A 20 year old woman has one month history of double vision, a two weeks history of slurred speech and difficulty chewing and swallowing food, and a one week history of weakness in her neck. Her symptoms are most pronounced at night. Ptosis in both eyes is exacerbated with sustained upward gaze. Eye movements are restricted in all directions. She is unable to hold her arms in place for more than 10 seconds when they are abducted at the shoulders. Which of the following is the most likely location of a lesion?
A- Upper motor neurones
B- Lower motor neurones
C- Neuromuscular junction
D- Myocytes in skeletal muscles
E- Myelin in peripheral nerves
A- Upper motor neurones
B- Lower motor neurones
C- Neuromuscular junction
D- Myocytes in skeletal muscles
E- Myelin in peripheral nerves