Ouabain, a cardiac glycoside, binds to the Na+-K+i-adenosine triphosphatase (Na+ pump) and prevents active transport of Na+ and K+ across cell membranes. We used [3H]ouabain to quantify the number and affinity of Na+ pumps in skeletal muscle from Quarter Horses with the muscular disorder hyperkalemic periodic paralysis (HYPP). [3H]Ouabain-binding properties of gluteal muscle from clinically normal and affected horses were used to determine whether altered Na+ pump number or affinity could contribute to the pathologic features of muscle in affected horses. Foals and adult horses with HYPP were compared with age-matched clinically normal horses. The number of [3H]ouabain-binding sites in adult gluteal muscle was not different between the 2 types of horses (85.7 +/- 8.9 pmol of [3H]ouabain-binding sites/g [wet muscle weight] in horses with HYPP vs 100.2 +/- 8.8 pmol/g in clinically normal adult horses). Gluteal muscles in HYPP-affected and clinically normal foals also contained a similar number of [3H]ouabain-binding sites (222.3 +/- 21.0 pmol/g vs 225.3 +/- 24.2 pmol/g, respectively). The affinity of these binding sites for ouabain was not different, between adults or foals, in clinically normal or affected horses. Our results indicate that membrane events underlying the periodic episodes of paralysis in horses with HYPP are not attributable to quantitative changes in Na+ pump number or affinity. Our data cannot exclude the possibility that the specific activity of the Na+ pump is altered in muscle from HYPP-affected horses.

OBJECTIVE To evaluate the effect of bilateral ventriculocordectomy via ventral laryngotomy on laryngeal airway resistance (LAR) in canine cadaver larynges. SAMPLE 6 clinically normal canine cadaver larynges. PROCEDURES LAR was determined for each specimen before (baseline) and after bilateral ventriculocordectomy with the epiglottis open and closed. After ventral laryngotomy was performed, the vocal cords were sharply excised, and the incised mucosal edges were apposed with 4-0 glycomer 631 suture in a simple continuous pattern. The thyroid cartilage was apposed with 3-0 polypropylene suture in a simple continuous pattern. RESULTS With the epiglottis closed, baseline median LAR was 27.6 cm H2O/L/s (range, 21.2 to 30.6 cm H2O/L/s), which did not differ significantly from the median LAR after bilateral ventriculocordectomy (24.7 cm H2O/L/s [range, 20.6 to 27.7 cm H2O/L/s]). With the epiglottis open, baseline median LAR was 7.3 cm H2O/L/s (range, 5.4 to 7.8 cm H2O/L/s), which did not differ significantly from the median LAR after bilateral ventriculocordectomy (7.2 cm H2O/L/s [range, 6.6 to 7.6 cm H2O/L/s]). CONCLUSIONS AND CLINICAL RELEVANCE Bilateral ventriculocordectomy did not affect LAR with an open epiglottis in canine cadaver larynges. Therefore, it may not be an effective treatment for laryngeal paralysis. It also did not affect LAR with a closed epiglottis, which may indicate protection against aspiration pneumonia.

A nerve muscle pedicle (NMP) graft was placed in the cricoarytenoideus dorsalis (CAD) muscle of 6 horses with induced left laryngeal hemiplegia. The NMP graft was created by use of the first cervical nerve and omohyoideus muscle. In 1 horse (control), the first cervical nerve was transected after placement of the NMP graft. One year after the surgical procedure, horses were examined endoscopically and then anesthetized. While the larynx was observed endoscopically, the first cervical nerve was stimulated. Horses were subsequently euthanatized, and the larynx was harvested. Prior to anesthesia, the endoscopic appearance of the larynx of all horses was typical of laryngeal hemiplegia. During anesthesia, stimulation of the first cervical nerve produced vigorous abduction of the left arytenoid in principal horses but not in the control horse. The right cricoarytenoideus lateralis and CAD muscles were grossly and histologically normal. Also, the left cricoarytenoideus lateralis was atrophic in all horses as was the left CAD muscle of the control horse. In contrast, the left CAD muscle harvested from principal horses had evidence of reinnervation with type 1 or type 2 fiber grouping. One year after the NMP graft procedure, horses with left laryngeal hemiplegia had reinnervation of the left CAD muscle. In another study, reinnervation was sufficient to allow normal laryngeal function during exercise. Combined, these data suggest that the NMP graft procedure is a viable technique for the treatment of left laryngeal hemiplegia in horses.

Effects of ventriculectomy and prosthetic laryngoplasty on upper airway flow mechanics and blood gas tensions in exercising horses with induced left laryngeal hemiplegia were assessed. Five adult horses were trained to stand, trot (4.5 m/s), and gallop (7.2 m/s) on a treadmill (6.38? incline). Inspiratory and expiratory airflows (VImax, VEmax, respectively) were measured using a 15.2-cm diameter pneumotachograph in a face mask. Inspiratory and expiratory transupper airway pressures (PuI, PuE respectively) were determined as pressure differences between barometric pressure and lateral tracheal pressure. Blood collected from exteriorized carotid arteries was analyzed for PaO2, PaCO2, pH, hemoglobin (Hb) content, and HCO3-values. Heart rate (HR) was determined with an HR monitor. Measurements were made with horses standing, trotting, and galloping before left recurrent laryngeal neurectomy (LRLN; base line), 14 days after LRLN, 30 days after ventriculectomy (44 days after LRLN), and 14 days after prosthetic laryngoplasty (58 days after LRLN). Before LRLN (base line), increasing treadmill speed for horses from standing to the trot and gallop progressively increased HR, respiratory frequency, VImax, VEmax, PuI, PuE, Hb, and PaCO2 values and decreased PaO2 pH, and HCO3- values; inspiratory and expiratory impedances were unchanged. After LRLN, inspiratory impedance and PuI were significantly (P < 0.05) increased in horses at the trot and gallop, and PaCO2 was significantly increased in horses at the gallop. The VImax and respiratory frequency were significantly (P < 0.05) decreased in horses at the gallop. Left recurrent laryngeal neurectomy had no effect on PuE VEmax, HR, PaO2, pH, Hb or expiratory impedance values. Ventriculectomy failed to improve upper airway flow mechanics induced by LRLN, whereas prosthetic laryngoplasty restored upper airway flow mechanics to base-line values.

A 5-year-old, castrated male, Maltese was presented with history of acute flaccid paralysis. The dog was presented with sudden loss of muscle tone and involuntary movements of hind limbs. Neurologic examination revealed reduced postural reaction in the bilateral hind limbs. MRI of brain showed moderate hydrocephalus, but other examination results were normal. Based on the characteristic episodes and examination results, canine cataplexy was suspected. Treatment was initiated with clomipramine as cataplexy control. Clinical signs resolved with 3-month medication. This case demonstrates therapeutic diagnosis of cataplexy. To the author’s knowledge, this is the first report of cataplexy treating with clomipramine.

Clinical, morphologic, and morphometric findings are reported in 14 young Dalmatians with laryngeal paralysis. Neurologic signs, including megaesophagus, were observed in 13 of 14 dogs. Electromyographic abnormalities included fibrillation potentials and positive sharp waves in laryngeal, esophageal, facial, and distal appendicular muscles. Neurogenic atrophy was detected in intrinsic laryngeal and appendicular skeletal muscles. A diffuse, generalized polyneuropathy, dominated by axonal degeneration, was observed in recurrent laryngeal and appendicular peripheral nerves. Results of quantitative studies, using single teased fiber and cross-sectional nerve preparations, indicated that changes were more severe in distal parts of peripheral nerves, with preferential loss of medium sized (5.5 to 8 micrometers) and large-caliber (8.5 to 12 micrometers) myelinated nerve fibers. Ultrastructural alterations were observed in myelinated and unmyelinated nerve fibers. The term laryngeal paralysis-polyneuropathy complex is proposed for this apparent dying-back disorder, which is clinically, electrophysiologically, and pathologically different from laryngeal paralysis in young Bouvier des Flandres and Siberian Huskies. Prognosis for Dalmatians with laryngeal paralysis-polyneuropathy complex is guarded to poor. The condition is believed to be inherited.

Ouabain, a cardiac glycoside, binds to the Na+-K+i-adenosine triphosphatase (Na+ pump) and prevents active transport of Na+ and K+ across cell membranes. We used [3H]ouabain to quantify the number and affinity of Na+ pumps in skeletal muscle from Quarter Horses with the muscular disorder hyperkalemic periodic paralysis (HYPP). [3H]Ouabain-binding properties of gluteal muscle from clinically normal and affected horses were used to determine whether altered Na+ pump number or affinity could contribute to the pathologic features of muscle in affected horses. Foals and adult horses with HYPP were compared with age-matched clinically normal horses. The number of [3H]ouabain-binding sites in adult gluteal muscle was not different between the 2 types of horses (85.7 +/- 8.9 pmol of [3H]ouabain-binding sites/g [wet muscle weight] in horses with HYPP vs 100.2 +/- 8.8 pmol/g in clinically normal adult horses). Gluteal muscles in HYPP-affected and clinically normal foals also contained a similar number of [3H]ouabain-binding sites (222.3 +/- 21.0 pmol/g vs 225.3 +/- 24.2 pmol/g, respectively). The affinity of these binding sites for ouabain was not different, between adults or foals, in clinically normal or affected horses. Our results indicate that membrane events underlying the periodic episodes of paralysis in horses with HYPP are not attributable to quantitative changes in Na+ pump number or affinity. Our data cannot exclude the possibility that the specific activity of the Na+ pump is altered in muscle from HYPP-affected horses.