The main structural problem occurring in the nose is that of a deviation of the nasal septum. The septum is the (normally) midline structure of the nose, made up of cartilage and bone, that divides the nose into its two halves. The septum can deviate due to prior trauma. This may have occurred in childhood as an otherwise slight innocuous injury - the cartilage may then grow in an abnormal way and hence patients often cannot recall any specific injury. There is some thought that a septal deviation can even occur secondary to the nose being squashed as we are born through the birth canal.

Whatever the cause for the deviation, septal deflections can block breathing in the nose on one or other side and are particularly troublesome during the night when patients find it difficult to breathe, particularly if lying on their side.