Muscle cramping and tingling in left leg and foot

My husband is 66 years old and was diagnosed with ocular myasthenia 1 year ago.  His medication has been altered many times but most recently he had been on a regimen of Prednisone and Mestinon.  Dosage: Prednisone 15mg. alternating with 10mg. (every other day) and Mestinon 60 mg. daily and he was asymptomatic.  Three weeks ago his physician altered his dosage to the following: Prednisone 15mg. alternating with 5mg. (every other day) and Mestinon 60 mg. daily. This is a decrease of 5 mg. of Prednisone every other day.  My husband takes his medication every morning. Recently, he is experiencing painful muscle cramping in his left leg (from calf to hip) and tingling in his left foot which occurs in the morning within 5 minutes after getting up and continues for 1 1/2 hours. This phenomenon occured once before when he was taking 270 mg. of Mestinon daily (this was prior to the introduction to Prednisone).  He notices that if he sleeps in bed he will experience the pain in the morning but if he sleeps on the couch and stays on his left side he does not experience the pain.  He wonders also if head elevation has an impact as his head is increasingly elevated (over bed position) when he sleeps on the couch.  Could this problem be caused by the change in medication, positions in sleeping or some other underlying condition?

[CCF neuro MD MM]

This problem is unlikely to vbe related to the underlying myasthenia problem, or to the medication regime. It may possibly be related to position, but is more likely to be related to position of the lower back than to head position.
Positional changes alone should not cause this problem, so I suspect that there may be a separate problem in the lumbar spine area, this si most likely to be related to a disc problem. The next step would be to have this ara investigated either by neuroimaging of the lumbar spine and / or EMG to see if a sepecific nerve root is implicated.
Further investigations would need to be guided by a neurological examination which should be your next step.

[Van]

Could you please see my comment below in regards to a reply on "strange symptoms". I am so worried and would appreciate any info you could give me. Thanks!