A 36 year old male presents with a
history of pain and weakness of his right shoulder. 10 days prior to the onset
of symptoms he had an upper respiratory tract infection but apart from that
there was no significant past medical history. He was not on any medication
On examination you note wasting of his
right supraspinatus and infraspinatus muscles. There is weakness of initiation
of abduction and external rotation of his right shoulder. The rest of the
neurological examination of the upper limb is unremarkable. Reflexes are
normal and there is no sensory loss.
In this patient which of the following
investigations is most likely to reveal the diagnosis?
Creatinine phosphokinase levels
IgG acetyl choline receptor antibody
MRI spinal cord