POST TRAUMATIC SYRINX AT C4/C5 ; CANT USE ARM--HELP

Hi,3 months ago I was unfortunately hit by a car while I was jogging. Spent a long time in the ICU.    I cant move or feel my left arm, yet i still have weak movement and hot/cold/sharp sensory in left hand.  Thought I had a brachial plexus trauma, so I got an MRI. (I am, err was, a 3rd year med student)  MRI shows syrinx at c4/c5 level.  I have a few questions:

1) If syrinx is decompressed and drained, will my motor control of arm return?
2) Anyone ever heard of anything like this?  ie, same but other arm/legs?  prognosis?
3) Also I have a left foot-drop, likely a common peroneal nerve lesion.  Can there be more than one syrinx in my spinal cord, and should i get a lumbar MRI for this?
4) Can a c4/c5 syrinx cause Horner Syndrome?  I have those symptoms now.  But Horner's generally involves some sort of T1 lesion.

Thank you very much in advance.