Frequency of clinically diagnosed small fiber neuropathy in a neuropathy population

We reviewed the files of outpatients with polyneuropathy or multiple mononeuropathy over a two-year period (2002–2003), to assess the relative incidence of small fiber sensory neuropathy (SFSN), diagnosed with clinical criteria. The cohort included a total of 97 patients (41 men, 56 women), age 11–85 years (median 64), 91 with polyneuropathy and 6 with multiple mononeuropathy. Twenty-seven patients with SFSN (27.8%) were identified (7 men, 20 women), age 11–76 years (median 62). SFSN was idiopathic in 8 cases, and secondary to other diseases in 19 cases, mainly diabetes or glucose intolerance (8 cases) and mixed cryoglobulinemia (6 cases). The most frequent manifestations of SFSN were burning feet (12 cases) and restless legs syndrome (12 cases). Duration of neuropathy was 2.2 + 2.06 years, whereas in the other patients with polyneuropathy was 9.02 + 13.6 (p = 0.011). Treatment with drugs for neuropathic pain was effective in 9 out of 16 cases (56.2%). In this series, SFSN diagnosed by minimal clinical criteria showed an unexpectedly high relative incidence among miscellaneous peripheral neuropathies. This can be due to overdiagnosis of SFSN, as we included patients diagnosed using minimal clinical criteria; on the other hand, the diagnostic sensitivity of additional tests (quantitative sensory examination and skin biopsy) is not definitive, thus diagnosis of SFSN is actually a frequent diagnostic challenge. The efficacy of treatment with drugs for neuropathic pain in many patients may provide further support for diagnosis.