Causes of Ptosis
Ptosis (drooping of the upper eyelid) can be caused by numerous conditions including myasthenia gravis, third nerve palsy, Horner syndrome, aponeurotic weakness, and mechanical factors. 1
Neurogenic Causes
Myasthenia Gravis
- Variable ptosis that worsens with fatigue
- Often accompanied by variable strabismus and diplopia
- Characteristic findings:
- Cogan lid-twitch sign (twitching of upper eyelid when returning gaze from downward to primary position)
- Improvement with rest or ice pack test (application for 2 minutes)
- Worsening of contralateral eye ptosis upon manual elevation of the affected eyelid
- Slow ocular saccades
- 50% of patients present with ocular symptoms only, and 50-80% of these develop generalized myasthenia within a few years 1
- Associated with autoimmune thyroid disease and thymoma 1
- Diagnostic tests:
- Anti-acetylcholine receptor antibodies (positive in ~50% of ocular myasthenia)
- Anti-MuSK antibodies (in some seronegative cases)
- Single-fiber electromyography (positive in >90% of cases)
- Tensilon (edrophonium) test (86% sensitive in ocular myasthenia)
Third Nerve Palsy
- Often accompanied by:
- Extraocular muscle weakness (especially medial rectus, superior rectus, inferior rectus, inferior oblique)
- Pupillary involvement (in compressive lesions)
- Causes include:
- Microvascular disease (diabetes, hypertension) - typically pupil-sparing
- Aneurysm (especially posterior communicating artery) - typically pupil-involving
- Tumors (meningioma, schwannoma, metastatic lesions)
- Trauma
- Viral illnesses including COVID-19
- Demyelinating disease 1
Horner Syndrome
- Ptosis with associated:
- Miosis (pupillary constriction)
- Anhidrosis (decreased sweating)
- May be caused by carotid dissection (medical emergency) 2
Myogenic Causes
- Congenital ptosis (present at birth)
- Muscular dystrophies
- Chronic progressive external ophthalmoplegia
Aponeurotic Causes
- Age-related weakening of the levator aponeurosis
- Most common cause of acquired ptosis in adults
- Can occur after eye surgery, trauma, or chronic inflammation
Mechanical Causes
- Excess skin or fat of the upper eyelid (dermatochalasis)
- Eyelid tumors or masses
- Eyelid edema or inflammation
- Scarring of the eyelid
Evaluation Algorithm
Assess for emergency causes:
- Pupillary involvement (mydriasis suggests aneurysm)
- Miosis (suggests Horner syndrome, possible carotid dissection)
- Daily variation (suggests myasthenia gravis)
Determine onset:
- Present at birth (congenital)
- Acquired (develop later in life)
Evaluate severity:
- Minimal (1-2 mm)
- Moderate (3-4 mm)
- Severe (>4 mm, covering pupil)
Assess levator function:
- Good (>8 mm)
- Fair (5-7 mm)
- Poor (<4 mm)
Look for associated symptoms:
- Diplopia (suggests myasthenia gravis or cranial nerve palsy)
- Strabismus
- Pupillary abnormalities
- Fatigue-related worsening (suggests myasthenia)
Perform specific tests:
- Ice pack test (for myasthenia gravis)
- Rest test
- Cogan lid-twitch sign
- Phenylephrine test
Clinical Pearls and Pitfalls
- Never dismiss persistent ptosis as merely stress-related without proper evaluation, as it may be the first sign of a life-threatening condition 3
- Pupil-involving third nerve palsy requires urgent neuroimaging to rule out aneurysm 1
- Partial third nerve palsy with incomplete ptosis may still be due to a compressive lesion, even if the pupil is spared 1
- Ocular myasthenia can precede generalized myasthenia in 50-80% of cases, which can lead to life-threatening respiratory failure 1
- The amount of ptosis does not correlate with its etiology - even minimal ptosis can be caused by serious conditions 2
- In children, untreated congenital ptosis can lead to amblyopia and permanent vision loss 4
By systematically evaluating ptosis with attention to associated symptoms and specific clinical tests, clinicians can determine the underlying cause and implement appropriate management to prevent morbidity and mortality.