for bilateral 6th nerve palsy. The abducens nerve has a long, isolated course intracranially; tumors can affect the bilateral abducens nerve before other areas of the brain are affected.
Resources
EyeWiki
The pattern of onset and associated symptoms can be very important in determining the etiology of an abducens nerve palsy. Sudden onset suggests a vascular etiology, while slowly progressive onset suggests a compressive etiology. Subacute onset suggests a demyelinating process.
American Association for Pediatric Ophthalmology & Strabismus
The most common causes of sixth cranial nerve palsy are stroke, trauma, viral illness, brain tumor, inflammation, infection, migraine headache and elevated pressure inside the brain. The condition can be present at birth; however, the most common cause in children is trauma. In older persons, a small stroke is the most common cause. Sometimes the cause of the palsy is never determined despite extensive investigation.
StatPearls
The sixth cranial nerve, the abducens nerve, is responsible for ipsilateral eye abduction. Dysfunction of the abducens nerve can occur at any point of its transit from the pons to the lateral rectus muscle, resulting in sixth nerve palsy.
WikiEM
Increased intracranial pressure (ICP): Because of its position and intracranial length, increased ICP from any cause can lead to injury and dysfunction.
