Case Studies
Case 3: A case of progressive bulbar failure with double vision
A 65-year-old lady presents with a three month history of double vision, dysphagia, and fatigue. She is a smoker of 10 cigarettes a day and has a previous medical history of thyroid disease which was treated with radio active iodine and replacement thyroxine therapy. On examination she has restricted eye movements, bilateral ptosis and proximal limb weakness. Her forced vital capacity is 2.8 litres. Her routine blood tests are normal. Her chest X-ray shows lower lobe collapse and pneumonia.
Your Answer:
Correct answer: Given the extensive nature of the weakness involving the eye muscles, the eyelids, and the proximal muscles it is almost certainly in the neuromuscular junction although could possibly involve the nerve or muscle. The proximal limb weakness with involvement of the eyes would make myasthenia the most likely diagnosis.
Your Answer:
Correct answer: Patients with a history of thyroid disease can develop thyroid eye disease in which they get restriction of eye movements and often bulging of the eyes so called exophthalmos. Whilst she could have restricted eye movements as a consequence of a thyrotoxicosis and thyroid disease which could give her proximal weakness it would not give her the bilateral ptosis.
Your Answer:
Correct answer: Some patients can develop the remote effects of cancer as a cause of their neurological problems - so called paraneoplastic syndromes. However myasthenia gravis is normally associated with thymomas and thus the history of smoking is probably not relevant in this case. Whilst the chest X-ray may reveal an underlying cancer related to the smoking history it seems unlikely that this relates to her neurology as the Lambert Eaton myasthenic syndrome which is associated with lung cancer does not cause a restriction of eye movements. The more likely explanation of her chest X-ray signs is that she has had an aspiration pneumonia as a result of her palatal weakness and dysphagia.
Your Answer:
Correct answer: The diagnosis of myasthenia gravis can be achieved using blood tests looking for anti acetylcholine receptor and MUSK antibodies. Neurophysiology will reveal deficits at the neuromuscular junction and one can go on to perform a Tensilon test where one gives a short acting acetylcholinesterase inhibitor which enhances transmission at the neuromuscular junction and will transiently improve her neurology if she does have myasthenia gravis.
Your Answer:
Correct answer: Myasthenia gravis is a fatigable condition and often patients report worsening symptoms as the day goes on as the muscles get used. This might account for why she is better.
Your Answer:
Correct answer: The typical management of patients with myasthenia gravis is to improve transmission at the neuromuscular junction using oral acetylcholinesterase inhibitors. However the underlying condition is an immunological one and thus they require immunosuppressive therapy. Typically this is done orally with steroids along with other agents such as azathioprine and cyclosporin. It is always recommended that one starts steroids at low dose as paradoxically patients with myasthenia gravis can get much worse initially with high dose steroid medication, although the evidence that this is totally the case with myasthenia and steroid therapy is debatable.