Pathology Study Of Auditory Function And Spiral Ganglion Cell After Cerebral Concussion

Objective: During the otology clinical, we usually meet handicap of hearing resulted from craniocerebral trauma. Cerebral concussion was often faced in clinical diagnosing and was 80 percentage of craniocerebral trauma. Clinical situation of cerebral concussion were dizziness, headache, the faculty of memory decrease, anxiety, depression, tinnitus, and hearing decrease and so on. The otolaryngologists were paying more and more attention to the dysfunction of auditory after cerebral concussion. To study the change of audiology and pathological foundation in the later period of cerebral concussion. The guinea pigs were made into the model of cerebral concussion by the self-made pendulum shocking in this experiment. To provide rational pathological foundation for clinical diagnose and the disabled appraisement of forensic medicine, we tested the auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) of the guinea pigs ,observed their cochlear structure ,hair cell and spiral ganglion cell by the light microscope ,scanning electron microscope(SEM) and the transmission electron microscope(TEM).Methods: The fourty male and female guinea pigs with white hair and red eyes were randomly divided into four groups which are A(normal),B(four weeks after cerebral concussion),C(six weeks after cerebral concussion),and D(eight weeks after head concussion) by average. Testing ABR and DPOAE separately in the four groups of A, B, C, and D in the environment of sound isolation room. ABR in which stimulative sound was click , pulse width was 0.1ms and superposition number of times was 1000 were measured and analyzed in all groups. The response threshold value (dB SPL) were recorded by the stimulus sound intensity in the wave III disappeared and the latency of every wave in the 90dB SPL.and the measure were repeated twice . Measuring the amplitudes of DPOAE in which two signals of pure tone f1 and f2 were measured and analyzed in all groups and were recorded when the amplitudes were higher 3dB SPL than the background nose. The parameters of DPOAE have several aspects as followed: (1) The fixed ratio of f2 and f1 was 1.2. (2) The stimulative sound intensity: L1=65 dB SPL and L2=55dB SPL. (3) The amplitudes of DPOAE were measured in the nine frequencies that was (f1×f2) 1/2= 0.5, 0.7, 1, 1.4, 2, 3, 4, 6, 8kHz and repeated two hundred times. The data about amplitudes of DPOAE, threshold values , latency and interval of ABR were memorized and analyzed by SPSS 13.0 statistical software. And all animals, cochlea and spiral ganglion cell were made samples after they were put to death and were observed under the light microscope , SEM and TEM.Results:1 Results of ABR Auditory threshold of ABR in group B 25.0±3.33 dB , group C19.0±3.16 dB , group D 18.0±3.50dB showed a significant difference from that of group A 13.50±5.30 dB (p<0.05). Latency period of wave I, II ,III ,IV, V and the interval of I-- III,I--V,III--V of group B were longer than that of group A, (P < 0.05). latency period of wave I,IV,V and the interval of I-- V,III --V of group C were longer than that of group A (P < 0.05). Latency period of wave III of and the interval of I -- III of group D were longer than that of group A (P < 0.05).2 Results of DPOAE The amplitude at 0.7, 1 and 2 kHz in group B were lower than that of group A (P < 0.05), the amplitude at 2 kHz in group C were lower than that of group A (P < 0.05), the amplitude at 1 and 2kHz in group D were lower than that of group A (P < 0.05).3 Results of morphology The light microscope showed no signs damage of Corti and the Corti's tunnel, the analogical appearance showed under the SEM, and the cellular organs of spiral ganglion cell (SGC) showed no index injury by the TEM in normal guinea pigs; On the four weeks post-concussion , the organs of Corti and the Corti's tunnel were deformed by the light microscopy ; the scanning electronic microscopy of the guinea pig's cochlear showed that there were chaos, depletion and cilia clisis on the four weeks post-concussion, the cellular organs of SGC under TEM were swelled, bubble degeneration appeared , and rough endoplasmic reticulus were expanded ;On six and eight weeks post-concussion, the Corti's organ and tunnel were deformed by the light microscopy no including eight week post-concussion , there were cilia clisis in inner hair cell under the SEM, the cellular organs of SGC under TEM showed that mitochondrias were swelled and located edge of the cell.Concussion:1 The abnormity of ABR and DPOAE after Cerebral concussion show that cerebral concussion do damage to auditory-brainstem pass at different degree.2 The auditory threshold value are increased after cerebral concussion and its value reach to the largest at four weeks, the amplitudes of DPOAE are decresed mainly at 1 and 2 kHz , these results are consistent with the changes of morphology.3 Cerebral concussion can result in the impairment of not only the Corti's organ ,but also the cellular organs of SGC.4 Deafness after cerebral concussion result from no one organ's damage, maybe many organs cooperation on auditory-brainstem pass.