Maturation of somatosensory evoked potentials upon posterior tibial nerve stimulation.

Somatosensory evoked potentials produced in response to posterior tibial nerve stimulation were studied in 42 normal infants and children, ages 4 months to 16 years. The maturation of afferent conduction from the lower limb was evaluated for the peripheral nerve, spinal cord, and central nervous system. Although the maturation of conduction in the peripheral nerve (from the ankle to the popliteal fossa and from the popliteal fossa to L3) was complete by 6 years of age, afferent conduction in the spinal cord (from L3 to C7) was not complete until 12 years of age or older. Spinal evoked potentials investigated in the thoracolumbar area revealed a phase-reversed potential located between the lower thoracic spine and upper lumbar spine in over 80% of patients. Reciprocal velocities for the major cortical positive potential P1 (corresponding to P37 in adults) and its onset, N1, steadily decreased with age and leveled off at greater than 12 years of age and by 12 years of age, respectively. The propagation velocity from L3 to the cerebral cortex also increased steadily with age, leveling off at greater than 12 years of age. Accordingly, the maturation of afferent conduction in the central nervous system was not complete until after 12 years of age.