nodulus

The nodulus, also known as the inferior nodulus or lobule X, is the inferior portion of the cerebellar vermis and forms part of the flocculonodular lobe along with the flocculus. It is located on the inferior surface of the cerebellum between the floccular region and the midline vermis.

Anatomy and connections: The nodulus is a component of the vestibulocerebellum, receiving afferent input from vestibular pathways and proprioceptive signals. Its Purkinje cells provide inhibitory output to the vestibular nuclei via pathways that include the fastigial nucleus, helping to regulate vestibular and postural control. The nodulus works in concert with the flocculus to integrate information about head position and movement, gravity, and linear acceleration.

Function: The nodulus participates in processing otolith-vestibular information and contributes to balance, posture, and gaze stabilization. It plays a role in the velocity storage mechanism that prolongs the vestibulo-ocular reflex after head rotation, aiding sustained eye movements during motion. Through its connections, the nodulus helps coordinate head and trunk posture with eye movements, supporting stable vision during movement.

Clinical significance: Lesions or infarcts affecting the nodulus can produce truncal ataxia, titubation (a forward-backward tremor of the trunk), and gait instability. Disturbances of vestibulo-ocular reflexes may occur, potentially with nystagmus or altered gaze stabilization. Because it is part of the vestibulocerebellum, the nodulus is relatively sparing of limb coordination compared with other cerebellar regions, though broader vermian involvement can amplify ataxic signs.