Magnetic resonance imaging features of presumed intracerebral hemorrhages in dogs show a significant association between apparent diffusion coefficient peripheral layer and estimated bleeding age and commonly exhibit a T2 blackout effect.

In humans, intracranial hematomas commonly exhibit a T2 blackout effect (BOE) with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps. Published descriptions of comparable findings in dogs with intracerebral hemorrhages are lacking. Aims of this retrospective observational study were to describe the appearance of presumed intracerebral hemorrhages (PICHs) in DWI regardless of the underlying etiology and presence of T2 blackout effect (T2 BOE) in dogs and to test potential associations with DWI and ADC findings versus the estimated age of the hemorrhage. Magnetic resonance imaging studies of dogs with presumed PICHs based on the combined evaluation of T2*W gradient echo and/or susceptibility-weighted imaging, T1W and T2W images were enrolled. The age of the hemorrhage was estimated according to published criteria based on T1W and T2W sequences. The association between the age of the hemorrhage and the appearance of each finding (stratified or mixed), their signal intensities in DWI/ADC and the presence of the T2 BOE, was evaluated. A total of 35 PICHs were included: 13 of them were stratified and 22 had a mixed aspect. Only the ADC appearance of the peripheral layer in stratified PICHs was significantly associated with estimated age of the hemorrhage (p = .033), being hypointense in all hyperacute cases and hypo-/isointense in acute cases. The T2 BOE was present in 29/35 PICHs. The DWI sequences showed limited utility to date PICHs in this study population. As in humans, the T2 BOE was commonly seen in DWI and ADC maps of dogs with PICHs.

Rapport de cas Computed tomography and magnetic resonance imaging findings in a dog with suspected intracerebral hemorrhage.

A 1-year-old, intact female, mixed-breed dog (border collie and springer spaniel) was initially evaluated for lethargy, fever, and ataxia and subsequently evaluated 2.5 y later following the onset of seizures. Over a 3-year interval, the dog underwent 3 computed tomography (CT) and 1 magnetic resonance imaging (MRI) examinations. A voluminous hyperattenuating lesion with a mass effect, exhibiting weak postcontrast enhancement and associated with surrounding diffuse parenchymal hypoattenuation, was observed in the first CT examination (3 d after initial clinical signs). The second CT examination (11 d later) revealed a hypoattenuating lesion with ring postcontrast enhancement. A clear reduction of the size of the mass, which presented as hyperattenuating with a severely postcontrast-enhanced center, was noted in the third CT examination (2.5 y after initial clinical signs and 3 mo after onset of seizures). The MRI examination, performed 3 mo after the third CT examination, showed a small lesion, T2*-gradient echo hypointense, with no peripheral halo noted in T2-weighted fluid-attenuated inversion recovery and with serpentiform enhancement from within the lesion to the meningeal region. These sequential imaging findings were consistent with intracerebral hemorrhage. Key clinical message: To the authors' knowledge, this is the first case of hyperthermia associated with intracerebral hemorrhage in a dog, although this is a common finding in human medicine. An intracerebral hemorrhage should be included in the differential diagnosis of an intracerebral mass, and performing sequential imaging examinations can help clarify the diagnosis.

Résultats de la tomodensitométrie et de l'imagerie par résonance magnétique chez un chien suspecté d'hémorragie intracérébrale. Une chienne de race mixte femelle intacte âgée d'un an (border collie et épagneul springer) a été initialement évaluée pour de la léthargie, fièvre et ataxie, puis évaluée 2,5 ans plus tard après le début des crises. Sur un intervalle de 3 ans, le chien a subi trois examens de tomodensitométrie (TDM) et un examen d'imagerie par résonance magnétique (IRM). Une volumineuse lésion hyperatténuante avec effet de masse, présentant un faible rehaussement post-contraste et associée à une hypo-atténuation parenchymateuse diffuse environnante, a été observée au premier examen TDM (3 j après les premiers signes cliniques). Le deuxième examen TDM (11 jours plus tard) a révélé une lésion hypo-atténuante avec un rehaussement post-contraste en anneau. Une nette réduction de la taille de la masse, qui se présentait comme hyperatténuante avec un centre fortement rehaussé après contraste, était notée au troisième examen TDM (2,5 ans après les premiers signes cliniques et 3 mois après le début des crises). L'examen IRM, réalisé 3 mois après le troisième examen par TDM, a montré une petite lésion, écho hypo-intense de gradient T2*, sans halo périphérique noté dans la récupération d'inversion atténuée par fluide en pondération T2 et avec un rehaussement serpentiforme de l'intérieur de la lésion vers la région méningée. Ces résultats d'imagerie séquentielle étaient compatibles avec une hémorragie intracérébrale.Message clinique clé :À la connaissance des auteurs, il s'agit du premier cas d'hyperthermie associée à une hémorragie intracérébrale chez un chien, bien qu'il s'agisse d'une observation courante en médecine humaine. Une hémorragie intracérébrale doit être incluse dans le diagnostic différentiel d'une masse intracérébrale, et la réalisation d'examens d'imagerie séquentiels peut aider à clarifier le diagnostic.(Traduit par Dr Serge Messier).

Ulinastatin alleviates early brain injury after intracerebral hemorrhage by inhibiting oxidative stress and neuroinflammation via ROS/MAPK/Nrf2 signaling pathway

Purpose: Spontaneous intracerebral hemorrhage (ICH) is still a major public health problem, with high mortality and disability. Ulinastatin (UTI) was purified from human urine and has been reported to be anti-inflammatory, organ protective, and antioxidative stress. However, the neuroprotection of UTI in ICH has not been confirmed, and the potential mechanism is unclear. In the present study, we aimed to investigate the neuroprotection and potential molecular mechanisms of UTI in ICH-induced early brain injury in a C57BL/6 mouse model. Methods: The neurological score, brain water content, neuroinflammatory cytokine levels, oxidative stress levels, and neuronal damage were evaluated. Results: UTI treatment markedly increased the neurological score, alleviated brain edema, decreased the levels of the inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), IL-6, and NF-κB, decreased the levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and upregulated the levels of glutathione (GSH), superoxide dismutase (SOD), and Nrf2. This finding indicated that UTI-mediated inhibition of neuroinflammation and oxidative stress alleviated neuronal damage after ICH. The neuroprotective capacity of UTI is partly dependent on the ROS/MAPK/Nrf2 signaling pathway. Conclusions: UTI improves neurological outcomes in mice and reduces neuronal death by protecting against neural neuroinflammation and oxidative stress.

CT venography and pathological characterization of crus haemorrhage in Pekin ducks.

The crus haemorrhage is one of the main causes of carcass defects in Pekin duck processing houses. However, its pathologic features are currently unclear. In order to examine the injury to the hind limb veins and illustrate the pathologic characteristics of crus haemorrhage in Pekin ducks, a total of 68 Pekin ducks with crus haemorrhage (test group) and 10 unaffected ducks (control group) were collected in this study. Five ducks randomly selected from each group were examined by computed tomographic venography with 2.0 mm thickness, 120 kVp, and 90 mA. Pathological changes were observed macroscopically, and under a microscope and electron microscope. The computed tomographic venography results showed no differences in the main hind limb veins between Pekin ducks with crus haemorrhage and the control. Macroscopic results demonstrated that the haemorrhage only occurred in crural muscles, most frequently in musculus gastrocnemius and musculus tibialis cranialis. In severe cases, muscular rupture and multiple intermuscular blood clots could be observed. Histological analysis showed rupture of myofibers and massive red blood cells between muscle bundles. Besides, infiltration of connective tissues and inflammatory lesions could be seen. However, no differences were observed in other organs between these two groups. The main ultrastructural characteristics were myofibrillar rupture and split, accompanied by mitochondrial membrane disintegration and vacuolization. All these results indicate that the haemorrhage in crus is a focal myopathy with the characteristics of bleeding, rupture, and inflammatory lesions. Research highlights CTV was a feasible method to evaluate the hind limb veins in Pekin ducks. The focal myopathy presented here only affected crural muscles. The focal myopathy was characterized by bleeding, rupture and inflammatory lesions.

Acute intraparenchymal cerebral haemorrhage in an Iberian golden eagle - a case report.

BACKGROUND: In birds there are reports of intracranial lesions but not of the clinical, computed tomographic and histopathologic features of acute intraparenchymal cerebral haemorrhage in Iberian golden eagle. CASE PRESENTATION: The following report describes a case of a 30-year-old Iberian golden eagle (Aquila chrysaetos homeyeri) with no history of trauma, presented with acute opisthotonus, left head tilt and circling, anisocoria, positional nystagmus, and ataxia. The main differential diagnosis were hypovitaminosis B or E and intracranial disease due to trauma, infection, toxins or masses. A computed tomography (CT) of the head was performed with an 8-slices scanner and evidenced a hyperdense (63-65 HU) non-enhancing homogeneous well delineated round area in the midbrain, with 6 mm in its highest diameter. The attenuation values and the non-enhancing nature of the lesion strongly suggested the diagnosis of acute intraparenchymal haemorrhage, which was histologically confirmed after necropsy. CONCLUSIONS: In birds with a central neurological dysfunction, the diagnosis of acute brain haemorrhage should be considered when the CT evidences a non-enhancing, homogeneous, well circumscribed hyperattenuated round area.

Putative Cerebral Microbleeds in Dogs Undergoing Magnetic Resonance Imaging of the Head: A Retrospective Study of Demographics, Clinical Associations, and Relationship to Case Outcome.

BACKGROUND: Cerebral microbleeds (CMBs) are focal intraparenchymal signal voids on gradient-echo magnetic resonance imaging (MRI), corresponding to regions of chronic hemorrhage. In humans, they are associated with systemic disease and shorter survival times. Although similar findings have been identified in dogs, their epidemiology and clinical correlations have not been investigated. OBJECTIVE: To determine epidemiological features, clinical associations, and associations with outcome for putative CMB-like foci (putative microbleeds [pMBs]) identified by T2*-weighted MRI in dogs. ANIMALS: Five hundred and eighty-two dogs undergoing 3T brain MRI between 2011 and 2016. METHODS: Retrospective case-control study. Demographic, diagnostic, and clinicopathological data were obtained from medical records and phone follow-up. Demographic variables were compared between dogs with and without evidence of pMBs. For dogs with such evidence, and a subset of matched controls, associations with clinical presentation, concurrent disease, and survival times were evaluated. RESULTS: Dogs with pMBs were older (P < .001) and smaller (P = .004) than unaffected dogs. Compared to matched controls, they presented more frequently for vestibular signs (P = .030). Cortical atrophy occurred concurrently with pMBs in 26% (14/54) of dogs. Diagnosed renal disease was not significantly associated with pMBs, but proteinuria was more common in dogs with pMBs than in matched controls (odds ratio = 3.01, P = .005). Dogs with pMBs had a shorter median survival time than did matched controls (P = .011). CONCLUSIONS AND CLINICAL IMPORTANCE: Putative microbleeds occurred in 54 of 582 (9.3%) of dogs undergoing brain MRI, but may not be a normal consequence of aging. They were associated with shorter survival time and proteinuria in the study population.

Construction of a Cerebral Hemorrhage Test System Operated in Real-time.

The real-time monitoring and evaluation of the severity and progression of cerebral hemorrhage is essential to its intensive care and its successful emergency treatment. Based on magnetic induction phase shift technology combined with a PCI data acquisition system and LabVIEW software, this study established a real-time monitoring system for cerebral hemorrhage. To test and evaluate the performance of the system, the authors performed resolution conductivity experiments, salted water simulation experiments and cerebral hemorrhage experiments in rabbits and found that when the conductivity difference was 0.73 S/m, the phase difference was 13.196°. The phase difference change value was positively proportional to the volume of saline water, and the conductivity value was positively related to the phase difference of liquid under the same volume conditions. After injecting 3 mL blood into six rabbits, the average change in the blood phase difference was -2.03783 ± 0.22505°, and it was positively proportional to the volume of blood, which was consistent with the theoretical results. The results show that the system can monitor the progressive development of cerebral hemorrhage in real-time and has the advantages of low cost, small size, high phase accuracy, and good clinical application potentiality.

Temporal Evolution of MRI Characteristics in Dogs with Collagenase-Induced Intracerebral Hemorrhage.

Intracerebral hemorrhage (ICH) is one of the most lethal types of stroke. Neuroimaging techniques, particularly MRI, have improved the diagnostic accuracy of ICH. The MRI characteristics of the evolving stages of ICH in humans-but not those in dogs-have been described. In this study, we document the temporal MRI characteristics in a canine model of collagenase-induced ICH. Specifically, ICH was induced in 5 healthy beagles by injecting 500 U of bacterial collagenase from Clostridium histolyticum, which was delivered into the parietal lobe over 5 min by using a microinfusion pump. T1- and T2-weighted, fluid-attenuated inversion recovery, gradient-echo (GRE), and diffusion-weighted (DWI) imaging and measurement of the apparent diffusion coefficient (ADC) were performed serially at 6 different time points (before and 12 h, 3 d, 5 d, 10 d and 24 d after hemorrhage) by using a 3-T MR system. The temporal changes of T1 signal intensity (SI) corresponded well with the reported human data. The temporal changes of T2 and GRE sequences, with the exception of T2 and GRE hyperintensities at the early subacute stage, also matched. ADC measurements were high at the early subacute stage, and DWI-SI positively correlated with T2- and GRE-SI from the early subacute stage onward. In conclusion, MRI is an ideal method for characterizing the temporal evolution of parenchymal alterations after ICH in dogs. These data might be useful for differentiating clinical stages of ICH in dogs.

Central vestibular disease in a blue and gold macaw (Ara ararauna) with cerebral infarction and hemorrhage.

A 24-year-old female blue and gold macaw (Ara ararauna) was presented for an acute onset of left head tilt. On examination, the macaw was dehydrated and had a 120-degree left head tilt, decreased proprioception of the left pelvic limb, and intermittent vertical nystagmus. Results of hematologic testing and biochemical analysis revealed severe leukocytosis with lymphopenia and heterophilia and a high uric acid concentration. Radiographs showed bilateral intertarsal joint osteoarthritis and a healed ulnar fracture. Magnetic resonance imaging of the brain revealed focal T2 and fluid-attenuated inversion recovery hyperintense lesions in the right cerebral hemisphere and in the midbrain. The midbrain lesion showed susceptibility artifact on the T2* sequence, suggesting hemorrhage. In the T2* sequence, iron accumulation (as seen with hemorrhage) distorts the magnetic signal, resulting in the production of a susceptibility artifact, which can then be visualized as a region of hypointensity. The bird was hospitalized but died despite intensive care. Necropsy revealed multiple cerebral vascular lesions including an acute cerebral infarct, a ruptured midbrain aneurysm, and multifocal systemic atherosclerosis. To our knowledge, this is the first report of a cerebral aneurysm in a bird. This report correlates the clinical presentation, imaging, and histopathologic findings in a macaw with central vestibular disease and demonstrates how advanced imaging techniques can identify hemorrhagic lesions through the T2* sequence.

Influencia del grado de lesión neurológica sobre la eficacia de la terapia celular en un modelo de traumatismo craneoencefálico grave / Influence of the level of neurological deficit on the efficacy of cell therapy in a model of severe traumatic brain injury

Objetivo: Determinar si el nivel de déficit neurológico influye en la eficacia de la terapia celular con células madre mesenquimales (CMM) de la médula ósea en un modelo experimental crónico de lesión cerebral traumática. Material y métodos: Se sometió a ratas Wistar adultas a un modelo de lesión cerebral traumática. Dos meses después, se clasificaron en función de su nivel de déficit neurológico mediante dos tests funcionales: Escala de valoración sensitivo-motora y Tiempo de permanencia en la zona interior (Video-Tracking-Box test, VTB test). Se inyectó suero salino solo o CMM en suero salino en el tejido cerebral dañado de los animales que obtuvieron la clasificación neurológica de lesión moderada o grave según el nivel permanente de su déficit funcional. Todos los animales se evaluaron durante los dos meses siguientes para determinar la posible eficacia de la administración de las CMM. Al finalizar el estudio, los animales se eutanasiaron y se estudiaron sus cerebros. Resultados: Se constata una recuperación funcional significativa en los animales con lesión moderada que recibieron las CMM, pero no en los animales con lesión grave cuando se compara con los controles. Conclusiones: Las conclusiones obtenidas sugieren que la gravedad de la lesión neurológica puede influir en la potencial eficacia de la terapia celular cuando es aplicada en una lesión cerebral traumática crónica (AU)

bjective: To study if the level of neurological deficit influences the efficacy of cell therapy with bone marrow stromal cells (BMSC), in an experimental model of chronic traumatic brain injury (TBI). Material and methods: Adult Wistar rats were subjected to a model of traumatic brain injury. Two months later they were classified according to their level of neurological deficit. For that, two functional tests: Scale of sensory- motor assessment and time spent in the inner zone in the Video-Tracking-Box test, were used. Saline alone or BMSC in saline was injected into the damaged brain tissue of animals suffering a permanent level of functional deficit classified as moderate or severe. All experimental groups were evaluated during the next two months to determine the potential effectiveness of the intracerebral administration of BMSC. At the end of the study animals were euthanized and their brains were studied. Results: The results show a significant functional recovery in animals with moderate injury who received BMSC, but there was no significant recovery in animals with severe traumatic brain injury when compared with controls. Conclusion: The severity of neurologic injury may influence the potential efficacy of cell therapy applied to chronic TBI (AU)

MRI characteristics of cerebral microbleeds in four dogs.

Cerebral microbleeds in people are small foci of hemosiderin-containing macrophages in normal brain parenchyma. They are the remnant of previous hemorrhage and occur with greater frequency in older individuals. Our purpose was to describe the magnetic resonance (MR) appearance of cerebral microbleeds in four dogs. These lesions appeared as round, hypointense foci measuring ≤4 mm on T2*-gradient-recalled echo images. They were less conspicuous or absent on T2-weighting, being iso- or hypointense, and uniformly invisible on T1-weighted images. No contrast enhancement was seen in any of the cerebral microbleeds. Necropsy-derived histopathologic analysis of one brain confirmed these lesions to be chronic cerebrocortical infarcts containing hemosiderin. The MR changes seen in dogs were analogous to what has been described in people and will be helpful in distinguishing cerebral microbleeds from other brain lesions.

Feline cerebrovascular disease: clinical and histopathologic findings in 16 cats.

Sixteen cats with cerebrovascular disease confirmed via histology to be of nontraumatic and nonneoplastic origins are described. In addition, the anatomy of the arterial supply of the cat's brain is reviewed. It is suggested that this unique arterial design may influence the incidence of cerebrovascular accidents in this species. Of the 16 cats reviewed, seven cats had ischemic infarctions, five had hemorrhagic infarctions, and four were diagnosed with intracranial hemorrhage. The median age was 8 yr and 9.5 yr in cats with infarctions and intracranial hemorrhages, respectively. Clinical signs were severe, acute, consistent with the localization of the cerebrovascular lesion, and influenced by underlying pathology. Four cats with infarction showed lateralized neurologic signs. Four cats with infarctions were diagnosed with pulmonary disease antemortem and three cats had hyperthyroidism. Cerebrospinal fluid analysis and computed tomography scans were available in two cats. None of the infarctions were grossly visible. All cats with hemorrhagic infarcts had severe liver pathology and nephritis was identified in four cats. Hypoxia was a feature in four cats and one cat suffered cardiac failure. In conclusion, the clinical picture is influenced by the type of cerebrovascular disease, the localization of the intracranial lesions, and any underlying pathology.

Ischaemic and haemorrhagic stroke in the dog.

Cerebrovascular disease results from any pathological process of the blood vessels supplying the brain. Stroke, characterised by its abrupt onset, is the third leading cause of death in humans. This rare condition in dogs is increasingly being recognised with the advent of advanced diagnostic imaging. Magnetic resonance imaging (MRI) is the first choice diagnostic tool for stroke, particularly using diffusion-weighted images and magnetic resonance angiography for ischaemic stroke and gradient echo sequences for haemorrhagic stroke. An underlying cause is not always identified in either humans or dogs. Underlying conditions that may be associated with canine stroke include hypothyroidism, neoplasia, sepsis, hypertension, parasites, vascular malformation and coagulopathy. Treatment is mainly supportive and recovery often occurs within a few weeks. The prognosis is usually good if no underlying disease is found.

Disseminated angiostrongylosis with fatal cerebral haemorrhages in two dogs in Germany: a clinical case study.

Canine angiostrongylosis is a nematode infection in domestic dogs and wild carnivores. Few single case reports describing the occurrence of this disease in Germany exist and until recently angiostrongylosis has not been considered endemic in this country. The present report focuses on clinical, pathological and parasitological findings in two cases of fatal disseminated canine angiostrongylosis associated with multifocal haemorrhages in the central nervous system. Both animals, which lived in Germany, presented with rapidly progressive neurological signs including depression, ataxia, unilateral central blindness and epileptic seizures. Blood work revealed grossly elevated D-dimers and mild thrombocytopenia. Both animals were subsequently euthanised due to progressive clinical aggravation. Necropsy showed cerebral and lung haemorrhages in both animals. Multiple sections of nematode larvae consistent with Angiostrongylus vasorum were identified on histopathological sections of the brain, heart, kidney and lung in both animals and a predominantly granulomatous inflammation with the occurrence of multinucleated giant cells was observed. Adult nematodes were found in the larger lung arteries of one dog and Angiostrongylus infection was subsequently confirmed by PCR-analysis and sequencing in both dogs. A. vasorum larvae were not detected by faecal Baermann examination performed in one of the dogs. It was concluded that canine angiostrongylosis should be considered as differential diagnosis in dogs in Germany, even if faecal examination is negative. There is currently still a lack of studies investigating the occurrence of angiostrongylosis in dogs and intermediate hosts in Germany which would be necessary to survey the endemic realities of this disease.

Imaging diagnosis--metastatic hemangiosarcoma causing cerebral hemorrhage in a dog.

A 9-year-old male Appenzeller mountain dog had progressive severe ataxia and central vestibular syndrome that was localized clinically to the brain stem. The cerebrospinal fluid characteristics were suggestive of hemorrhage into the subarachnoid space. On computed tomography (CT), hyperattenuating masses were found in the left lateral ventricle extending into the cerebrum, and another involving the cerebellum and brainstem. The hyperattenuation of the masses in noncontrast images and the absence of contrast enhancement were consistent with hemorrhage. The dog underwent euthanasia. A metastatic hemangiosarcoma in the brain, causing acute bleeding in the left lateral ventricle and the brainstem, was found. A solitary mass in the left myocardium was thought to be the primary site. CT characteristics of intracranial hemorrhage are reviewed.

Cerebral and conjunctival haemorrhages associated with von Willebrand factor deficiency and canine angiostrongylosis.

A case of angiostrongylosis is described in a 14-month-old golden retriever bitch. Conjunctival haemorrhage and neurological signs, referable to a space-occupying cerebral lesion, were associated with defective primary haemostasis caused by low levels of von Willebrand factor. Full clinical recovery followed treatment with desmopressin, fresh whole blood transfusion, fenbendazole and supportive care. The magnetic resonance image of the suspected organising haematoma is described. Similarities to the human condition, acquired von Willebrand syndrome, and a possible role for aberrant larval migration in haematoma formation are suggested.

Coexisting tricuspid valve dysplasia and ventricular septal defect in a young patas monkey (Erythrocebus patas).

A 1.5-kg, 6-mo-old male patas monkey (Erythrocebus patas) was cyanotic and panting. Evaluation of the heart by electrocardiography, thoracic radiography, two-dimensional echocardiography, and Doppler color-flow echocardiography revealed a ventricular septal defect (VSD) with right-to-left shunting as well as tricuspid valve dysplasia with dilated annulus of the tricuspid ring, dilated right atrium, dilated right ventricle, and deformity of the tricuspid valve. Because of the severity of the cardiac disease, the patas monkey had complications recovering from anesthesia and died 3 days later. Gross postmortem findings included VSD, tricuspid dysplasia, and cerebral hemorrhage.

Pathology of listerial encephalitis in chickens in Japan.

Neural signs (torticollis, drowsiness) and mortality were observed in five chickens of a native chicken flock (reared for meat) that included 450 male birds on a farm that had 2300 native chickens and 1120 layers. Histologic lesions were observed in the medulla oblongata, optic lobe, cerebellum, and spinal cord of the affected birds. The lesions, which were most severe in the medulla oblongata, were massive abscesses with rarefaction (demyelination and malacia) of the parenchyma with gram-positive bacteria. The degenerative and necrotic areas were characterized by fibrin thrombosis, hemorrhages, and congestion in the blood vessels. Immunohistochemically, the bacteria positive for L. monocytogenes antigen were observed in the medulla oblongata, cerebellum, and spinal cord. Ultrastructurally, the small rod-shaped and thin-cell-walled bacteria were observed in the parenchyma of the medulla oblongata. Listeria monocytogenes (serotype 4b) was isolated from the medulla oblongata and spinal cord. The pathogenesis of listerial encephalitis in chickens was discussed.