Does diplopia lasting 6 to 8 months confirm a microvascular ocular-motor palsy?

Persistent binocular diplopia in a 69-year-old exceeds the expected course of a correctly presumed isolated microvascular ocular-motor palsy and merits diagnostic reassessment rather than continued attribution to vascular ischemia.

Clinical course and diagnostic meaning

• Observational cohorts indicate that presumed microvascular CN III, IV, and VI palsies usually improve over 6–12 weeks. In a 46-patient cohort, 91.3% recovered, with mean recovery times of 7.5–10.5 weeks; another cohort reported a mean of 7.9 weeks.
• Recovery by about three months is typical but not absolute: some sixth-nerve palsies recover partially or later, occasionally up to one year. Thus, 6–8 months of diplopia does not exclude microvascular ischemia—but it does not establish it.
• In a prospective cohort of adults aged ≥50 with isolated ocular-motor palsies, 16.5% had nonmicrovascular causes, including patients with vascular risk factors.

Reassessment and safety

• If substantial recovery has not occurred by roughly 12 weeks, renewed examination and contrast-enhanced MRI of the brain and orbits are supported. At 6–8 months, this threshold has clearly been exceeded.
• Urgent assessment is warranted with progression, severe headache, anisocoria or pupil involvement (especially CN III), new focal neurologic signs, multiple cranial neuropathies, recurrent palsy, proptosis, or orbital swelling.

Alternative mechanisms and diagnoses

• Central, structural/compressive, and inflammatory disorders remain relevant; giant cell arteritis deserves consideration in an appropriate older patient.
• Fluctuating or fatigable diplopia, especially with variable ptosis, raises suspicion for ocular myasthenia; negative AChR antibodies or normal structural imaging do not reliably exclude it.
• A decompensated phoria is compatible with persistent symptoms when deviation is comitant, motility is full, and misalignment increases when fusion is disrupted.

Bottom line

• Persistent diplopia for 6–8 months should be treated as unresolved, not as diagnostic confirmation of microvascular palsy; targeted neuro-ophthalmic examination, imaging, and focused testing should guide the next steps.