Thanks Aaron for a great case! This is a person with a history of dementia and a thyroid nodule with subacute progressive dysarthria and weakness, found on exam to have bulbar symptoms and fatigability who was ultimately diagnosed with myasthenia gravis.
- ) This was a great case to review the differential for weakness
- ) When a patient has bulbar symptoms ("3 D's" diplopia, dysphagia, dysarthria), consider myasthenia gravis, ALS and myositis as part of your differential
- ) From our MKSAP question: if someone who has a diagnosis of Bell palsy does not improve over a few months, consider whether their condition can be caused by other etiologies that result in peripheral neuropathy
Want to learn more?
Differential of myasthenia gravis
Some other similar conditions to consider that can present like a new diagnosis of myasthenia gravis include:
- Basilar artery stroke – also can present with subacute progressive bulbar symptoms and weakness but usually consider in a patient who also has other stroke symptoms such as additional cranial nerve deficits, dizziness and ataxia, hemiparesis and sensory deficits
- Amyotrophic lateral sclerosis (ALS) – also can present with bulbar deficits and respiratory weakness but generally is chronic progressive and has upper motor neuron signs as well with tongue fasciculations
- Cavernous sinus syndrome – can also present with ocular symptoms but generally has V sensory and Horner syndrome deficits
- Inflammatory myositis – can also present with weakness and bulbar symptoms and rarely respiratory weakness but generally proximal muscle (except IBM) and CK elevation
- Lambert-Eaton syndrome – also a disorder of the NMJ but usually see improved strength rather than fatigability and usually does not involve respiratory muscle weakness
- Botulism toxicity – also a disorder of the NMJ but also with descending paralysis and autonomic dysfunction
- Recall that features that point towards myasthenia gravis include fluctuating weakness and fatigability
- Also thanks Aaron for this great JAMA evidence based clinical exam reference on likelihood ratios for physical exam findings associated with myasthenia gravis
Here is a great oft-cited review article that walks through pathophysiology, diagnosis and management. And here isa nice chart that walks through management of myasthenia gravis and myasthenic crisis.
Aaron also reviewed the Cochrane guidelines meta analysis of the benefit of IVIG in these paients.