Vestibular syndrome associated with temporohyoid joint fusion and temporal bone fracture in three horses.

The presented research discusses three cases of horses suffering from an acute onset of vestibulocochlear and facial nerve dysfunction due to a stress fracture in the temporal bone of the skull; the fracture as a secondary effect of chronic inflammation with a contributing factor of bacterial meningoencephalitis and the outcomes of their treatment.

Overview

• This research focuses on three cases of horses who developed an unexpected (acute) onset of vestibulocochlear and facial nerve dysfunction triggered by a stress fracture in a particular portion of the temporal bone (petrous part).
• The onset of these nerves’ dysfunction is typically associated with symptoms such as abnormal balance (vestibular dysfunction) and problems with facial expressions and sensations (facial nerve dysfunction).
• This condition in the horses’ study was secondary to chronic inflammatory changes occurring in the petrous part of the temporal bone and another bone near the base of the skull, the proximal stylohyoid bone.

Temporohyoid Joint Fusion

• One essential finding from the research was the fusion of the temporohyoid joint, which is a pivotal joint where the stylohyoid bone connects with the temporal bone.
• The temporohyoid joint fusion noticed in these cases was likely a byproduct of the chronic inflammatory changes in the bones.
• Joint fusion in this region can have significant consequences as it interferes with the normal range of motion and could lead to stress fracture under certain conditions.

Bacterial Meningoencephalitis as a Complicating Factor

• The study also identified bacterial meningoencephalitis – an inflammation of the brain and meninges (the membranes protecting the brain and spinal cord) caused by bacteria – as a complicating factor that possibly contributed to the horses’ condition.
• While it’s not clearly stated how this condition led to the symptoms in the three horses, it’s likely this inflammation exacerbated the chronic changes in the affected bones and contributed to the fusion of the temporohyoid joint.

Treatment Outcomes

• In terms of treatment, it resulted in the reduction of the severity of clinical signs in two of the three cases, which indicates that the damage incurred was partially reversible.
• However, the treatment could not completely rectify the condition as residual compensated vestibular deficits (an ongoing disorder of the balance system) persisted in these horses.