An Approach To Bilateral Partial Ptosis (Part 1)

The usual stem of CNS station would be:
Examine this patient's cranial nerve.

It would be lucky if on inspection, there is obvious partial ptosis. The immediate next step would be thinking of the following 3 possibilities:

1. Is it bilateral Horner syndrome?
2. Is it bilateral 3rd CN palsy? (Rather unlikely to appear in real exam if it is due to central cause rather than peripheral)
3. Is it neuromuscular weakness?
   

Our Part 1 will concentrate on neuromuscular weakness
During CN examination, we have effectively ruled out Horner and CN III palsy. So, it is likely partial ptosis due to neuromuscular weakness. At this point, there should be at least 5 differential diagnosis in our mind:

1. Myasthenia Gravis/ LEMS
2. Gullain Barre Syndrome (Miller-Fisher)
3. Dystrophic Myotonia
4. Fasciomusculoscapular dystrophy
5. Oculopharyngeal Muscular Dystrophy
   

Brothers with Dystrophic Myotonia

Therefore, at the end of CN examination, we need to do something extra to get the most likely diagnosis. Do as follow:

1. Check for fatiguability (eye lids, upper limbs, nasal speech)
2. Check for thymectomy scar (may be hidden by patient's dress, and it would be fatal for missing the scar)
3. Check for diplopia on extreme gaze
4. Check for myotonia, by percussing the thenar muscle, and ask patient to grip hands
5. Check lower limb reflex for areflexia in GBS
6. Check for winged scapula
   

During presentation, we need to mention about the possibility of medical emergency, in this situation, we should mention:

1. "I would like to complete my examination by requesting a bed side spirometry to assess for respiratory mucle weakness" -for suspected Myasthenia/LEMS/GBS
2. "I would like to examine upper and lower limb for ascending weakness and aflexia" -for GBS
   

In view of the complexity of each disease, it would be rather less possible to discuss each in details. Maybe in next few sessions....

Related posts:
Ptosis for PACES 1
Ptosis for PACES 2