title: CIDP variants in diabetes: measuring treatment response with a small nerve fiber test.
abstract: BACKGROUND
  Chronic inflammatory demyelinating polyneuropathy (CIDP) is eleven times more common among people with diabetes than the general population and is treatable with appropriate immunotherapy. Treatment response is usually measured clinically (symptomatic and functional improvement). We present a case of a patient with type 2 diabetes (T2D) and CIDP whose treatment response was measurable with the Sudoscan sudomotor function test. This test may represent a new objective evaluation of the treatment of CIDP.
  
  
  METHODS
  The patient is a 60year old male initially referred to our center in August 2012, at which time he was diagnosed with CIDP based on AAN electrodiagnostic criteria (NCS). Autonomic functions were significant for low heart rate variability response to expiration/inspiration (E/I), Valsalva maneuver and the ratio of the RR interval for the 30th to the 15th beat upon standing (1.08, 1.12, 1.05 respectively), and frequency analysis of the total spectral power, the standard deviation of the normal RR intervals (sdNN) and their root mean squared (rmsSD). Sudoscan electrochemical skin conductances (ESC), measuring small nerve fiber function on the palms and soles, were very low: 23 μS in the feet and 32 μS in the hands. After one cycle of intravenous immunoglobulin (IVIG: 6 doses total, 75g each) the patient had no change in symptoms of burning, numbness, shooting pains, and gait impairment. However, E/I, Valsalva, and 30:15 ratios (1.19, 1.36, 1.39 respectively) were improved, as were NCS. Sudoscan scores for feet and hands were unchanged (23 μS and 32 μS). In March 2013, the patient's autonomic functions worsened (E/I, Valsalva, and 30:15 ratios 1.1, 1.07, 1.12 respectively), but feet and hand ESC started to show improvement (35 μS and 52 μS respectively). Azathioprine was started. Eight days after a second cycle of IVIG in January 2014, the patient reported for the first time less burning, shooting pains and tingling. E/I, Valsalva, and 30:15 ratios remained low (1.03, 1.07, and not analyzable, respectively), while foot and hand ESC scores continued to improve (43 μS and 55 μS respectively).
  
  
  CONCLUSIONS
  CIDP diagnosis and treatment response are difficult in the diabetic patient. We found that NCS and autonomic function tests did not correlate well with clinical status while numerical Sudoscan scores matched closely symptomatic changes. ESC have been found to correlate well with peripheral small fiber function and neuropathic symptoms in DPN. The findings in this patient warrant further investigation of the use of Sudoscan to monitor CIDP response to therapy.
authors.affiliation: Impeto Medical, Inc., San Diego, CA. Electronic address: marie-laure.nevoret@impeto-medical.com.
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Névoret
authors.affiliation: Eastern Virginia Medical School, Norfolk, VA.
authors.forename: Aaron I
authors.initials: AI
authors.lastname: Vinik
mesh_terms: D001341:Autonomic Nervous System / Q000187:drug effects / Q000503:physiopathology; D001379:Azathioprine / Q000627:therapeutic use; D003131:Combined Modality Therapy; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D003929:Diabetic Neuropathies / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D055664:Electrochemical Techniques / Q000295:instrumentation; D005712:Galvanic Skin Response / Q000187:drug effects; D006801:Humans; D016756:Immunoglobulins, Intravenous / Q000627:therapeutic use; D007155:Immunologic Factors / Q000627:therapeutic use; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D036421:Nerve Fibers, Unmyelinated / Q000187:drug effects / Q000378:metabolism; D009431:Neural Conduction / Q000187:drug effects; D009437:Neuralgia / Q000209:etiology / Q000517:prevention & control*; D020277:Polyradiculoneuropathy, Chronic Inflammatory Demyelinating / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology / Q000628:therapy*; D012720:Severity of Illness Index; D013545:Sweat Glands / Q000187:drug effects / Q000294:innervation / Q000503:physiopathology; D016896:Treatment Outcome
chemical_list: D016756:Immunoglobulins, Intravenous; D007155:Immunologic Factors; D007166:Immunosuppressive Agents; D001379:Azathioprine
keywords: CIDP; Chronic inflammatory demyelinating polyneuropathy; Peripheral neuropathy; Small fiber neuropathy; Sudomotor function