Fibromyalgia (FM) Cases with Tingly, Funny Feelings – How Can You Tell If You Have a Small Fiber Neuropathy Instead?

There is evidence that a small fiber neuropathy is responsible for a subset of FM cases – particluarly if there is more burning, numb feelings and  severe pain (neuropathic symptoms). A group with these symptoms was biopsied but predicting who would have a small fiber neuropathy was not necessarily possible.

Int J Neurosci. 2013 Jan;123(1):38-41.
Usefulness of skin biopsies in the evaluation and management of patients with suspected small fiber neuropathy.
Saperstein DS, Levine TD, Levine M, Hank N. abstract here

I have previously written how small fiber neuropathy is common in FM:
|Is Fibromyalgia(FM) a Small Fiber Neuropathy?

One study documented that 76% of their FM cases complained of “paresthesias” – numb funny feelings:

A subset of fibromyalgia patients have findings suggestive of chronic inflammatory demyelinating polyneuropathy and appear to respond to IVIg
X. J. Caro, E. F. Winter and A. J. Dumas
Rheumatology 2008;47;208–211  free article here

The article  even went so far is to find that a further subgroup of thier patients with abnormal nerve studies actually had something called Chronic Inflammatory Demyelinating Polyneuropathy and this condition can respond to Immunoglobulin infusions.

In original top article, they found

• “patients had sensory symptoms of numbness or dysesthetic sensations such as burning or stinging”
• At least 1/2 of cases had pain

Investigations included:

• complete blood count,
• electrolytes, creatinine, blood urea nitrogen,
• liver function tests,
• fasting glucose, 2-hr oral glucose tolerance test,
• ANA,
• ESR,
• thyroid function tests,
• vitamin B12,
• serum immune fixation electrophoresis
• methylmalonic acid,  homocysteine, – used in assessment of B12 deficiency but thought of as “limited value and I don’t do them
  see:
  The limited value of methylmalonic acid, homocysteine and holotranscobalamin in the diagnosis of early B12 deficiency

They found

• impaired glucose tolerance (17%),
•  diabetes mellitus (8%),
• vitamin B12 deficiency (7%),
• ethanol abuse (4%).

• 2 biopsy sites – proximal thigh and distal calf

Results by whether or not Biopsies were positive:

Features suggestive there is a small fiber neuropathy included:

• Twice as likely to have pain symptoms – that would include all of Fibromyalgia patients though
• length dependent symptoms (more symmetrical distal stocking glove pattern)
• Facial symptoms would make it more likely FM – (I do see facial numbness with scalene spasms affecting upper cervical anterior plexus)
• Biopsies were read by  Therapath (New York, USA) – has developed quite a reputation
  Url:  http://www.therapath.com/
  
• They found with a positive biopsy, response to neuropathic agents was twice as likely (84% versus 42%)

Comment – Fibromyalgia patients with significant tingling  issues might want to consider getting tested – it would mean biopsies sent to the USA at your expense. Having said that, most labs can do proper counts:
Journal of the Neurological Sciences Volume 228, Issue 1 , Pages 65-69, 15 January 2005
The reliability of skin biopsy with measurement of intraepidermal nerve fiber density
A. Gordon Smith et al  abstract here

found good comparison between labs

Comment – Fibromyalgia is a denigrated disease and many victims feel that acutely – finding one has a small fiber neuropathy instead would help there. It might help against insurance companies, legitimising one’s complaints. In our province, it would allow access to Lyrica, should tricyclics (which if one looks closesly at the literature does poorly in neuropathic pain) fail. The idea of FM being one disease is quickly becoming history.