Craniocervical abnormalities in Chihuahuas

Craniocervical abnormalities such as Chiari-like malformation (CM), syringomyelia (SM), and craniocervical junction (CCJ) overcrowding cause, in cavalier King Charles spaniels (CKCS) and Griffon Bruxellois dogs, pain and motor deficits. This study describes the occurrence of these abnormalities and their association with clinical signs in Chihuahuas. Furthermore, it describes for the first time the occurrence of the molera, a persistent bregmatic fontanelle, and evaluates whether it is accompanied by similar bony defects on other cranial surfaces. Finally, it investigates their clinical relevance. We examined with magnetic resonance imaging and computed tomography 53 Finnish Chihuahuas with or without CM- or SM-related clinical signs. In this population, CM was ubiquitous (100%), and it was frequently accompanied by SM (38%). Furthermore, CCJ overcrowding was common: atlantooccipital overlapping occurred in 70%, and the mean degree of neural tissue deviation at the medulla, indicating medullary elevation, was 23.2% and at the atlantoaxial junction, indicating dorsal spinal cord compression, 24.3%. We used a questionnaire designed for this study to describe the clinical signs of 22 (50%) clinically affected dogs among the 44 dogs included in the analysis. Most commonly the dogs were scratching their head or neck with or without making skin contact (73%). Half the dogs (53%) had gait abnormalities, rubbed their face (46%), or had spinal hyperesthesia (46%), and slightly less than half (41%) were occasionally vocalizing. Syringomyelia and more severe neural tissue deviation at the CCJ predisposed to clinical signs. Furthermore, we used magnetic resonance images in an extended dog population with and without SM to evaluate the morphometric traits of the caudal cranial fossa and CCJ. This population included 53 Finnish and an additional 46 Chihuahuas, 132 CKCSs, and 42 Affenpinschers examined in the UK. Increased cranial height and close position of the atlas to the occiput, hence more extreme brachycephaly, predisposed to SM. We then used computed tomography to describe persistent fontanelles in the Finnish Chihuahuas: they occurred in 92% and occupied not only the location of the molera but also all cranial surfaces. The mean number of the persistent fontanelles in each dog was 2.8, and most of them (62%) occupied locations similar to the locations of the fontanelles observed in newborn children. We developed a novel method to measure the persistent fontanelle area, and showed that Chihuahuas with a low body weight, CM/SM-related clinical signs, SM, large lateral ventricles, or CCJ overcrowding had larger persistent fontanelles. This finding challenges the current notion of persistent fontanelles as being clinically irrelevant. Although the pathomechanism of these lesions is currently unknown, similar cranial defects emerge in children with disorders of cranial growth such as craniosynostosis.Koirilla Chiari-tyyppinen epämuodostuma, jossa pikkuaivot tyräytyvät niska-aukkoon, kallo-kaularankaliitoksen ahtauma sekä niiden seurauksena kehittyvä syringomyelia, eli selkäytimen ontelotauti altistavat krooniselle kivulle, raajojen heikkoudelle ja koordinaatio-ongelmille. Kyseisiä rakenteellisia poikkeamia esiintyy yleisesti cavalier king charlesin spanieleilla ja griffoneilla, joita yhdistää pyöreä kallonmuoto. Tutkimuksemme tavoitteena oli selvittää, esiintyykö kallonmuodoltaan näitä rotuja muistuttavalla chihuahualla vastaavia rakenteellisia poikkeamia ja niihin yhdistettyjä oireita sekä selvittää, mitkä kallonpiirteet altistavat syringomyelialle. Lisäksi kartoitimme päälaen kallonaukileen, eli moleran, yleisyyttä chihuahuoilla sekä selvitimme, esiintyykö vastaavia kallonaukileita päälaen lisäksi muilla kallon pinnoilla. Arvioimme myös kallonaukileiden lukumäärän tai koon yhteyttä rakenteellisiin poikkeamiin tai oireiden olemassaoloon. Tutkimukseemme osallistui 53 suomalaista chihuahuaa, joille tehtiin pään ja kaularangan viipale- ja magneettikuvaus. Magneettikuvauksessa todettiin, että tutkimukseen osallistuneista koirista kaikilla oli Chiari-tyyppinen epämuodostuma, ja reilulla kolmasosalla (38%) oli syringomyelia. Vastaavasti viipalekuvauksessa todettiin, että kahdella kolmasosalla (70%) ensimmäisen kaulanikaman etäisyys kallopohjasta oli poikkeuksellisen lyhyt. Lisäksi usealla koiralla havaittiin magneettikuvauksessa ydinjatkoksen mutka sekä selkäytimen alkuosan yläpuolinen puristus. Nämä rakenteelliset poikkeamat ilmentävät kallo-kaularankaliitoksen ahtaumaa, aiheuttavat hermokudoksen puristusta ja häiritsevät aivoselkäydinnesteen virtausta. Tutkimukseen osallistuneista koirista 44 valikoitui oireanalyysiin, ja puolella näistä koirista oli oireita: Yleisin oire oli pään tai kaulan alueen toistuva rapsuttaminen (73%), kun taas puolella koirista (53%) oli koordinaatio-ongelmia tai raajojen heikkoutta, pään alueen runsasta hankaamista (46%) tai rangan kosketusarkuutta (46%). Lisäksi hieman alle puolet koirista (41%) vingahteli joko asentoa vaihtaessaan tai ilman ilmeistä syytä. Vertaillessamme oireilevia ja oireettomia koiria havaitsimme, että syringomyelian lisäksi, poiketen muista roduista, kallo-kaularankaliitoksen ahtauma oli tärkeä oireille altistava rakenne. Seuraavaksi tutkimuksemme arvioi 273 koiran magneettikuvien avulla kallon ja kallo-kaularankaliitoksen syringomyelialle altistavia piirteitä. Kuvattujen koirien joukossa oli suomalaisten chihuahuoiden lisäksi englantilaisia chihuahuoita, cavaliereja sekä apinapinsereitä. Analyysi osoitti, että korkea kallonmuoto sekä kallo-kaularankaliitoksen ahtauma altistivat syringomyelialle. Viimeiseksi tutkimme kallonaukileiden esiintyvyyttä sekä niiden käytännön merkitystä viipale- ja magneettikuvauksen sekä oireanalyysin avulla. Osoitimme, että kallonaukileita esiintyy miltei kaikilla chihuahuoilla (92%), kaikilla kallonpinnoilla - ei siis vain päälaella - ja että suurin osa (62%) kallonaukileista sijaitsi vastavilla kohdin kuin vastasyntyneillä lapsilla havaitut kalloaukileet. Lisäksi havaitsimme, että chihuahuoilla kallonaukileita oli enemmän ja ne olivat suurempia niillä koirilla, joilla oli syringomyelia, kallo-kaularankaliitoksen ahtauma tai niistä aiheutuvia oireita. Vaikka kallonaukileet eivät itsessään aiheuta chihuahuoilla sairauden oireita, niiden runsaampi esiintyminen oireilevilla tai rakenteeltaan poikkeavilla koirilla haastaa vallalla olevan käsityksen niiden harmittomuudesta. Lapsilla vastaavia muutoksia voidaan havaita esimerkiksi kallon kasvuhäiriöiden yhteydessä. Tulevaisuudessa tarvitaan lisätutkimuksia koirien kallonaukileiden vielä avoimen syntymekanismin selvittämiseksi

Craniometric Analysis of the Hindbrain and Craniocervical Junction of Chihuahua, Affenpinscher and Cavalier King Charles Spaniel Dogs With and Without Syringomyelia Secondary to Chiari-Like Malformation

Objectives To characterize and compare the phenotypic variables of the hindbrain and craniocervical junction associated with syringomyelia (SM) in the Chihuahua, Affenpinscher and Cavalier King Charles Spaniel (CKCS). Method Analysis of 273 T1-weighted mid-sagittal DICOM sequences of the hindbrain and craniocer-vical junction from 99 Chihuahuas, 42 Affenpinschers and 132 CKCSs. The study compared 22 morphometric features (11 lines, eight angles and three ratios) of dogs with and without SM using refined techniques based on previous studies of the Griffon Bruxellois (GB) using Discriminant Function Analysis and ANOVA with post-hoc corrections. Results The analysis identified 14/22 significant traits for SM in the three dog breeds, five of which were identical to those reported for the GB and suggest inclusion of a common aetiology. One ratio, caudal fossa height to the length of the skull base extended to an imaginary point of alignment between the atlas and supraoccipital bones, was common to all three breeds (p values 0.029 to <0.001). Associated with SM were a reduced occipital crest and two acute changes in angulation i) 'sphenoid flexure' at the spheno-occipital synchondrosis ii) 'cervical flexure' at the foramen magnum allied with medulla oblongata elevation. Comparing dogs with and without SM, each breed had a unique trait: Chihuahua had a smaller angle between the dens, atlas and basioccipital bone (p value <0.001); Affenpinschers had a smaller dis-tance from atlas to dens (p value 0.009); CKCS had a shorter distance between the spheno-occipital synchondrosis and atlas (p value 0.007). Conclusion The selected morphometries successfully characterised conformational changes in the brain and craniocervical junction that might form the basis of a diagnostic tool for all breeds. The severity of SM involved a spectrum of abnormalities, incurred by changes in both angulation and size that could alter neural parenchyma compliance and/or impede cerebrospinal fluid channels.Peer reviewe

Response to letter to editor regarding Seizure-precipitating factors in dogs with idiopathic epilepsy

Non peer reviewe

Seizure-precipitating factors in dogs with idiopathic epilepsy

Background: Stress, sleep deprivation, and infectious diseases are important seizure-precipitating factors in human epilepsy patients. However, these factors have not been thoroughly studied in epileptic dogs. Objective: Seizure-precipitating factors are common in dogs with idiopathic epilepsy and the occurrence of these factors associate with the dogs' signalment, personality, and epilepsy-related factors. Animals: Fifty dogs with diagnosed idiopathic epilepsy from the hospital populations of University Veterinary Teaching Hospital of University of Helsinki and Referral Animal Hospital Aisti. Methods: In a retrospective cross-sectional observational study, owners were interviewed about their dogs' possible seizure-precipitating factors according to a predefined questionnaire. The dogs were identified and selected by searching the medical records of the participating animal hospitals. Results: The prevalence of seizure-precipitating factors in the study population was 74% (37/50). The most frequently reported factors included stress-related situations, sleep deprivation, weather, and hormonal factors. In dogs with focal onset seizures, the number of precipitating factors was 1.9 (95% CI 1.1-3.4) times higher compared to dogs with generalized seizures. Conclusions and Clinical Importance: Seizure-precipitating factors are common in dogs with idiopathic epilepsy, and the nature of these factors is consistent with those of human patients. Aside from antiepileptic medication, acknowledging and avoiding seizure-precipitating factors could help veterinarians achieve better treatment outcomes.Peer reviewe

Persistent fontanelles in Chihuahuas. Part II : Association with craniocervical junction abnormalities, syringomyelia, and ventricular volume

Background Persistent fontanelles (PFs) are, in Chihuahuas, almost ubiquitous. Furthermore, Chihuahuas are predisposed to other craniomorphological abnormalities, including syringomyelia (SM), ventriculomegaly, and craniocervical junction (CCJ) overcrowding resulting in neural tissue deviation. It is, however, undetermined if PFs are more common in dogs with these structural abnormalities, and their etiology is unknown. Hypothesis/Objectives Persistent fontanelles are more numerous and larger in Chihuahuas with low body weight, older age, SM, dilated fourth ventricle, ventriculomegaly, and CCJ overcrowding. Animals Fifty client-owned Chihuahuas. Methods Cross-sectional study evaluating the association of both the number of cranial sutures affected by PFs (NAS) and total fontanelle area (TFA), based on computed tomography with SM, fourth ventricle dilatation, lateral ventricle volume, and extent of neural tissue compression at the CCJ based on magnetic resonance images. Results The NASs was higher and TFA larger in dogs with low body weight (NAS: P = .007; 95% confidence interval [CI] = 0.384-0.861; TFA: P = .002; 95% CI = -1.91 to -0.478), larger lateral ventricles (NAS: P Conclusions and Clinical Importance Persistent fontanelles are associated with small size, SM, ventriculomegaly, and CCJ overcrowding.Peer reviewe

Persistent fontanelles in Chihuahuas. Part I. Distribution and clinical relevance

Background The Chihuahua dog breed is known for frequent occurrence of a bregmatic fontanelle on the dorsal skull. A common conception is that this skull defect is a clinically irrelevant finding. No studies, however, describe its prevalence or whether it is accompanied by other persistent fontanelles (PFs). Although Chihuahuas are predisposed to Chiari-like malformation (CM) and syringomyelia (SM), it is unknown whether PFs occur more commonly in dogs with clinical signs that are caused by CM or SM. Hypothesis/Objectives To describe the number and location of PFs at cranial sutures (CSs) and to compare the occurrence of these PFs in dogs with and without CM/SM-related clinical signs. We hypothesized that PFs also occur commonly at lateral and caudal cranial surfaces, affect a higher number of CSs, and are larger in dogs with CM/SM-related clinical signs. Animals Fifty client-owned Chihuahuas with or without CM/SM-related clinical signs. Results Of the 50 dogs evaluated, 46 (92%) had either 1 or several PFs. The mean +/- SD number of PFs was 2.8 +/- 3.0 (range, 0-13). A total of 138 PFs occupied 118 CSs with 57 (48%) located dorsally, 44 (37%) caudally, and 17 (14%) laterally. The number of CSs affected by PFs was significantly higher (P Conclusions and Clinical Importance Persistent fontanelles are very common in this group of Chihuahuas and appear at dorsal, lateral, and caudal cranial surfaces. They are more numerous and larger in Chihuahuas with CM/SM-related clinical signs.Peer reviewe

Adherent-invasive Escherichia coli associated with granulomatous colitis and extraintestinal dissemination in a Sphynx cat

This case report describes a case of granulomatous colitis (GC) associated with adherent-invasive Escherichia coli (AIEC) with extension to cecum and ileum and dissemination to multiple lymph nodes, the spleen, and brain in a 10-year-old, male Sphynx cat. The cat had an episode of diarrhea 4 months prior to consultation due to sudden blindness. Signs rapidly progressed to ataxia, seizures, and death. Gross and histologic findings were consistent with granulomatous inflammation in all affected organs. In situ hybridization confirmed the presence of intracellular E. coli within enterocytes and infiltrating macrophages, and whole genome sequencing identified virulence traits commonly linked to AIEC strain. This is the first characterization of GC in a cat associated to AIEC resembling the metastatic form of Crohn's disease in humans and GC of dogs. Extraintestinal involvement might provide evidence of the ability of AIEC to promote granulomatous inflammation beyond the gut.Peer reviewe

Descriptive boxplots of variables associated with SM status significant for both Chihuahua and CKCS cohorts.

<p>The mean values for SM0, SM1 and SM2 have been linked with a colour coded line for each breed. In addition, a thin grey line has been drawn between mean values SM0 directly to SM2. Unless indicated by red bar/s, the significance is between SM0 and SM2.</p

Significant variables for SM status identified in ANOVA after Tukey correction.

<p><b><i>*</i></b> Traits identified as significant in previous GB study. <i>L =</i> angle. Significant p values ≤ 0.05 for SM affectedness are highlighted in bold.</p

Scatterplots for canonical Discriminant Analysis for three breeds, Chihuahua, Affenpinscher and CKCS.

<p><b>Chihuahua</b>: Left to right, there is less risk of SM left to right as angle 3 decreases and angle 4 increases (atlas further caudal from the supraoccipital and basioccipital bones) <b>Affenpinscher:</b> Left to right, increased risk of SM with decreasing line cj and increasing f-diam) <b>CKCS</b>: Left to right, increasing risk of SM with increasing line id and ratio f-diam: ai (i.e. dogs that are more brachycephalic).</p