perilymphatic

Perilymphatic is an anatomical and physiological term relating to perilymph, the fluid that fills the perilymphatic spaces of the inner ear. These spaces lie between the osseous (bony) labyrinth and the membranous labyrinth and surround the sensory organs involved in hearing and balance.

The perilymphatic spaces include the scala vestibuli and scala tympani of the cochlea, as well as the vestibule and the semicircular canals. In health, these spaces contain perilymph, a clear fluid that provides mechanical coupling for the transfer of sound and motion from the skull and middle ear to the sensory hair cells of the inner ear. The perilymphatic compartments form a continuous system that interfaces with other fluids of the cranial cavity.

Perilymph has a composition somewhat similar to cerebrospinal fluid, with high sodium and relatively low potassium, which supports the electrochemical environment of the sensory epithelia. It is continuously circulated and, in many mammals, connected to the subarachnoid space via the cochlear aqueduct, allowing physiological pressure exchange between the perilymphatic space and CSF.

Physiologically, perilymphatic fluid transmits mechanical energy from the vibrating stapes through the scala vestibuli to the endolymphatic space, helping to drive the movement of hair cell stereocilia that underlie hearing and balance. The integrity of these spaces is essential for normal auditory and vestibular function.

Clinically, disruption of the perilymphatic space, such as a perilymph fistula or barotraumatic injury, can lead to vertigo, hearing loss, or imbalance. Perilymphatic structures are sometimes evaluated in inner-ear surgery and imaging, where their status can influence outcomes.