What are the next steps for a patient with limited medial, superior, and inferior movement of the left eye?

Third Nerve Palsy: Immediate Neuroimaging and Systematic Workup Required

A left eye that cannot move medially, superiorly, and inferiorly indicates a left third nerve palsy, which requires urgent neuroimaging with MRA or CTA to rule out life-threatening aneurysm, followed by systematic evaluation for other causes including tumor, trauma, and infection. 1

Immediate Diagnostic Workup

Neuroimaging (First Priority)

• MRA or CTA is mandatory to evaluate for aneurysm, which is a potentially fatal cause of third nerve palsy 1
• If high suspicion for aneurysm persists despite normal MRA/CTA, proceed to catheter angiography after brain MRI with and without contrast with specific attention to the third nerve 1
• Brain MRI with and without contrast should be performed to evaluate for tumors (meningioma, schwannoma, metastatic lesions), demyelinating disease, and leptomeningeal disorders 1

Additional Diagnostic Testing

• If neuroimaging is normal, obtain serologic testing for infectious diseases including syphilis and Lyme disease 1
• Consider lumbar puncture with glucose, protein, cell count, cytology, and culture if imaging is unrevealing 1
• Evaluate for other causes including trauma, subarachnoid hemorrhage, viral illnesses (including COVID-19), and demyelinating disease 1

Clinical Assessment Details

Key Examination Findings to Document

• Determine if ptosis is complete (many patients with complete ptosis are not troubled by diplopia until the lid is elevated) 1
• Assess pupillary involvement (pupil-involving third nerve palsy increases concern for aneurysm)
• Perform forced duction testing to distinguish between paretic muscles (which may be responsive to resection) versus completely paretic muscles (where resection will not be effective) 1
• Evaluate Bell's response, as extremely impaired response increases risk of exposure keratopathy if ptosis surgery is performed 1

Management of Diplopia

Observation Phase

• Many patients with complete ptosis do not experience diplopia until the lid is elevated and may not require immediate diplopia management 1

Non-Surgical Management

• Botulinum toxin chemodenervation of antagonist extraocular muscles or the levator can temporize while waiting for recovery 1
• Occlusion (eye patch, occlusive contact lens, or MIN lens) for times when diplopia is most bothersome 1
• Prisms (press-on or ground-in) may be helpful following partial recovery, though the incomitant nature of the deficit results in diplopia with minimal shift of gaze from primary position 1
• For accommodation deficit causing reading difficulty, prescribe uniocular progressive lenses or bifocals with the bifocal segment placed high in the frame when infraduction is compromised 1

Surgical Management Considerations

Timing and Complexity

• Surgical management is complicated, and success depends on the number of muscles involved and the degree of involvement 1
• Surgery should be deferred until the cause is addressed and sufficient time has passed to assess for spontaneous recovery

Partial Third Nerve Palsy (Ability to Adduct Past Midline)

• Lateral rectus recession combined with medial rectus resection (with or without adjustment), with or without vertical transposition typically responds well 1
• Ipsilateral superior oblique weakening or weakening of its anterior intorting fibers may reduce hypotropia and intorsion from inferior oblique weakness 1
• Recession with or without posterior fixation of contralateral eye muscles can expand the field of binocular single vision 1

Complete Third Nerve Palsy

• Requires some form of lateral rectus weakening procedure: supramaximal recession, extirpation, or suturing to the periosteum of the lateral orbital rim 1
• May combine with nasal transposition of superior oblique muscle toward medial rectus insertion or maximal medial rectus resection for tethering effect 1
• Nasal transposition of split lateral rectus muscle to medial rectus insertion has shown notable success and is safest when placing split ends within 4mm of the medial rectus to reduce risk of choroidal effusion 1
• This procedure is easiest when prior lateral rectus recession has not been performed and best avoided if aberrant regeneration is present 1
• Traction sutures or botulinum toxin augmented supramaximal lateral rectus recession with supramaximal medial rectus resection may prevent recurrent exotropia 1

Important Surgical Caveats

• Ptosis surgery should be approached cautiously if Bell's response is extremely impaired due to increased risk of exposure keratopathy 1
• Post-operative prism correction may be required to allow fusion in primary or reading position 1
• Patients often have significant diplopia outside the region of binocular fusion and may benefit from part-time occlusion or fogging contact lens for high-risk activities like driving 1
• Patients with concomitant brain or brainstem injury may have central fusion disruption and be unable to fuse despite satisfactory alignment 1

Specialist Referral

• Diagnosis and management requires expertise in neuro-ophthalmology and adult strabismus 1
• Orthoptists working under ophthalmologist supervision can assist in examination, diagnosis, and non-surgical management 1