To explore the efficacy of low dose naltrexone (LDN) in a group of patients with biopsy-confirmed cryptogenic small fiber neuropathy (SFN).

SFN affects somatic and autonomic fibers and can present with disabling pain and autonomic symptoms. Management  involves a multimodal approach with rehabilitation, optimal treatment of co-morbid conditions, and pharmacological treatment using antidepressants, anticonvulsants, and topical agents. LDN, an opioid receptor antagonist, has emerged as a potential treatment option for diabetic neuropathy and management of chronic pain in fibromyalgia. However, limited evidence exists regarding the efficacy of LDN in management of patients with cryptogenic SFN.

In a retrospective analysis, 44 patients with biopsy-confirmed cryptogenic SFN were identified in a university neuropathy clinic. Of these, the outcomes of patients started on LDN were further analyzed. In these patients, LDN was titrated to doses ranging as high as 4.5mg. The MGH-SSS was administered prior to LDN initiation and at varying intervals in order to assess for symptomatic response to LDN.

Out of the 84 patients who underwent biopsies, 44 had positive findings confirming SFN, and 13 patients were started on LDN. Adequate follow up MGH-SSS screenings were obtained from 8 patients who completed two surveys separated by 6 to 24 months. Follow up surveys indicated a decrease in all 5 composites scores on the MGH-SSS including “sensory”, “circulation”, “gastrointestinal”, “pelvic”, and “miscellaneous” scores. The largest mean decrease was noted in “sensory” composite scores (6.25) and the smallest decrease was noted in “pelvic” composite scores (1.38).

Our study reveals a potential role for LDN in the management of cryptogenic SFN. Results are confounded by limited sample size along with variable LDN dosing and survey intervals. Nevertheless, follow up studies may be beneficial in establishing the benefit of LDN in SFN using larger sample sizes and assessing for response over a longer interval.