Neurologic dysfunction in hypothyroid, hyperlipidemic Labrador Retrievers

BACKGROUND: Hypothyroidism has been associated with a variety of neurologic signs, but the mechanism for this association is not completely understood. Hypothyroidism also is associated with hyperlipidemia that predisposes to atherosclerosis, increased blood viscosity, and thromboembolic events. OBJECTIVE: The objective is to characterize neurologic signs potentially associated with hyperlipidemia and atherosclerosis in canine hypothyroidism. ANIMALS: This study used dogs referred to North Carolina State University Veterinary Teaching Hospital for evaluation of neurologic signs. MATERIALS AND METHODS: A retrospective study was conducted in which medical records of dogs with neurologic signs and a diagnosis of hypothyroidism and hyperlipidemia were reviewed. Details of the history, presenting signs, results of routine blood tests, thyroid tests, cerebrospinal fluid (CSF) analysis and diagnostic imaging, and response to therapy were compiled. RESULTS: Three Labrador Retrievers and one Labrador Retriever cross fit the inclusion criteria. All dogs were hypothyroid and severely hyperlipidemic. Neurologic signs included tetraparesis, central and peripheral vestibular signs, facial paralysis, and paraparesis. Two dogs had an acute history and rapid resolution of signs consistent with an infarct, the presence of which was confirmed in 1 of the dogs by magnetic resonance imaging. Two dogs had chronic histories of cranial neuropathies and paraparesis. One of these dogs had evidence of iliac thrombosis and atherosclerosis on ultrasound examination. All dogs improved with thyroid hormone supplementation. CLINICAL RELEVANCE: Labrador Retrievers may be predisposed to the development of severe hyperlipidemia in association with hypothyroidism. One possible consequence of severe hyperlipidemia is the development of neurologic signs due to atherosclerosis and thromboembolic events.     

Neurological Manifestations of Hypothyroidism: A Retrospective Study of 29 Dogs

Neuromuscular signs in association with hypothyroidism are described in 29 dogs. Eleven dogs had lower motor neuron signs, 9 had peripheral vestibular deficits, 4 had megaesophagus, and 5 had laryngeal paralysis. Primarily older (mean = 9.5 years), large-breed dogs were affected, and there was no sex or breed predisposition. Duration of clinical signs before presentation ranged from 2 to 8 weeks (mean = 5 weeks). The diagnosis was based on (1) results of neurological examination (29 dogs); (2) electromyographic abnormalities (18 dogs), including fibrillation potentials (n = 18), positive sharp waves (n = 15), and complex repetitive discharges (n = 4); (3) high serum cholesterol concentration (10 dogs; mean = 335 mg/dL); (4) low response to thyroid-stimulating hormone (29 dogs; mean T₄ prestimulation concentration = 0.8 μg/dL; mean T₄ poststimulation = 1.2 μg/dL); and (5) good response to thyroxine supplementation (26 dogs). Dogs with vestibular deficits had abnormal brainstem auditory-evoked responses (BAER), including increased latencies of P₁-P₆ and decreased amplitude of P_4,5-N₅. Seven other dogs had similar BAER abnormalities without manifesting clinical signs of vestibular involvement. Three dogs with vestibular signs had fibrillation potentials and positive sharp waves without exhibiting lower motor neuron signs. All dogs were supplemented with levothyroxine (0.02 mg/kg P0 bid). The follow-up period ranged between 6 and 30 months (mean, 14 months). Serum T₄ concentrations were measured at least 3 times for each dog every 2 months (mean T₄ concentration = 2.6 μg/dL). All but 1 dog with lower motor neuron signs and 1 dog with vestibular signs recovered after 2 months (mean, 57 days). Signs of megaesophagus became progressively less severe over 4 months. Dogs with laryngeal paralysis improved partially after 5 months. We suggest that either vestibular or lower motor neuron signs, megaesophagus, or laryngeal paralysis may be the only clinical signs of an underlying, more generalized polyneuropathy associated with hypothyroidism. Electro-diagnostic abnormalities may be detected before clinical disease develops.     

Neurologic manifestations associated with hypothyroidism in four dogs

Hypothyroidism was believed responsible for peripheral and central neurologic abnormalities in 4 dogs. Clinical signs consisted of abnormalities of gait and postural reactions and dysfunction of multiple cranial nerves in all 4 dogs. Circling, hypermetria, and spontaneous verticle nystagmus were observed in some of the dogs. Hypothyroidism was diagnosed in all 4 dogs on the basis of low resting serum thyroxine concentration and inadequate response to thyroid stimulating hormone. After thyroid hormone supplementation, resolution of neurologic abnormalities was complete in 2 dogs and partial in the other 2 dogs.     

Diagnostic imaging findings and endocrine test results in dogs with pituitary-dependent hyperadrenocorticism that did or did not have neurologic abnormalities: 157 cases (1989-2005)

OBJECTIVE: To compare imaging findings in dogs with pituitary-dependent hyperadrenocorticism (PDH) that did or did not have neurologic abnormalities. Design-Retrospective case series. ANIMALS: 157 dogs with PDH that did (n = 73) or did not (84) have neurologic abnormalities. PROCEDURES: Medical records were reviewed for the presence and nature of clinical signs of CNS disease, and computed tomographic and magnetic resonance images were reviewed for evidence of a pituitary tumor. RESULTS: 60 of the 84 (71%) dogs without neurologic abnormalities and 48 of the 73 (66%) dogs with neurologic abnormalities had a detectable pituitary tumor. However, 17 of the 84 (20%) dogs without neurologic abnormalities had a pituitary macrotumor (ie, a tumor > or = 10 mm in height), and 41 of the 73 (56%) dogs with neurologic abnormalities did not have a detectable pituitary tumor or had a pituitary microtumor. Vague signs of CNS dysfunction (ie, lethargy, inappetence, and mental dullness) were more specific for detection of pituitary macrotumors than were CNS-specific signs (ie, seizure or blindness). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that there was no apparent relationship between a pituitary tumor and development of neurologic abnormalities in dogs with PDH. In addition, neurologic abnormalities in dogs with pituitary macrotumors were often vague (ie, lethargy, inappetence, and mental dullness).     

Results of magnetic resonance imaging in dogs with vestibular disorders: 85 cases (1996-1999)

OBJECTIVE: To determine results of magnetic resonance (MR) imaging in dogs with vestibular disorders (VD) and correlate results of MR imaging with clinical findings. DESIGN: Retrospective study. ANIMALS: 85 dogs. PROCEDURE: Information on signalment, clinical signs, and presumptive lesion location was obtained from the medical records, and MR images were reviewed. RESULTS: 27 dogs had peripheral VD, 37 had central VD, and 21 had paradoxical VD. Of the 27 dogs with peripheral VD, 11 (41%) had MR imaging abnormalities involving the ipsilateral tympanic bulla compatible with otitis media (6 also had abnormalities involving the petrous portion of the ipsilateral temporal bone compatible with otitis interna), 7 (26%) had MR imaging abnormalities compatible with middle ear neoplasia, 2(7%) had an ipsilateral cerebellopontine angle lesion, and 7 (26%) did not have MR imaging abnormalities. All dogs with central and paradoxical VD had abnormalities evident on MR images. Of the 37 dogs with central VD, 13 (35%) had an extra-axial lesion, 6 (16%) had an intra-axial lesion, and 18 (49%) had multiple intra-axial lesions. In 23 (62%) dogs with central VD, lesions on MR images corresponded with location suspected on the basis of clinical signs. Of the 21 dogs with paradoxical VD, 12 (57%) had an extra-axial lesion, 5 (24%) had an intra-axial lesion, and 4 (19%) had multiple intra-axial lesions. Location of lesions on MR images agreed with location suspected on the basis of clinical signs in 19 (90%) dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that MR imaging may be helpful in the diagnosis and treatment of VD in dogs.     

Neurologic, endocrinologic, and pathologic findings associated with large pituitary tumors in dogs: eight cases (1976-1984)

Invasive tumors of the pituitary gland were diagnosed in 8 dogs. Seven of the dogs had been treated for pituitary-dependent hyperadrenocorticism before the onset of neurologic signs. All 8 dogs had behavior abnormalities and similar neurologic signs: 6 dogs had rotary nystagmus and 7 dogs had symmetric tetraparesis. Once neurologic signs developed, the clinical course in all 8 dogs had a mean duration of 4.7 +/- 2.0 months before death or euthanasia; 5 dogs had a clinical course of less than or equal to 2 months. Necropsy was performed in 7 dogs. The histologic diagnosis was malignant pituitary adenocarcinoma in 2 dogs and pituitary adenoma in 5 dogs.     

Treatment of hydrocephalus with ventriculoperitoneal shunting in twelve dogs

Objective: To report use of ventriculoperitoneal shunt in dogs for management of hydrocephalus for which no cause could be identified. Study Design: Case series. Animals: Dogs with hydrocephalus (n=12). Methods: Medical records (June 2003–June 2009) were reviewed to determine preoperative clinical findings, initial postoperative, and long‐term outcome. Additional follow‐up information was obtained from owners and referring veterinarians. Results: All dogs had signs of forebrain dysfunction, 7 had vestibular signs and 3 had signs of spinal pain. Postoperative complications included pain (n=4), undershunting because of shunt kinking (n=1) and seizures (n=1). Initial improvement occurred in all dogs and was sustained in 9 dogs, 1 of which required revision surgery. Conclusions: Sustained clinical improvement can be achieved in hydrocephalus with no active underlying cause by use of ventriculoperitoneal shunting.     

Laryngeal paralysis in dogs: a review of 23 cases

The medical records of 23 dogs with laryngeal paralysis were reviewed. Although the condition developed mainly in old, large- or giant-breed dogs, a wide range of breeds was involved. The age of affected animals ranged from 7 months to 14 years. Respiratory distress, exercise intolerance, noisy breathing, and hoarse bark were common signs of the paralysis. Laboratory evaluations for hypothyroidism were performed on 11 dogs; only 3 were judged to have primary hypothyroidism. Males, particularly if castrated, were more frequently affected than females. A neurologic examination was performed on 6 dogs; 4 of them were found to have generalized neuromuscular disease.     

Molecular identification of Ehrlichia ewingii infection in dogs: 15 cases (1997-2001)

OBJECTIVE: To determine historical, physical examination, hematologic, and serologic findings in dogs with Ehrlichia ewingii infection. DESIGN: Retrospective study. ANIMALS: 15 dogs. PROCEDURE: In all dogs, infection with E ewingii was confirmed with a polymerase chain reaction (PCR) assay. Follow-up information and clarification of information recorded in the medical records was obtained by telephone interviews and facsimile correspondence with referring veterinarians and owners. RESULTS: Fever and lameness were the most common findings with each occurring in 8 dogs. Five dogs had neurologic abnormalities including ataxia, paresis, proprioceptive deficits, anisocoria, intention tremor, and head tilt. Neutrophilic polyarthritis was identified in 4 dogs. No clinical signs were reported in 3 dogs. The predominant hematologic abnormality was thrombocytopenia, which was identified in all 12 dogs for which a platelet count was available. Reactive lymphocytes were seen in 5 of 13 dogs. Concurrent infection with another rickettsial organism was identified in 4 dogs. Of the 13 dogs tested, 7 were seroreactive to E canis antigens. Morulae consistent with E ewingii infection were identified in neutrophils in 8 dogs. Treatment with doxycycline, with or without prednisone, resulted in a rapid, favorable clinical response in the 9 dogs for which follow-up information was available. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that PCR testing for E ewingii infection should be considered in dogs with fever, neutrophilic polyarthritis, unexplained ataxia or paresis, thrombocytopenia, or unexplained reactive lymphocytes, and in dogs with clinical signs suggestive of ehrlichiosis that are seronegative for E canis. Following treatment with doxycycline, the prognosis for recovery is good.     

Signs of neurologic dysfunction in dogs with central versus peripheral vestibular disease

OBJECTIVE: To determine the frequency of specific signs of neurologic dysfunction in dogs with central vestibular disease (CVD) or peripheral vestibular disease (PVD) and whether the degree of head tilt, rate of nystagmus, and number of beats of postrotatory nystagmus can be used to help distinguish CVD from PVD. DESIGN: Prospective clinical study. ANIMALS: 40 client-owned dogs with vestibular system dysfunction. PROCEDURE: A standard neurologic examination was performed, along with an expanded vestibular system examination that assessed the degree of head tilt, rate of nystagmus, and number of beats of postrotatory nystagmus. RESULTS: Dogs with CVD were significantly more likely to be nonambulatory than were dogs with PVD. Dogs with PVD were significantly more likely to veer or lean in 1 direction and to have resting nystagmus than were dogs with CVD. Median rate of resting nystagmus was significantly higher for dogs with PVD, but no significant differences between groups were detected in regard to presence or degree of head tilt, presence of positional ventral strabismus, and number of beats of postrotatory nystagmus. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that nonambulatory tetraparesis is significantly more common in dogs with CVD and veering and leaning are significantly more common in dogs with PVD. Although neither the degree of head tilt nor the number of beats of postrotatory nystagmus could be used to distinguish CVD from PVD, rate of resting nystagmus may be useful in distinguishing the 2 conditions.     

Blood–brain‐barrier disruption in chronic canine hypothyroidism

Background: Central nervous system (CNS) manifestations of hypothyroidism have been associated with cerebrovascular complications. Reports of cerebrospinal fluid (CSF) abnormalities are rare in hypothyroid dogs. Objective: The aim of this study was to determine if chronic hypothyroidism causes blood–brain‐barrier (BBB) abnormalities that are detectable using indirect CSF biomarkers. Methods: The study included 18 normal, euthyroid, female mixed‐breed dogs. Hypothyroidism was induced by ¹³¹iodine administration in 9 dogs; 9 served as untreated controls. Evaluations included physical and neurologic examination, complete CSF analysis, serum and CSF protein electrophoresis, measurement of plasma vascular endothelial growth factor (VEGF) and serum S‐100B concentrations, and calculation of CSF albumin quota (AQ) and were conducted at baseline and 6, 12, and 18 months after induction of hypothyroidism. Data were analyzed using repeated measures ANOVA. Results: At baseline, differences between groups were not detected for any variable. Throughout the study, controls dogs remained free of neurologic disease and had test variables that remained within reference intervals. Two hypothyroid dogs developed CNS signs during the study, and evidence of cerebrovascular disease was found at necropsy. At 12 and 18 months, the CSF total protein, VEGF, S‐100B, and fractional albumin concentrations, and AQ were significantly higher (P<.04) in hypothyroid dogs than controls. Among test variables assayed in serum or plasma, the only significant difference was a higher S‐100B concentration in hypothyroid dogs (P=.003) at 18 months. Conclusions: BBB integrity is disrupted in chronic hypothyroidism. Significant increases in CSF concentrations of VEGF and S100‐B in hypothyroid dogs indicate dysfunction in both endothelial and glial elements of the BBB.     

Polyglandular endocrinopathy type II (Schmidt's syndrome) in a Dobermann pinscher

A three‐year‐old, female neutered, Dobermann pinscher was presented for investigation of lethargy, episodic collapse, ataxia and myxoedema. Primary hypothyroidism and primary cortisol‐deficient hypoadrenocorticism were diagnosed based on history, physical examination and compatible hormonal analysis. Increased serum concentrations of thyroglobulin autoantibodies and 21‐hydroxylase autoantibodies indicated an immune‐mediated aetiology. The case was complicated by lymphadenopathy with hand‐mirror lymphocytes, classically identified in lymphoma. A polymerase chain reaction test for antigen receptor rearrangement indicated polyclonality and therefore reactive lymphadenopathy. The dog's clinical signs resolved following introduction of levothyroxine and prednisolone. Prioritising the problem‐based approach in this case facilitated the diagnosis of hypoadrenocorticism in addition to hypothyroidism due to the persistence of clinical signs despite thyroxine replacement. Importantly, atypical adrenal gland dysfunction was not misinterpreted as inadequate therapeutic response to thyroxine supplementation. The observation that polyglandular endocrinopathy type II can occur in dogs suggests that in dogs with a suboptimal response to treatment for hypothyroidism or hypoadrenocorticism comorbid endocrinopathies should be investigated.     

Prevalence of serum thyroid hormone autoantibodies in dogs with clinical signs of hypothyroidism

OBJECTIVE: To determine prevalence of thyroid hormone autoantibodies (THAA) in serum of dogs with clinical signs of hypothyroidism. DESIGN: Cohort study. SAMPLE POPULATION: 287,948 serum samples from dogs with clinical signs consistent with hypothyroidism. PROCEDURE: Serum THAA were detected by use of a radiometric assay. Correlation and chi2 analyses were used to determine whether prevalence varied with breed, age, sex, or body weight. Only breeds for which > or = 50 samples had been submitted were used for analysis of breed prevalence. RESULTS: Thyroid hormone autoantibodies were detected in 18,135 (6.3%) samples. The 10 breeds with the highest prevalence of THAA were the Pointer, English Setter, English Pointer, Skye Terrier, German Wirehaired Pointer, Old English Sheepdog, Boxer, Maltese, Kuvasz, and Petit Basset Griffon Vendeen. Prevalence was significantly correlated with body weight and was highest in dogs between 2 and 4 years old. Females were significantly more likely to have THAA than were males. CONCLUSIONS AND CLINICAL RELEVANCE: Thyroid hormone autoantibodies may falsely increase measured triiodothyronine (T3) and thyroxine (T4) concentrations in dogs; results suggest that T3 concentration may be falsely increased in approximately 57 of 1,000 dogs with hypothyroidism and that T4 concentration may be falsely increased in approximately 17 of 1,000 dogs with hypothyroidism. Results also suggested that dogs of certain breeds were significantly more or less likely to have THAA than were dogs in general.     

Comparison of serum-free thyroxine concentrations determined by standard equilibrium dialysis, modified equilibrium dialysis, and 5 radioimmunoassays in dogs

Measurement of serum-free thyroxine (fT4) concentration provides a more accurate assessment of thyroid gland function than serum thyroxine (T4) or 3,5,3'-triiodothyronine (T3). Techniques for measuring serum fT4 concentration include standard equilibrium dialysis (SED), radioimmunoassay (RIA), and a combination of both (modified equilibrium dialysis [MED]). This study compared results of serum fT4 measurements by means of SED, MED, and 5 RIAs in 30 healthy dogs, 10 dogs with hypothyroidism, and 31 euthyroid dogs with concurrent illness for which hypothyroidism was a diagnostic consideration. Serum fT4 concentrations were comparable when determined by the SED and MED techniques, and mean serum fT4 concentrations were significantly (P < .01) lower in dogs with hypothyroidism than in healthy dogs and euthyroid dogs with concurrent illness. Significant (P < .05) differences in fT4 concentrations were identified among the 5 RIAs and among the RIAs and MED and SED. Serum fT4 concentrations were consistently lower when fT4 was determined by the RIAs, compared with either equilibrium dialysis technique. Serum fT4 concentrations were significantly lower (P < .01) in dogs with hypothyroidism than in healthy dogs for all RIAs; were significantly lower (P < .05) in dogs with hypothyroidism than in euthyroid dogs with concurrent illness for 4 RIAs; and were significantly lower (P < .01) in euthyroid dogs with concurrent illness than in healthy dogs for 4 RIAs. RIAs had the highest number of low serum fT4 concentrations in euthyroid dogs with concurrent illness. This study documented differences in test results among fT4 assays, emphasizing the importance of maintaining consistency in the assay used to measure serum fT4 concentrations in the clinical or research setting.     

Bufo marinus intoxication in dogs: 94 cases (1997-1998)

OBJECTIVE: To determine history, clinical and electrocardiographic abnormalities, treatment, and outcome of dogs exposed to toxins produced by the Bufo marinus toad. DESIGN: Retrospective study. ANIMALS: 94 dogs. PROCEDURE: Medical records of dogs examined between July 1997 and July 1998 for which a diagnosis of toad intoxication had been made on the basis of history and physical examination findings were reviewed. RESULTS: Most (66) dogs were treated during the spring and summer. For 54 dogs, exposure to toads had been witnessed. For the remaining 40, toad intoxication was diagnosed on the basis of history and clinical signs. The most common clinical signs were neurologic abnormalities, hyperemic mucous membranes, ptyalism, recumbency or collapse, tachypnea, and vomiting. The oral cavity was lavaged with tap water in all dogs. Fifty-two dogs were hospitalized for treatment. Body weight of dogs hospitalized > 2 hours was significantly less than that of dogs treated as outpatients. The most common electrocardiographic findings were sinus arrhythmia, sinus tachycardia, and normal sinus rhythm. Eighty-nine dogs recovered fully, 4 died, and 1 was euthanatized. CONCLUSIONS AND CLINICAL RELEVANCE: In areas in which B marinus toads are endemic, toad intoxication should be considered in the differential diagnosis for dogs with an acute onset of neurologic abnormalities, hyperemic mucous membranes, and ptyalism, especially during the spring and summer months. The prognosis is good for dogs with toad intoxication that receive appropriate treatment.     

Association of clinical and magnetic resonance imaging findings with outcome in dogs suspected to have ischemic myelopathy: 50 cases (2000-2006)

OBJECTIVE: To determine whether clinical signs or magnetic resonance imaging findings were associated with outcome in dogs with presumptive ischemic myelopathy. DESIGN: Retrospective case series. ANIMALS: 50 dogs. PROCEDURES: Medical records and magnetic resonance images were reviewed. A neurologic score from 1 (normal) to 5 (most severe degree of dysfunction) was assigned on the basis of neurologic signs at the time of initial examination. Follow-up information was obtained from the medical records and by means of a telephone questionnaire completed by owners and referring veterinarians. RESULTS: Median neurologic score at the time of initial examination was 3 (range, 2 to 5). Median follow-up time was 584 days (range, 4 to 2,090 days). Neurologic score at the time of initial examination and extent of the lesion seen on magnetic resonance images (quantified as the lesion length-to-vertebral length ratio and as the percentage cross-sectional area of the lesion) were significantly associated with outcome. Sensitivity of using a lesion length-to-vertebral length ratio > 2.0 or a percentage cross-sectional area of the lesion > or = 67% to predict an unsuccessful outcome was 100%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that severity of neurologic signs at the time of initial examination and extent of the lesions seen on magnetic resonance images were associated with outcome in dogs with ischemic myelopathy.     

Inner ear fluid‐attenuated inversion recovery MRI signal intensity in dogs with vestibular disease

The inner ear contains endolymph and perilymph. The second is comparable and in continuity with the cerebrospinal fluid (CSF) so it is expected to suppress in fluid‐attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) if normal. Even though inner ear FLAIR abnormalities have been extensively described in humans with inner ear disease, its diagnostic value in dogs is yet to be proven. The goal of this retrospective cohort study was to investigate the diagnostic utility of FLAIR MRI in dogs with vestibular disease. A review of medical records identified 101 dogs that had brain MRI performed because of vestibular signs. Based on the final diagnosis, patients were allocated to three groups: otitis media/interna, idiopathic vestibular disease, and central vestibular disease. Additionally, a control group (n = 73) included dogs with normal MRI and without vestibular signs. Inner ears were delineated using a region of interest, and signal intensity was measured in FLAIR and T2‐weighted images. The percentages of suppression in FLAIR were calculated and compared between affected and unaffected sides of each individual and between groups using a general linear mixed model. Correlation between suppression and CSF cell count and protein concentration was assessed. Affected inner ears in dogs with otitis media/interna had decreased suppression in FLAIR compared to the unaffected side (P < .001), and all other groups (P < .01). No significant correlation was detected between CSF results and suppression. These results show the diagnostic value of FLAIR in otitis media/interna due to lack of suppression in the affected inner ear.     

Aural Cholesteatoma in Twenty Dogs

Objective— To determine the clinical course in dogs with aural cholesteatoma. Study Design— Case series. Animals— Dogs (n=20) with aural cholesteatoma. Methods— Case review (1998–2007). Results— Twenty dogs were identified. Clinical signs other than those of chronic otitis externa included head tilt (6 dogs), unilateral facial palsy (4), pain on opening or inability to open the mouth (4), and ataxia (3). Computed tomography (CT) was performed in 19 dogs, abnormalities included osteoproliferation (13 dogs), lysis of the bulla (12), expansion of the bulla (11), bone lysis in the squamous or petrosal portion of the temporal bone (4) and enlargement of associated lymph nodes (7). Nineteen dogs had total ear canal ablation–lateral bulla osteotomy or ventral bulla osteotomy with the intent to cure; 9 dogs had no further signs of middle ear disease whereas 10 had persistent or recurrent clinical signs. Risk factors for recurrence after surgery were inability to open the mouth or neurologic signs on admission and lysis of any portion of the temporal bone on CT imaging. Dogs admitted with neurologic signs or inability to open the mouth had a median survival of 16 months. Conclusions— Early surgical treatment of aural cholesteatoma may be curative. Recurrence after surgery is associated with advanced disease, typically indicated by inability to open the jaw, neurologic disease, or bone lysis on CT imaging. Clinical Relevance— Presence of aural cholesteatoma may affect the prognosis for successful surgical treatment of middle ear disease.     

Evaluation of an enzymatic immunoassay for free thyroxine determination in canine serum

Free thyroxine (FT4) and cholesterol were measured in 400 dogs with either suspected hypothyroidism or dermatological signs such that hypothyroidism needed to be ruled out. Hypothyroidism was diagnosed in 68 dogs from the history, physical examination and stated lower reference limit (<7 pmol/L) for FT4 in euthryoid dogs. Dogs with FT4 concentrations in the range 6–9 pmol/L were finally categorized as hypo- or euthyroid either on the basis of retesting after 2 months or on their clinical response to thyroid replacement therapy over at least 2 months.The enzyme immunoassay evaluated in this paper is considered to be of clinical value and offers many advantages compared with radioimmunoassays.Abbreviations FT4 free thyroxine fraction - MEIA microparticle enzyme immunoassay - RIA radioimmunoassays - T4 thyroxine - TBG thyroxine-binding globulin