A child who was implanted at 5 years of age, after a long period of profound deafness, is seen for review. Cortical responses to speech are recordable, but P1 latency is well above the age-appropriate range and has changed little over a year of device use.
Findings
P1 is present but markedly delayed compared with the age-appropriate latency, and has not normalised with device use.
Diagnostic question
What does the persistently delayed P1 most likely indicate?