Early Detection of Small-Fiber Neuropathy in Diabetes

A laser-induced pain somatosensory-evoked potentials and pupillometric study

Over the last 15 years, many authors have pointed out that small nerve fibers may be selectively damaged in the early stages of diabetes, leading to an early impairment of pain and temperature sensations and to a decline in autonomic nervous function (1,2).

The CO₂ pain-induced laser somatosensory-evoked potential (pSEP) evaluation may represent a new quantitative and objective approach to evaluate pain and temperature sensation functions (3–8). Recently, Agostino et al. (9) reported small-fiber dysfunction assessed by pSEPs in diabetic patients with different degrees of peripheral nerve damage.

A total of 27 diabetic patients (12 type 1 [group 1] and 15 type 2 [group 2]) and 27 age-, sex-, and height-matched control subjects were included in the study. In group 1 (6 men and 6 women), the mean age was 33.6 ± 9 years, the duration of diabetes was 13.5 ± 6.7 years, and the glycated hemoglobin was 6.1 ± 1.3%; two patients had nephropathy and three had background retinopathy. In group 2 (7 men and 8 women), the mean age was 55.3 ± 8.8 years, the duration of diabetes was 8.2 ± 6.2 years, and the glycated hemoglobin was 6.8 ± 1.5%; three patients had nephropathy and four had background retinopathy. The patients reported no history of autonomic and somatic neuropathy and had negative clinical examinations (evaluated using the Neuropathy Symptom Score [NSS], the Neurological Symptom Profile [NSP], and the Neurologic Disability Score [NDS]) (10); normal nerve conduction velocity and P100 latency at visual-evoked potentials (VEPs) recording; no severe diabetic retinopathy or other opthalmological diseases; no recurrent ketoacidosis, ketonuria, or hypoglycemia; no psychiatric disorders or alcohol consumption; no cognitive impairment; and no other diseases or treatment with medications known to influence nervous system function. Two control groups (groups 3 and 4) were included …