How is sixth nerve palsy, potentially requiring lateral rectus (sixth nerve) plasty, managed in patients with Cerebral Venous Sinus Thrombosis (CVST)?

Management of Sixth Nerve Palsy in CVST Patients

Primary Treatment Priority: Address the Underlying CVST First

In patients with cerebral venous sinus thrombosis (CVST) presenting with sixth nerve palsy, the immediate priority is anticoagulation therapy to treat the CVST itself, as the sixth nerve palsy is typically a secondary manifestation of elevated intracranial pressure rather than a primary indication for surgical intervention. 1

Initial Management Algorithm

Step 1: Confirm CVST Diagnosis and Initiate Anticoagulation

• Initiate IV heparin or subcutaneous low molecular weight heparin (LMWH) immediately upon CVST confirmation, even in the presence of intracranial hemorrhage that occurred as a consequence of CVST 1
• The presence of sixth nerve palsy in CVST typically indicates elevated intracranial pressure, which is not a contraindication to anticoagulation 1
• Continue oral anticoagulation for 3-12 months or lifelong depending on the underlying etiology 1

Step 2: Monitor for Neurological Deterioration

• If neurological improvement or stability occurs, continue anticoagulation and observe the sixth nerve palsy 1
• If neurological deterioration with severe mass effect occurs, consider endovascular therapy or decompressive hemicraniectomy as lifesaving procedures 1

Management of the Sixth Nerve Palsy Component

Observation Period (First 6 Months)

• The sixth nerve palsy should be monitored and observed initially, as most cases secondary to elevated intracranial pressure from CVST will resolve spontaneously once the CVST is treated 1, 2
• Neuroimaging with MRI brain with and without contrast is mandatory to confirm the diagnosis and exclude other pathology 1, 3, 2
• Fundoscopy must be performed to look for papilledema as an indicator of elevated intracranial pressure 1, 3, 4

Symptomatic Management During Observation

• Occlusion therapy with a patch over one eye, Bangerter filter, or satin tape applied to glasses lens can reduce diplopia 1
• Temporary Fresnel prisms or ground-in base-out prisms can be used if the deviation remains stable and fusion can be achieved 1
• Botulinum toxin A injection into the ipsilateral medial rectus muscle (typically 3-5 units) may help reduce secondary contracture, decrease compensatory head position, and reduce the magnitude of final deviation 1, 5, 6

Surgical Intervention (Only After 6 Months of Persistent Deviation)

Indications for Surgery

• Strabismus surgical management is generally offered only when the deviation persists after 6 months from onset 1
• Surgery should be deferred until the CVST is fully treated and the patient is neurologically stable 1

Surgical Options Based on Residual Lateral Rectus Function

For Small Deviations with Residual Abducting Force Past Midline:

• Ipsilateral medial rectus recession combined with lateral rectus resection typically responds well 1, 7
• Alternative: contralateral medial rectus recession with or without posterior fixation, with or without ipsilateral lateral rectus resection 1

For Larger Deviations with No Abducting Force (Confirmed by Force Generation Testing):

• Vertical rectus transposition procedure is necessary, often combined with medial rectus weakening by recession or botulinum toxin injection 1
• Superior rectus transposition alone with simultaneous medial rectus recession has advantages including lower risk of anterior segment ischemia and fewer additional procedures needed 1, 8
• Full vertical rectus transposition (both superior and inferior rectus muscles) can be performed, but carries higher risk of anterior segment ischemia 1
• Partial tendon transfer or loop myopexy decreases the incidence of anterior segment ischemia since three extraocular muscles are not operated on simultaneously 1
• Staging the procedure (transpositions first, followed months later by medial rectus recession) also decreases the risk of anterior segment ischemia 1

Critical Pitfalls to Avoid

Do Not Rush to Surgical Intervention

• The sixth nerve palsy in CVST is typically secondary to elevated intracranial pressure and will often resolve with treatment of the underlying CVST 1, 2
• Premature surgery before 6 months may be unnecessary as spontaneous resolution is common 1, 2

Do Not Withhold Anticoagulation

• Intracranial hemorrhage that occurred as a consequence of CVST is not a contraindication for anticoagulation 1
• The sixth nerve palsy itself is not a contraindication to anticoagulation therapy 1

Counsel Patients Appropriately

• Even after successful strabismus surgery, patients should be advised that the goal is to eliminate diplopia in primary position and create a reasonable field of single binocular vision 1
• Patients will most likely continue to have diplopia in extreme lateral gaze due to the underlying neurological deficit 1

Monitoring and Follow-up

During Anticoagulation Phase:

• Monitor for neurological improvement or deterioration 1
• Assess blood pressure, as hypertension is a major risk factor for vasculopathic complications 3, 2
• Repeat neuroimaging if lack of improvement occurs within 4-6 weeks 1, 2

During Observation of Sixth Nerve Palsy:

• Follow-up is necessary to determine if the palsy spontaneously resolves 1, 2
• In the absence of resolution or improvement after 4-6 weeks, repeat MR imaging of the brain with and without contrast may be indicated 1, 2