Does anyone know what Prolongation within the Subarachnoid and extra axial spaces anteriorly mean?

I had this MRI done because of my Optic Neuritis in right eye getting worse with another blind spot in lower left quad and more periphrial problems. Depth perception at times driving is difficult. Seeing (no pun intended, lol) if this means this might be the cause of my Optic Neuritis. I have been dealing with this for a year with other symptoms mimicing MS. Also I have nerve jabs and numbness on my upper lip and the top of head. That is why I had the MRI done. He said he wanted to see if there were lesions on the brain

Next stop Neuro says is the Lumbar Puncture. All my blood work came out ok for other diseases that could mimic MS. Not sure possible MS is my issue now.
More questions and no answers ... the saga goes on