Retrospective study of neurological signs and management of seven English horses with temporohyoid osteoarthropathy

This retrospective study summarises the case details, presenting signs, management and outcome in cases of temporohyoid osteoarthropathy (THO) and describes the findings of diagnostic imaging modalities. The condition appears to be relatively rare in Europe and the objective of this study is to make clinicians aware that THO can have a range of various neurological and clinical presentations. The records of 2 referral equine practices in England were reviewed and 7 horses with THO diagnosed on guttural pouch endoscopy indentified. The clinical and neurological signs, diagnostic procedures, treatment and outcomes were reviewed. Although small, this group is the largest case series of THO from Europe. One horse was a yearling, whereas THO is generally considered usually to affect middle aged and older horses. Computed tomography was used to confirm the diagnosis and demonstrated stylohyoid bone fractures in 2 cases while there was mild increased radionuclide uptake in one of 2 cases undergoing nuclear scintigraphy. Treatment is still controversial, although ceratohyoidectomy led to complete resolution of signs in 2 of 5 cases thus treated and improvement in the other 3. One horse with mild signs treated with antimicrobials and nonsteroidal anti‐inflammatory drugs made a full recovery while another, presented with head shaking and managed with a phased exercise programme, improved but did not resolve completely.     

Shear mouth secondary to temporohyoid osteoarthropathy

Temporohyoid osteoarthropathy (THO) is a progressive disease of unknown aetiology that can result in pain during normal movement of the tongue and larynx during mastication and deglutition. Shear mouth is a rare, poorly described condition, which may be associated with painful dental disease. This report describes a case of shear mouth attributable to THO. The THO was surgically treated by undertaking a left-sided ceratohyoidectomy (CHO) and the shear mouth resolved over the course of 18 months.     

Bilateral ceratohyoidectomy for the resolution of clinical signs associated with temporohyoid osteoarthropathy

Temporohyoid osteoarthropathy (THO) is a progressive bilateral disease of unknown aetiology that most commonly affects adult horses. Irrespective of aetiology, THO frequently results in pain or fracture of the petrous temporal bone during normal movement of the tongue and larynx. In an effort to decrease pain and reduce the likelihood of petrous temporal bone fracture, partial stylohyoidectomy and ceratohyoidectomy have been developed. Serious complications have been reported following stylohyoidectomy and therefore the current recommendation is to perform unilateral ceratohyoidectomy. Benefits of ceratohyoidectomy include a lower risk of vascular and nerve damage and a reduced risk of clinical signs recurrence when compared with stylohyoidectomy. This report describes a case of THO in which clinical signs recurred approximately 2 years after unilateral ceratohyoidectomy was performed. Due to this complication, resection of the contralateral ceratohyoid bone was performed, which resulted in complete resolution of clinical signs. Although the clinical signs are frequently unilateral, the disease is most commonly a progressive bilateral condition and some horses may not have complete resolution of clinical signs when unilateral ceratohyoidectomy is performed. Therefore, if clinical signs persist after unilateral ceratohyoidectomy, a therapeutic consideration should include bilateral ceratohyoidectomy. This report suggests a favourable short‐term prognosis for a horse treated with bilateral ceratohyoidectomy.     

Epidemiological features and association with crib‐biting in horses with neurological disease associated with temporohyoid osteoarthropathy (1991–2008)

A retrospective study of 43 cases of temporohyoid osteoarthropathy was performed to evaluate the epidemiological features and a possible association with crib‐biting. Data collected from records included case details, what diagnostics were utilised, whether medical or surgical treatment was administered, and outcome. Owners were contacted via telephone and asked whether the horse had displayed crib‐biting behaviour. Forty‐three horses were diagnosed with neurological disease associated with temporohyoid osteoarthropathy, 62.8% of which were Quarter Horse‐types. Median age at presentation was 10 years and median duration of neurological signs prior to presentation was 3 days. Skull radiographs and guttural pouch endoscopy were used to definitively diagnose temporohyoid osteoarthropathy in 72% of the cases. Of 43 horses, 21 received medical treatment and 15 surgical treatment, with an overall survival rate of 55.8%. Crib‐biting was observed in 31.3% of cases and there was a significant association between being afflicted with THO and likelihood of possessing the behaviour. Horses with neurological disease associated with THO were 8 times more likely to be crib‐biters compared to the general population.     

Temporohyoid osteoarthropathy in two young horses

Two cases of temporohyoid osteoarthropathy (THO) in young Australian horses are described. The pathogenesis of THO is yet to be fully elucidated, but current theories include extension of infection from otitis media or interna to the temporohyoid joint or a primary but non‐infectious degenerative condition within the temporohyoid joint. The young age of the horses and the unilateral distribution suggested an infectious aetiology. Both horses partially responded to treatment with broad‐spectrum antimicrobial and anti‐inflammatory drugs with concurrent management of ulcerative keratitis. The management of violent head shaking in one horse included the administration of gabapentin, an anticonvulsant known to have antihyperalgesic effects and reduce neuropathic pain.     

Histopathology and computed tomography of age‐associated degeneration of the equine temporohyoid joint

Reasons for performing study: The aetiology of temporohyoid osteoarthropathy (THO) is unknown; both primary infectious and degenerative causes have been suggested. Hypothesis: There is a significant association between increasing age and severity of temporohyoid joint degeneration. To examine the histopathology of the temporohyoid articulation in aged horses and to compare the appearance of the joint with computed tomography (CT) and peripheral quantitative CT (pQCT). Methods: pQCT scans of the temporohyoid articulations were obtained bilaterally from 31 horses (range age 1–44 years) post mortem and images were graded by 2 blinded observers on 2 occasions for the presence of osteophytes, irregularity of the joint surface and mineralisation. Eight heads had been examined previously by CT, with the images similarly graded for the shape and density of the proximal stylohyoid bones, bone proliferation surrounding the joint, mineralisation of the tympanohyoid cartilage and the relationship of the petrous temporal bone to the stylohyoid bone. Sixteen temporohyoid joints were then evaluated histologically. Results: There was significant association between the mean pQCT degeneration score and age (rho = 0.75; P<0.0001), between the pQCT and CT score (rho = 0.63; P = 0.01) and between the degenerative changes identified within each temporohyoid joint within each horse (rho = 0.81; P<0.0001). Age‐associated changes included the development of a club shape by the proximal stylohyoid bone, rounding of the synostosis with the petrous temporal bone and extension of osteophytes from the petrous temporal bone to envelope the stylohyoid head and bridge the joint. In no horse was there any evidence of osteomyelitis within the petrous temporal bone, stylohyoid bone or tympanohyoid cartilage. Conclusions: This study provides evidence that age is associated with increasing severity of degenerative changes in the equine temporohyoid joint and that similar changes are commonly found bilaterally. Potential relevance: The changes identified appear similar, albeit milder to the changes reported in horses with THO, suggesting that degenerative, rather than infectious causes may underlie the aetiology of THO. Future work should be directed at examining the histopathology of clinical THO cases.     

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

Temporohyoid osteoarthropathy is a well‐recognized cause of equine neurologic disease. Temporal bone fractures associated with temporohyoid osteoarthropathy have been recognized with CT, however, little information is available regarding these fractures. The aims of this retrospective analytical study were to assess the prevalence of these fractures and to describe the specific configurations and associated imaging and clinical features. Fracture of the temporal bone was identified with CT in 16 of 39 included horses. All fractures were unilateral, minimally displaced and extended through the temporal bone in a rostrodorsal to caudoventral orientation. Two fracture configurations were identified: in nine cases, the fracture extended the full width of the petrous pyramid into the cranial vault and in seven cases, the fracture only extended through the lateral part of the petrous temporal bone, not involving the cranial vault. Fusion of the temporohyoid joint was present in 13 of the 16 fracture cases. Quarter Horses were over‐represented in the fractured population (14/16). All horses with fractures had ipsilateral neurologic deficits. Patient outcomes were not significantly different between temporohyoid osteoarthropathy horses with and without temporal bone fractures (P = 0.68). However, six of the nine patients with cranial vault involvement did not return to their previous use. Findings support previous studies indicating that temporal bones should be carefully assessed for concurrent fractures when temporohyoid osteoarthropathy is identified in CT images, especially when there is fusion of the temporohyoid joint. An improved awareness of specific fracture configurations will help with detection of these fractures.     

Brainstem auditory-evoked responses in horses with temporohyoid osteoarthropathy

Background: Facial and vestibulocochlear nerve dysfunction occurs commonly in horses with temporohyoid osteoarthropathy (THO); however, auditory dysfunction has not been thoroughly assessed.
Objective: To determine if auditory abnormalities occur in horses with THO.
Animals: Eleven diseased and 8 control horses.
Methods: This is a prospective study in which brainstem auditory-evoked responses (BAER) were recorded in 11 horses diagnosed with THO through neurologic, endoscopic, radiographic, or computed tomographic examinations. BAER findings were compared with those recorded from 8 adult control horses.
Results: All horses with THO were found to have BAER abnormalities that included complete unilateral BAER loss (82%, n = 9/11), partial unilateral BAER loss (18%, n = 2/11) on the most affected side, and contralateral partial BAER loss (46%, n = 5/11). Nine horses had bilateral THO based on diagnostic imaging findings; of these, 5 (56%) horses also had bilateral BAER abnormalities. The complete absence of BAER in affected horses was most consistent with peripheral sensorineural hearing loss. There was a significant association between complete BAER loss and neurologic and diagnostic abnormalities.
Conclusions and Clinical Importance: Auditory abnormalities such as complete or partial BAER loss are common in horses with THO. The BAER test is an objective diagnostic tool that can aid along with other diagnostic modalities in the assessment, management, and follow-up of horses with THO. Furthermore, BAER studies may help to elucidate the pathophysiology of THO in horses.     

Computed tomographic diagnosis: Traumatic lingual process fracture and surgical resection

A 9‐year‐old mare was presented with abnormal behaviour and head‐shaking when ridden. Pathology of the hyoid apparatus was suspected and computed tomographic (CT) examination of the head was suggested. Computed tomographic images revealed a fractured lingual process (LP) of the basihyoid bone. Surgical resection of the fractured LP was performed. The mare recovered uneventfully and symptoms improved 10 weeks post‐operatively.     

Complications and survival associated with surgical compared with medical management of horses with duodenitis-proximal jejunitis

REASONS FOR PERFORMING STUDY: Based on clinical observation, it is hypothesised that horses with duodenitis-proximal jejunitis (DPJ) that are treated surgically have a shorter duration, smaller volume, and slower rate of nasogastric reflux (NGR) compared to horses treated medically, are more likely to develop diarrhoea than medically managed cases, and have a higher incisional infection rate than a sample population of horses undergoing abdominal exploration for gastrointestinal disease other than DPJ. OBJECTIVES: To compare: 1) duration, volume and rate of NGR and the percentage of horses with diarrhoea between medically and surgically treated DPJ cases; and 2) incisional infection rate in horses with DPJ undergoing abdominal exploration to a sample population of horses undergoing abdominal exploration for gastrointestinal disease other than DPJ. METHODS: Medical records of cases with DPJ diagnosed 1995-2006 were reviewed. Information obtained included subject details, presenting clinical findings, treatment category (medical/surgical), complications (diarrhoea, incisional infection), and outcome (survival/nonsurvival). Data were analysed using a Chi-squared test and a mixed model analysis of variance. Level of significance was P<0.05. RESULTS: Compared to medical cases, surgical cases had significantly decreased survival, a longer duration and larger total volume of NGR, and were more likely to develop diarrhoea. The incisional infection rate for horses with DPJ undergoing abdominal exploration was 16% compared to 7% for the sample population of horses. CONCLUSIONS: Surgical treatment of horses with DPJ did not lead to resolution of NGR faster than medical treatment. Surgical cases were more likely to develop diarrhoea and did not have a significantly higher incisional infection rate than the sample population.     

Clinical features and outcomes of severe ulcerative keratitis with medical and surgical management in 41 horses (2000–2006)

The clinical features and outcomes of equine ulcerative keratitis with and without conjunctival graft surgery were assessed using a retrospective study. Medical records of horses hospitalised from July 2000-January 2006 for ulcerative keratitis were included if a diagnosis of melting ulcer, descemetocele or iris prolapse was made, or if surgery was recommended due to severity of corneal disease, and aggressive medical therapy using a subpalpebral catheter was instituted. Treatment and outcome variables were evaluated with and without conjunctival graft surgery. Forty-one horses, 21 that had surgery and 20 for whom surgery was recommended but not performed, were included. Horses were hospitalised for an average of 24 days, with 37/41 melting ulcers, 17/41 descemetoceles and 3/41 iris prolapses, with no statistical difference in frequencies between groups. Bacterial or fungal organisms were cultured from 22/39 cases, with 10 Aspergillus spp. and 8 Pseudomonas spp. Infectious organisms were seen on corneal cytology in 23/30 cases. Surgical cases were hospitalised for an average of 4.9 days prior to surgery. Abdominal discomfort was observed in 8/41 hospitalised horses, with 5/8 operated horses developing caecal impactions. Thirty-five horses retained an intact globe, including 18/20 treated medically and 17/21 that had surgery. Hospitalisation cost was 24% more for cases that had surgery than for medical cases. It was concluded that there was no statistical difference in length or cost of hospitalisation between surgical and nonsurgical groups. Outcomes from both groups were similar, with a high frequency of globe retention.