Sensorineural: involving the inner ear, cochlea, or auditory nerve
Conductive: any mechanical factor blocking external sound from gaining access to the inner ear; ex: cerumen impaction, middle ear fluid, ossicular chain fixation
Mixed: both sensorineural and conductive<unk> 
Should evaluate for recent medication changes, family history of<unk> , personal history of trauma, recent scuba diving or flying (barotrauma), cold water exposure, onset/progression of<unk> , high- vs low-pitch<unk> , history of ear surgeries
Most common causes: presbycusis (i.e. natural aging of the auditory system), followed by noise-induced<unk> 
90% of cases are due to Sensorineural<unk> , 10% due to Conductive causes
Most bilateral cases that present gradually are benign.  Sudden onset, unilateral<unk>  is more concerning for a serious cause.
Hearing loss
Sudden Sensorineural Hearing Loss 
Hydrocephalus
Infections: 
Failure to thrive 
Barotrauma
Failure to thrive
Penetrating trauma