Red blood cell deformability in sudden sensorineural deafness: another aetiology?Red blood cell deformability (RCD) was measured by a filtration technique in 12 patients with sudden sensorineural deafness. Five patients had reduced deformability, including 3 out of 4 patients with a recent upper respiratory tract infection. This may be an important factor in sudden deafness, more likely as a complicating factor of other disorders rather than as a truly primary aetiology. Factors and diseases which alter RCD are discussed and a possible link between the viral and vascular causes of idiopathic sudden deafness is suggested. While several lines of therapy seem promising there is still no clinically proved method for improving RCD. With the development of an acceptable therapeutic regimen, we feel that the possibility of reduced RCD should be considered and that a deformability test be included in the work‐up of patients with a sudden sensorineural hearing los