Myeloencephalopathy with Rosenthal fiber formation in a miniature poodle

Long-term survival of a dog with Alexander disease

A 1-year- and 11-month-old spayed female toy poodle had showed progressive ataxia and paresis in the hindlimbs since 11 months old. Magnetic resonance imaging revealed high signal intensity on T2-weighted and fluid-attenuated inversion recovery images at the thoracic and lumbar spinal cord. The dog’s neurological condition slowly deteriorated and flaccid tetraparesis was exhibited. At 4 years and 11 months old, the dog died of respiratory failure. On postmortem examination, eosinophilic corkscrew bundles (Rosenthal fibers) were observed mainly in the thoracic and lumbar spinal cord. Histological features were comparable to previously reported cases with Alexander disease. This is a first case report to describe the clinical course and long-term prognosis of a dog with Alexander disease.

Rosenthal Fiber Encephalopathy in a Dog Resembling Alexander Disease in Humans

A young male Bernese mountain dog presented with neurologic abnormalities consisting of nonambulatory tetraparesis, generalized tremors, and depressed mental status. At necropsy only a mild enlargement of the lateral ventricles was seen. The histologic examination revealed the presence of eosinophilic deposits consistent with Rosenthal fibers (RFs) throughout the white matter of the central nervous system. There was also a marked proliferation of abnormally large astrocytes and limited myelin changes. RFs were most prominent in perivascular, subpial, and subependymal areas, where they were perpendicularly located, producing a pallisaded arrangement. immunohistochemically, RFs were strongly positive for glial fibrillary acidic protein (GFAP), and when they were examined ultrastructurally they appeared as electron-dense amorphous masses located within the processes of astrocytes, most particularly in the perivascular feet. The histologic and immunohistochemical findings of this canine case were consistent with the published neuropathologic descriptions of Alexander disease in humans and in a few dogs, a rare condition that in humans has been shown to be caused by dominant mutations in the GFAP gene.

A canine orthologue of the human GFAP c.716G>A (p.Arg239His) variant causes Alexander disease in a Labrador retriever

Alexander disease (AxD) is a fatal neurodegenerative disorder of astrocyte dysfunction in man, for which already a number of causal variants are described, mostly de novo dominant missense variants in the glial fibrillary acidic protein (GFAP). A similar disorder was already phenotypically described in animals but without the identification of causal variants. We diagnosed a Labrador retriever with a juvenile form of AxD based on clinical (tetraparesis with spastic front limbs mimicking 'swimming puppy syndrome') and pathological (the detection of GFAP containing Rosenthal fibers in astrocytes) features. In order to identify a causal variant, the coding sequences of the four detected GFAP transcript variants (orthologues from human transcript variants α, γ, δ/ɛ and κ) were sequenced. From the five detected variants, a heterozygous c.719G>A nucleotide substitution resulting in a p.Arg240His substitution was considered to be causal, because it is orthologous to the heterozygous de novo dominant c.716G>A (p.Arg239His) hotspot variant in man, proven to cause a severe phenotype. In addition, the variant was not found in 50 unrelated healthy Labrador retrievers. Because the condition in dogs is morphologically similar to man, it could be a promising animal model for further elucidating the genotype/phenotype correlation in order to treat or prevent this disease.

Alexander disease in a dog: case presentation of electrodiagnostic, magnetic resonance imaging and histopathologic findings with review of literature

Background

Alexander disease is a rare neurodegenerative disorder that has not often been described in dogs. None of the existing descriptions include electrodiagnostic or magnetic resonance imaging workup. This is the first presentation of the results of an electrodiagnostic evaluation including electromyography, motor nerve conduction velocity, F-wave, the brainstem auditory evoked response and magnetic resonance imaging of a dog with Alexander disease.

Case presentation

A six month old male entire Bernese mountain dog was presented with central nervous system symptoms of generalized tremor, general stiffness, decreased proprioceptive positioning, a reduced menace response, decreased physiological nystagmus, myotonic spasms and increased spinal reflexes which progressed to lateral recumbency. The electromyography revealed normal muscle activity and a decreased motor nerve conduction velocity, temporal dispersion of the compound muscle action potential, prolonged F-wave minimal latency, lowered F-ratio, decreased latency, and lowered amplitude of the brainstem auditory evoked potentials. The magnetic resonance imaging examination revealed ventriculomegaly and linear hyperintensity on the border of the cortical grey and white matter. The histopathological examination confirmed the presence of diffuse degenerative changes of the white matter throughout the neuraxis. A proliferation of abnormal astrocytes was found at the border between the white matter and cortex. There was also a massive accumulation of eosinophilic Rosenthal fibers as well as diffuse proliferation of abnormally large astrocytes and unaffected neurons.

Conclusion

This is the first histopathologically confirmed case of Alexander disease in a dog with a full neurological workup. The results of the electrodiagnostic and magnetic resonance imaging examinations allow for a high-probability antemortem diagnosis of this neurodegenerative disorder in dogs.

Clinicopathologic and MRI Characteristics of Presumptive Hypertensive Encephalopathy in Two Cats and Two Dogs

Two dogs and two cats were evaluated for the acute-onset of abnormal mentation, recumbency, and blindness. All cases had systemic hypertension, ranging from 180 mm Hg to 260 mm Hg. MRI of the brain disclosed noncontrast-enhancing, ill-defined, T2-weighted (T2W) hyperintensities in the white matter of the cerebrum in the areas of the frontal, parietal, temporal, and occipital lobes. Lesions were also observed in the caudate nuclei and thalamus (n = 1 in each). Intracranial hemorrhage was observed in one animal. Diffusion-weighted imaging (DWI) was consistent with vasogenic edema in two animals. Retinal lesions were observed in three animals. Hypertension was secondary to renal disease in three animals. A primary underlying disorder was not identified in one animal. Normalization of blood pressure was achieved with amlodipine either alone or in combination with enalapril. In one cat, hypertension spontaneously resolved. In three cases, neurologic improvement occurred within 24–48 hr of normalization of blood pressure. The presumptive diagnosis of hypertensive encephalopathy was supported by the MRI findings and neurologic dysfunction coincident with systemic hypertension in which the neurologic dysfunction improved with treatment of hypertension. The prognosis appears good for the resolution of neurologic deficits with normalization of blood pressure in animals with hypertensive encephalopathy.

A Rosenthal Fiber Encephalomyelopathy Resembling Alexander’s Disease in 3 Sheep

We report an encephalomyelopathy in three 18-month-old Merino sheep with features of adult-onset Alexander’s disease (AD), a human primary astrocytic disorder. The signature histologic finding was the presence of numerous hypereosinophilic, intra-astrocytic inclusions (Rosenthal fibers), mainly in perivascular, subpial, and subependymal sites, especially in the caudal brain stem and spinal cord. Although AD usually results from mutations in the glial fibrillary acidic protein ( GFAP) gene, no such mutation was detected in these sheep. However, the annual clinical presentation of this disorder in a few sheep in the affected flock is suggestive of a familial pattern of occurrence.

Fibrinoid leukodystrophy (Alexander's disease-like disorder) in a young adult French bulldog

The paper describes clinical and pathological features of Alexander's disease (AD)-like disorder in a 1 year and 8 months old French bulldog. Clinically, the dog exhibited megaesophagus, emaciation and weakness without any specific neurological symptoms. The dog died of aspiration pneumonia. On the gross observation of formalin-fixed brain, discolored foci were observed in the white matter of the cerebellum and brain stem. Histologically, numerous Rothenthal fibers and hypertrophic astrocytes were distributed especially in the perivascular, subependymal and subpial area of both the cerebrum and cerebellum. The Rosenthal fibers were intensely immunopositive for GFAP and ubiquitin. Demyelination of the white matter was occasionally found in the brain stem. The present case is likely to be categorized in the adult form of AD, though previous AD-like cases in dogs were in the juvenile form.

A novel leucodystrophy in a dog

A diffuse, bilaterally symmetrical leucoencephalopathy was observed in a 2-month-old female crossbred puppy with a clinical history of progressive tetraparesis with front limb hypermetria, head tremor and seizures. Severe myelinolytic lesions with significant macrophage infiltration were confined to the white matter, mainly of the cerebellum and spinal cord. Moderate loss of myelin with severe gliosis predominated in the cerebrum. Axonal degeneration and axonal loss accompanied myelin degeneration. This disease was classified as a leucodystrophy. The clinical signs and certain features of the lesions (morphology and distribution), differed from those in previously described degenerative myelinolytic diseases in animals. The possible occurrence of the disorder in a littermate suggested a genetic basis.

Alexander's disease: clinical, pathologic, and genetic features

Alexander's disease, a rare and fatal disorder of the central nervous system, most commonly affects infants and young children but can also occur in older children and sometimes adults. In infants and young children, it causes developmental delay, psychomotor retardation, paraparesis, feeding problems, usually megalencephaly, often seizures, and sometimes hydrocephalus. Juvenile cases often do not have megalencephaly and tend to have predominant pseudobulbar and bulbar signs. In both groups, characteristic magnetic resonance imaging findings have been described. In adult cases, the signs are variable, can resemble multiple sclerosis, and might include palatal myoclonus. In all cases, the examination of brain tissue shows the presence of widely distributed Rosenthal fibers. Almost all cases have recently been found to have a heterozygous, missense, point mutation in the gene for glial fibrillary acidic protein, which provides a new diagnostic tool. In most cases, the mutation appears to occur de novo, not being present in either parent, but some adult cases are familial.

Alexander's disease in a Bernese mountain dog

We present a case of Alexander's disease (AD) in a Bernese mountain dog. The male dog had a clinical history of tremors of the hind legs and posterior weakness, which deteriorated rapidly to posterior paresis and tetraparesis. After a disease duration of 4 weeks the dog was euthanatized at 13 weeks of age. Macroscopically the brain showed moderate enlargement of the lateral ventricles. Histologically there was marked proliferation of astrocytes with abnormally large cell bodies in the white matter of the brain and the white and gray matter of the spinal cord. In these regions numerous round, club-shaped, or elongated deposits consistent with Rosenthal fibers (RFs) were found. They were most prominent in perivascular, subependymal, and subpial areas where they were perpendicularly arranged. Additionally there was considerable loss of myelin. Immunohistologically the RFs were positive for glial fibrillary acidic protein and alpha B-crystallin. Under the electron microscope the RFs were found to be located in the cell bodies and processes of astrocytes and appeared as osmiophilic irregularly formed bodies of uneven size with distinct borders that were tightly associated with glial filaments. The histological, immunohistochemical, and ultrastructural findings of this canine case of AD are identical with those in human cases.