biopsy for small nerve fiber

Hi - I am still searching for factors that may have come together to cause what has happened to me. This is a complex and long story. I have had very appropriate care from my Internist to primary neurologist, extensive testing, and referrals to tertiary care specialists. 2nd opinions on back issues etc. I will try to list major timeline elements.
Some minor changes in gait and some unexplained falls occurring as far back as 2016-17. Neuro workup and imaging at that time late 2017.
2018 -Spinal stenosis dx with L3,4,5 spinal fusion. Complete recovery. Full activity.
2019 -L total knee replacement. Excellent recovery. Very active.
2021 -Torn left hamstring with surgical repair. Very good recovery.
2022 February - Traumatic fall. Pain initially but lessening with time and mobility increasing steadily. Did not seek medical care at that time as basically was doing pretty well.
In the fall of 22 Increasing concern about gait becoming more abnormal again and experiencing increasing back pain.
Dec 2nd of 2022 -Spine film showed fx of L1 subsequently had Kyphoplasty by neurosurgeon.
December 15th 2022 - I had my 1st episode of loss of balance. Single episode, Not dizziness or fainting or spinning sensation but actual loss of balance while standing.
2023 Early spring - gait abnormality continues to be concerning by me and my family. Referred to PT for balance improvement. Had EMG etc with only slight changes noted. Had to stop PT after a couple weeks as back pain was getting much worse.
More films etc. I have significant issues throughout my entire spine- degenerative changes, spondylolisthesis and stenosis. I also have significant osteoarthritis in many joints throughout my body.
March 2023 - Neurosurgeon felt the bundle of symptoms at this time is related to lower spine following my fusion from 2018. "Straight back syndrome". Plan was to do major spine surgery to correct that whole area.
Mid March 23 - Waiting to get on surgery schedule.
Late March - over very few days my symptoms became much worse. Balance is so bad that I had to get a walker just to get around my home. Then suddenly within days I lost some sensation in both feet, then unable to wiggle my toes of either foot or lift either forefoot. Loss of sensation became worse. Only lower extremities are involved. Paresthesia in my feet and up my legs also. All symptoms were on the lateral side of ankles and legs.
March 31st 2023 Saw my neurosurgeon and my primary neurologist regarding how I was scared because I was drastically losing function. They watched me try to walk. Repeated EMG and sensory testing showed major change from what it was 10 or so days before. "Demyelinating Neuropathy".
March 31st -Hospitalized for GBS treatment - 5 days of IVIG, spinal tap, etc.
April 5th - Discharged using walker 99% of the time because of poor balance combined with bilateral footdrop. Started outpatient rehab.
April 23 through Sept 24 - Various tertiary referrals and extensive laboratory testing in attempt to get definitive diagnosis. Almost all testing was normal. Ataxia screen resulted in a positive for my being a carrier of a pathologic recessive gene called POL G (mitochondrial disorder) that can rarely cause ataxia in an older population when usually this is expressed neonatally or very early childhood.
I had a L Sural nerve biopsy.
I am continuing rehab including aquatic therapy. Now using one prong cane and flexible OFA on left foot only. Early on, I wore rigid OFAs on both feet. I use walking sticks for outdoors and irregular surfaces. Walker is getting dusty in the corner. There are ups and downs but the general trendline is improvement over 17 months. Still improving.
Getting IVIG every month now as a trial since April of 24. Also have had a couple steroid trials in the past.
Potential for trying the new FDA approved drug for CIDP. Vyvgart or Vyvgart Hytrulo later this year.
So still wondering what all is involved here. Cerebellar issue? Parkinson variation? Spinal issue? CIDP?
Thanks for your interest and comments.
Ann

It sounds like you are very close to a diagnosis with all your positive results. At least you know that there is a reason, or reasons for your situation. It just hasn’t all been pulled together into a single diagnosis. With all of your test results, you could get a referral to the best teaching facility where all it takes is one good doctor who has seen this exact presentation and knows what it is. (I’m close to UAB, so go there). I don’t have that diagnosis, and I’m starting to accept what I’ve been told by several of my medical team group - at this point, knowing exactly what it is won’t change the treatment. I don’t like that statement, but might have to accept it. You have a recessive gene identified. That’s huge. Research more about that, and see if a group somewhere is doing more research on that. My genetic testing was normal, except for one small blip that was deemed insignificant. But the lab that did it told me to check back every few years, as new genomes are always being identified. That’s important, because my sister has the same symptoms as me.
My symptoms started 9 years ago. Get ready for a slow as molasses journey into finding your diagnosis!

Thank you so much for replying with your positive but also realistic message. I would love to go to Mayo or University of MN. Mayo does not accept any out of network Medicare Advantage plans at least in 2023when I was looking at going there. If you are too young for Medicare, remember that about Advantage plans which are not good when a serious potentially long term illness comes about. I cannot change to a gap plan or other choices. Only choice is another Advantage plan or traditional Medicare which is then hat I am responsible for 20% of all Medicare allowable charges. We are reviewing option now for next year. Some places have a hold on accepting anymore neuro patients. At least my Advantage plan is a PPO and is a very large one.
Warmest regards to you and your sister.