biopsy for small nerve fiber

That is true, but for a “gold standard” test, it has a very high margin of error so even for someone who has symptoms and a negative skin punch biopsy, it doesn’t necessarily change the diagnosis. It also doesn’t identify the cause. A negative EMG/NCS for me in the presence of sensory symptoms…still gave me a small fiber neuropathy diagnosis.

I did the biopsy because I was hoping for more certainty since otherwise small fiber sensory neuropathy is a clinical diagnosis (no objective test to “prove” it). Even if it was positive it would have been for my own peace of mind, sort of.

For my biopsy, one sample was “low normal” and the other was inconclusive because the sample didn’t have enough of whatever it is they need to count 🤷🏻‍♀️.

So…I walked away with two tiny scars (tiny, but I am darker skinned so have a tendency for more scarring), what was categorized as a negative test for small fiber neuropathy that didn’t rule it out, and the same diagnosis I started with, with the same treatment options I had before I did the biopsy.

Like with anything, there are pros and cons to weigh. For me it didn’t change anything when really what I wanted was treatment. I think sometimes doctors don’t explain the nuances well or put more emphasis on diagnoses but not treatment, especially for chronic conditions.

It’s noninvasive, usually covered by insurance, and not painful though, so it’s relatively low risk.

I understand, but my experience was different. I had four neurologists tell me that at least 30% of skin punch biopsies are negative…despite patients still having symptoms. Maybe that’s the same percentage with idiopathic SFN, which is a huge number. My main neurologist told me this is why someone would say, “It won’t necessarily change the treatment.”

It’s important to find a cause, if one is findable, and the skin punch biopsy can help point to a cause, but in a lot of cases it does not. And even if one does find a cause, the treatment may be the same, i.e. it’s common with fibromyalgia but there’s no direct treatment for fibromyalgia, just symptoms management.

Mine was inconclusive (one sample was “low normal” and the others were not a good sample; I can’t remember exactly, but it wasn’t worth doing again), I have no history of diabetes, a normal glucose tolerance test, no exposure to a chemical, nor B12 deficiency, chemotherapy, never took any medications regularly until that point, etc. It was obvious it was length-dependent because in the time I waited for an appointment, the symptoms began in my feet and crept up higher. All of that was apparent before the skin punch biopsy.

I still decided to do it because I wanted certainty about whether I did or did not have small fiber neuropathy and not some other more resolvable condition. Sadly it didn’t give me that.

My small fiber neuropathy is assumed to be autoimmune because I have an assumed diagnosis of a seronegative inflammatory arthritis (no objective biomarker and joint damage would may not be apparent for decades without treatment despite severe pain) and an objective diagnosis of POTS, which affects the autonomic nervous system—which also relies on small fiber nerves. Treating the inflammatory arthritis improved the joint pain, but not the SFN. IVIG would be my “hail Mary” pass but it’s a toss-up.

I have osteoarthritis, apparently, though it never bothered me until all of my PN symptoms started. The rheumatologist thinks I may have inflammatory arthritis in my hands though. I go back to him November 8, but looking on my patient portal at all the bloodwork, there is nothing showing autoimmune-related conditions. I just took myself off statins after reading some studies; 3 months trial is suggested in Peripheral Neuropathy:When the Numbness, Weakness, and Pain Won't Stop by Norman Latov. I'm desperate to slow this down at least.
Will insurance cover the IVIG therapy?

If you can return to that pain clinic and get the skin biopsy, just follow their frustrating guidelines and do it. It’s one more possible answer. Get ready for a parade of slow, irrational and frustrating series of doctor visits and tests. I won’t tell you how long it took to get a diagnosis of idiopathic length-dependent small fiber polyneuropathy. And treatment that works! And I’m a nurse!
I advise getting the skin biopsy when it’s offered. Start reading, and save hard copies of all your test results and lab results.
You are one of many on this path. Good luck!

Have you found treatment that works?

If you can return to that pain clinic and get the skin biopsy, just follow their frustrating guidelines and do it. It’s one more possible answer. Get ready for a parade of slow, irrational and frustrating series of doctor visits and tests. I won’t tell you how long it took to get a diagnosis of idiopathic length-dependent small fiber polyneuropathy. And treatment that works! And I’m a nurse!
I advise getting the skin biopsy when it’s offered. Start reading, and save hard copies of all your test results and lab results.
You are one of many on this path. Good luck!

I had my nerve biopsy yesterday; 3 places on left leg, which is somewhat worse than the right. I had messaged my rheumatologist who made the referral about the experience I had on my first appointment, and he actually contacted the doctor that does the biopsy. I was told it would take at least a month, possibly 2 months to come back from the lab. He is leaving this practice, so I will have an appointment with a different doctor when the report from lab comes in. I am canceling the injection until I know more.

What treatment worked for you??
I am a nurse also. I am scheduled for a punch biopsy in Nov. Hoping that it leads to some sort of diagnosis or helps to clarify things at least.
I am 75 now. I have led a very active and healthy life. I have no heart disease, diabetes, cancer, hypertension, or osteoporosis. What I do have is lots of degenerative arthritis and have had many orthopedic surgeries related to that: Bilateral knee replacements 2009/2019, Spinal Fusion at L3,4,5 in 2018, Torn hamstring surgically repaired 2021, Kyphoplasty L1 2022. I also have long term familial tremors of both hands that slowly increased over the years.
The history of my current situation actually runs from about 2017 to 2022. During those years I experienced occasional and increasing unexplained falls. My family and I observed that something was different about my gait. That being that I was catching my toe and tripping or misplacing my step. I sought medical help at that time with PCP and referral to neurologist. Had appropriate testing at that time including brain MRI. Testing was negative but toe catching was able to be observed once with observation by that neurologist. To watch and wait was the plan. Along the way, I did perceive increasing muscle fatigue in lower extremities when doing a typical walk of 2.5 miles between 2021-22. Also, I could not walk as fast as I was used to being able to. As listed above I did have ortho surgeries in and around that time frame. Related??
In the spring of 2023, there was a change in my symptoms with increased back pain and weakness in legs and significant decrease in ability to climb stairs due to strength not pain. To begin with my increased back pain and symptoms were thought to be related to the condition of my spine. There were plans for a major back surgery. However, before surgery could be scheduled, there was an acute increase in symptoms of bilateral numbness in toes and feet, inability to lift forefoot or to move my toes and severe loss of balance and ataxic gait requiring 100% use of a walker. I seem to be losing function hour to hour. Sensory Motor Nerve Conduction study showed major change over a matter of days from previous study and indicated nerve demyelination. I was hospitalized at that time and treated for GBS for 5 days with IVIG. I stabilized but the symptoms did not go away.
What followed were months of extensive testing and image studies to rule out whatever could be ruled out. What turned up besides the abnormal S/M conduction studies was a recessive gene (POL G) I inherited and that has potential for pathologic expression, mild elevation of spinal fluid Protein and GAD levels. I also had a Sural nerve biopsy that showed essentially normal nerve i.e. no demyelination. At Multiple consults/2nd opinions at specialty centers followed. You know the drill.
I HAVE seen improvement slowly over time. I can walk now with just the use of a cane and I can cruise counters and walls at home fairly well, but balance is still a major issue as well as a residual L footdrop. I must be very careful and always be conscious of my footfall and balance issues. It is exhausting. I fall about 1 x per month despite my best efforts to stay upright.
I am on monthly IVIG. I cannot correlate anything with IVIG treatments. I could not tolerate steroid blasts.
Your experience has buoyed my hopes that the Skin Biopsy may lead to some additional clarity. Thank you.

Hi amkie, I see your L3-4-5 fusion in 2018. I'm curious of the status of your L5-S1 joint. It's commonly the culprit in footdrop, after peroneal nerve damage. And if it was beginning to be compromised prior to your fusion. The added pressure from the fusion could have finished the job. I'm dealing with similar symptoms. From practically the same surgeries... And it seems as with most no concrete answers, just concrete feet. 🙂

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