Scheibers Aplasia (cochleosaccular dysplasia)oScheibe's aplasia is the most common form seen in inherited congenital hearing losses, especially those having autosomal recessive inheritance. In this type of aplasia, the bony labyrinth is fully formed, as are the membranous utricle and semicircular canals. The parts inferior (saccule and cochlear duct) is represented by mounds of undifferentiated cells. The tectorial membrane is reduced in size. The scala media is collapsed and Reissner's membrane may lie directly on the mound of undifferentiated cells and the stria. The stria vascularis and organ of Corti show abortive strands of connective tissue. The wall of the saccule is flattened and lies on the aplastic sensory epithelium and otolithic membrane.Also knowOther important causes of congenital Genetic Hearing LossoMichel's aplasia is characterized by total lack of development of the inner ear. In some cases even the petrous portion of the temporal bone is not developed, whereas in others it is present but is underdeveloped at the usual site of the labyrinth.oMondini's aplasia has been described as a flattened cochlea with development only of the basal coil. Instead of two and one-half turns in the bony cochlea, there may be only one and one-half turns, with the middle and apical turns occupying a common space or cloaca. The vestibular structures and their associated neural elements may be similarly underdeveloped.oAlexander's aplasia is characterized by aplasia of the cochlear duct. The organ of Corti and adjacent ganglion cells of the basal coil of the cochlea are most affected, resulting in a high frequency hearing loss.">