Connection between the inner ear and the lymphatic system

Objective. The aim of this study was to identify the lymphatic drainage of the inner ear in guinea pigs. Study Design. Prospective study. Methods. The prospective study was performed in guinea pigs by injection of keyhole lim pet hemocyanin (KLH) into either the right-side scala tympani or the middle ear cavity. The left side was not injected and served as a control. Fiftee n minutes after injection, the animals were killed by intracardiac perfusio n with paraformaldehyde and tissue specimens (right and left temporal bones , cervical lymph nodes, and the spleen) were collected. The presence of KLH in each specimen was determined by immunohistochemical assay of frozen sec tions using polyclonal mouse anti-KLH antibodies. Results. After injection into the middle ear, labeled cells were identified in the parotid, superfic ial ventral, mandibular, and deep cranial cervical lymph nodes. However, af ter inner ear injections KLH was present in only the parotid and superficia l ventral cervical nodes. The spleen contained KLH-positive cells following injection into either the middle or inner ear, but not all animals contain ed labeled spleen cells. Conclusions. The inner ear has a connection to the lymphatic drainage system. Because fewer lymph nodes contained labeled cel ls after inner ear injection than after middle ear injection, it is conclud ed that the inner ear does not simply drain to the middle ear and subsequen tly to the lymph nodes but seems likely to have its own connections.