What is the cause and recommended workup for ptosis that worsens with exposure to cold?

Ptosis That Worsens with Cold: Myasthenia Gravis Until Proven Otherwise

Ptosis that paradoxically improves (not worsens) with cold exposure is pathognomonic for myasthenia gravis, and this patient requires urgent workup to prevent life-threatening progression to generalized disease with respiratory failure. 1

Critical Distinction: Cold Improves, Not Worsens, Myasthenic Ptosis

The question asks about ptosis worsening with cold, but the most clinically significant cold-related ptosis phenomenon is the opposite: ptosis that improves with cold application (the "ice pack test"). This is highly specific for myasthenia gravis and represents a medical urgency. 1

The Ice Pack Test

• Apply ice pack over closed eyes for 2 minutes for ptosis evaluation
• A reduction of ptosis by approximately 2mm or more is highly specific for myasthenia gravis 1
• This phenomenon relates to diminished anticholinesterase activity at cooler temperatures 1
• The ice test improved ptosis by 2.3mm more than heat testing in confirmed myasthenia patients 2

Why This Matters: Mortality Risk

50-80% of patients presenting with isolated ocular myasthenia (ptosis and diplopia) will progress to generalized myasthenia gravis within a few years, which can cause life-threatening respiratory failure. 1 Early recognition and treatment prevents this progression.

Diagnostic Workup Algorithm

Clinical Examination Features to Identify:

• Variable ptosis that worsens with fatigue (prolonged upgaze)
• Cogan lid-twitch sign: brief eyelid overshoot on refixation from downgaze
• Contralateral ptosis worsening when manually elevating the more affected eyelid
• Slow ocular saccades
• Variable strabismus that changes during prolonged examination
• Pupils typically normal (pupillary involvement suggests 3rd nerve palsy instead) 1

Confirmatory Testing:

1. Ice pack test (2 minutes): >2mm improvement is highly specific 1

2. Rest test (without ice): Can also demonstrate improvement 1

3. Serologic testing:

   • Anti-acetylcholine receptor antibodies (AChR-Ab): Positive in 80% of generalized MG, 50% of ocular MG
   • Anti-MuSK antibodies: Positive in one-third of seronegative patients
   • LRP4 antibodies: Associated with both generalized and ocular MG 1

4. Electrophysiology:

   • Single-fiber electromyography: Gold standard, >90% sensitive for ocular myasthenia 1
   • Repetitive nerve stimulation: Only 33% sensitive for ocular myasthenia 1

5. Edrophonium (Tensilon) test: 95% sensitive for generalized MG, 86% for ocular MG, but requires monitored setting with atropine available due to muscarinic side effects (bradycardia, bronchospasm, hypotension) 1

Management to Prevent Mortality

First-Line Treatment:

• Pyridostigmine bromide 2-4 times daily, though only 50% of strabismus-associated myasthenia responds 1

More Effective Treatment:

• Corticosteroids: 66-85% positive response rate 1
• Immunosuppressive therapy: Azathioprine is effective; efgartigimod alfa-fcab recently FDA-approved for anti-AChR positive patients 1
• Thymectomy: Always indicated with thymoma; may substantially reduce symptoms in certain subpopulations 1

Common Pitfall

Do not confuse the direction of temperature effect: The classic myasthenic finding is ptosis that improves with cold (ice pack test positive), not worsens. If ptosis truly worsens with cold exposure, consider alternative diagnoses such as:

• Horner syndrome (though temperature typically not a factor)
• Mechanical ptosis
• Other neurogenic or myogenic causes 3, 4

The heat test actually worsens myasthenic ptosis by 1.1mm compared to rest, while ice improves it by 1.3mm compared to rest. 2