Use of scintigraphy for diagnosis of equine paranasal sinus disorders

OBJECTIVES: To describe and analyze subjective and objective scintigraphic findings in horses with paranasal sinus disorders. ANIMALS: Horses with suspected disorders of the paranasal sinuses or cheek teeth (n = 48) and control horses (n = 30). METHODS: 99Technetium-methylenediphosphate (99Tc-MDP; 7500 MBq) was administered for scintigraphic examination of the skull. Abnormal patterns of increased radionuclide uptake (IRU) were identified and subjectively described. Scintigrams and radiographs were blindly assessed by 2 clinicians and the accuracy of the imaging modalities was compared. Objective analysis was performed by comparing regions of interest (ROI) drawn over areas of abnormal IRU to the equivalent area on the unaffected side using the Mann-Whitney test. An ROI ratio (affected:non-affected sides) was also calculated for each lesion. RESULTS: Twenty-eight horses were diagnosed with primary (15) or secondary (13) sinusitis. Nine primary sinusitis cases had focal area(s) of moderate or marked IRU in addition to a more diffuse uptake in the affected sinus(es). kappa was marginally higher for scintigraphic assessment of paranasal sinus disorders than for radiographic assessment. There were significant differences in mean counts/pixel in ROI drawn on the affected side compared with the non-affected side. There was considerable overlap between the magnitudes of ROI ratios found with many different disorders. CONCLUSIONS: Scintigraphy can be useful for differentiation of sinusitis of dental origin from other causes of sinusitis. Quantitative analysis of scintigrams is not reliable for identification of particular disorders. CLINICAL RELEVANCE: Focal areas of moderate or marked IRU may be observed with primary sinusitis. Careful 3-dimensional localization of the lesion, along with consideration of other clinical and diagnostic findings should be performed to prevent false-positive diagnoses of periapical infection in such instances.     

Clinical anatomy of the equine sphenopalatine sinus

REASONS FOR PERFORMING STUDY: Disorders of the equine sphenopalatine sinus, including empyema and neoplasia, have been reported to cause damage to cranial nerves II and V. However, the clinical anatomy of these sinuses is not well described in horses. OBJECTIVE: To examine the anatomy of the sphenopalatine sinuses in a range of equidae and, in particular, to examine the relationship of these sinuses to adjacent major nerves and vessels. METHODS: The anatomy of the sphenoidal and palatine paranasal sinuses was examined in 16 equidae, primarily using transverse skull sections. Relevant structures were documented and photographed. RESULTS: There was much variation between individual horses in sphenopalatine sinus anatomy. The sphenoidal sinuses were small in young horses and appeared to become larger and more complex with age. Variation was present in the extent that the sphenopalatine sinus extended into the basisphenoid bone. The septum dividing left and right sphenoidal sinuses was frequently not midline, but was intact in all cases. The sphenoidal and palatine sinuses communicated in most horses. In such cases, what could accurately be termed the (combined) sphenopalatine sinuses usually drained directly into the caudal maxillary sinuses. Additionally, in 5 out of 16 cases, some compartments of the sphenoidal sinus also drained into the ethmoidal sinus. The dorsal and lateral walls of the sphenoidal sinus were very thin and directly adjacent to cranial nerves II, III, IV, V and VI and major blood vessels. CONCLUSIONS: The equine sphenoidal and palatine sinuses are very variable in their anatomy, but are always in close proximity to multiple cranial nerves and major blood vessels. POTENTIAL RELEVANCE: Many cranial nerves and blood vessels could be damaged with disorders involving the sphenopalatine sinus, potentially causing major and variable neurological syndromes, haemorrhage and extension of sepsis.     

Acquisition and interpretation of radiographs of the equine skull

The complex anatomy of the equine skull creates a radiographic challenge. However, radiographs are a commonly required tool in diagnosing dental and sinonasal disease, as well as other disorders of the equine skull. High quality, complete radiographic studies are essential for adequate evaluation. Radiographic technique and interpretation are reviewed in this paper.     

Conformation of the equine skull: a morphometric study

There is a lack of an established method for quantifying equine skull morphology. This study proposes a method that is valid for use on both live and deceased horses. A total of nine head measurements (skull length, cranial length, nasal length, ratio of cranial:nasal length, cranial width, zygomatic width, mandibular depth, nasal profile area, cranial profile area) and six indices (skull index, cranial index, nasal index, mandibular index, nasal profile index, cranial profile index) were recorded from 30 horses from a variety of breeds whilst the soft tissues of the head were intact. A line was drawn level with the palpable notches caudal to the caudal lacrimal process of each orbit to estimate the suture line of the nasal and frontal bones and distinguish between the neurocranium and splanchnocranium. There were positive correlations between many of the head measurements. This method also illustrated significant differences in the skull morphology of three breeds (Arabians, thoroughbreds and standardbreds).     

Peripheral nerve sheath tumour of the equine maxillary sinus

This case report describes an 8‐year‐old Belgian Warmblood mare that was initially diagnosed and treated for a dental sinusitis. Despite removal of the diseased teeth and appropriate treatment, the sinusitis did not resolve. Over time, growth of a peripheral nerve sheath tumour of the left maxillary sinus became apparent, with recurrence after surgical removal. The clinical, radiographic, computed tomography, magnetic resonance imaging and pathological (gross and histological) findings of the first reported peripheral nerve sheath tumour of the equine paranasal region are described and illustrated.     

Management of equine skull fractures using fixation with polydioxanone sutures

Ten horses presented with severe distortion of the facial contour, crepitus on palpation and mild to moderate epistaxis. Individual horses also showed ocular damage, ptosis, severe dyspnoea and movement of the facial bones concurrent with respiration. The fracture fragments were exposed using a large curvilinear incision and elevated using a retractor, periosteal elevator, chisel or Steinmann pin. The fracture fragments were unstable following reduction and fixation was necessary. Stabilisation was achieved with polydioxanone sutures placed through holes drilled in opposing sides of the fracture lines. Polydioxanone sutures provided good stability and had better handling properties than wire. There was good apposition of fracture edges and minimal complications. Use of polydioxanone sutures can also avoid the expense and complexity of plate fixation in selected cases, and should be considered as an alternative to fixation with stainless steel wire in any facial fracture that adjoins stable bone.     

Effects of external thermal manipulation on laminar temperature and perfusion scintigraphy of the equine digit

AIMS: To assess the effects of external thermal manipulation on the soft-tissue and vascular perfusion of the equine digit using nuclear scintigraphy and documented tissue temperatures. METHODS: Six horses were used in a randomised crossover design. Each horse was treated with external heat (47 degrees C) or external cold (4 degrees C) applied to a digit for 30 minutes. The opposite front foot was untreated and used for control measurements. Nuclear scintigraphy was performed before, during, and after therapy to assess vascular and soft-tissue perfusion to the digit in response to therapy. Dorsal hoof wall laminar-tissue temperatures were recorded before, during, and after therapy using a thermistor. RESULTS: Treatment with topical cold therapy significantly decreased soft-tissue perfusion of the digit to 80.5% of the pre-cooled values. Conversely, the application of external heat significantly increased soft-tissue perfusion of the digit 25.1% above the pre-heated values. Vascular perfusion showed similar, but not statistically significant trends. External cold application to the digit caused a significant mean decrease in laminar-tissue temperatures of 11.6 degrees C during therapy, while external heat application to the digit caused a significant mean increase in laminar-tissue temperatures of 3.9 degrees C. CONCLUSION: The external application of heat and cold to the normal equine foot could effectively alter soft-tissue perfusion and laminar-tissue temperatures within 30 minutes of treatment. The application of hot water and ice water to the digit was a safe, well-tolerated, and economical therapy. CLINICAL RELEVANCE: Cooling the foot could decrease enzymatic reactions associated with laminitis, and warming could increase local perfusion when desired.     

Effect of topical phenylephrine on the equine pupil

The mydriatic effect of 10% phenylephrine was evaluated in 9 horses. Base-line pupillary size in mesopic conditions and during light stimulation was ascertained before application of pharmacologic agents. In study 1, 10% phenylephrine was applied to each eye (n = 5 horses). After 15 minutes, the pupillary size was determined in both lighting conditions. Phenylephrine was again applied to each eye, and after an additional 15 minutes, the pupillary size was determined. In study 2, 1% tropicamide was applied to each eye (n = 4 horses), and after 30 minutes, the pupillary size was determined in both lighting conditions. Tropicamide and phenylephrine were applied to each eye immediately after determination of pupillary size, and after an additional 30 minutes, the pupillary size was determined. There was no significant change (P greater than 0.9) in pupillary size when phenylephrine was used alone or when phenylephrine was used in an eye that had been dilated with tropicamide.     

Comparison between radiography and computed tomography for diagnosis of equine skull fractures

The equine head is a complex structure prone to traumatic injuries. To determine the value and limitations of radiography and (CT) for the diagnosis of skull fracture, the differences between the two modalities were described. Two observers retrospectively reviewed the radiographic and CT images of 18 horses with a skull fracture. To allow direct comparison between the two modalities, a simplified fracture classification system was used. In 3/18 cases the evaluation of the radiographic examination concluded no injuries visible. In 2/15 cases soft tissue involvement was not detected and in 7/15 cases the extension of the fracture was underestimated with radiography. Radiography classified 4/10 multiple fractures incorrectly as single fracture and 5/15 comminuted fractures on CT were diagnosed as simple fracture with radiography. The number of fragments was underestimated with radiography in 14/15 cases. In conclusion, radiography is able to diagnose a skull fracture in most cases. Skull fractures however are not similarly classified after radiographic and CT evaluation, which causes a difference in interpretation and perception of the fractures. Therefore, CT should be the modality of choice for surgical planning and prognosis.     

The distribution of ganglion cells in the equine retina and its relationship to skull morphology

It has recently been reported that a strong correlation exists between the distribution of retinal ganglion cells and nose length in the domestic dog. To determine if this phenomenon occurs in another domestic species with diverse skull morphology, the current study examined the distribution of retinal ganglion cells in 30 horses from a variety of breeds. There was a significant variation in the density of ganglion cells found across the retinae. Breed was a significant predictor for ganglion cell density within the visual streak. A strong positive correlation exists between the density of ganglion cells in the visual streak and nasal length. Significant variation was also seen in the area centralis but did not correlate with any of the recorded skull measurements. The findings of this study provide us with further understanding of the equine visual system and the level of variation that exists between individuals of the same species.     

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.     

Effect of exercise on the partitioning of equine respiratory resistance

Pleural, tracheal, pharyngeal and mask pressures as well as airflow and tidal volume of five ponies on a treadmill (incline 8.3 degrees) were recorded simultaneously while resting, walking, trotting slowly, trotting fast, after standing for 30 secs and 5 mins after the end of the exercise. The curves obtained were used to calculate total pulmonary resistance (RL), lower airway resistance (RLA) and upper airway resistance (RUA). The latter was also divided into nasal resistance (Rnas) and laryngeal plus extrathoracic tracheal resistance (Retr + lar). Furthermore, the inspiratory and expiratory components of each of these R values were estimated. Levels of RL, RLA and RUA were increased significantly during exercise but, during the recovery period, the values were significantly lower than those pre-exercise. RUA represented 82 per cent of RL at rest and this percentage did not change significantly during and after exercise. The nasal resistance to RUA ratio was always higher than 0.5. The fact that RL increased with exercise intensity was due to the increase of RUA during inspiration, and mainly a result of the increase of RLA during expiration. At fast trot, RLA represented 5 and 50 per cent of RL during inspiration and expiration respectively. It was concluded that heavy exercise induces in ponies an increase of RL, one reason for which could be the partial collapse of the extrathoracic and intrathoracic airways during inspiration and expiration respectively.     

Effect of local analgesia on movement of the equine back

REASONS FOR PERFORMING STUDY: Diagnostic infiltration of local anaesthetic solution is commonly used in cases of equine back pain. Evaluation is subjective and it is not known how local analgesia of the back affects horses without clinical signs of back pain. OBJECTIVES: To evaluate the effect of infiltration of local anaesthetics on the movement of the back in horses without clinical signs of back pain, and to evaluate the usefulness of kinematic studies as an objective and quantitative tool in evaluating local analgesia in clinical practice. METHODS: The kinematics of the back in 10 clinically sound horses were measured on 2 occasions at walk and trot before and after injections with mepivacaine and sodium chloride around the interspinous spaces between T16 and L2. The kinematics were compared between the 2 occasions before injections and before and after each injection. RESULTS: The range of motion (ROM) for dorsoventral flexion-extension (FE) of the back was increased significantly in all measured segments other than T10 at walk, as was lateral bending (LB) at T10, L3 and L5 after injection of mepivacaine. For lateral excursion (LE), total movement increased at all measured segments. At trot the only affected segment was L3, where the injection with mepivacaine decreased the ROM for FE. After injection of sodium chloride the ROM for FE increased at T13 and T17 at walk. Lateral bending and LE were not affected at walk. At trot, LB increased at L3 and L5. CONCLUSIONS AND POTENTIAL RELEVANCE: Diagnostic infiltration of local anaesthetic solution affects the function of the back in clinically sound horses, which must be considered when interpreting the use of this clinical aid in assessing clinical cases of back dysfunction. Kinematics can qualitatively and quantitatively evaluate the effect of local analgesia of the back.     

Transnasal endoscopic treatment of equine sinus disease in 14 clinical cases

Transnasal endoscopic sinus treatment was used in four horses diagnosed with primary sinusitis and 10 horses with dental sinusitis. Pre-existing (n = 5) or surgically created (n = 9) sinonasal fistulae were used as portals for transnasal endoscopic exploration, debridement and lavage of the inflamed sinus cavities. Endoscopic sinonasal fistulation was performed using either trans-endoscopic diode laser fibre (four cases) or an electrocautery instrument under endoscopic control (five cases). All procedures were performed on standing sedated horses with the use of local anaesthesia. In six cases, the ventral concha was fenestrated in order to gain a portal into the ventral conchal and rostral maxillary sinus. In two cases the dorsal concha was fenestrated to access the caudal group of the paranasal sinuses. One case required fenestration of the ventral conchal bulla due to its empyema. Post-operative bleeding was controlled with a nasal cavity tamponade for 24 h. Endoscopic lavage and debridement of the inflamed sinuses were performed every 2–3 days. Medical treatment consisted of antibiotic and anti-inflammatory drugs. In the cases of dental sinusitis, the underlying dental pathology was addressed. Median hospitalisation time was 10 days (range 5–25 days) and the median number of endoscopic procedures (including the initial procedure) was 4 (range 3–7). Cases were followed-up by telephone consultations with their owners. Intervals between discharge and last follow-up ranged from 4 to 22 months (median 9.5 months). Complete recovery was reported in 10 cases, clinical improvement (occasional nonpurulent discharge) in two cases. Two cases were readmitted due to recurrence of the purulent nasal discharge; both subsequently underwent trephination of the affected sinuses and made a full recovery after removal of the remaining pathological sinus content.