abnormal cochlea morphology abnormal basement membrane morphology abnormal cochlear basement membrane morphology any structural anomaly in the continuous basement membrane found within the membranous labyrinth of the cochlea, known to extend from the limbus, down to the inner sulcus, across the basilar membrane, up to the external sulcus to the spiral prominence and radiating into the spiral ligament ensheathing the root cell processes MPheno.ontology MP:0004598