Morphological and morphometrical maturation of ventral cochlear nucleus in human foetus

Development of the hair cells of the human cochlea: A scanning electron microscopic study

Introduction

In the mammalian auditory system, the cochlea is the first to attain structural and functional maturity. Although ultrastructural details of the developing cochlea of lower animals have been elucidated in the last few decades, comprehensive studies on human cochlea are lacking.

Materials and Methods

In the present investigation we studied the development and maturation of the hair cells of ten human fetal cochlea from gestational weeks (GW) 12 to 37 by scanning electron microscopy.

Result

We observed undifferentiated hair cells possessing numerous surface projections and long kinocilium during GW 14. At GW16, the primitive hair cells were arranged in one inner and four outer rows and had globular apices indicating the initiation of stereocilia formation. By GW 22, the globular apices were replaced by linear stereocilia and occasional kinocillia. Mature hair cells with sterocilia were observed in the basal turn at 30th week of gestation. At GW 37, the stereocilia were arranged in a typical "V" shaped pattern at the middle and apical coil, while the stereocilia of the basal turn were shorter in length resembling the adult cochlea. The inner hair cells were long and slender while outer hair cells were pear shaped, kinocilium were absent and the tunnel of Corti were well formed.

Conclusion

It is concluded that in human, the morphological maturation of the hair cells starts in the basal turn around GW 22 and continues till 37th week in the apical turn indicating that early maturation of the cochlea may have a role on development of the higher auditory pathway connections.

Neuroanatomical Alterations in Patients With Tinnitus Before and After Sound Therapy: A Voxel-Based Morphometry Study

According to previous studies, many neuroanatomical alterations have been detected in patients with tinnitus. However, few studies have reported on the morphological changes observed following sound therapy. To explore the brain anatomical alterations in patients with idiopathic tinnitus using voxel-based morphometry (VBM) analysis before and after effective 12 weeks sound therapy. The protocol was registered on ClinicalTrials.gov, ID: NCT02774122. In this study, we collected data from 27 matched healthy control (HC) individuals and 27 idiopathic tinnitus patients before and after 12 weeks of sound therapy by using adjusted narrow band sound. 3.0T MRI system and high-resolution 3D structural images were acquired with a 3D-BRAVO pulse sequence. Structural image data preprocessing was performed using the VBM8 toolbox. The Tinnitus Handicap Inventory (THI) score was acquired in the tinnitus group to assess the severity of tinnitus and tinnitus-related distress. Mann-Whitney U Test, Wilcoxon Signed-Ranks test, and Pearson's correlation analysis were used in the statistical analysis. We found significantly decreased gray matter (GM) volume in the left thalami, right thalami, and cochlear nucleus among the tinnitus patients before sound therapy (baseline) compared to the HC group. However, we did not find significant differences in brain regions between the 12-week treatment and HC groups. According to the results of Wilcoxon Signed-Ranks test, the 12-week sound therapy group demonstrated significant greater brain volume compared with the baseline group among these brain regions. Decreased THI score and changed GM volume were not correlated. This is a useful study for observing the characteristics of neuroanatomical changes in patients with idiopathic tinnitus before and after sound treatment. The study characterized the effect of sound therapy on brain volume. It found that sound therapy had a normalizing effect on the bilateral thalami and cochlear nucleus. Clinical Trial Registration: www.ClinicalTrials.gov, NCT02774122.