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[Otoacoustic emissions measurements in children during the chemotherapy because of the acute lymphoblastic leukemia].

INTRODUCTION
Chemotherapy is associated with an increased risk of ototoxic changes. The predictive value of conventional pure-tone audiometry on early detection of ototoxicity has been questioned. Otoacoustic emissions (OAEs) appear to be more sensitive to cochlear insult than the conventional pure-audiometry. The purpose of our study was (a) investigation the clinical usefulness of Distortion Product Otoacoustic Emissions (DPOAEs) as early indicator of chemotherapy-induced ototoxicity, (b) determination which of the protocols of chemotherapy is most ototoxic as measured by DPOAEs, (c) comparison of the short-term and long-term effects of chemotherapy on DPOAEs.


MATERIAL AND METHODS
Tonal audiometry (0,25-8 kHz), immitance audiometry and DPOAEs were measured in 10 children with acute lymphoblastic leukemia (ALL). Measurements were performed before and after each protocol of ALL IC-BFM 2002 chemotherapy: protocol I: vincristine (VCR), L-asparaginase (L-ASP), daunorubicin (DNR), cyclophosphamide (CPM), cytarabine (ARA-C), 6-mercaptopurine (6-MP), methotrexate (MTX); protocol mM: 6-MP, MTX; protocol II: VCR, doxorubicin (DOX), L-ASP, CMP, ARA-C, thioguasine (6-TG), MTX; protocol III: VCR, DOX, L-ASP, CMP, ARA-C, 6-TG, MTX. DPOAEs were measured using ILO2 92 Otodynamics Analyser. Cochlear activity was evaluated by recording 2f1-f2 DPOAEs with L1 = 65 and L2 = 60 dB SPL. Comparisons of the DP-grams amplitudes were performed between baseline measurements and those recorded before and after each chemotherapy course.


RESULTS
Our results indicate that: a)DPOAE is a more sensitive technique for the assess of chemotherapy-induced ototoxicity than conventional audiometry, b) with DPOAE monitoring very subtle hearing changes can be detected, c) DPOAE amplitude was significantly decreased at all frequencies studied in 50% children with leukemia, d) depression of DPOAE amplitude was evident only during and after first protocol, e) long-term DPOAE monitoring reviled reversibility of ototoxicity in all children, f) a large individual variability in the DPOAE response following the chemotherapy was observed, g) in a few cases a transient increase in DPOAE amplitude had been observed before it was reduced.


CONCLUSIONS
Distortion product otoacoustic emissions measurements are very sensitive on early detection of the changes in cochlear function and are recommended for monitor hearing in patients during chemotherapy.