Burning feet seem to be a common symptom of CFS. Small fiber neuropathy is a known cause:
CLINICAL PAIN MEDICINE
ISSUE: 9/2010 | VOLUME: 9:09
Small Fiber Neuropathy Demonstrated in Pain Syndromes
Andrew Wilner, MD
TorontoNearly half of patients with a painful condition had evidence
of small fiber neuropathy on skin biopsy, according to research
presented at the 2010 annual meeting of the American Academy of
Neurology meeting (poster P05.231).
Devanshi Gupta, MD, and John Harney, MD, neurologists at Dallas
Neurological Associates, Richardson, Texas, and co-authors of the
paper, reviewed 48 patients who underwent skin biopsy for evaluation
of small fiber neuropathy. Of the patients, 30 had a painful
condition, such as fibromyalgia, chronic fatigue syndrome, chronic
pain syndrome or some combination of the above. Of these, 13 (43%) had
evidence of small fiber peripheral neuropathy determined by reduced
epidermal nerve fiber densities on punch biopsy of the skin. Although
some of these patients had positive electromyography and nerve
conduction velocity tests for neuropathy, others did not.
We have found an overlap between small fiber neuropathy and chronic
pain in many patients, observed Dr. Gupta.
Punch biopsies were taken 10 cm proximal to the lateral malleolus
(abnormal <5.4 fibers/mm) and 20 cm from the anterior iliac crest on
the thigh (abnormal <6.8 fibers/mm). Specimens were sent to Therapath
Lab for interpretation.
Dr. Gupta advised that physicians consider a skin biopsy for
evaluation of small fiber neuropathy in patients who present with
sharp, shooting pains, orthostatic hypotension, autonomic symptoms,
trophic skin changes, incontinence, sexual dysfunction or other
neuropathic symptoms. One should consider a small fiber neuropathy
particularly in patients with comorbidities such as diabetes,
Sjogrens syndrome or vitamin deficiency, according to Dr. Gupta.
There are other ways to diagnose a small fiber neuropathy, Dr. Gupta
observed, but skin biopsy is the easiest way and provides an
objective number, which can be followed. The technique takes a little
practice, but it is straightforward to learn.
Small fiber neuropathy should be suspected if there is distal limb
(lower extremity greater than upper extremity) pain or decreased pain
sensation, W. King Engel, MD, director and professor of neurology and
pathology, Neuromuscular Center, Good Samaritan Hospital, University
of Southern California, Keck School of Medicine, Los Angeles. I do
not do skin biopsy exams. I am concerned about false-negatives. Skin
biopsy abnormalities must not be the sine qua non of diagnosing small
fiber neuropathy. A careful clinical sensory exam for hypo- and/or
hypersensitivity, along with the history, is the best way to diagnose
a small fiber neuropathy. However, a punch biopsy of skin can support
the diagnosis of small fiber neuropathy.
Dr. Engel cautioned that the reproducibility of results of different
biopsies taken at the same time in the same region probably is not
consistent enough for following improvement or worsening
When you see chronic pain overlapping with symptoms of small fiber
neuropathy, it is very correct to pursue a thorough investigation,
Dr. Gupta concluded. If you diagnose a small fiber neuropathy,
patients may respond to specific treatment for neuropathic pain.
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