Neurologic Deficits Including Auditory Loss and Recovery of Function in Horses with Temporohyoid Osteoarthropathy

Abstract

BackgroundAuditory loss is a common deficit in horses with temporohyoid osteoarthropathy (THO), however, recovery of function is unknown.Hypothesis/ObjectivesTo investigate neurologic function with emphasis in audition in horses with THO after treatment. To describe anatomical alterations of the petrous temporal bone that might result in auditory loss.AnimalsTwenty‐four horses with a clinical diagnosis of THO.MethodsProspective study. A brainstem auditory evoked response (BAER) study was done as part of the criteria for inclusion in horses with a clinical diagnosis of THO from the years of 2005 to 2014. Physical and neurologic status and BAER findings were recorded. Brainstem auditory evoked response variables were compared by using Wilcoxon sign test. Fisher's exact test was also used. Significance was set at P < 0.05.ResultsThe most common signs included auditory loss (100% of horses), vestibular and facial nerve dysfunction (83%), and exposure ulcerative keratitis (71%). Concurrent left laryngeal hemiparesis was observed in 61% of horses through endoscopy. Auditory dysfunction was bilateral in 50% of the cases (complete and partial), and unilateral affecting more commonly the right ear (R = 8, L = 4). Short‐ and long‐term follow‐up revealed persistent auditory loss in all horses based on abnormal response to sound, and further confirmed through a BAER in 8 horses.Conclusions and Clinical ImportanceAuditory dysfunction appears to be a permanent neurologic deficit in horses diagnosed with THO despite overall neurologic improvement.

Outcomes after medical and surgical interventions in horses with temporohyoid osteoarthropathy

“…Common clinical signs of THO include facial and/or vestibulocochlear nerve dysfunction and head tossing. Less common signs include dysphagia and seizure-like activity [4,5,[7][8][9][10][11]. Some of the common behavioural signs associated with THO are head shaking, ear rubbing and bit avoidance [4,9,12].…”

“…Less common signs include dysphagia and seizure-like activity [4,5,[7][8][9][10][11]. Some of the common behavioural signs associated with THO are head shaking, ear rubbing and bit avoidance [4,9,12]. Diagnosis is based on a combination of clinical signs and diagnostic imaging, including guttural pouch endoscopy, skull radiography and/or computed tomography (CT) [4,8,9,[11][12][13][14].…”

Highlights of recent clinically relevant papers

“…Auditory loss is common in horses with temporohyoid osteoarthropathy (THO); however, recovery of function is unknown. In this study Monica Aleman and colleagues in the USA investigated neurological function with emphasis on audition in horses with THO after treatment and reported anatomical alterations of the petrous temporal bone that might result in auditory loss .…”

The prevalence of temporal bone fractures is high in horses with severe temporohyoid osteoarthropathy

“…However, antemortem diagnosis of temporal bone fractures was uncommon prior to the advent of CT, as these fractures are often not radiographically apparent. Previous studies have reported temporal bone fractures using CT in 25% (4/16) to 36% (4/11) of horses with temporohyoid osteoarthropathy, however, these reports did not include detailed descriptions of the fracture configurations. Bacterial meningitis, seizures, and death have been reported as sequelae of these temporohyoid osteoarthropathy‐associated temporal bone fractures .…”

“…Temporohyoid osteoarthropathy is a disorder characterized by progressive osseous proliferation surrounding and eventually bridging the temporohyoid joint. Temporohyoid osteoarthropathy leads to a variety of clinical presentations ranging from behavior changes (head shaking, resistance to the bit, and ear rubbing) to severe neurologic dysfunction mainly referable to the facial and vestibulocochlear nerves …”