The aetiology and outcome of dogs with juvenile‐onset seizures were investigated. One hundred and thirty‐six dogs whose first seizure occurred before the age of one year were investigated. One hundred and two dogs were diagnosed with idiopathic epilepsy (IE), 23 with symptomatic epilepsy (SE), nine with reactive seizures (RS) and two with probable symptomatic epilepsy (pSE). The outcome was known in 114 dogs; 37 per cent died or were euthanased as a consequence of seizures. The mean survival time of this population of dogs was 7.1 years. Factors that were significantly associated with survival outcome included the diagnosis of SE and the number of antiepileptic drugs (AEDs) used before investigation. The use of one AED before investigation and a diagnosis of SE were associated with a negative outcome, whereas receiving no AED medications before referral was associated with a longer survival. For dogs with IE, survival time was shortened if the dog was a border collie or with a history of status epilepticus;receiving no AEDs before referral in the IE group was associated with a positive outcome. Seizure‐free status was achieved in 22 per cent of dogs diagnosed with IE. While the survival times were longer than previously reported in canine epilepsy, similar remission rates to those reported in childhood epilepsy, where a 70 per cent remission rate is documented, were not seen in the canine juvenile population.

The epidemiology of inflammatory diseases affecting the central nervous system (CNS) in dogs is largely unknown. We aimed to report the relative proportion of different causes of inflammatory disease affecting the CNS in dogs and identify predictors for infectious vs. immune-mediated conditions and predictors for the most common diseases affecting the brain and the spinal cord. This was a retrospective cohort study over a 10-year period in 2 referral institutions using multivariable and multinomial logistic regression for identification of risk factors. In total, 1,140 client-owned dogs diagnosed with inflammatory disease affecting the CNS were included. Fifteen different diagnoses were identified, with immune-mediated (83.6%) disease being more common than infectious conditions (16.4%). The most common immune-mediated conditions diagnosed were meningoencephalitis of unknown origin (47.5%) and steroid-responsive meningitis–arteritis (30.7%), and the most common infectious conditions were discospondylitis (9.3%) and otogenic intracranial infection (2.2%). Older age (p < 0.001, OR = 1.019, 95% CI: 1.014–1.024), higher body weight (p < 0.001, OR = 1.049, 95% CI: 1.025–1.074), male sex (p = 0.009, OR = 1.685, 95% CI: 1.141–2.488), longer duration of the clinical signs before presentation (p < 0.001, OR = 1.011, 95% CI: 1.006–1.017), progressive nature of the clinical signs (p < 0.001, OR = 2.295, 95% CI: 1.463–3.599), identification of a possibly associated preceding event (p = 0.0012, OR = 1.93, 95% CI: 1.159–3.213), and hyperesthesia on presentation (p < 0.001, OR = 2.303, 95% CI: 1.528–3.473) were associated with a diagnosis of infectious diseases. Our data shows that immune-mediated diseases are more common than infectious conditions as a cause for inflammatory CNS disease in dogs. The risk factors for the most common diagnoses were identified from signalment, history, and findings of the physical and neurological examinations to give valuable information that can guide clinicians with their investigations.

Background: Meningoencephalitis of unknown origin (MUO) comprises a group of debilitating inflammatory diseases affecting the central nervous system of dogs. Currently, no validated clinical scale is available for the objective assessment of MUO severity. Objectives: Design a neurodisability scale (NDS) to grade clinical severity and determine its reliability and whether or not the score at presentation correlates with outcome. Animals: One hundred dogs with MUO were included for retrospective review and 31 dogs were subsequently enrolled for prospective evaluation. Methods: Medical records were retrospectively reviewed for 100 dogs diagnosed with MUO to identify the most frequent neurological examination findings. The NDS was designed based on these results and evaluated for prospective and retrospective use in a new population of MUO patients (n = 31) by different groups of independent blinded assessors, including calculation of interobserver agreement and association with outcome. Results: The most common clinical signs in MUO patients were used to inform categories for scoring in the NDS: seizure activity, ambulatory status, posture and cerebral, cerebellar, brainstem, and visual functions. The intraclass correlation coefficient (ICC) for prospective use of the NDS was 0.83 (95% confidence interval [CI], 0.68-0.91) indicating good agreement, and moderate agreement was found between prospective and retrospective assessors (ICC, 0.71; 95% CI, 0.56-0.83). No association was found between NDS score and long-term outcome. Conclusions and Clinical Importance: The NDS is a novel clinical measure for objective assessment of neurological dysfunction and showed good reliability when used prospectively in MUO patients but, in this small population, no association with outcome could be identified.

Background: Meningoencephalitis of unknown origin (MUO) comprises a group of noninfectious inflammatory diseases affecting the central nervous system of dogs. Previous studies have reported individual risk factors for survival but prognostication for MUO remains challenging. Objectives: Identify clinical prognostic variables in dogs with MUO. Animals: A retrospective study of 447 dogs presented to 2 UK referral hospitals and diagnosed with MUO. Methods: Medical records of dogs diagnosed with MUO were retrospectively reviewed. Multivariable logistic regression was used for the identification of risk factors for survival and Cox proportional hazards analysis for the identification of risk factors for clinical relapse. Results: Eighty-two percent (366/447) of dogs with presumptive MUO survived to discharge and 63.5% (284/447) were alive at 6 months; 36% of the latter (103/284) had persistent neurological deficits. Breed (pugs; P = .03), epileptic seizures (P < .001), paresis (P < .001), and higher neurodisability scale (NDS) score (P < .001) at presentation were negatively associated with survival to 6 months. Dogs with persistent deficits had higher NDS scores on presentation (P = .001). Median follow-up time was 11 months (interquartile range [IQR], 1-24) and 50.6% (160/316) relapsed during treatment (median time to relapse, 7 months; IQR, 2-15). Incomplete resolution of the clinical signs during the 6 months after diagnosis (P < .001), higher NDS score (P < .001), and longer duration of the clinical signs (P < .001) were associated with relapse. Conclusions and Clinical Importance: Knowledge of risk factors associated with survival, incomplete recovery and clinical relapse in MUO can help guide monitoring and treatment and improve owner communications regarding prognosis for this debilitating disease.

Background: Although idiopathic episodic head tremor (IEHT) in dogs is well-known, little is known about structural brain lesions causing structural episodic head tremor (SEHT). Hypothesis/Objectives: Describe semiology, magnetic resonance imaging (MRI) findings and outcome of dogs with IEHT or SEHT. We hypothesized that structural lesions affecting the middle cranial fossa or mesencephalic aqueduct could lead to SEHT. Animals: One hundred dogs with IEHT (n = 71) or SEHT (n = 29). Methods: Retrospective, multicenter, study of dogs with episodic (nonintentional) head tremor and brain MRI between 2004 and 2022. Results: Lesions on MRI in SEHT dogs were localized to the middle cranial fossa (15/29), cerebrocortex (3/29), brainstem (2/29), fourth ventricle (1/29) or multifocal (8/29) with thalamus involvement (6/8). Secondary compression of the mesencephalic aqueduct (19/29), third ventricle or interthalamic adhesion or both (14/29) was common. The most common underlying condition in dogs with SEHT was a pituitary mass. Dogs with SEHT were older, had additional neurological signs and were more likely to be euthanized after diagnosis (P < .001 for all) compared to IEHT dogs. Two SEHT dogs had only tremor. In IEHT dogs, 8/10 owners reported that the tremor decreased or abated over time (range, 106-2315 days) without treatment. Tremor remission occurred in SEHT dogs treated for underlying meningoencephalitis. Conclusions and Clinical Importance: Presence of additional neurological signs and older age may indicate an underlying structural cause for episodic (nonintentional) head tremor involving the mesencephalic aqueduct, third ventricle, interthalamic adhesion or some combination of these. An intracranial structural abnormality cannot be excluded in dogs with normal neurological examination.