Electrodiagnostic evaluation of peripheral nerve function in rheas and barred owls

OBJECTIVE: To establish reference values for electrodiagnostic evaluation of peripheral nerve function in birds. ANIMALS: 6 rheas and 6 barred owls. PROCEDURE: Birds were anesthetized with propofol or isoflurane in oxygen. Using a computer-based electromyograph system and needle electrodes for stimulation and recording, electromyography (EMG) was performed on the pectoral, biceps brachialis, and gastrocnemius muscles, and evoked EMG was performed on the tibial and ulnar nerves. Motor nerve conduction velocity (MNCV) was calculated. Repetitive stimulation was performed on these 2 nerves. Late F waves were recorded for each nerve, when possible. RESULTS: Activity was evident during insertion of the electrodes, but muscles tested were electrically quiescent after spontaneous EMG. Motor nerve conduction velocity was faster in the tibial nerve than ulnar nerve but did not differ significantly between species. Mean +/- SEM MNCV was 132.3+/-7.8 m/s for the tibial nerve and 59.7+/-7.8 m/s for the ulnar nerve. A significant difference was not observed in responses at the fourth or ninth stimulation during repetitive stimulation. Subsequent to the initial stimulation, amplitudes were +/-22.7% of the initial motor potential amplitude. Recorded F waves were inconsistent, which may have been associated with technique. CONCLUSIONS AND CLINICAL RELEVANCE: Reference range (mean +/-2 SEM) for MNCV was 34.1 to 75.3 m/s for the ulnar nerve and 116.7 to 147.9 m/s for the tibial nerve in barred owls and rheas. After repetitive stimulation, motor potential amplitudes may be +/-22.7% of the initial amplitude response.     

Electrodiagnostic evaluation in feline hypertrophic muscular dystrophy

Standard needle electromyography (EMG) of 56 muscles and nerve conduction velocities (NCV) of the ulnar and common peroneal nerves were investigated in each of six cats affected with hypertrophic feline muscular dystrophy, 10 related heterozygote carriers and 10 normal cats. The EMG findings were considered normal in carrier and control cats, and consisted of 33% normal readings, 22% myotonic discharges, 18% fibrillation potentials, 11% prolonged insertional potentials, 10% complex repetitive discharges and 6% positive sharp waves in affected cats. Muscles of the proximal limbs were most frequently affected. No differences in NCV were found between the three cat groups. It was concluded that dystrophin-deficient dystrophic cats have widespread and frequent EMG changes, predominantly myotonic discharges and fibrillation potentials, which are most pronounced in the proximal appendicular muscles.     

Electrodiagnostic evaluation of deafness in two English setter littermates

Two English Setter littermates (male and female) were evaluated for hearing difficulties at 4, 16, and 24 months of age. Auditory function was evaluated by behavioral response to pure-tone sounds, tympanometry, brain stem auditory evoked response, and acoustic reflex testing. Hereditary sensorineural deafness was diagnosed in both dogs. The extent of the hearing deficit, as characterized by these tests, was slightly different between the dogs, as well as between the ears in 1 dog.     

A method of assessing auditory and brainstem function in horses

Brainstem auditory evoked potential (BAEP) waveforms were recorded as a means of objectively evaluating auditory and brainstem function in horses. BAEP recordings were readily and repeatably recorded from horses, under minimal restraint, using signal averaging equipment. Clearly identified BAEP waveforms were obtained with compression clicks of 30-100 dB (HHL) at 10 Hz applied in the external auditory meatus of one ear and masking white noise (10 dB lower) in the other ear. Vertex positive (upwards) waveforms I through V were obtained with an active, subdermal electrode over the ipsilateral and contralateral zygomatic processes of the temporal bones and the reference electrode over the vertex. Recording sweep duration was 10 ms, amplifier sensitivity 10 microV/division, display gain x 10 and low and high amplifier filters set at 200 Hz to 2 kHz. Such recordings can be useful in evaluation of all clinical cases suspected of showing degrees of deafness, vestibular disease or brainstem disease, and in monitoring the progress of such cases.     

Electrodiagnostic examination. Somatosensory evoked potentials and electromyography.

The anatomic/physiologic basis and uses of somatosensory evoked potential recordings are presented. A brief summary of the use of electromyography in spinal cord diseases is included.     

Use of BAER to identify loss of auditory function in older horses

Objective To use the brainstem auditory evoked response (BAER) to test the hypothesis that auditory function could be worse in older horses than in younger horses. Procedure BAER waveforms in response to click stimuli were measured in five younger horses (5–8 years) and four older horses (17–22 years). Results Compared with the younger horses, the older horses showed significantly (P < 0.02) worse BAER thresholds and significantly (P < 0.02) worse BAER wave V amplitudes to the 90 decibels above normal hearing level stimulus. These results were consistent with partial deafness in the older horse group. Conclusion BAER assessment can be used to identify partial deafness in older horses. Such horses should be managed appropriately, with particular care taken in noisy environments where hearing loss could put the horse and/or its owner at risk of harm.     

Evoked otoacoustic emissions: An alternative test of auditory function in horses

Reasons for performing study: Deafness has been reported in horses due to a variety of causes and objective auditory assessment has been performed with brainstem auditory evoked potential testing. Evoked otoacoustic emission (OAE) tests are widely used in human patients for hearing screening, detecting partial hearing loss (including frequency‐specific hearing loss) and monitoring cochlear outer hair cell function over time. OAE tests are noninvasive, quick and affordable. Two types of OAE are commonly used clinically: transient evoked OAEs (TEOAEs) and distortion product OAEs (DPOAEs). Detection of OAEs has not been reported and OAE testing has not been evaluated for auditory assessment in horses. Objectives: To investigate whether TEOAEs and DPOAEs can be recorded in horses, and to evaluate the use of human OAE screening protocols in horses with apparently normal hearing. Methods: Sixteen systemically healthy horses with normal behavioural responses to sound were included. OAE testing was performed during general anaesthesia using commercially available equipment and the final outcome for each ear for the TEOAE test (after a maximum of 3 runs) and the DPOAE test (after one run) were compared. Results: TEOAEs and DPOAEs can be recorded in horses. Using the chosen TEOAE protocol, 96% of ears achieved a pass. Seventy percent of ears passed DPOAE testing, despite all of these ears passing TEOAE testing. Conclusions: Using the chosen stimulus and analysis protocols, TEOAEs were recorded from most ears; however, a smaller proportion of ears passed the DPOAE protocol, suggesting that this may be overly stringent and require further optimisation in horses. Potential relevance: OAE testing is rapid and easily performed in anaesthetised horses. It provides frequency‐specific information about outer hair cell function, and is a promising tool for audiological assessment in the horse; however, it has not been assessed in conscious or sedated animals.     

Evaluation of auditory function in a population of clinically healthy cats using evoked otoacoustic emissions

Cats may demonstrate deafness due to a variety of aetiologies and the current preferred method for assessing auditory function is the brainstem auditory evoked response (BAER). The BAER has largely been replaced by otoacoustic emission (OAE) testing in human neonatal deafness screening as the equipment is more readily available, is cheaper and the test is less invasive and simpler. This is the first study to demonstrate that transient evoked OAEs (TEOAE) and distortion product OAEs (DPOAE) can be recorded in cats using commercially available equipment. Protocols for recording the emissions and analysing the results are given. DPOAE testing is suggested to be quicker in this population of healthy cats and shows promise in rapidly providing detailed information about auditory function at a variety of different frequencies.     

Brainstem auditory evoked potential wave V latency-intensity function in normal Dalmatian and Beagle puppies

This study investigated whether Dalmatian puppies with normal hearing bilaterally had the same click-evoked brainstem auditory potential characteristics as age-matched dogs of another breed. Short-latency brainstem auditory potentials evoked by condensation and rarefaction clicks were recorded in 23 1.5- to 2-month-old Dalmatian puppies with normal hearing bilaterally by a qualitative brainstem auditory evoked potential test and in 16 Beagle dogs of the same age. For each stimulus intensity, from 90 dB normal hearing level down to the wave V threshold, the sum of the potentials evoked by the 2 kinds of stimuli were added, giving an equivalent to the alternate click polarity stimulation. The slope of the L segment of the wave V latency-intensity curve was steeper in Dalmatian (-40 +/- 10 micros/dB) than in Beagles (-28 +/- 5 micros/dB, P < .001) puppies. The hearing threshold was lower in the Beagle puppies (P < .05). These results suggest that interbreed differences may exist at the level of cochlear function in this age class. The wave V latency and wave V-wave I latencies differences at high stimulus intensity were different between the groups of puppies (4.3 +/- 0.2 and 2.5 +/- 0.2 milliseconds, respectively, for Beagles; and 4.1 +/- 0.2 and 2.3 +/- 0.2 milliseconds for Dalmatians, P < .05). A different maturation speed of the neural pathways is one possible explanation of this observation.     

Radiographic evaluation of esophageal function in Chinese Shar Pei pups.

Liquid barium esophagography was done in 29 clinically normal Chinese Shar Pei pups and observed fluoroscopically, beginning when they were approximately 3 months old and repeated periodically until they were at least 18 months old, if possible. Of these dogs, 69% had relatively slow stimulation of secondary waves, 48% had generalized poor esophageal tone or motility, and 38% had esophageal redundancy. Sequential studies revealed apparent improvement with age for those dogs initially showing slow motility, provided that redundancy was not also present. Another group of 9 Chinese Shar Pei pups had histories of either regurgitation or vomiting. Five of these had hiatal hernia and 2 had megaesophagus.     

A method for the simultaneous evaluation of exocrine pancreatic function and intestinal absorptive function in dogs.

Exocrine pancreatic function was evaluated in 13 dogs, using the chymotrypsin-labile peptide N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA). This peptide releases p-aminobenzoic acid (PABA) in the presence of pancreatic chymotrypsin. The amount of PABA in blood or urine after BT-PABA administration then served as an index of pancreatic function. Similarly, a xylose absorption test has been described in the literature to evaluate absorptive function of the small intestine. Here, the pentose sugar d(+)xylose was given orally, and blood xylose concentrations were then measured at intervals. Since both tests were performed in nearly the same way, they were combined into a single test. A solution containing BT-PABA (30 mg/ml) and xylose (100 mg/ml) was administered perorally to dogs with and without pancreatic duct ligation. In the unoperated (control) dogs, peak blood concentrations for PABA occurred between 60 and 120 minutes and xylose concentrations were maximal between 30 and 90 minutes. Pancreatic duct ligation reduced PABA concentrations at 90 minutes to one-sixth of the values in control dogs. Xylose absorption, however, was not altered by pancreatic duct ligation. In this way, digestive and absorptive functions were both evaluated, using a single 90-minute test.     

Thromboelastographic evaluation of hemostatic function in dogs with disseminated intravascular coagulation

BACKGROUND: There is considerable variation in the coagulation profile of dogs with disseminated intravascular coagulation (DIC), making it difficult to assess overall hemostatic function. OBJECTIVES: To characterize the overall hemostatic state in dogs with DIC, by use of tissue factor-activated thromboelastography (TF-TEG), and to determine whether there is an association between hemostasis and outcome. ANIMALS: 50 dogs with DIC. METHODS: Dogs admitted to the intensive care units, with an underlying disease known to predispose to DIC, were prospectively assessed with TF-TEG. Citrated blood samples were collected daily during hospitalization and an extended coagulation panel and TF-TEG were performed. Diagnosis of DIC was based on expert opinion. RESULTS: Hemostatic dysfunction was observed on the TF-TEG profile in 33/50 of the dogs, of which 22/50 were hypercoagulable and 11/50 were hypocoagulable based on the TF-TEG G value alone. There were significant differences in k, alpha, and MA values (P < .0001) among hypo-, normo-, and hypercoagulable dogs. There was a significant difference in case fatality rate between hypo- (64%) and hypercoagulable (32%) dogs (relative risk = 2.38; P= .04). Dogs that died had significantly lower antithrombin activity (P= .03) and higher d-dimer concentration (P= .03) than survivors. CONCLUSIONS: The most common overall hemostatic abnormality in dogs diagnosed with DIC was hypercoagulability, and there was significant difference in survival between hyper- and hypocoagulable dogs. The results suggest TF-TEG is valuable in the assessment of hemostatic function in dogs diagnosed with DIC.     

Thyrotropin stimulation test for evaluation of thyroid function in psittacine birds

Serum thyroid hormone concentrations were determined before and after thyrotropin (thyroid stimulating hormone [TSH]) stimulation in caged psittacine birds to determine whether the TSH stimulation test could be used to evaluate thyroid function in this class of birds. The mean (+/- SD) resting thyroxine concentrations (ng/ml) for the species studied were: cockatoos, 13.63 +/- 6.53 (n = 6); Amazon parrots, 8.19 +/- 6.90 (n = 8); scarlet macaws, 1.34 +/- 0.51 (n = 9); blue and gold macaws, 3.41 +/- 1.78 (n = 8); African gray parrots, 1.42 +/- 0.44 (n = 6); conures, 1.76 +/- 0.77 (n = 5); and cockatiels, 11.83 +/- 6.76 (n = 3). The mean (+/- SD) thyroxine concentrations (ng/ml) 4 to 6 hours after TSH stimulation were 35.10 +/- 13.16, 27.40 +/- 15.93, 6.46 +/- 3.10, 12.36 +/- 6.34, 9.30 +/- 2.90, 13.50 +/- 7.71, and 39.0 +/- 5.66, respectively. Serum tri-iodothyronine concentration did not increase significantly after TSH stimulation. The results demonstrated that the TSH stimulation test can be used to evaluate thyroid function in caged psittacine birds.