The role of different neurophysiological tests in the differential diagnosis of diabetic axonal neuropathy and lumbosacral radiculopathy.

OBJECTIVE To evaluate the role of different neurophysiological tests in the differential diagnosis of diabetic axonal neuropathy (DAN) and lumbosacral radiculopathy (LSR). METHODS This study was conducted at Al-Kadhimiya Teaching Hospital, Baghdad, Iraq, from July 2006 to February 2007. Twenty-seven healthy subjects, 44 type 2 diabetics, and 36 LSR patients were studied. The HbA1c level, plain x-ray, and MRI of the lumbosacral region and different electrophysiological tests were assessed. RESULTS The sural sensory nerve action potential (SNAP) amplitude values were reduced in 56.3%, and the sural/radial amplitude ratio (SRAR) values were reduced in 71.8% in the diabetic patients, but not in the LSR group. The peroneal compound muscle action potential (CMAP) amplitude was low in 70.45% DAN patients versus 35.5% LSR patients. Peroneal F-minimum (Fmin) values were prolonged in 56.8% DAN versus 32.25% LSR patients. The Fpersistence (Fp) values were low in 72.7% of DAN, versus 45.2% of LSR patients. However, the Fchronodispersion (Fc) was abnormal in 71% of LSR versus 11.4% of DAN patients. CONCLUSION The SRAR was found to be more significant than the sural SNAP amplitude alone in the differential diagnosis of the 2 groups. Abnormal peroneal Fc and Fp seems to be valuable tests in the detection of LSR and DAN patients.