Neuropathic pain in cats: Mechanisms and multimodal management.

PRACTICAL RELEVANCE: Chronic pain is a significant welfare concern in cats, and neuropathic pain, which arises from aberrant processing of sensory signals within the nervous system, is a subcategory of this type of pain. To comprehend this condition and how multimodal pharmacotherapy plays a central role in alleviating discomfort, it is crucial to delve into the anatomy of nociception and pain perception. In addition, there is an intricate interplay between emotional health and chronic pain in cats, and understanding and addressing the emotional factors that contribute to pain perception, and vice versa, is essential for comprehensive care.Clinical approach:Neuropathic pain is suspected if there is abnormal sensation in the area of the distribution of pain, together with a positive response to trial treatment with drugs effective for neuropathic pain. Ideally, this clinical suspicion would be supported by confirmation of a lesion at this neurolocalisation using diagnostic modalities such as MRI and neuroelectrophysiology. Alternatively, there may be a history of known trauma at that site. A variety of therapies, including analgesic, anti-inflammatory and adjuvant drugs, and neuromodulation (eg, TENS or acupuncture), can be employed to address different facets of pain pathways.Aim:This review article, aimed at primary care/ general practitioners, focuses on the identification and management of neuropathic pain in cats. Three case vignettes are included and a structured treatment algorithm is presented to guide veterinarians in tailoring interventions.Evidence base:The review draws on current literature, where available, along with the author's extensive experience and research.

Clinical predictors of syringomyelia in Cavalier King Charles Spaniels with chiari-like malformation based on owners' observations.

BACKGROUND: Syringomyelia (SM) is a prevalent inherited developmental condition in Cavalier King Charles Spaniels (CKCSs) with Chiari-like malformation (CM), accompanied by a variety of clinical manifestations, including signs of neuropathic pain. Magnetic resonance imaging (MRI) is the gold standard in SM diagnosis. However, it is desirable to establish clinical predictors that can identify CKCSs with a large clinical syrinx that needs treatment, as some owners cannot afford or lack access to MRI. The aims of the study were to investigate owner-reported clinical signs of SM and clinical predictors of a large clinical syrinx, using predictive values of significant signs, individually and in combinations. Eighty-nine CKCSs participated in this retrospective study. Based on MRI diagnosis, dogs were distributed into three groups: CM without syrinx or with a maximum transverse width < 2 mm (n = 13), CM with small syrinx 2.00-3.99 mm (n = 26) and CM with large syrinx ≥4 mm (n = 50). A structured investigator-owner interview using a standardized questionnaire was used to collect data regarding clinical signs of CM and SM. The statistical tests Pearson's chi-square, Fisher's Exact and Spearman's rank order were used to assess the difference in owner-reported signs between groups. For signs with significant differences, positive and negative predictive values (PPV and NPV) were calculated. RESULTS: Following clinical signs were reported significantly more frequent in dogs with a large syrinx: phantom scratching, bilateral scratching of the neck or shoulder, aversion when that area is touched, or exacerbation of clinical signs when the dog is emotionally aroused. Each individual sign had a high PPV, indicative of a large clinical syrinx. The PPV increased further when the signs phantom scratching, aversion to touch to the head, neck or shoulder, and a preferred head posture during sleep were present in combination. CONCLUSIONS: Specific clinical signs can be used individually and in combination as clinical predictors of a large clinical syrinx in CKCSs with CM and SM. General practitioners can utilize this information to identify CKCSs with a large syrinx to initiate necessary treatment. This is particularly useful in cases where access to or affordability of an MRI diagnosis is limited.

Respiratory compromise in French bulldogs presented with intervertebral disc extrusion.

BACKGROUND: French bulldogs hospitalised for the management of intervertebral disc extrusion (IVDE) are frequently affected by respiratory compromise, typically brachycephalic-associated upper respiratory obstruction and/or aspiration events. We evaluated the occurrence of such respiratory compromise events in French bulldogs presented to two referral hospitals. METHODS: Clinical data for French bulldogs diagnosed with IVDE were retrospectively collated, including severity of neurological deficits, neuroanatomical localisation, diagnosis, details of respiratory compromise, treatment and outcome. RESULTS: A total of 306 dogs diagnosed with IVDE were included. Sixty dogs (19.6%) experienced respiratory compromise, of which 31 dogs (10.1%) progressed to cyanosis, collapse or respiratory arrest. LIMITATIONS: The study was limited by its retrospective nature. Furthermore, the duration of hospitalisation was not evaluated and the decision for euthanasia was often multifactorial. CONCLUSION: One in five French bulldogs presented with IVDE experienced respiratory compromise. The detrimental welfare effects of this warrant further discussion.

Bacterial meningitis secondary to otogenic infection in 10 French bulldogs: A retrospective case series.

Background: There is limited published information to guide the clinical management of bacterial meningitis/encephalitis in dogs. Methods: This was a retrospective case series comprising 10 French bulldogs from two referral centres. The cases were diagnosed with bacterial meningitis/encephalitis suspected secondary to otogenic infection based on detection of abnormal fluid/soft tissue opacity within the middle/inner ear, associated meningeal/intracranial involvement through MRI, the findings of cerebro-spinal fluid (CSF) analysis suggestive of sepsis and/or clinical improvement following antibiosis. Results: Ten dogs were included (three female and seven male), with a median age of 60 months. Dogs presented with acute onset (median 2 days), progressive history of vestibular signs and/or intra-oral or cervical pain. Five dogs had gross signs of concurrent otitis externa. Common MRI findings included material within the tympanic bulla with adjacent meningeal enhancement. Analysis of CSF documented pleocytosis in all eight dogs, intracellular bacteria seen in three with positive bacteriological culture in two dogs. One dog was euthanised following diagnosis. Nine remaining dogs received antimicrobial therapy and six underwent surgical management. Three dogs treated surgically were neurologically normal within 2 weeks and the remaining three improved. Two dogs treated medically improved and one had complete resolution reported within a 4-week follow-up period. Study limitations include its retrospective nature and small sample size with minimal longer term follow-up. Conclusions: Bacterial meningitis/encephalitis in French bulldogs can require both medical and surgical treatment to achieve a favourable outcome.

Investigation of the presence of specific neural antibodies in dogs with epilepsy or dyskinesia using murine and human assays.

BACKGROUND: Autoimmune mechanisms represent a novel category for causes of seizures and epilepsies in humans, and LGI1-antibody associated limbic encephalitis occurs in cats. HYPOTHESIS/OBJECTIVES: To investigate the presence of neural antibodies in dogs with epilepsy or dyskinesia of unknown cause using human and murine assays modified for use in dogs. ANIMALS: Fifty-eight dogs with epilepsy of unknown cause or suspected dyskinesia and 57 control dogs. METHODS: Serum and CSF samples were collected prospectively as part of the diagnostic work-up. Clinical data including onset and seizure/episode type were retrieved from the medical records. Screening for neural antibodies was done with cell-based assays transfected with human genes for typical autoimmune encephalitis antigens and tissue-based immunofluorescence assays on mouse hippocampus slices in serum and CSF samples from affected dogs and controls. The commercial human und murine assays were modified with canine-specific secondary antibody. Positive controls were from human samples. RESULTS: The commercial assays used in this study did not provide unequivocal evidence for presence of neural antibodies in dogs including one dog with histopathologically proven limbic encephalitis. Low titer IgLON5 antibodies were present in serum from one dog from the epilepsy/dyskinesia group and in one dog from the control group. CONCLUSION AND CLINICAL IMPORTANCE: Specific neural antibodies were not detected using mouse and human target antigens in dogs with epilepsy and dyskinesia of unknown origin. These findings emphasize the need for canine-specific assays and the importance of control groups.

Non-traumatic hemorrhagic myelopathy in dogs.

BACKGROUND: Non-traumatic spinal cord hemorrhage (NTSH) is an uncommon cause of myelopathy in dogs. OBJECTIVES: Describe the clinical characteristics, concurrent medical conditions and underlying causes, magnetic resonance imaging (MRI) findings and outcome in dogs with NTSH. ANIMALS: Dogs diagnosed with NTSH using gradient echo T2-weighted (GRE) sequences with or without histopathological confirmation of hemorrhage were included. Dogs with a traumatic cause were excluded, including those with compressive intervertebral disc extrusion. METHODS: Retrospective descriptive study; the databases of 2 referral hospitals were searched between 2013 and 2021. RESULTS: Twenty-three dogs met inclusion criteria. The onset of signs was acute and progressive in 70% of cases; spinal hyperesthesia was variable (48%). Hemorrhage was identified in the thoracolumbar spinal segments in 65% of dogs. An underlying cause was identified in 65% of cases. Angiostrongylus vasorum represented 18% of the total cohort, followed by steroid-responsive meningitis arteritis (SRMA; 13%). Overall, 64% of dogs had a good or excellent outcome, regardless of cause; which was increased to 100% for SRMA, 75% for A. vasorum and 75% for idiopathic NTSH. Outcome was not associated with neurological severity. Recovery rate was 67% and 50% for nociception-intact and nociception-negative dogs, respectively. CONCLUSIONS: Larger prospective studies would be required to define prognostic factors for dogs with NTSH, but outcome appeared to be most influenced by the underlying cause, as opposed to neurological severity at presentation.

A TNR Frameshift Variant in Weimaraner Dogs with an Exercise-Induced Paroxysmal Movement Disorder.

BACKGROUND: Some paroxysmal movement disorders remain without an identified genetic cause. OBJECTIVES: The aim was to identify the causal genetic variant for a paroxysmal dystonia-ataxia syndrome in Weimaraner dogs. METHODS: Clinical and diagnostic investigations were performed. Whole genome sequencing of one affected dog was used to identify private homozygous variants against 921 control genomes. RESULTS: Four Weimaraners were presented for episodes of abnormal gait. Results of examinations and diagnostic investigations were unremarkable. Whole genome sequencing revealed a private frameshift variant in the TNR (tenascin-R) gene in an affected dog, XM_038542431.1:c.831dupC, which is predicted to truncate more than 75% of the open read frame. Genotypes in a cohort of 4 affected and 70 unaffected Weimaraners showed perfect association with the disease phenotype. CONCLUSIONS: We report the association of a TNR variant with a paroxysmal dystonia-ataxia syndrome in Weimaraners. It might be relevant to include sequencing of this gene in diagnosing humans with unexplained paroxysmal movement disorders. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Vertebral giant cell tumour of bone in a domestic shorthair cat.

Case summary: A 10-year-old male neutered domestic shorthair cat was presented with a 5-month history of progressive non-ambulatory paraparesis. Initial vertebral column radiographs revealed an L2-L3 expansile osteolytic lesion. Spinal MRI showed a well-demarcated, compressive expansile extradural mass lesion affecting the caudal lamina, caudal articular processes and right pedicle of the second lumbar vertebra. The mass was hypointense/isointense on T2-weighted images, isointense on T1-weighted images and had mild homogeneous contrast enhancement after gadolinium administration. MRI of the remaining neuroaxis and CT of the neck, thorax and abdomen with ioversol contrast revealed no additional neoplastic foci. The lesion was removed by en bloc resection via a dorsal L2-L3 laminectomy, including the articular process joints and pedicles. Vertebral stabilisation was performed with titanium screws placed within L1, L2, L3 and L4 pedicles with polymethylmethacrylate cement embedding. Histopathology revealed an osteoproductive neoplasm composed of spindle and multinucleated giant cells without detectable cellular atypia or mitotic activity. On immunohistochemical evaluation, osterix, ionised calcium-binding adaptor molecule 1 and vimentin labelling were observed. Based on the clinical and histological features, a giant cell tumour of bone was considered most likely. Follow-up at 3 and 24 weeks postoperatively demonstrated significant neurological improvement. Postoperative full-body CT at 6 months showed instability of the stabilisation construct but absence of local recurrence or metastasis. Relevance and novel information: This is the first reported case of a giant cell tumour of bone in the vertebra of a cat. We present the imaging findings, surgical treatment, histopathology, immunohistochemistry and outcome of this rare neoplasm.

Serum anti-GM2 and anti-GalNAc-GD1a ganglioside IgG antibodies are biomarkers for immune-mediated polyneuropathies in cats.

Recent work identified anti-GM2 and anti-GalNAc-GD1a IgG ganglioside antibodies as biomarkers in dogs clinically diagnosed with acute canine polyradiculoneuritis, in turn considered a canine equivalent of Guillain-Barré syndrome. This study aims to investigate the serum prevalence of similar antibodies in cats clinically diagnosed with immune-mediated polyneuropathies. The sera from 41 cats clinically diagnosed with immune-mediated polyneuropathies (IPN), 9 cats with other neurological or neuromuscular disorders (ONM) and 46 neurologically normal cats (CTRL) were examined for the presence of IgG antibodies against glycolipids GM1, GM2, GD1a, GD1b, GalNAc-GD1a, GA1, SGPG, LM1, galactocerebroside and sulphatide. A total of 29/41 IPN-cats had either anti-GM2 or anti-GalNAc-GD1a IgG antibodies, with 24/29 cats having both. Direct comparison of anti-GM2 (sensitivity: 70.7%; specificity: 78.2%) and anti-GalNAc-GD1a (sensitivity: 70.7%; specificity: 70.9%) antibodies narrowly showed anti-GM2 IgG antibodies to be the better marker for identifying IPN-cats when compared to the combined ONM and CTRL groups (P = .049). Anti-GA1 and/or anti-sulphatide IgG antibodies were ubiquitously present across all sample groups, whereas antibodies against GM1, GD1a, GD1b, SGPG, LM1 and galactocerebroside were overall only rarely observed. Anti-GM2 and anti-GalNAc-GD1a IgG antibodies may serve as serum biomarkers for immune-mediated polyneuropathies in cats, as previously observed in dogs and humans.

Myoclonus in older Cavalier King Charles Spaniels.

BACKGROUND: Myoclonus is observed in older Cavalier King Charles Spaniels (CKCS) but a full description is lacking. OBJECTIVES: The presence, age of onset, characteristics and treatment of myoclonic episodes were retrospectively evaluated in a cohort of CKCS which presented to 1 board-certified neurologist. Clinical data, imaging studies, presence of seizures and their management, as well as other comorbidities were noted. ANIMALS: Thirty-nine CKCS that were presented to 2 institutions between 2001 and 2018 with signs consistent with myoclonus. Clinical examination, blood sampling, advanced diagnostic imaging, cerebrospinal fluid analysis, and record keeping of other comorbidities was performed. METHODS: This is a retrospective case series, describing the presence of myoclonus in CKCS. RESULTS: Clinical signs reported were spontaneous in onset, lasted a few seconds and consisted of rapid blinking with head nodding and variable extension down the thoracic limbs. Myoclonus occasionally led to stumbling of the thoracic limbs or collapse. Mean age of onset was 8.38 years (SD ±1.96). Thirteen of 39 dogs with myoclonus had paroxysmal events, such as generalized seizures (9/13). CONCLUSIONS AND CLINICAL IMPORTANCE: Myoclonus occurs in middle-aged to older CKCS and seems to be another epiphenomena of this breed. A link to epilepsy might be present.

Clinical features, treatment and outcome of discospondylitis in cats.

OBJECTIVES: There is a paucity of information on feline discospondylitis. This study aimed to describe the signalment, clinical and laboratory findings, aetiological agents, treatment and outcome in cats affected by discospondylitis. METHODS: This was a retrospective review of the medical records of cats diagnosed with discospondylitis at four referral institutions. RESULTS: A total of 17 cats were identified. Most were domestic shorthair cats (76.5%) and male (58.8%), with a median age of 9 years (range 0.9-14) and a median duration of clinical signs of 3 weeks (range 0.3-16). All cats presented with spinal hyperaesthesia; 3/17 had pyrexia. Neurological dysfunction was found in 64.7% of cats, which was indicative of a T3-L3 or L4-S2 spinal segment, associated nerve root or associated nerve neurolocalisation. Haematology, serum biochemistry and urinalysis revealed occasional inconsistent non-specific changes. All cats underwent urine culture; 9/17 cats also had a distinct tissue cultured. Positive bacterial cultures were obtained in two cats (11.8%) for Staphylococcus species (urine, blood and intradiscal fine-needle aspirate) and Escherichia coli (urine); both presented with multifocal discospondylitis. Treatment was non-surgical in all cats, with sustained antibiotic therapy for a median of 3 months (range 1-9). Analgesia provided included non-steroidal anti-inflammatory drugs, alone or in combination with gabapentin. Restricted exercise was advised for a minimum of 4 weeks. Outcome information available in 12 cats was excellent in terms of pain control and neurological function in 10 cats (83.3%) at the time of stopping antibiotics. Recurrence occurred in one case, which had received a single antibiotic for 6 weeks, and relapsed 4 months after presentation. One other case failed to improve and was euthanased during the course of hospitalisation. CONCLUSIONS AND RELEVANCE: Feline discospondylitis is uncommon and no obvious signalment predisposition was found in this study. Spinal hyperaesthesia was universally present, with neurological dysfunction also highly prevalent. Bacterial culture was unrewarding in most cases. Amoxicillin-clavulanic acid or cephalosporins are reasonable choices for first-line antibiotics. Prognosis was favourable, with no long-term evidence of recurrence in cats on sustained antibiotic therapy, for a mean duration of 3 months.

Primary orthostatic tremor and orthostatic tremor-plus in dogs: 60 cases (2003-2020).

BACKGROUND: Orthostatic tremor (OT) is a rare movement disorder characterized by high-frequency (>12 Hz) involuntary, rhythmic, sinusoidal movements affecting predominantly the limbs while standing. OBJECTIVE: To describe the signalment, presenting complaints, phenotype, diagnostic findings, treatment, and outcome of a large sample of dogs with OT. ANIMALS: Sixty dogs diagnosed with OT based on conscious electromyography. METHODS: Multicenter retrospective case series study. Dogs were included if they had a conscious electromyography consistent with muscle discharge frequency >12 Hz while standing. RESULTS: Fifty-three cases were diagnosed with primary OT (POT). Giant breed dogs represented most cases (83%; 44/53). Most dogs (79%; 42/53) were younger than 2 years of age at onset of signs, except for Retrievers which were all older than 3.5 years of age. The most common presenting complaints were pelvic limb tremors while standing (85%; 45/53) and difficulty when rising or sitting down (45%; 24/53). Improvement of clinical signs occurred in most dogs (85%; 45/53) treated medically with phenobarbital, primidone, gabapentin, pregabalin or clonazepam, but it was mostly partial rather than complete. Orthostatic tremor-plus was seen in 7 dogs that had concurrent neurological diseases. CONCLUSIONS AND CLINICAL IMPORTANCE: Primary OT is a progressive disease of young, purebred, giant/large-breed dogs, which appears to begin later in life in Retrievers. Primary OT apparently responds partially to medications. Orthostatic tremor-plus exists in dogs and can be concomitant or associated with other neurological diseases.

Spinal ectopic choroid plexus papilloma in a cat.

CASE SUMMARY: A 10-year-old male neutered Russian Blue cat was presented with a 2-month history of progressive non-ambulatory paraparesis. Spinal MRI revealed a well-demarcated, compressive intradural extramedullary mass at the level of T1 vertebra. The mass had subtle hyperintensity on T2-weighted images, was isointense on T1-weighted images and had diffuse, marked enhancement following gadolinium administration. Neuroaxis MRI, including limited brain sequences, excluded other visible lesions. Thoracic and abdominal radiographs were unremarkable. The mass was resected via a dorsal C7-T2 laminectomy and durotomy. Histopathology revealed a neoplasm composed of columnar-to-polygonal cells forming bilayered palisading patterns with a few apical cilia. Three mitoses were noted in 10 high-power fields. This was consistent with an epithelial neoplasm and initially a metastatic adenocarcinoma was considered most likely. Full-body CT with contrast and including the brain found rhinitis but did not identify any additional neoplastic foci. Biopsies of the nasal cavity and fine-needle aspiration of the spleen and liver were unremarkable. On immunohistochemical evaluation, pan-cytokeratin and E-cadherin immunolabelling was observed; however, synaptophysin, thyroglobulin, chromogranin A and glial fibrillary acidic protein was not detected. This, along with the histological morphology and absence of a primary tumour, was compatible with an ectopic choroid plexus neoplasm. Follow-up performed at 3, 14 and 24 months postoperatively revealed neurological improvement without recurrence. RELEVANCE AND NOVEL INFORMATION: We describe the presentation, histopathological and immunohistochemical features and outcome of a case of a rare ectopic choroid plexus neoplasm in the spinal cord of a cat.

Olivopontocerebellar degeneration associated with 3-hydroxy-3-methylglutaric aciduria in a domestic shorthair cat.

CASE SUMMARY: A rescue charity-owned 6-month-old neutered female domestic shorthair cat was presented with progressive tetraparesis, increased extensor muscle tone and signs of spinocerebellar ataxia, including hypermetria. The cat's male sibling, with similar progressive neurological signs, had been euthanased 2 months previously. An inherited metabolic disorder was suspected. Urine for determination of organic acid concentration was obtained and the cat was prescribed carnitine and taurine supplementation. The cat was euthanased 3 months later following progressive neurological signs, including ataxia, tetraparesis, tendency to fall, bilateral absent menace response and intention tremor. A selective post-mortem examination was obtained, taking samples from the brain, cervical spinal cord, tibial branch of the sciatic nerve, muscle, liver and kidneys. Organic acid analysis results received after euthanasia revealed a marked elevation of 3-hydroxy-3-methylglutaric acid (45 mmol/mol creatine [normal range 0-2]) and isovalerylglycine (27 mmol/mol creatinine [normal range 0-2]). 3-Hydroxy-3-methylglutaric acid was deemed clinically relevant as it is a metabolite of 3-hydroxy-3-methylglutaryl-CoA lyase, the enzyme involved in the final step of leucine degradation. Post-mortem examination revealed diffuse, chronic-active, severe olivoponto-(spino)-cerebellar degeneration. RELEVANCE AND NOVEL INFORMATION: This is the first report of 3-hydroxy-3-methylglutaric aciduria in the veterinary literature and the first description of the neuropathology of this disorder in any species. 3-Hydroxy-3-methylglutaric aciduria in humans occurs rarely and is due to a deficiency in 3-hydroxy-3-methylglutaryl-coenzyme A lyase.

Slosh Simulation in a Computer Model of Canine Syringomyelia.

The exact pathogenesis of syringomyelia is unknown. Epidural venous distention during raised intrathoracic pressure (Valsalva) may cause impulsive movement of fluid ("slosh") within the syrinx. Such a slosh mechanism is a proposed cause of syrinx dissection into spinal cord parenchyma resulting in craniocaudal propagation of the cavity. We sought to test the "slosh" hypothesis by epidural excitation of CSF pulse in a computer model of canine syringomyelia. Our previously developed canine syringomyelia computer model was modified to include an epidural pressure pulse. Simulations were run for: cord free of cavities; cord with small syringes at different locations; and cord with a syrinx that was progressively expanding caudally. If small syringes are present, there are peaks of stress at those locations. This effect is most pronounced at the locations at which syringes initially form. When a syrinx is expanding caudally, the peak stress is typically at the caudal end of the syrinx. However, when the syrinx reaches the lumbar region; the stress becomes moderate. The findings support the "slosh" hypothesis, suggesting that small cervical syringes may propagate caudally. However, when the syrinx is large, there is less focal stress, which may explain why a syrinx can rapidly expand but then remain unchanged in shape over years.

Canine Lafora Disease: An Unstable Repeat Expansion Disorder.

Canine Lafora disease is a recessively inherited, rapidly progressing neurodegenerative disease caused by the accumulation of abnormally constructed insoluble glycogen Lafora bodies in the brain and other tissues due to the loss of NHL repeat containing E3 ubiquitin protein ligase 1 (NHLRC1). Dogs have a dodecamer repeat sequence within the NHLRC1 gene, which is prone to unstable (dynamic) expansion and loss of function. Progressive signs of Lafora disease include hypnic jerks, reflex and spontaneous myoclonus, seizures, vision loss, ataxia and decreased cognitive function. We studied five dogs (one Chihuahua, two French Bulldogs, one Griffon Bruxellois, one mixed breed) with clinical signs associated with canine Lafora disease. Identification of polyglucosan bodies (Lafora bodies) in myocytes supported diagnosis in the French Bulldogs; muscle areas close to the myotendinous junction and the myofascial union segment had the highest yield of inclusions. Postmortem examination of one of the French Bulldogs revealed brain Lafora bodies. Genetic testing for the known canine NHLRC1 mutation confirmed the presence of a homozygous mutation associated with canine Lafora disease. Our results show that Lafora disease extends beyond previous known breeds to the French Bulldog, Griffon Bruxellois and even mixed-breed dogs, emphasizing the likely species-wide nature of this genetic problem. It also establishes these breeds as animal models for the devastating human disease. Genetic testing should be used when designing breeding strategies to determine the frequency of the NHLRC1 mutation in affected breeds. Lafora diseases should be suspected in any older dog presenting with myoclonus, hypnic jerks or photoconvulsions.

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 ≤ .001) and total PF area was significantly larger (P = .003) in dogs with CM/SM-related clinical signs. 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.