Hi Diana
I don't want to alarm you ... but get your son into A&E, explain that your son is having difficulties with his bladder and bowles .... the reason I say this is... I went thru this, I had a 'bulging' lower disc in my spine, and where it was hindering my toliet functions, I found that this numbness of bowles and bladder became painful, I couldn't squeeze my anal passage, as it had no strength, so they operated straight away to remove the disc.....
they had said that keeping my 'toilet' areas subdued for a long length of time, would eventually cause massive problems down there, and eventually would be reliant on 'cathata bags' and like, for the rest of my life and would not be able to go to the toilet normally.
Insist on a MRI scan, as there may be something when he broke his back that is hindering this function.
It does sound like he has nerve damage, causing the non-sensation in his toes, etc, but please get him immediately to a Hospital.
I can't understand why the neurologist isn't being insistant on treatment.
To get the problem investigated and sorted prior to any further damage should be they're priority.
You both take care, Speak soon Diana
Ginger