Treatment of oromaxillary fistulae in nine standing horses (2002–2006)

Reasons for performing study: There is minimal published information on equine oromaxillary fistulae that are unrelated to cheek teeth (CT) repulsion or on the conservative treatment of these atypical fistulae. Objectives: To report equine oromaxillary fistulae unrelated to CT extraction and describe their management in standing horses. Methods: Case details of oromaxillary fistulae of atypical aetiology occurring at 2 referral centres between 2002–2006, including their treatment and response to treatment were examined. Results: Nine cases of oromaxillary fistula were recorded, mainly in aged horses (median 22 years). Fistulae were associated with CT diastemata in 7 cases, fractured CT in one and a central defect in a worn CT in another. After removing food and exudate from the sinuses, 6 cases were treated successfully by filling the diastema or dental defect with polymethylmethacrylate (PMMA). Following dental extraction, the other 3 cases were treated successfully by use of PMMA alveolar packing. Conclusion: Older horses can spontaneously develop oromaxillary fistulae, usually secondary to CT diastemata. In the absence of apical infection, this disorder can usually be treated successfully in standing horses by treating the sinusitis and sealing the oral aspect of the diastema with PMMA. Potential relevance: Older horses with sinusitis should be assessed for the presence of CT diastemata and oromaxillary fistulae. If detected, these disorders can be treated successfully in the standing horse.     

Dental bridging as a treatment for large oral fistulae in two horses

Chronic orocutaneous, oronasal, or orosinus fistulae can be challenging to repair. This report describes placement of a dental bridge as a treatment for oral fistulae and outcome in two horses. A 12-year-old, Westphalian gelding was presented for nasal discharge because of an oromaxillary fistula after dental repulsion of the Triadan 209 4 years earlier. The second case, a 5-year-old Oldenburg mare was presented for an orocutaneous fistula 7 weeks after dental repulsion of the Triadan 208. Both were treated by placing an 8-shaped cerclage wire, inserted through the rostral and caudal interdental spaces and crossing at the level of the missing tooth. Polymethylmethacrylate (PMMA) was then used to seal the fistula. No significant complications occurred during or after the surgery. In both cases clinical signs did not recur. In the first case the dental bridge is currently (5 years after the intervention) in place. In Case 2 the construction was removed after 1.5 years and the fistula had healed completely. This case report suggests that placing a dental bridge composed of cerclage wire and PMMA should be considered as an easy, noninvasive and efficient way to manage large oromaxillary or orocutaneous fistulae.     

Levator labii superioris muscle transposition to treat oromaxillary sinus fistula in three horses

OBJECTIVE: To describe surgical transposition of the levator labii superioris muscle to treat oromaxillary sinus fistula in horses. STUDY DESIGN: Clinical study. ANIMALS: Three horses with chronic oromaxillary sinus fistula. METHODS: After severing its tendinous insertion, the muscle belly of the levator labii superioris muscle was retracted and transposed through the oromaxillary sinus fistula. The tendon exited the oral cavity through a full-thickness buccal incision created adjacent to the oral end of the fistula and was then tunneled subcutaneously in a ventral direction before being anchored by sutures to the cheek tissues. RESULTS: Fistulae healed with few complications and with good cosmetic and functional results. CONCLUSIONS: Oromaxillary sinus fistula associated with molariform tooth loss in horses can be treated successfully by transposition of the levator labii superioris muscle. CLINICAL RELEVANCE: Transposition of the levator labii superioris muscle should be considered for resolution of chronic oromaxillary sinus fistula in horses.     

Treatment of horses for a facial or oral fistula

A sinocutaneous or nasocutaneous fistula is usually a sequel to a comminuted fracture of one or more facial bones, whereas an oronasal or oromaxillary sinus fistula occurs most commonly after a maxillary alveolus fails to fill with healthy granulation tissue after its tooth has been lost. Horses with a sinocutaneous or nasocutaneous fistula can be treated by covering the fistula with transposed muscle, which in turn is covered by adjacent skin or a free skin graft, or by covering the fistula with periosteum transposed from adjacent bone, itself covered by adjacent skin or left uncovered to heal by second intention. Horses with an oronasal or oromaxillary sinus fistula can usually be treated successfully by temporarily occluding the oral aspect of the fistula, to prevent feed from entering the fistula, until the apical end of the alveolus fills with healthy tissue. Other methods of treatment include covering the oral aspect of the fistula with a mucoperiosteal flap or filling the fistula with a transposed facial muscle.     

Endoscopic Examination and Treatment of Paranasal Sinus Disease in 16 Horses

Sixteen horses with suspected paranasal sinus disease had endoscopic examination of the paranasal sinuses with a 4.0 mm arthroscope either while standing and sedated (14 horses) or under general anesthesia (two horses). Endoscopic diagnosis included sinusitis (four horses), sinus cyst (three horses), hemorrhage (three horses), neoplasia (three horses), and tooth root abnormalities (two horses). No abnormalities were detected in one horse. Endoscopic findings concurred with the radiographic findings in 13 horses (81%). Samples of sinus contents for bacteriologic (eight horses) and histologic examinations (five horses) were obtained using sinus endoscopy. Diagnostic sinus endoscopy was combined with debridement, lavage, and suction as a therapeutic technique in 10 horses. In three horses, sinus exploration was performed after diagnostic endoscopy confirmed sinus disease, whereas in three horses, further therapy was not recommended after sinus endoscopy. Clinical signs of sinus disease resolved in 11 horses (69%) overall and in eight of 10 horses (80%) with sinusitis, cyst formation, or hemorrhage using endoscopic techniques alone. Mild, local subcutaneous emphysema occurred at the portal sites in all horses, but healing occurred without additional complications, latrogenic damage to sinus structures occurred in one horse. Sinus endoscopy was useful in the diagnosis and management of paranasal sinus disease and avoided the need for exploratory sinusotomy in some horses.     

Head and neck abscessation and thrombophlebitis following cheek tooth extraction in a pony

Due to their long hypsodont reserve crowns, extraction of equid cheek teeth can be difficult and result in more complications than the extraction of their shorter brachydont counterparts although the more recent resumption of oral extraction has greatly reduced such complications. The more common post-extraction sequelae in equids include non-healing alveoli due to retained dental or alveolar sequestrae which may lead to oromaxillary or oronasal fistula formation, chronic external sinus tract formation or osteomyelitis of the supporting bones. Collateral damage to adjacent teeth has also occasionally been reported during dental repulsion. Systemic complications following equine cheek tooth extraction have been infrequently described, including a small number of cases of exodontia-related bacterial meningioencephalitis. This is surprising, as dental manipulation can lead to bacteraemia in many species, including horses. Infections at distant sites related to the spread of dental pathogens have been well described in humans and in small animals. This report describes deep abscessation of the masseter muscles followed by extensive thrombophlebitis of the jugular, facial and rostral cervical veins following oral cheek tooth extraction in a pony affected by pituitary pars intermedia dysfunction (PPID) that was successfully treated by abscess drainage and thrombectomy of the affected veins.     

Equine paranasal sinus disease: a long-term study of 200 cases (1997-2009): treatments and long-term results of treatments

Reasons for performing study: There is limited objective information available on the treatment and the long‐term response to treatment of the different types of equine sinus disease. Objectives: To document the treatments and long‐term response to these treatments in 200 cases of equine sinus disease (1997–2009). Methods: The treatments of horses affected with subacute primary sinusitis (n = 52); chronic primary sinusitis (n = 37); dental sinusitis (n = 40); sinus cyst (n = 26); traumatic (n = 13); dental‐related oromaxillary fistula (n = 8); sinus neoplasia (n = 10); mycotic sinus disease (n = 7); and intrasinus progressive ethmoid haematoma (n = 7) and the long‐term response to these treatments were retrospectively reviewed. Results: Treatments evolved throughout the study and latterly were as conservative as possible, including sinoscopic lavage and standing sinusotomy, with a maxillary sinusotomy approach preferred for the mainly mature horses treated in this study. Removal of intrasinus inspissated pus, including transendoscopically (by sinusotomy and via existing sinonasal fistulae), was the main treatment for chronic primary sinusitis and sinonasal fistulation was seldom performed latterly. Attempted oral extraction of infected cheek teeth, even if unsuccessful, facilitated subsequent dental repulsion, resulting in few post operative problems. Sinus cyst removal carried an excellent prognosis. Except for cases of sinus neoplasia (only 22% cured), an excellent long‐term response to treatment (91% fully cured, 7% partially cured) was obtained for all other types of sinus disease following a median of one treatment. Conclusions: More conservative treatments, including removal of intrasinus inspissated pus by sinoscopy, pre‐existing sinonasal fistula or sinusotomy, are effective for chronic primary sinus disease. Standing sinusotomy, mainly using a small maxillary site, was suitable for most cases of sinus disease in mature horses.     

Sinoscopic Treatment of Rostral Maxillary and Ventral Conchal Sinusitis in 60 Horses

Objective— To evaluate the use of sinoscopy for detection and treatment of ventral conchal sinus (VCS) and/or rostral maxillary sinus (RMS) disease in horses.
Study Design— Case series
Animals— Horses (n=60) with suspected paranasal sinus disease.
Methods— Horses were evaluated by sinoscopy through a conchofrontal sinus (CFS) portal with ventral conchal bulla (VCB) fenestration. Other endoscopic sinus approaches and adjunctive diagnostic tests; oral examination, computed tomography, radiography, scintigraphy and endoscopic examination of the upper portion of the respiratory tract were used in some horses.
Results— The CFS approach permitted adequate observation of the RMS and VCS in 53 horses (88%). Hemorrhage caused by VCB fenestration prevented examination of the RMS and/or VCS in 12 horses (21%). Observation of lesions was possible in all horses diagnosed with neoplasia, sinus cysts, and progressive ethmoidal hematomas. Endoscopy of the paranasal sinuses was useful diagnostically in 82% of horses with primary sinusitis. Other diagnostic modalities were usually required to confirm a diagnosis of dental sinusitis.
Conclusions— Trephination into the CFS with VCB fenestration is a minimally invasive technique that provides consistent access to the RMS and VCS. It facilitates diagnosis of many sinus disorders and endoscopically guided treatment of many horses with sinus cysts and primary sinusitis, in combination with sinus lavage.
Clinical Relevance— Many diseases affecting the RMS and VCS can be diagnosed and resolved endoscopically using a CFS approach with VCB fenestration, thus avoiding the need for osteoplastic sinus surgery and its associated risks and complications.     

Use of magnetic resonance imaging for identifying subchondral bone damage in horses: 11 cases (1999-2003)

OBJECTIVE: To assess the use of magnetic resonance (MR) imaging for identifying subchondral bone damage in the distal limbs of horses. DESIGN: Retrospective study. ANIMALS: 11 horses. PROCEDURE: Medical records of horses with lameness and subsequent evidence of subchondral bone damage as determined by MR imaging were reviewed. Severity and duration of lameness, results of diagnostic local anesthesia and diagnostic testing, surgical and necropsy findings, and treatment were recorded. Outcome was determined by follow-up information obtained from the owner or referring veterinarian. RESULTS: Lameness was localized by physical examination and diagnostic local anesthesia. Lameness was localized to the metacarpophalangeal or metatarsophalangeal joint in 4 horses, distal interphalangeal joint in 5 horses, and tarsocrural joint in 2 horses. The duration of lameness ranged from 2 weeks to 20 months. Magnetic resonance imaging of the affected joints revealed abnormal fluid accumulation within the subchondral bone. None of the abnormalities observed by MR imaging were detected by radiography. Subchondral bone damage was diagnosed in all horses. Arthroscopy of the affected joint was performed in 4 horses. Communication with the articular surface of the affected bone was suspected on the basis of results of MR imaging in 4 horses and was confirmed by arthroscopy in 1 horse and by necropsy in 1 horse. CONCLUSIONS AND CLINICAL RELEVANCE: Magnetic resonance imaging was useful for providing a diagnosis when other imaging techniques did not definitively identify the cause of lameness. Subchondral bone damage was clearly identified by MR imaging and should be considered as a cause of lameness in horses in which radiographic findings are unremarkable.     

Hemangiosarcoma in 11 young horses

Hemangiosarcoma is a rare neoplasm of horses and hemangiosarcoma in young horses might behave differently than in mature horses. The purpose of this study was to identify the characteristics of hemangiosarcoma occurring in horses < or = 3 years of age. Medical records from 1982 to 2004 were searched for horses < or = 3 years of age with a histopathologic diagnosis of hemangiosarcoma. Eleven records were identified. Thoroughbred and Thoroughbred crosses predominated. Age ranged from 9 days to 3 years. All horses presented with cutaneous or leg swellings or joint effusion. Physical examination findings included tachycardia, fever, and depression. Laboratory abnormalities included anemia (5/11), hyperfibrinogenemia (4/11), hypofibrinogenemia (3/11), thrombocytopenia (2/11), and neutrophilic leukocytosis (1/11). Ultrasonographic and radiographic evaluation was not diagnostic in any case. Antemortem histopathologic diagnosis was obtained in 10 cases. Six of 11 horses were euthanized. Surgical resection was performed in 5 horses, 2 of which were later euthanized. Diagnosis was confirmed histologically at postmortem examination in all euthanized horses. Two cases resolved spontaneously. Early histopathologic diagnosis may allow cure if the mass is localized and amenable to surgical resection. In cases where the horse is medically stable, and masses are not interfering with quality of life, a period of observation may be warranted.     

Historical and clinical features of 200 cases of equine sinus disease

The historical and clinical findings in 200 referred cases of equine sinus disease were reviewed retrospectively. Univariable and multivariable analyses were performed to detect significant differences in historical or clinical features between various categories of sinus disease. The causes of sinus disease were classified as subacute primary (less than two months duration) (n=52), chronic primary (more than two months duration) (n=37), dental (n=40), sinus cyst (n=26), traumatic (n=13) or mycotic sinusitis (n=7), sinus neoplasia (n=10), dental-related oromaxillary fistula (n=8) and intrasinus progressive ethmoid haematoma (n=7). The majority of sinus disorders were of chronic duration at the time of referral and most (including 97 per cent of chronic primary sinusitis cases) had not responded to previous antibiotic therapy and/or sinus lavage in some cases. Clinical signs included unilateral nasal discharge in most cases, including purulent or mucopurulent discharge in all horses with primary, dental and mycotic sinusitis. Haemorrhagic nasal discharge was a feature of traumatic sinusitis and intrasinus progressive ethmoid haematomas. Firm facial swellings and nasal airflow obstruction were features of sinus cysts and neoplasms. Ipsilateral lymphadenitis was a more prominent feature of sinus disease with active infections such as primary, dental or mycotic sinusitis.     

Transmaxillary anchored silicon embedded gauze plug in the post-operative treatment of a large oromaxillary fistula caused by a supernumerary cheek tooth

A 9-year-old Hungarian sport horse gelding was presented to the clinic in poor condition displaying malodorous bilateral purulent nasal discharge. Oral examination revealed the presence of supernumerary 111 and 211. Bilateral diastema formation between the third maxillary molars and the supernumerary teeth with deep periodontal pockets and massive food impactions were diagnosed endoscopically. Radiography revealed inhomogenous sinus opacities in the left and right paranasal sinuses. Following bilateral oral extractions of the supernumerary cheek teeth and third maxillary molars, bilateral oromaxillary fistula formations were diagnosed (about 17 mm diameter on the right side). Bilateral frontal and right-sided maxillary trephinations and resection of the right bulla of the maxillary septum were performed. Massive food impactions of the left and right paranasal sinuses were removed under endoscopic control. Repeated trans-endoscopic sinus lavage was performed post-operatively. After 2.5 months, the large right-sided oromaxillary communication was temporarily closed with a transmaxillary anchored, gauze-cored silicon plug on an outpatient basis. Follow-up examination after 187 days revealed complete closure of the oromaxillary fistula and absence of sinusitis. In a 1.5-year follow-up control, no pathological conditions were found.     

Gastric squamous cell carcinoma in the horse: Seven cases (2009–2019)

This report describes gastric squamous cell carcinoma (GSCC) in seven horses. It records the clinical signs, treatment and outcomes. Main clinical signs were mostly nonspecific and included weight loss, anorexia, fever, tachycardia and tachypnoea. Some more suggestive clinical signs were observed such as recurrent choke, halitosis and hypersalivation. Chronic anaemia and hypoalbuminaemia were common findings. Gastroscopy identified a gastric mass in four cases (57.1%); however, visualisation of the stomach was precluded in the other three horses due to distal oesophageal neoplastic infiltration and compression. Gastric wall thickening was noticed using abdominal ultrasonography in four horses (57.1%). Neoplastic cells could only be detected in the peritoneal fluid of 2 out of 7 horses. Endoscopic-guided or transabdominal ultrasound-guided biopsies allowed an ante-mortem diagnosis in three horses (42.8%). Gastric masses were identified at post-mortem examination and metastasis were confirmed in the liver and/or the spleen for 4/4 cases. In the cases for which palliative therapy was attempted, most of the horses were subjected to euthanasia within 4 weeks. In conclusion, GSCC is an uncommon neoplastic disease in horses. A combination of diagnostic tests is often necessary to achieve a diagnosis, which is frequently only made late in the course of the disease. As a result, GSCC is commonly associated with a poor short-term prognosis.     

The prevalence of secondary dentinal lesions in cheek teeth from horses with clinical signs of pulpitis compared to controls

Reasons for performing study: With the advent of detailed oral examination in horses using dental mirrors and rigid endoscopy, secondary dentinal lesions are observed more frequently. More information regarding the association of secondary dentinal defects with apical dental disease would improve the sensitivity of oral examination as a diagnostic aid for pulpitis. Objectives: To assess prevalence and severity of secondary dentinal defects observed on examination of occlusal surfaces of cheek teeth (CT) from horses showing clinical signs of pulpitis compared to asymptomatic controls. Methods: Records from all cases of equine CT exodontia at the University of Bristol over a 4 year period were examined. Case selection criteria included the presence of clinical signs of pulpitis, an intact extracted tooth and availability of a complete history and follow up. Cases where coronal fracture or periodontal pocketing featured were excluded. CT from cadavers with no history of dental disease served as normal controls. Triadan positions and eruption ages of control teeth were matched with those of teeth extracted from cases. CT from selected cases and control teeth were examined occlusally. Secondary dentinal defects were identified and graded. Prevalence of occlusal lesions in CT with pulpitis and controls was compared. Results: From the records of 120 horses where exodontia was performed, 40 cases matched selection criteria. Twenty‐three mandibular and 21 maxillary CT were extracted from cases. The controls consisted of 60 mandibular and 60 maxillary CT from 7 cadaver skulls. Secondary dentinal defects were significantly over‐represented in CT extracted from cases of pulpitis (P<0.001). Of diseased mandibular CT, 56.5% had defects compared to none of the controls. Of diseased maxillary CT, 57% had defects compared with 1.6% of controls. Multiple defective secondary dentinal areas and severe lesions were more prevalent in diseased mandibular CT compared with diseased maxillary CT. Conclusions and practical significance: Careful examination of occlusal secondary dentine is an essential component in investigation of suspected pulpitis in equine CT.     

CT FEATURES OF ALVEOLITIS AND SINUSITIS IN HORSES

Sinusitis is a common disorder in horses and may result from trauma, dental diseases, or space-occupying lesions. Radiography can only provide a limited amount of information. Computed tomography (CT) has been documented as an alternative imaging method. Eighteen horses (mostly Warmblood) with signs of chronic sinusitis were examined preoperatively with CT to assist in diagnosis of the underlying cause. There was a group of common CT features in horses with dental disease and sinusitis. The first molar was the most frequently affected maxillary cheek tooth. Hypoattenuation of the cementum, destruction of the enamel, and filling of the infundibular cavity with gas were the most frequent CT findings associated with caries. Gas bubbles within the bulging root area or fragmentation of the root in combination with swelling of the adjacent sinus lining were the most important CT features of dental decay. CT findings associated with sinusitis included excessive thickening of the respiratory epithelium in the rostral maxillary sinus; the caudal maxillary sinus was less often involved. The infraorbital canal, the nasomaxillary duct, and the frontomaxillary aperture were usually involved. The maxillary bone, however, especially the facial crest, was involved in nearly every horse, being characterized by endosteal sclerosis, thickening, periosteal reaction, and deformation leading to facial swelling in chronic infections. CT images allowed identification of involvement of individual teeth more clearly to reveal the diseased one for treatment. Three-dimensional imaging allowed improved understanding of the extent and severity of the pathologic change.     

Heterotopic polydontia as a cause for a cystic lesion in the paranasal sinus of a Thoroughbred filly

A 1-year-old Thoroughbred filly with left bony facial distortion was diagnosed with a multilobar expansile mass within the caudal maxillary and frontal sinuses on computed tomography (CT). Typical findings associated with a sinus cyst, including expression of amber fluid from the mass and a thick lining that could be peeled from the sinus walls, were found on surgical exploration of the sinus under general anaesthesia. Histological examination of firm structures within the fluid-filled cyst contained all components of embryologically normal dental tissue. The filly recovered well and entered training to race as a 2-year-old, as remodelling of the bony distortion and narrowing of the nasal passage was sufficient for airflow. Previous reports of paranasal cystic lesions in horses suggest developmental abnormalities as a causative factor, especially in young horses. Furthermore, heterotopic polydontia is reported as the underlying aetiology in some human paranasal sinus cysts. While polydontia has been reported in the paranasal sinuses and nasal passages of horses, this is the first case report that finds them associated with a cystic lesion within the paranasal sinus.     

CLINICAL AND DIAGNOSTIC IMAGING CHARACTERISTICS OF LATERAL DIGITAL FLEXOR TENDINITIS WITHIN THE TARSAL SHEATH IN FOUR HORSES

Lateral digital flexor tendonitis is a rarely reported cause of hind limb lameness in performance horses. The purpose of this retrospective study was to describe clinical and diagnostic imaging findings for a group of horses with lateral digital flexor tendinitis within the tarsal sheath. Equine cases with a diagnosis of lateral digital flexor tendonitis and magnetic resonance imaging (MRI) studies of the affected region were retrieved from North Carolina University's medical record database. Recorded data for included horses were signalment; findings from history, physical examination, lameness examination, and all diagnostic imaging studies; treatment administered; and outcome. Four horses met inclusion criteria. Lameness was mild/moderate in severity and insidious in onset in all patients. Responses to flexion tests were variable. All horses showed positive improvement (70–90%) in lameness after tarsal sheath analgesia. Radiographic, scintigraphic, and ultrasonographic findings were inconclusive. For all horses, MRI characteristics included increased T2, PD, and STIR signal intensity within the lateral digital flexor tendon in the area of the tarsal sheath. Tarsal sheath effusion was slight in three horses, and mild/moderate in one horse. With medical treatment, two horses were sound at 6‐month followup, one horse was sound at 1‐year followup, and one horse had a slight persistent lameness (grade 1/5) at 9‐month followup. Findings supported the use of MRI for diagnosing lateral digital flexor tendonitis within the tarsal sheath in horses. Affected horses may have a good prognosis for return to athletic performance following appropriate medical treatment.     

Repair of oronasal fistulae using auricular cartilage grafts in five cats

OBJECTIVE: To describe repair of chronic palatine defects in cats, with free cartilage graft harvested from either the pinna (scapha) or vertical ear canal (annular cartilage). STUDY DESIGN: Retrospective study. ANIMALS: Cats (n=5) with chronic oronasal fistula. METHODS: Cartilage was harvested from either the scapha or annular cartilage and epithelium removed. After preparation of the edges of the palatal defect by separation of the oral and palatal mucosa circumferentially, the graft was inserted between the epithelial layers and secured without tension. The graft acted as a scaffold for migration of granulation tissue and epithelialization. RESULTS: Oronasal fistulae were successfully repaired in 5 cats (3 pinna grafts; 2 annular cartilage grafts); 1 cat required a second graft after the first graft was dislodged. CONCLUSIONS: Auricular cartilage provides a reliable framework for repair of oronasal fistulae in cats. CLINICAL RELEVANCE: Chronic oronasal fistulae refractory to conventional repair can be treated by use of auricular free graft (pinna or annular cartilage) without disfigurement. Use of annular cartilage to support palatal repairs offers surgeons an additional option when other methods have failed. We recommend using conchal cartilage as the initial treatment approach for repair of small oronasal fistulae in cats.     

Diagnostic validity of electroencephalography in equine intracranial disorders

Electroencephalography (EEG) is a valuable diagnostic test to identify functional disturbances in brain activity. The purpose of this study was to assess the validity of EEG as a diagnostic indicator of intracranial diseases in horses. The validity of EEG was estimated by comparing clinical, clinicopathologic, and histopathologic findings to EEG findings in 20 horses examined for seizures. collapse, or abnormal behavior between 1984 and 1997. A bipolar left-to-right, back-to-front montage and a bipolar circular montage were recorded from sedated (4) and anesthetized (16) horses. Visual and semiquantitative masked analysis of EEG recording Ist was validated on 10 horses presented for problems other than intracranial diseases. EEG pattern was normal in 7 of the 20 clinically affected horses. Abnormal EEG patterns included high-voltage slow waves and discrete paroxysmal activity with or without generalized activity in 13 horses. Histopathologic diagnoses in 10 horses included meningoencephalitis, neuronal necrosis, congenital anomalies. cerebral edema. and abscess. All of these horses had abnormal EEG patterns (sensitivity, 100%) with a positive neuroanatomic correlation in 7 animals. Localization of histopathologic and EEG abnormalities did not correlate in 15% of the horses (3/20). The cause of neurologic signs could not be explained at postmortem examination in 10 animals and the EEG pattern was normal in 7 of these horses (specificity, 70%). In conclusion, equine EEG was a sensitive tool in the diagnosis of intracranial disorders.     

AORTO-CARDIAC FISTULAS IN SEVEN HORSES

This report describes the history, clinical, electrocardiographic and echocardiographic findings, treatment, outcome, and post-mortem findings in seven horses with aorto-cardiac fistula. Affected horses included 5 stallions, one gelding and one mare; 2 each of the Thoroughbred, Arabian and Standardbred breeds and one Thoroughbred-cross with a mean ± s.d. age of 12 ± 4 years, range 6–18 years. The presenting sings were acute distress (four horses), exercise intolerance (two horses) and the lesion was detected during a routine examination in one horse. Five horses had monomorphic ventricular tachycardia on admission and one other had a history of this arrhythmia. Five horses had a characteristic continuous murmur loudes in the right fourth intercostal space. Echocardiography (six horuses) and/or post-mortem examination (four horses) revealed the horses had aorto-cardiac fistulas arising from the right aortic sinus in all five horses in which the site was recorded. Two horses had ruptured aneurysmall dilatations of the aortic wall at this site. Fistulas extended into the right ventricle in four horses; the right atrium in two horses, the left ventricle in one horse, and five horses had dissecting tracts in the septal myocardium. Horses survived for periods ranging from 24th to 4 years. Aorto-cardiac fistula should be considered in the differential diagnosis for horses presenting with acute distress, bounding arterial pulse, a right-sided continuous murmur and/or monomorphic ventricular tachycardia, particularly in middle-aged or older stallions. Echocardiography is the technique of choice for confirming the diagnosis and demonstrating accompanying cardiac changes.