One of the two otolith organs in the inner ear. The saccule detects vertical linear acceleration and gravity when the head is tilted, working alongside the utricle to give the brain a continuous picture of head position in space.
Medical definition
The saccule (from the Latin sacculus, small bag) is a fluid-filled chamber in the vestibule of the inner ear, positioned vertically when the head is upright. Like the utricle, its sensory surface — the macula sacculi — is covered by a gelatinous membrane embedded with otoconia (calcium carbonate crystals). When the head tilts or the body moves vertically (stepping off a kerb, riding in a lift, jumping), the weight of the otoconia deflects the membrane and bends the hair cells beneath it. This sends signals to the brain about vertical movement and head tilt. The saccule is innervated by the inferior branch of the vestibular nerve, while the utricle and the anterior and horizontal semicircular canals are supplied by the superior branch — a distinction that matters clinically because superior vestibular neuritis spares the saccule.
Why it matters for vertigo
The saccule is assessed with cervical vestibular evoked myogenic potentials (cVEMP). This test delivers a loud sound stimulus to the ear and measures the reflex relaxation of the sternocleidomastoid muscle — a reflex arc that runs from the saccule through the inferior vestibular nerve. Absent or asymmetric cVEMP responses indicate saccular dysfunction on the affected side. This is useful in Meniere’s disease (where saccular hydrops is part of the pathology), superior vestibular neuritis (where saccular function is preserved, distinguishing it from labyrinthitis), and vestibular schwannoma (where cVEMP helps localise which division of the nerve is compressed). Saccular otoconia can also become displaced in BPPV, most commonly into the posterior semicircular canal.
Where I see this in clinic
I find the saccule most relevant in two situations. First, when explaining BPPV to patients: understanding that otoconia crystals normally sit in both the utricle and saccule, and that displacement from either can cause BPPV, helps patients understand why recurrence is possible even after a successful maneuver. Second, in cases of suspected labyrinthitis versus vestibular neuritis — labyrinthitis affects the entire inner ear including the cochlea and saccule, while vestibular neuritis typically spares them. Saccular function testing, where available, adds precision to this distinction.
Related terms
Utricle – the partner otolith organ that detects horizontal acceleration. Otolith – the broader system comprising both utricle and saccule. Otoconia – the crystals housed in both otolith organs. Vestibular neuritis – typically spares the saccule, distinguishing it from labyrinthitis.
Medical Disclaimer: This glossary entry is for educational purposes only. Consult Dr. Prateek Porwal directly. WhatsApp: 7393062200.