Hi and welcome fellow ozzie,
I'm sorry to say this but if you have multiple spinal cord lesions there are not many other medical conditions that can cause both brain and spinal cord lesions, MS is the most common cause of demyelinting brain and or cord lesions so it's honestly unlikely to be one of the MS mimic's specifically because you have spinal cord lesions.
What i will say though is MS spinal cord lesions are not normally big enough to transverse the cord like Traverse Myelitis cord lesions, MS spinal cord lesion typically causes symptoms on one side of the body (unilateral) but an asymmetrical bilateral symptom pattern presenting or developing over time will also happen.....but presenting with a symmetrical or mirror image symptom pattern would usually point away from neurological conditions like MS.
The only exception i'm aware of is when TM was the presenting demyelination attack of MS, MS research has discovered TM can develop into MS, though most people dx with TM don't usually go on to develop MS...
"Transverse myelitis can appear as the first symptom in conditions such as multiple sclerosis (MS) or neuromyelitis optica (NMO). A person with transverse myelitis who also has an abnormal brain MRI with more than two lesions has an increased chance (as high as 90 percent) of going on to develop MS."
You don't mention any specific's about the brain lesions eg size, shape, if you have dawsons fingers, locations, if any lit up with contrast etc etc but the possibility of a neurological condition like MS not being the most likely cause would be the untypical symmetrical or mirror like symptom pattern your saying your experiencing.....this medhelp explanation of how MS works might make MS symptom pattern a little easier to understand;
It's genuinely not uncommon to need a second or even a third opinion before accepting being diagnosed with MS so i would suggest you consider seeing an MS specialising neurologist at one of the MS clinics in your state if your struggling to accept MS is the right dx for you. If you don't know where they are your local MS society chapter will be able to advice you on where your MS clinics are located, they will also be able to provide you with access to your local support group and services too.
I hope that helps......JJ