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Abstract Obstructive or nonobstructive hypertensive hydrocephalus is reported in choroid plexus tumors. Choroid plexus tumors typically present as T2‐weighted hyperintense intraventricular masses with occasional cerebrospinal fluid‐drop metastasis. Acquired neoplastic nonobstructive hydrocephalus without visible mass lesion in magnetic resonance imaging is not reported in dogs. A 4.5‐year‐old Rhodesian Ridgeback presented with reduced mental status, unilaterally absent pupillary light reflex, and neck pain. Magnetic resonance imaging revealed a nonobstructive hydrocephalus and widened lumbar subarachnoid space with no evidence of a primary mass lesion. Postmortem examination confirmed a disseminated choroid plexus tumor affecting the ependyma and choroid plexi of all ventricles and the cerebral and lumbar subarachnoid space. Disseminated choroid plexus carcinomatosis should be considered as a possible cause of hypertensive hydrocephalus even in absence of a primary mass.

The trigeminal nerve is responsible for innervating the periorbita. Ultrasound-guided trigeminal block is employed in humans for trigeminal neuralgia or periorbital surgery. There are no studies evaluating this block in dogs. This study aims to evaluate and compare two approaches (coronoid and temporal) of the trigeminal nerve block. We hypothesised superior staining with the coronoid approach. Thirteen dog heads were used. After a preliminary anatomical study, two ultrasound-guided injections per head (right and left, coronoid and temporal approach, randomly assigned), with an injectate volume of 0.15 mL cm−1 of cranial length, were performed (iodinated contrast and tissue dye mixture). The ultrasound probe was placed over the temporal region, visualising the pterygopalatine fossa. For the temporal approach, the needle was advanced from the medial aspect of the temporal region in a dorsoventral direction. For the coronoid approach, it was advanced ventral to the zygomatic arch in a lateromedial direction. CT scans and dissections were conducted to assess and compare the position of the needle, the spread of the injectate, and nerve staining. No significant differences were found. Both approaches demonstrated the effective interfascial distribution of the injectate, with some minimal intracranial spread. Although the coronoid approach did not yield superior staining as hypothesised, it presents a viable alternative to the temporal approach. Studies in live animals are warranted to evaluate clinical efficacy and safety.

IntroductionIn veterinary medicine, abdominal computer tomographic (CT) examinations regularly require a minimum of two scans, with a native scan (true unenhanced, TUE) as a reference for the subsequent contrast-enhanced CT scan (CECT). Spectral detector CT (SDCT) offers the possibility to calculate virtual non-contrast (VNC) images from the post-contrast scan, but this has not yet been investigated in veterinary medicine. The purpose of this study was to assess the reliability of VNC images for abdominal organs in 44 dogs without abdominal pathologies by evaluating their quantitative and qualitative parameters compared to TUE images. We hypothesized that the subtraction of iodine is sufficient in the VNC series compared to the TUE series and that the image quality of the SDCT series is superior to conventional CT images.MethodsCorresponding attenuation values in the VNC and TUE series regarding the regions of interest (ROI) in different parenchymal organs and major vessels of the abdominal cavity were assessed by means of a two one-sided t-test (TOST) and Bland–Altman plots. Additionally, the signal-to-noise ratio (SNR) was calculated for each ROI in the different series. In the second step, two board-certified veterinary radiologists made a qualitative assessment of VNC images vs. TUE images in consensus by rating the iodine subtraction, image noise, and image quality of VNC images based on a specific 5-point Likert scale.ResultsThe difference in corresponding Hounsfield units (HUs) between TUE and VNC images was less than 10 HU in 78.67% of all ROIs. Regarding the limit of less than 10 HU, in the performed TOST, significant p-values of

IntroductionThe understanding of epileptic seizure pathogenesis has evolved over time, and it is now generally accepted that not only are cortical and subcortical areas involved but also the connection of these regions in the white matter (WM). Recent human neuroimaging studies confirmed the involvement of the WM in several epilepsy syndromes. Neuroimaging studies investigating WM integrity with diffusion tensor imaging (DTI) in canine idiopathic epilepsy are lacking. This study aimed to test the hypothesis that WM diffusion changes can be found in dogs affected by idiopathic epilepsy.MethodTwenty-six dogs with idiopathic epilepsy (15 Border Collies and 11 Greater Swiss Mountain dogs) and 24 healthy controls (11 Beagle dogs, 5 Border Collies, and 8 Greater Swiss Mountain dogs) were prospectively enrolled. Most dogs with idiopathic epilepsy (17/26) were enrolled within 3 months after seizure onset. Diffusion tensor imaging of the brain with 32 diffusion directions (low b value = 0 s/mm2; maximal b value = 800 s/mm2) was performed in a 3 Tesla scanner. Tract-based spatial statistics (TBSS), a voxel-based approach, was used to investigate changes in fractional anisotropy (FA) and mean diffusivity (MD) in the idiopathic epilepsy group compared to the healthy control group. Additionally, FA and MD were investigated in the region of corpus callosum and cingulate white matter in both groups.ResultsWe observed subtle changes in WM DTI between the idiopathic epilepsy group and the healthy control group limited to cingulate WM, with a significantly lower FA in the idiopathic epilepsy group compared to the healthy control group in the region of interest (ROI) approach (p = 0.027). No significant changes were found between the idiopathic epilepsy group and the healthy control group in the TBSS analysis and in the corpus callosum in the ROI approach.ConclusionThis study supports the cingulate area as a target structure in canine epilepsy. The subtle changes only might be explained by the short duration of epilepsy, small sample sizes, and the higher variability in canine brain anatomy. Furthermore, all included dogs showed generalized tonic-clonic seizures, possibly affected by generalized epilepsy syndrome, which are also associated with less pronounced DTI changes in humans than focal epilepsy syndromes.

Abstract Nerve root enlargement with increased contrast uptake has been reported in dogs and humans secondary to nerve root compression. In cats, nerve root enlargement and contrast uptake only have been reported in association with inflammatory and neoplastic diseases, but not as a sequela to nerve root compression. An 8‐year‐old oriental short hair cat was presented with acute neurologic deficits consistent with left‐sided sciatic nerve deficit and possible L6‐S1 myelopathy. Magnetic resonance imaging (MRI) was performed and identified compression of the cauda equina and L7 nerve root associated with intervertebral disc herniation (IVDH) at L6‐L7 as well as widespread sciatic nerve enlargement with moderate rim enhancement. A hemilaminectomy was performed to evacuate herniated disc material. The nerve root was biopsied and submitted for histological evaluation. Interstitial nerve edema was diagnosed. Follow‐up MRI 3 months postoperatively showed complete remission of the changes. Nerve root thickening together with contrast enhancement may represent nerve edema in cats secondary to IVDH.

Abstract Background Retrospective research recently identified a possible relationship between duration of surgery and outcome in severely affected dogs treated surgically for acute thoracolumbar intervertebral disk herniation (TL‐IVDH). Hypothesis That increased duration of surgery is associated with poorer outcome in dogs with absent pain perception treated surgically for TL‐IVDH. Animals Two hundred ninety‐seven paraplegic dogs with absent pain perception surgically treated for acute TL‐IVDH. Methods Retrospective cohort study. Medical records of 5 institutions were reviewed. Inclusion criteria were paraplegia with absence of pain perception, surgical treatment of TL‐IVDH, and 1‐year postoperative outcome (ambulatory: yes or no). Canine data, outcome, and surgery and total anesthesia duration were retrieved. Results In this study, 183/297 (61.6%) dogs were ambulatory within 1 year, 114 (38.4%) dogs failed to recover, including 74 dogs (24.9%) euthanized because of progressive myelomalacia. Median anesthesia duration in dogs that regained ambulation within 1 year of surgery (4.0 hours, interquartile range [IQR] 3.2‐5.1) was significantly shorter than those that did not (4.5 hours, IQR 3.7‐5.6, P = .01). Multivariable logistic regression demonstrated a significant negative association between both duration of surgery and total anesthesia time and ambulation at 1 year when controlling for body weight and number of disk spaces operated on. Conclusions and Clinical Importance Findings support a negative association between increased duration of anesthesia and outcome in this group of dogs. However, the retrospective nature of the data does not imply a causal relationship.

Susceptibility-weighted imaging (SWI), an MRI sequence for the detection of hemorrhage, allows differentiation of paramagnetic and diamagnetic substances based on tissue magnetic susceptibility differences. The three aims of this retrospective study included a comparison of the number of areas of signal void (ASV) between SWI and T2*-weighted imaging (T2*WI), differentiation of hemorrhage and calcification, and investigation of image deterioration by artifacts. Two hundred twelve brain MRIs, 160 dogs and 52 cats, were included. The sequences were randomized and evaluated for presence/absence and numbers of ASV and extent of artifacts causing image deterioration by a single, blinded observer. In cases with a CT scan differentiation of paramagnetic (hemorrhagic) and diamagnetic (calcification) lesions was made, SWI was performed to test correct assignment using the Hounsfield Units. Non-parametric tests were performed to compare both sequences regarding detection of ASV and the effect of artifacts on image quality. The presence of ASV was found in 37 SWI sequences and 34 T2*WI sequences with a significant increase in ASV only in dogs >5 and ≤ 15 kg in SWI. The remaining weight categories showed no significance. CT examination was available in 11 cases in which 81 ASV were found. With the use of phase images, 77 were classified as paramagnetic and none as diamagnetic. A classification was not possible in four cases. At the level of the frontal sinus, significantly more severe artifacts occurred in cats and dogs (dogs, p < 0.001; cats, p = 0.001) in SWI. The frontal sinus artifact was significantly less severe in brachycephalic than non-brachycephalic dogs in both sequences (SWI, p < 0.001; T2*WI, p < 0.001). In conclusion, with the advantages of better detection of ASV in SWI compared with T2*WI and the opportunity to differentiate between paramagnetic and diamagnetic origin in most cases, SWI is generally recommended for dogs. Frontal sinus conformation appears to be a limiting factor in image interpretation.

Abstract Cerebral cortical laminar necrosis (CLN) is a consequence of severe hypoxic, ischemic, or hypoglycemic events. In humans, these cortical lesions show characteristic linear T1‐weighted (T1W) hyperintensity in the late subacute stage. Limited information reporting magnetic resonance imaging (MRI) findings in dogs affected by CLN is available. A 3‐year‐old Belgian Shepherd dog was referred 8 days after sudden onset of blindness after general anesthesia. Neurological examination showed central blindness and mild ataxia. Three‐Tesla MRI examination of the brain revealed bilateral asymmetrical areas of T2‐weighted hyperintensity within the occipital, parietal, temporal, and frontal cortex, involving gray and white matter. Furthermore, linear T1W‐hyperintense lesions were found in the cerebral cortex of the same areas and showed heterogeneous contrast enhancement. Perfusion‐weighted images revealed hyperperfusion in the affected regions. Lesions were compatible with subacute CLN with corresponding edema suspected to be secondary to anesthesia‐related brain hypoxia. Three‐Tesla MRI enabled identification of the laminar pattern of the cortical lesions.

Bilateral carotid artery ligation has been reported as a lifesaving procedure to control severe hemorrhage. However, reports are sparse and little information is available regarding the potential risks associated with this procedure. We report an ischemic brain infarct as a complication after vascular surgery. A 3-year old, male intact border collie was presented for acute onset of forebrain signs 5 days after bilateral carotid artery ligation. Multimodal brain MRI including morphologic sequences, MR angiography, diffusion- and perfusion-weighted images were performed. MRI revealed a well-defined intra-axial lesion of the left caudate nucleus, with increased T2 and decreased T1 signal intensity and moderate heterogeneous peripheral contrast enhancement. The cerebral blood flow was reduced relative to the contralateral caudate nucleus. Images were consistent with a subacute lacunar ischemic infarct of the left striate artery. Additionally, multiple arterio-arterial anastomosis arising from the vertebral arteries were visible in the angiography sequences. Ischemic infarct due to thromboembolism should be considered as a possible complication associated with bilateral carotid artery ligation. Collateral blood supply can develop as early as 5 days after surgery.

Corpus callosum abnormalities (CCA) rarely occur in dogs and are related to hypo/adypsic hypernatremia and seizures. Hypoplasia and dysplasia of the corpus callosum (CC) with concomitant lobar holoprosencephaly is the most common variant. It is currently uncertain using conventional MRI if canine CCA reflects the failure of commissural fibers to develop or the failure of the commissural fibers to cross hemispheres. Diffusion tensor imaging was performed in a 4-year-old Staffordshire mix breed dog with CCA and an age-matched healthy Beagle. In comparison to the control dog, CC tractography of the affected dog depicted only axonal tracts corresponding to the temporal CC fibers. The cingulum bundles appeared supernumerary with unorganized architecture, extending into the ipsilateral cerebral cortex, and therefore strongly suggested homology to Probst bundles reported in humans with CCA. The presence of Probst bundles in canine CCA could represent compensatory neuroplasticity-mediated networking and may contribute the fair prognosis reported in affected dogs.

A 9-month-old female Weimaraner was presented to the emergency service due to episodes of fever and neck pain. Physical examination revealed a stiff neck posture and elevated body temperature. Shortly after clinical examination was performed, the dog developed peracute onset of non-ambulatory tetraparesis compatible with a C1–C5 spinal cord (SC) lesion. Immediately thereafter (

Case summary An 8-year-old female spayed British Shorthair cat that underwent surgical portosystemic shunt (PSS) attenuation developed progressive neurological signs 7 days postoperatively. Neurological signs progressed, despite medical management, and seizure activity became rapidly refractory to anticonvulsants. The diagnosis of post-attenuation neurological signs (PANS) was made based on the timing of the occurrence of clinical signs following surgery, absence of hyperammonaemia and suggestive MRI findings of the brain. The cat developed status epilepticus that required treatment with general anaesthesia and mechanical ventilation, from which the cat could not be effectively weaned without the recurrence of seizures. Therapeutic plasma exchange (TPE) was performed as a rescue therapy for PANS and associated refractory status epilepticus. A total of two plasma volumes were processed during one single TPE session. The seizure activity resolved immediately after the TPE session, the cat showed progressive improvement of neurological signs and remained stable thereafter. No significant complications associated with the TPE were observed. The cat was discharged 11 days after admission and was fully recovered. Relevance and novel information This is an unusual report of PANS diagnosed in a cat based on clinical and MRI findings. The cat developed refractory status epilepticus and had a positive outcome following TPE as rescue therapy. The MRI findings in this report could be useful for the diagnosis of PANS in cats. We speculate that TPE could be taken into consideration as a possible therapeutic intervention in PANS syndrome.