AFIP SYSTEMIC PATHOLOGY

JPC SYSTEMIC PATHOLOGY

NERVOUS SYSTEM

January 2017

N-M06

 

Signalment (JPC 151004):  3-year old Charolais bull

 

HISTORY:  Presented for a two-month history of chronic posterior paresia. Clinical examination showed right hock stiffness with right leg mobility reduction.

 

HISTOPATHOLOGIC DESCRIPTION:  Cerebellum with brainstem: Multifocally and randomly within the cerebellar white matter and scattered randomly throughout the white matter of the brainstem, there are numerous, up to 50 um in diameter, round to oval, acellular, eosinophilic, granular plaques. Markedly hypertrophic glial cells are often present adjacent to plaques (presumed oligodendrocytes). The adjacent neuropil occasionally contains eosinophilic, up to 6 um, swollen, degenerate axons within dilated myelin sheaths (spheroids) and mild increased vacuolation (spongiosis).  Within the meninges is granular brown black pigment (melanin).

 

MORPHOLOGIC DIAGNOSIS:  Cerebellum and brainstem, white matter:  Eosinophilic plaques, multifocal, severe, chronic, with axonal degeneration, mild spongiosis and gliosis, Charolais, bovine.

 

ETIOLOGIC DIAGNOSIS:  Idiopathic leukodystrophy (oligodendroglial dysplasia/dysmyelination)

 

CONDITION:  Progressive ataxia of Charolais cattle

 

GENERAL DISCUSSION: 

·       Unique heritable disease in Charolais cattle due to oligodendrocyte dysplasia which leads to dysmyelination that results in progressive ataxia

·       Affects both sexes equally with onset from 6 months to 2 years of age

·       Affects purebred Charolais and ¾ crossbred Charolais cattle

·       Slow, progressive disease

 

PATHOGENESIS: 

·       Heritable defect of oligodendroglial production and maintenance of myelin sheaths in paranodal areas; thought to be autosomal recessive

·       Nodes of Ranvier are wide due to failure of oligodendoglia to ensheathe the anodal axon as it grows longitudinally resulting in abnormalities of impulse conduction

·       Dysplasia is not considered to be due to a defect in the production of myelin, but rather of failure to ensheathe properly

 

TYPICAL CLINICAL FINDINGS:  

·       Progressive onset beginning with hind limb weakness and ataxia leading to subsequent recumbency

·       Collapse of one hind limb with a tendency to fall to one side is a consistent finding

·       Head bobbing when excited

·       Irregular, pulsatile micturition in females

·       Mentation and muscle tone are normal

 

TYPICAL GROSS FINDINGS: 

·       No gross lesions

 

TYPICAL LIGHT MICROSCOPIC FINDINGS: 

·       Multiple discrete, ovoid, pale, eosinophilic, granular to amorphous, noncellular plaques that measure 30-80 um in diameter in the white matter

·       Located mainly in the cerebellum, optic nerve, optic tract, internal capsule, corpus callosum, lateral lemniscus, medial longitudinal fasciculus and pontine decussation

·       Plaques may be traversed by axons that have little to no myelin

 

ULTRASTRUCTURAL FINDINGS: 

·       Widened nodes of Ranvier

·       Paranodal whorls of myelin that originate from hypertrophied oligodendrocytes

·       Enlarged oligodendrocyte cell bodies and increased numbers of mitochondria

 

ADDITIONAL DIAGNOSTIC TESTS:

·       LFB (Luxol-fast blue) to demonstrate accumulation of myelin

·       Bielschowsky silver stain to demonstrate axons within tangled mat of myelin

·       Definitive diagnosis is solely by histopathologic examination

 

DIFFERENTIAL DIAGNOSIS: 

·       Plaques are distinctive

 

COMPARATIVE PATHOLOGY: 

·       Reported in Charolais cattle and two bullmastiff dogs (lesions in the brainstem and spinal cord)

 

References: 

1.      Cantile C, Youssef S. Nervous system. In: Maxie MG ed. Jubb, Kennedy, and Palmer's Pathology of Domestic Animals. Vol 1, 6th ed. St. Louis, MO: Elsevier; 2016:341.

2.      Cordy DR. Progressive ataxia of Charolais cattle-an oligodendroglial dysplasia. Am J Pathol. 1986;23:78-80. 

3.      Morrison JP, Scatzberg SJ, DeLahunta A, Ross JT, Bookbinder P, Summers BA. Oligodendroglial dysplasia in two bullmastiff dogs. Vet Pathol. 2006;43:29-35.

4.      Patton CS. Progressive ataxia in Charolais cattle. Vet Pathol.1977;14:535-537.

5.      Progressive Charolais ataxia in calves. Vet Rec. 2015;176(2):42-45.

6.      Summers BA, Cummings JF, de Lahunta A. Veterinary Neuropathology. St. Louis, MO: Mosby-Year Book Inc.; 1995:286-287.

7.      Zicker SC, Kasari TR, Scruggs DW, Read WK, Edwards JF. Progressive ataxia in a Charolais bull.  J Am Vet Med Assoc. 1988;192:1590-1592.

 

 


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