Causes of Bilateral Ptosis (Most → Least Common)

1. Aponeurotic (Involutional) Ptosis — Most Common Overall

• Age-related dehiscence or disinsertion of the levator aponeurosis
• Typically bilateral but often asymmetric
• Also caused by: prolonged contact lens wear, post-ocular surgery, ocular trauma
• High eyelid crease with good levator function

2. Myasthenia Gravis — Most Common Acquired Neuromuscular Cause

• Autoimmune blockade of acetylcholine receptors at the neuromuscular junction
• Ptosis is fatigable — worsens throughout the day, improves after rest
• Bilateral in ~70% of cases at presentation
• May have Cogan's lid twitch, positive ice pack test
• Positive anti-AChR or anti-MuSK antibodies

3. Congenital (Simple Congenital) Ptosis — Most Common Cause in Children

• Dysgenesis/fibrosis of the levator muscle
• Usually unilateral but ~25–30% are bilateral
• Poor levator function, low or absent eyelid crease
• Risk of amblyopia in severe cases

4. Myogenic Ptosis — Mitochondrial Myopathy / CPEO

• Chronic Progressive External Ophthalmoplegia (CPEO): caused by mitochondrial DNA mutations
  • Symmetric, slowly progressive bilateral ptosis + limitation of eye movements
  • Diplopia is a late feature because all movements reduce equally
• Kearns-Sayre Syndrome (CPEO variant): adds retinal pigmentary changes + cardiac conduction defects
• Peripheral muscle biopsy shows ragged-red fibers

5. Blepharophimosis-Ptosis-Epicanthus Inversus Syndrome (BPES)

• Autosomal dominant; mutation in FOXL2 gene
• Always bilateral, severe ptosis with poor levator function
• Associated: telecanthus, epicanthus inversus, blepharophimosis
• Type I: associated with premature ovarian insufficiency

6. Neurogenic Ptosis — Bilateral CN III Palsy

• Bilateral third nerve palsies are uncommon but can occur with:
  • Midbrain lesions (infarct, hemorrhage, tumor)
  • Wernicke's encephalopathy
  • Meningitis/meningoencephalitis
  • Neurosarcoidosis

7. Horner Syndrome (Bilateral)

• Bilateral Horner's is rare; each side requires its own lesion
• Partial ptosis (1–2 mm) with miosis, anhidrosis
• Causes: bilateral carotid dissection, syringomyelia, bilateral Pancoast tumors

8. Myotonic Dystrophy (Steinert Disease)

• Autosomal dominant CTG repeat expansion in DMPK gene
• Bilateral ptosis + characteristic facial features (hatchet face, frontal baldness)
• Associated with cataracts, cardiac arrhythmias, myotonia, testicular atrophy

9. Oculopharyngeal Muscular Dystrophy (OPMD)

• Autosomal dominant; GCG repeat expansion in PABPN1 gene
• Late-onset (5th–6th decade) bilateral ptosis + progressive dysphagia
• More common in French-Canadians and Bukharan Jews

10. Drug-Induced Ptosis

• Botulinum toxin (iatrogenic spread)
• Opioids, barbiturates, CNS depressants
• Guanethidine (sympathetic blockade)

11. Mechanical Ptosis

• Bilateral lid edema (angioedema, nephrotic syndrome, hypothyroidism)
• Infiltrative lid lesions (amyloidosis, neurofibromatosis)
• Severe blepharochalasis

12. Marcus Gunn Jaw-Winking (Bilateral — Very Rare)

• Aberrant synkinesis between CN V (pterygoid branch) and levator muscle
• Bilateral cases are exceptionally rare

Summary Table