New electrophysiological assessments for the early diagnosis of encephalopathy and peripheral neuropathy in chronic uraemia.

The clinical manifestations of neuropathy in chronic uraemia are late in occurring. However, at an early stage it is possible to detect damage to either the central or peripheral nervous system by means of modern electrophysiological investigation methods. We examined 29 patients with CRF (plasma creatinine 7.0 +/- 4.0 mg%) on conservative diet. The following electrophysiological tests were carried out at least once: Electroencephalogram (EEG), Electromyogram (EMG), Motor Nerve Conduction Velocity (MNCV), Sensory Nerve Conduction Velocity (SNCV), Visual Evoked Potentials (VEPs) using the pattern reversal transient stimulation method. At the same time the following blood tests were performed: BUN, creatinine, uric acid, glucose, cholesterol, triglycerides, lipid electrophoresis, total protein (electrophoretic method), Na, K, Ca, P, red cells blood count and PTH. MNCV, SNCV and VEPs appeared to slow down early, sometimes even where there were no clinical symptoms. In addition, there is a direct correlation with decreasing renal function. MNCV and SNCV were correlated directly, reciprocally although the compromise of SNCV appeared an earlier phenomenon. The significant direct correlation between MNCV, SNCV and serum PTH suggests that the latter has an important peripheral neurotoxic role. VEP recording permits detection of early abnormalities in the central nervous system with residual renal function values around 40%.