JPC SYSTEMIC PATHOLOGY

NERVOUS SYSTEM

January 2023

N-M06 (NP)

 

Signalment (JPC #4067774): 3-year old Charolais bull

 

HISTORY: Presented for a two-month history of chronic posterior paresis. 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 100 µm in diameter, round to oval, acellular, eosinophilic, granular plaques. The adjacent neuroparenchyma contains increased numbers of glial cells (gliosis) and occasionally contains eosinophilic, up to 6 µm, swollen, axons within dilated myelin sheaths (spheroids) and mild increased vacuolation (spongiosis). Within the meninges is multifocal scant granular brown black pigment (melanin). 

 

MORPHOLOGIC DIAGNOSIS: Cerebellum and brainstem, white matter: Eosinophilic plaques, multifocal, severe, chronic, with mild axonal degeneration, 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 8 months to 2 years of age
• Affects purebred Charolais and ¾ crossbred Charolais cattle
• Slow, progressive disease

 

PATHOGENESIS:  

• Presumably genetic defect of oligodendroglial production and maintenance of myelin sheaths in paranodal areas 
• 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, head tremors and ataxia leading to subsequent recumbency
• Tendency for aggressive behavior 

• Irregular, pulsatile micturition in females
• Mentation and muscle tone are normal

 

TYPICAL GROSS FINDINGS:  

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:  

• Multiple characteristic discrete, ovoid, pale, eosinophilic, granular to amorphous, noncellular plaques that measure 30-80 µm in diameter in the white matter
• Located mainly in the white matter of the cerebellum, ventral and lateral spinal cord funiculi, optic nerve, optic tract, internal capsule, corpus callosum, lateral lemniscus, medial longitudinal fasciculus, and pontine decussation
• Increased number of astrocytes and oligodendrocytes

• Plaques may be traversed by axons 

 

ULTRASTRUCTURAL FINDINGS:  

• Abnormally elongated nodes of Ranvier
• Paranodal whorls of myelin that originate from hypertrophied oligodendrocytes
• Enlarged oligodendrocyte cell bodies and increased numbers of mitochondria

• Old plaques contain disorganized myelin lamellae and masses of oligodendrocyte processes

 

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:  

 

COMPARATIVE PATHOLOGY:  

 

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. Miller AD, Porter BF. Nervous System. In: Zachary JF, McGavin MD, eds. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier Mosby; 2022: 946.
3. Summers BA, Cummings JF, de Lahunta A. Veterinary Neuropathology. St. Louis, MO: Mosby-Year Book Inc.; 1995:286-287.
4. Vandevelde M, Higgins RJ, Oevermann, A.  Veterinary neuropathology: essentials of theory and practice, 1st ed.  Ames, IA: Wiley-Blackwell; 2012:176-177.

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