Auditory processing following infantile spasms: An event-related potential study.

OBJECTIVES: To investigate acoustic auditory processing in patients with recent infantile spasms (IS). METHODS: Patients (n = 22; 12 female; median age 8 months; range 5-11 months) had normal preceding development, brain magnetic resonance imaging (MRI), and neurometabolic testing (West syndrome of unknown cause, uWS). Controls were healthy babies (n = 22; 11 female; median age 6 months; range 3-12 months). Event-related potentials (ERPs) and psychometry (Bayley Scales of Infant Development, Second Edition, BSID-II) took place at a month following IS remission. RESULTS: Following a repeated pure tone, uWS patients showed less suppression of the N100 at the mid-temporal electrodes (p = 0.006), and a prolonged response latency (p = 0.019). Their novelty P300 amplitude over the mid-temporal electrodes was halved (p = 0.001). The peak of the novelty P300 to environmental broadband sounds emerged later over the left temporal lobe in patients (p = 0.015), the lag correlating with duration of spasms (r = 0.547, p = 0.015). BSID-II scores were lower in patients (p < 0.001), with no correlation to ERP. SIGNIFICANCE: Complex acoustic information is processed poorly following IS. This would impair language. Treatment did not reverse this phenomenon, but may have limited its severity. The data are most consistent with altered connectivity of the cortical acoustic processing areas induced by IS.

Temporal lobe impairment in West syndrome: event-related potential evidence.

OBJECTIVE: This study investigates auditory processing in infants with West syndrome (WS) using event-related potentials (ERPs). METHODS: ERPs were measured in 25 infants with mainly symptomatic WS (age range = 3-10 months) and 26 healthy term infants (age range = 3-9 months) using an auditory novelty oddball paradigm. The ERP recordings were made during wakefulness and repeated in stage II sleep. RESULTS: The obligatory components (P150, N250, P350) and novelty response components (P300, Nc) were recordable during both sleep and wakefulness in patients and controls. All ERP latencies decreased with age in controls but not in the WS group (age × group interaction, F = 22.3, p < 0.0001). These ERP latency alterations were not affected by pharmacological treatment for WS. INTERPRETATION: This study demonstrated a persistently altered ERP signature in patients with a recent history of infantile spasms. The prolongation of auditory obligatory and novelty ERPs in WS patients indicates a severe failure of temporal lobe maturation during infancy. It remains to be investigated whether this predicts long-term cognitive impairments characteristic for this epileptic encephalopathy.