IPM Take
The phrase “your test is normal” can become a verdict disguised as reassurance.
For people with small fibre neuropathy, it often means another referral, another delay and another encounter where pain is treated as less credible because routine studies do not capture the nerve fibres involved. But the answer is not to replace dismissal with unproven immune therapy. It is to build a serious pathway: recognise the symptoms, confirm the diagnosis properly, investigate treatable causes and generate evidence strong enough to guide treatment.
Executive Summary
At the 2026 Peripheral Nerve Society Annual Meeting, neurologist Matthew Evans discussed the unresolved question of immune-mediated small fibre neuropathy. He noted that an inflammatory cause may exist in a subset of patients, particularly where symptoms are non-length-dependent, begin abruptly after an immune trigger, or occur alongside conditions such as Sjögren syndrome or sarcoidosis.
He also stressed that small fibre neuropathy requires objective confirmation beyond symptoms alone. The diagnostic approach includes characteristic sensory or autonomic features, normal nerve-conduction studies to exclude large-fibre neuropathy, and evidence of small-fibre dysfunction or damage, commonly through skin biopsy or quantitative sensory testing.
The treatment evidence remains unsettled. Evans reported that the three randomised IVIG trials discussed in his review did not demonstrate benefit in the populations studied. A placebo-controlled trial in painful idiopathic small fibre neuropathy similarly found no significant pain benefit with IVIG. The message is not that patients should be dismissed. It is that the field needs better phenotyping, validated biomarkers and trials designed for the patients most likely to benefit.
Why it matters
- Patients / advocates: Burning pain, altered sensation and autonomic symptoms should not be minimised because routine nerve studies are normal.
- Clinicians: The task is to recognise small-fibre involvement, investigate treatable causes and resist the pressure to turn uncertainty into unsupported treatment.
- Researchers / academia: The field needs biomarkers that distinguish inflammatory phenotypes from broader idiopathic small fibre neuropathy, alongside trials that are biologically credible and clinically meaningful.
The word “normal” carries a lot of power in medicine.
For someone living with burning pain, temperature sensitivity, numbness, dizziness, sweating changes or unexplained autonomic symptoms, a normal nerve-conduction study can sound like the end of the investigation. It should not be.
Small fibre neuropathy sits in the blind spot of routine neurological testing. Standard nerve-conduction studies mainly assess large nerve fibres. Small fibres, which carry pain and temperature signals and contribute to autonomic function, can be damaged even when those conventional tests are unchanged.
That gap has consequences.
Patients may spend years moving between general practice, pain clinics, rheumatology and neurology without a coherent route to diagnosis. Symptoms are sometimes treated in isolation. Pain becomes the problem to manage, rather than a clue to investigate.
The latest discussion from the Peripheral Nerve Society meeting makes two things clear.
First, not all small fibre neuropathy is the same. Some patients may have a secondary or potentially inflammatory cause. Features such as non-length-dependent symptoms, abrupt onset after an immune trigger, or coexisting autoimmune disease can justify deeper investigation.
Second, interest in immune mechanisms should not become a shortcut to immune treatment. The available randomised evidence for IVIG has not established benefit in the groups studied. That matters, especially when patients are desperate for something that promises more than symptomatic relief.
This is where personalised medicine needs to be disciplined.
Personalisation is not giving every patient the most sophisticated intervention available. It is identifying the right clinical pattern, confirming the biology where possible, investigating secondary causes and being honest about uncertainty.
Small fibre neuropathy needs a pathway that is both more compassionate and more rigorous. It needs earlier recognition, access to appropriate diagnostic tools, specialist referral when the pattern is complex, and research that stops treating a biologically mixed patient population as one disease.
Pain should not have to become visible on the wrong test before it is believed.
