Yuji Ase

Aicardi syndrome accompanied by auditory disturbance and multiple brain tumors

We described a 5-month-old girl with Aicardi syndrome accompanied by auditory disturbance and multiple brain tumors. She was admitted to our hospital because she suffered from intractable flexor spasms. Physical examination revealed craniofacial asymmetry, left auricular deformity, scoliosis, and remarkable hypotonia with psychomotor retardation. Abnormal ophthalmological findings included chorioretinopathy with pale and round-shaped peripapillary lacunae, and there was modified hypsarrhythmia in her EEG. MRI revealed multiple brain tumors in the 3rd and the lateral ventricles which are considered to be choroid plexus papilloma with agenesis of the corpus callosum. ACTH therapy was administered because of the intractable seizures. After ACTH therapy, the thresholds of waves I and V were much improved. The interpeak latency of waves I-V of the left ear and the peak latency of wave I of the right ear had been lengthened. Acoustic reflex with contralateral stimulation showed no response in the left ear. These findings indicate that the auditory system is also involved in the Aicardi syndrome and that ACTH is effective for its dysfunction.

Distortion-product Otoacoustic Emissions in Experimentally Induced Hydropic Ears

The postoperative changes of distortion-product otoacoustic emissions (DPOAEs) and cochlear potentials were examined using 15 albino guinea pigs in which endolymphatic hydrops was induced by obliterating the endolymphatic sac. DPOAEs (geometric mean: 4,6 and 8 kHz) were measured once before and every week after surgery. At the 2nd (n = 5), 4th (n = 5) and 12th (n = 5) postoperative weeks, endocochlear potential (EP) and compound action potential (CAP) were measured. Although the reduction in DPOAEs at 8 kHz was first detected at the 12th week, the amplitude of DPOAEs at 4 and 6 kHz was already reduced at the first week and decreased gradually thereafter. In contrast to these results, the CAP threshold was not elevated at the 2nd week and a slight increase was first detected at the 4th week. The results obtained in the present study suggest that DPOAEs are more sensitive than CAP in detecting the presence of hydrops.

The Effect of the Sympathetic Nervous System upon Susceptibility to Acoustic Trauma

This study was designed to determine whether the sympathetic nervous system exerts a protective or enhancing effect in acoustic overstimulation. The compound action potential of the cochlea (CAP) was recorded in guinea pigs while the cervical sympathetic nervous system (SNS) was electrically stimulated or after it was surgically eliminated. The stimulation or the elimination of the cervical SNS has no effect on the threshold of CAP. The threshold shift in CAP after acoustic overstimulation (110, 115, or 130 dB SPL for 10 min) was measured in the cervical SNS stimulation group, in the cervical SNS elimination group, and in the control group. When the animal was under insufficient sedation, there was no difference among these three groups. However, the CAP threshold shift was significantly smaller in the cervical SNS stimulation group than in the other two groups when the animals were sufficiently sedated. The cervical SNS stimulation had some protective effect on the susceptibility to acoustic trauma when the systemic SNS activity was suppressed.

Effect of Acoustic Overstimulation on the Hydropic Ear

The effect of acoustic overstimulation (2 kHz pure tone) on the compound action potential (CAP) threshold was investigated at frequencies ranging from 2 to 16 kHz using albino guinea pigs, both normal and with experimentally induced endolymphatic hydrops. The hydropic ears were less susceptible to acoustic overstimulation than the normal ears. As the CAP threshold was raised, the frequency exhibiting the greatest CAP threshold shift increased in both animal groups. The tendency was more noticeable in the hydropic ears than in the normal ears. These results are discussed from the aspect of cochlear hydrodynamics.