What causes mydriasis and ptosis?

Causes of Mydriasis and Ptosis

The most common causes of concurrent mydriasis and ptosis are third cranial nerve palsy due to microvascular disease, aneurysmal compression (particularly of the posterior communicating artery), Miller Fisher syndrome, and iatrogenic causes such as botulinum toxin injection. 1

Third Nerve Palsy - Primary Causes

Aneurysmal Compression

• Posterior communicating artery aneurysms typically present with pupil-involving third nerve palsy (mydriasis) accompanied by ptosis 1, 2
• Often associated with headache and may present with incomplete oculomotor nerve deficits 3
• In a study of 12 patients with unruptured intracranial aneurysms, six patients presented with both ptosis and mydriasis 3
• Requires urgent vascular imaging as this is a potentially life-threatening condition 1

Microvascular Disease

• Associated with diabetes, hypertension, and hyperlipidemia 1
• Classically presents with pupil-sparing third nerve palsy, but can have mild pupillary involvement
• Typically presents with complete ptosis and extraocular muscle dysfunction 1
• Generally has better prognosis than aneurysmal causes, with recovery expected within 3 months 1

Neurovascular Compression

• The oculomotor nerve can be compressed between a tortuous posterior communicating artery and the posterior clinoid process 4
• This compression can cause isolated mydriasis without ptosis or diplopia in some cases 4
• High-resolution MRI with FIESTA sequences can reveal this type of neurovascular conflict 4

Immune-Mediated Causes

Miller Fisher Syndrome

• Characterized by a triad of ophthalmoplegia, ataxia, and areflexia 5
• Can present with mydriasis, ptosis, and ophthalmoplegia 5
• Associated with GQ1b-antibodies directed against gangliosides in peripheral nerve tissue 5
• May be triggered by infections or vaccinations 5
• Generally has good prognosis with spontaneous recovery in most cases 5

Iatrogenic Causes

Botulinum Toxin Injection

• Cosmetic botulinum toxin injections can cause unintended spread to nearby structures 6
• Can result in transient mydriasis and ptosis when the toxin affects the pupillary sphincter and levator palpebrae muscles 6
• Symptoms typically resolve within weeks to months 6

Diagnostic Approach

1. Comprehensive eye examination focusing on:

   • Pupillary responses
   • Degree of ptosis
   • Extraocular muscle function
   • Associated symptoms (headache, diplopia, ataxia) 1

2. Neuroimaging:

   • MRI with gadolinium and MRA or CTA is the preferred initial imaging 1
   • High-resolution T2-weighted images of cranial nerves
   • Vascular studies are mandatory if aneurysmal compression is suspected 1
   • CT may miss up to one-third of aneurysms 3

3. Laboratory testing:

   • Consider GQ1b antibody testing if Miller Fisher syndrome is suspected 5
   • Evaluate for diabetes, hypertension, and hyperlipidemia in cases of suspected microvascular etiology 1

Management Considerations

• Aneurysmal causes: Require urgent surgical intervention 1, 2
• Microvascular causes: Control of vascular risk factors; expect recovery within 3 months 1
• Miller Fisher syndrome: May require immunoglobulins in some cases; many recover spontaneously 5
• Iatrogenic causes: Topical apraclonidine 0.5% can help reduce ptosis temporarily; most cases resolve with time 6

Clinical Pearls and Pitfalls

• Pitfall: Assuming all third nerve palsies with pupillary involvement are due to aneurysms. While this is common, microvascular causes can occasionally affect the pupil as well 1
• Pitfall: Missing incomplete presentations. Not all patients will have the complete triad of mydriasis, ptosis, and ophthalmoplegia 3, 4
• Pearl: Recent onset of mydriasis and ptosis with headache strongly suggests an aneurysm until proven otherwise 3, 2
• Pearl: If symptoms persist beyond 3 months in presumed microvascular causes, reconsideration of diagnosis is warranted 1