Background: Nerve entrapments like carpal tunnel syndrome are more prevalent in patients with diabetes, especially in those with diabetic polyneuropathy. Our study aims were to investigate the validity of the Tinel sign in diagnosing tibial neuropathy and determine the prevalence of tibial nerve entrapment in both a diabetic and nondiabetic population.
Methods: Two hundred forty nonneuropathic subjects with diabetes and 176 diabetic subjects with neuropathy participating in the prospective Rotterdam Diabetic Foot Study and 196 reference subjects without diabetes and without neuropathy complaints were evaluated. All subjects underwent sensory testing of the feet, and complaints were assessed using the Michigan Neuropathy Screening Instrument. The Tinel sign was defined as discriminative and valid for diagnosing tibial nerve entrapment when the nerve-related Michigan Neuropathy Screening Instrument subscore of neuropathic symptoms differed at least 5 percent between the Tinel-positive and Tinel-negative subjects. When the sign was valid, prevalence estimates of tibial nerve entrapment at the tarsal tunnel were calculated.
Results: Significantly more neuropathic symptoms (p < 0.002) and higher sensory thresholds (p < 0.0005) were observed in (compressed) tibial nerve-innervated areas, indicating that a positive Tinel sign at the tarsal tunnel is a valid measure of tibial nerve abnormality. The prevalence of tibial nerve entrapment in diabetic patients was 44.9 percent (95 percent CI, 40.1 to 49.7 percent) versus 26.5 percent (95 percent CI, 20.3 to 32.7 percent) in healthy controls (p < 0.0001).
Conclusions: Tibial nerve entrapment is more prevalent in diabetic subjects than in controls. The significantly more frequently reported neuropathic complaints and concomitant sensory disturbances provide evidence for the role of superimposed entrapment neuropathy in diabetes-related neuropathy.
Clinical question/level of evidence: Diagnostic, IV.