Dorsal-to-palmar branch neuroanastomosis in horses undergoing palmar digital neurectomy does not reduce neuroma formation or improve outcome.

OBJECTIVE: Chronic foot pain, a common cause of forelimb lameness, can be treated by palmar digital neurectomy (PDN). Complications include neuroma formation and lameness recurrence. In humans, neuroanastomoses are performed to prevent neuroma formation. The aim of the study was to evaluate the outcome of horses undergoing dorsal-to-palmar branch neuroanastomosis following PDN. STUDY DESIGN: Retrospective case series. ANIMALS: Eighty-five horses with PDN and dorsal-to-palmar branch neuroanastomosis. METHODS: Medical records for horses undergoing this procedure at two hospitals between 2015 and 2020 were reviewed. Palmar and dorsal nerve branches of the PDN were transected and end-to-end neuroanastomosis was performed by apposition of the perineurium. Follow-up was obtained from medical records and telephone interviews. Success was defined as resolution of lameness for at least one year. RESULTS: Lameness resolved following surgery in 81/85 (95%) horses with 57/84 (68%) sound at one year. Postoperative complications occurred in 19/85 (22%) cases. The main limitations of the study were an incomplete data set, inaccurate owner recall, and variations in procedure. CONCLUSION: Compared to previous studies, this technique resulted in similar numbers of horses sound immediately after surgery, a comparable rate of postoperative neuroma formation but a higher recurrence of lameness rate at 1 year postoperatively. CLINICAL SIGNIFICANCE: End-to-end neuroanastomosis of the dorsal and palmar branches of the PDN does not reduce the rate of neuroma formation in horses. Long-term outcome was less favorable compared to previously reported PDN techniques.

Comparison of three methods of tonometry in horses presented for ophthalmic disease.

OBJECTIVE: To compare the measurement of intraocular pressure in horses with clinical ocular disease using three tonometry devices. ANIMALS STUDIED: A total of fifty horses were presented to the New Bolton Center Ophthalmology Service. PROCEDURE: Intraocular pressure was taken on 50 client-owned horses (100 eyes) using the TonoVet, TonoVet Plus and Tono-Pen Avia tonometers. Clinical equine patients included were presented to New Bolton Center for ophthalmic examination. Auriculopalpebral blocks were performed but horses were unsedated. RESULTS: All three tonometers were found to have strong agreement among them. The strongest agreement was between the TonoVet and the TonoVet Plus with the TonoVet on average 1.330 mmHg less than the TonoVet Plus (standard deviation 4.388 mmHg). This was followed by the TonoVet and the Tono-Pen Avia Vet with the TonoVet on average 2.531 mmHg greater than the Tono-Pen Avia Vet (standard deviation 4.124 mmHg). The weakest agreement was between the TonoVet Plus and the Tono-Pen Avia with the TonoVet Plus on average 3.854 mmHg greater than the Tono-Pen Avia (standard deviation 4.724 mmHg). CONCLUSIONS: All three tonometers showed strong agreement, however, the TonoVet and the TonoVet Plus carried the strongest agreement with the TonoVet Plus having slightly higher measurements overall compared with the TonoVet. Due to small variations between devices, it is recommended that the same device be used for serial measurements of intraocular pressure. However, all three devices are appropriate to use in horses presented for ophthalmic evaluation.

Neuromuscular blockade with atracurium for ophthalmic surgery in horses-Effects on surgical and anesthetic characteristics and recovery quality.

OBJECTIVE: To study the surgical, anesthetic and recovery qualities of horses receiving either a neuromuscular blocking agent (atracurium) or intravenous lidocaine (treatment groups A and L, respectively). ANIMALS STUDIED: A total of thirty horses presented for ocular surgery were used in this study. PROCEDURE: Horses were randomly assigned to receive either atracurium (group A) or a lidocaine constant rate infusion (group L). Surgical quality was graded on a scale from 1 (excellent)-5 (poor). While anesthetized, the heart rate, oxygen saturation and mean arterial blood pressure, and end-expiratory carbon dioxide and desflurane concentration were monitored and recorded every 5 minutes. Recovery was scored on a scale from 10 (best)-115 (worst). RESULTS: Horses in treatment group A needed significantly less desflurane then horses in treatment group L (p = 0.04). Horses in treatment group A had a significantly better surgery score of 1 (1-2) (median and range) then horses in treatment group L (2.5; 1-5) (p = 0.02). The quality of recovery was significantly better in horses in treatment group A compared with treatment group L, and horses needed significantly less time to reach the standing position. CONCLUSIONS: Atracurium and lidocaine CRI are safe methods of anesthesia for equine patients undergoing ocular surgery. Horses receiving atracurium needed less desflurane and had better surgery and recovery scores than horses receiving a lidocaine constant rate infusion.

Ocular disease in horses with confirmed ocular or central nervous system Borrelia infection: Case series and review of literature.

OBJECTIVE: To describe the clinical presentation, treatment, and clinical outcome of horses with ocular disease and evidence of systemic or ocular Lyme disease. ANIMALS STUDIED: Five horses met the inclusion criteria of ocular disease with evidence of B burgdorferi present in ocular or CNS tissues. PROCEDURE: The goal of this study was to describe the clinical presentation and progression of ocular disease when associated with ocular or CNS B burgdorferi infection in horses. A retrospective review of medical records was performed on horses admitted for ocular disease with evidence of B burgdorferi infection between 1998 and 2015. The diagnosis of B burgdorferi-associated uveitis was based on histopathologic lesions of lymphohistiocytic and suppurative uveitis/endophthalmitis and intralesional argyrophilic spirochetes in either ocular or CNS tissue consistent with Borrelia. Leptospiral uveitis was ruled out by PCR. RESULTS: All five horses in the current study had intraocular inflammation at the time of presentation. Medical management with anti-inflammatories was successful in controlling uveitis in the two horses in which treatment of uveitis was attempted. Systemic treatment with oral tetracyclines was unsuccessful in a single case in which treatment of Borrelia was attempted. Four horses were euthanized due to progression of neurologic disease. The surviving horse had an enucleation performed and did not show systemic signs. CONCLUSIONS: Infection with Borrelia burgdorferi should be considered in endemic areas as a differential for horses with ocular disease, in particular, uveitis. The prognosis for uveitis and neurologic disease associated with Lyme disease was poor in the current study.

Facial nerve paralysis in 64 equids: Clinical variables, diagnosis, and outcome.

BACKGROUND: Facial nerve paralysis (FNP) in equids is not well described in the veterinary literature. OBJECTIVE: To investigate the causes of FNP and associations among clinical variables, diagnosis, and outcome. ANIMALS: Sixty-four equids presenting with FNP between July 2000 and April 2019. Cases of postanesthetic FNP were excluded. METHODS: Medical records were retrospectively reviewed. Variables were evaluated for associations with outcomes (diagnosis and case outcome) using logistic regression. RESULTS: The most common cause of FNP was trauma (n = 20). Additional diagnoses included central nervous system (CNS) disease (n = 16), idiopathic (n = 12, 4 of which had adequate diagnostic investigation and were considered "true" idiopathic, and 8 of which were considered "not investigated" idiopathic), temporohyoid osteoarthropathy (n = 10), otitis media-interna (n = 3), lymphoma (n = 1), iatrogenic as a consequence of infiltration of local anesthetic (n = 1), and clostridial myositis (n = 1). Follow-up was available for 55 (86%) cases. Twenty-nine (53%) equids had full resolution of FNP, 14 (25%) were euthanized, 6 (11%) partially improved, and 6 (11%) were unchanged or worse. CONCLUSIONS AND CLINICAL IMPORTANCE: If FNP is the consequence of CNS disease, successful treatment of the primary disease likely leads to resolution of FNP. Most cases of FNP in equids are traumatic in origin. True idiopathic cases are uncommon.

Ocular and periocular hemangiosarcoma in six horses.

OBJECTIVE: To determine the characteristics of and prognosis for ocular and periocular hemangiosarcoma in horses. ANIMAL STUDIED: Six horses treated for ocular or periocular hemangiosarcoma. PROCEDURE: A retrospective review of medical records from 2007 to 2015 was performed to identify horses with a histologic diagnosis of ocular or periocular hemangiosarcoma. Signalment (age, sex, breed), duration of clinical signs, prior treatment, tumor size and location, medical and surgical treatment including postoperative chemotherapy, follow-up time, and outcome were obtained from medical records. Histopathology was reviewed by a board-certified pathologist. RESULTS: In six horses diagnosed with ocular or periocular hemangiosarcoma, no breed, age, or sex was overrepresented. Sites included the temporal limbus (3), third eyelid (2), and uvea (1). With the exception of one horse with uveal hemangiosarcoma, 5/6 horses had lightly pigmented periocular haircoat. Histologic features of ocular hemangiosarcoma in 6/6 cases included high cellularity, nuclear pleomorphism, and inflammation with a mitotic index ranging from 0 to 8 mitoses per 10 consecutive 400× fields. Five of six tumors displayed solar elastosis, indicating ultraviolet light-induced damage to sub-epithelial collagen. Treatment included surgical excision in all cases and was not associated with recurrence in 4/6. Three cases that received ancillary treatment with topical mitomycin C had no postoperative recurrence. Two cases with postexcisional recurrence had histologic evidence of incomplete excision. CONCLUSIONS: Complete surgical excision may be associated with resolution of periocular and ocular hemangiosarcoma in horses. Etiopathogenesis may include exposure to ultraviolet light.

Corneal sensitivity and tear production in 108 horses with ocular disease.

PURPOSE: To compare corneal sensitivity and tear production in horses with keratitis to horses with other ocular disease. METHOD: Retrospective medical record review was used to identify equine patients presented during a 1-year period for an ocular complaint who had Schirmer Tear Test (STT) or Corneal Touch Threshold (CTT) measured. Variables studied included patient age and sex; affected eye; category of presenting ocular complaint (keratitis vs. other ocular complaint); STT; and CTT. Patients with a complaint of ulcerative keratitis, immune-mediated keratitis, and stromal abscess were categorized in the keratitis group. Patients with a complaint of uveitis, as well as lid, lens, or retinal disease, were categorized in the group having other ocular disease. For patients presenting more than once in 2013, only the first visit at which STT or CTT was measured was included. For patients with bilateral disease, STT and CTT of both eyes were averaged. RESULTS: A total of 108 patients were included, 45 with keratitis and 63 with other ocular disease. Average age was 13.65 years, with more males (77) than females (31). Adjusted for age, STT in affected eyes did not differ significantly between the two groups (keratitis = 29.92 mm/min; other ocular disease = 27.96 mm/min), but CTT was significantly lower in patients with keratitis (33.78 mm) than in patients with other ocular disease (40.10 mm). CONCLUSIONS: Corneal sensitivity may be decreased in patients with keratitis. It is not known whether this is a cause or an effect of corneal disease.

Corneal edema in four horses treated with a superficial keratectomy and Gundersen inlay flap.

OBJECTIVE: To describe the clinical presentation, treatment, and outcome of four horses with severe corneal edema caused by suspected endothelial disease treated with a superficial keratectomy and Gundersen inlay flap and to determine whether this procedure (i) reduces corneal edema, (ii) reduces ocular pain, (iii) eliminates recurrent corneal ulceration, and (iv) improves vision in these horses. ANIMALS STUDIED: Four horses met inclusion criterion of (i) diagnosis with endothelial disease by a board-certified veterinary ophthalmologist and (ii) surgical treatment with a superficial keratectomy and Gundersen inlay flap. PROCEDURE: Retrospective medical record review of included horses was used to determine breed, age and sex of included horses, as well as details of medical and surgical therapy, and visual outcome. RESULTS: Four horses were presented with a complaint of focal corneal edema that progressed to diffuse corneal edema. Epithelial bullae and ulceration were present in all cases. The disease process was unresponsive to standard medical treatment with a hyperosmotic agent and topical and systemic anti-inflammatories. However, treatment with a superficial keratectomy and Gundersen inlay flap performed under general anesthesia was associated with (i) a significant decrease in corneal edema, (ii) increased comfort, (iii) elimination of corneal ulceration, and (iv) retention of vision postoperatively with little to no need for medical therapy. Follow-up time was 15, 12, 6, and 3 months. CONCLUSIONS: The superficial keratectomy and Gundersen inlay flap may provide a surgical alternative to chronic medical treatment of severe corneal edema in horses.

Interval prevalence of and factors associated with colic in horses hospitalized for ocular or orthopedic disease.

OBJECTIVE To determine interval (1-year) prevalence of and factors associated with colic in horses hospitalized for ocular or orthopedic disease. DESIGN Cross-sectional study. ANIMALS 105 horses with ocular disease and 197 horses with orthopedic disease admitted to a veterinary teaching hospital between July 1, 2011, and June 30, 2012. PROCEDURES Medical records were reviewed to determine whether colic (abnormal behavior prompting abdominal palpation per rectum or nasogastric intubation) was observed during hospitalization. Data were collected on putative risk factors for colic, including reason for admission, signalment, and medical or surgical interventions received. RESULTS No significant difference in interval prevalence of colic was identified between horses with ocular disease (8/105 [8%]) or orthopedic disease (9/197 [5%]). However, horses with ocular disease differed significantly from other horses in median age (10 vs 3 years, respectively); proportions of sexually intact males (3% vs 30%), Thoroughbreds (28% vs 62%), and those receiving general anesthesia (65% vs 80%); and median duration of hospitalization (3 vs 2 days). For every 1 mg/kg increase in daily NSAID dose, the odds of colic increased by 98%. No difference between groups was identified in median duration of colic (1 day), hospitalization (7 vs 3 days), or systemic NSAID administration (7 vs 5 days). Colic in both groups resolved with medical management for all but 1 horse with ocular disease. CONCLUSIONS AND CLINICAL RELEVANCE Horses hospitalized for ocular disease were at no greater odds for colic than were horses hospitalized for orthopedic disease. Medical management of colic appeared adequate for most horses.

Porcine urinary bladder extracellular matrix grafts (ACell Vet® Corneal Discs) for keratomalacia in 17 equids (2012-2013).

OBJECTIVE: To describe the clinical course, outcomes, and complications associated with use of commercially available porcine urinary bladder extracellular matrix (ECM) grafts (ACell Vet(®) Corneal Discs) in equid patients with keratomalacia, and to evaluate the efficacy of ECM grafts as a viable alternative to other biomaterials for corneal grafting in equid patients. ANIMALS: Sixteen horses and one donkey (17 eyes) with unilateral keratomalacia severe enough to warrant surgical repair between August 2012 and September 2013. PROCEDURE: Retrospective medical record review to identify equid patients meeting inclusion criteria of (i) diagnosis with keratomalacia severe enough to warrant surgical repair and (ii) surgical repair with an extracellular matrix graft. RESULTS: Eleven geldings, four mares, and two colts met inclusion criteria. Patients averaged 9 years of age. Twelve of 17 eyes (71%) were considered infected based on either corneal cytology (10/17, or 59%) or corneal culture (12/17, or 71%) positive for bacteria (8/17, or 47%) or fungi (9/17, or 53%). At the time topical medications were discontinued, 16 eyes (94%) were visual. One operated eye ruptured 5 days postoperatively and was enucleated. Keratouveitis developed in 14/14 eyes that underwent regular examinations approximately 2 weeks postoperatively which responded to systemic nonsteroidal anti-inflammatory drug therapy. CONCLUSIONS: Extracellular matrix grafts may be a viable alternative to other biomaterials for corneal grafting in equids. Advantages include commercial availability and shelf storage.

Characterization and outcome following excision of masses in the nictitating membranes of horses: 50 cases (1998-2012).

OBJECTIVE: To determine the histologic findings associated with masses in the nictitating membranes (third eyelids) of horses and to identify prognostic factors associated with recurrence and the outcome. DESIGN: Retrospective case series. ANIMALS: 50 horses with masses in a third eyelid. PROCEDURES: Medical records of horses with partial or complete excision of a third eyelid and submission for histologic evaluation between September 1998 and November 2012 were reviewed. Horses were included if follow-up information for at least 1 year after surgery was available. Information regarding signalment and treatment was obtained from the medical records. Histopathology reports were examined to determine surgical margins and vascular invasion. Data were analyzed by means of a χ(2) test to determine the association between recurrence and type of excision (partial or complete), surgical margins, vascular invasion, and use of chemotherapy as well as the association between partial excision of a third eyelid prior to referral and outcome. RESULTS: Squamous cell carcinoma was the predominant tumor type of the third eyelid. There was recurrence in 10 of 50 (20%) horses; recurrence was at a mean of 2.25 years and median of 1.5 years after excision. Partial excision prior to referral was associated with outcome. CONCLUSIONS AND CLINICAL RELEVANCE: In horses with masses in a third eyelid, recurrence and mortality rates were high, which suggested that long-term monitoring is important for all patients in which partial or complete third eyelid excision is performed.

Corneal dystrophy in Friesian horses may represent a variant of pellucid marginal degeneration.

OBJECTIVE: To describe the clinical presentation, treatment, and outcome of a corneal dystrophy in Friesian horses and to analyze affected horses' pedigrees to investigate its heritability. ANIMALS: Nine Friesians with bilateral disease were identified. PROCEDURE: Retrospective medical record review was used to identify Friesian horses exhibiting bilateral symmetric corneal lesions. Variables identified from medical records included patient sex and age at diagnosis; location, depth and size of corneal lesions; medical and surgical therapy instituted; and visual outcome. A four-generation pedigree for each included horse was used to construct a combined pedigree. RESULTS: The nine included horses had an average age at diagnosis of the first eye of 10.7 years, with males (8/9) significantly more frequently affected than females (1/9), P = 0.012. Lesions were inferior and averaged 5 mm in diameter. Depth ranged from superficial facets to perforations, which developed in nine of 18 eyes. Eight of nine perforations were surgically repaired, with seven of eight repaired eyes visual at last follow-up. All nine eyes that had not perforated remained visual. All affected horses shared a common ancestor within six generations. CONCLUSIONS: This form of corneal dystrophy in Friesian horses, characterized by bilateral symmetric stromal loss, appears to be progressive but responds well to surgical repair, occurs more frequently in males, may have a genetic component in Friesian horses, and may be a variant of pellucid marginal degeneration.

Shifting fundamental frequency in simulated electric-acoustic listening.

Previous experiments have shown significant improvement in speech intelligibility under both simulated [Brown, C. A., and Bacon, S. P. (2009a). J. Acoust. Soc. Am. 125, 1658-1665; Brown, C. A., and Bacon, S. P. (2010). Hear. Res. 266, 52-59] and real [Brown, C. A., and Bacon, S. P. (2009b). Ear Hear. 30, 489-493] electric-acoustic stimulation when the target speech in the low-frequency region was replaced with a tone modulated in frequency to track the changes in the target talker's fundamental frequency (F0), and in amplitude with the amplitude envelope of the target speech. The present study examined the effects in simulation of applying these cues to a tone lower in frequency than the mean F0 of the target talker. Results showed that shifting the frequency of the tonal carrier downward by as much as 75 Hz had no negative impact on the benefit to intelligibility due to the tone, and that even a shift of 100 Hz resulted in a significant benefit over simulated electric-only stimulation when the sensation level of the tone was comparable to that of the tones shifted by lesser amounts.

Low-frequency modulation of distortion product otoacoustic emissions in humans.

Low-frequency modulation of distortion product otoacoustic emissions (DPOAEs) was measured from the human ears. In the frequency domain, increasing the bias tone level resulted in a suppression of the cubic difference tone (CDT) and an increase in the magnitudes of the modulation sidebands. Higher-frequency bias tones were more efficient in producing the suppression and modulation. Quasi-static modulation patterns were derived from measuring the CDT amplitude at the peaks and troughs of bias tones with various amplitudes. The asymmetric bell-shaped pattern resembled the absolute value of the third derivative of a nonlinear cochlear transducer function. Temporal modulation patterns were obtained from inverse FFT of the spectral contents around the DPOAE. The period modulation pattern, averaged over multiple bias tone cycles, showed two CDT peaks each correlated with the zero-crossings of the bias tone. The typical period modulation pattern varied and the two CDT peaks emerged with the reduction in bias tone level. The present study replicated the previous experimental results in gerbils. This noninvasive technique is capable of revealing the static position and dynamic motion of the cochlear partition. Moreover, the results of the present study suggest that this technique could potentially be applied in the differential diagnosis of cochlear pathologies.