ISSN 2398-2985      

Ataxia

4ferrets
Contributor(s):

Sarah Brown

Agata Witkowska


Introduction

  • Cause: neurological clinical sign caused by damage to the proprioceptive pathways of the spinal cord, cerebellum or vestibular system.
  • Signs: incoordination of voluntary movements of the limbs, trunk and/or head and neck. May be difficult to differentiate true neurological ataxia from other clinical signs such as paresis, lameness, etc; particularly in species such as ferrets. Therefore, other non-neurological differential diagnoses should be considered when encountering clinical signs possibly consistent with ataxia.
  • Diagnosis: aim to localize site of lesion if possible and rule out differential diagnoses. A work-up may include bloodwork (biochemistry, hematology and electrolytes), testing for infectious causes (eg serology, PCRs, culture of discharges or blood culture where appropriate), imaging (radiography, ultrasonography and advanced imaging), echocardiography, cerebrospinal fluid collection and analysis and myelography.
  • Treatment: dependent on the underlying etiology. Fluid and nutritional support, plus careful nursing is vital along with regular assessments of quality of life.
  • Prognosis: dependent on the underlying etiology, feasibility of treatment and any long-term effects of the disease process, eg chronic balance and mobility issues. Many animals learn to cope with long-term balance and mobility deficits, but quality of life should be carefully monitored.

Pathogenesis

Etiology

  • Three main clinical presentations of true neurological ataxia with some overlap:
    • Sensory (proprioceptive).
    • Vestibular.
    • Cerebellar.
  • Ataxia always indicates neurological disease but may be difficult to identify and differentiate from, eg paresis. Metabolic causes of incoordination are also included in the differential diagnosis list given their common presentation in these species and the clinical challenges in differentiating from primary neurological disease.
  • Most common causes of ataxia:
    • Metabolic (very common cause of hindlimb ataxia/weakness):
    • Neurological - spinal cord:
      • Neoplastic: primary (eg chondroma), multiple myeloma, secondary (eg lymphoma affecting the vertebral body)
      • Trauma: fracture, luxation, intervertebral disk herniation.
      • Vascular: hematomelia due to hyperestrogenism (rare in female ferrets).
      • Infectious: diskospondylitis (rare), myelitis (rare).
      • Zoonotic.
    • Cerebellar:
      • Neoplastic.
      • Infections: canine distemper virus Canine distemper, rabies Rabies, toxoplasmosis toxoplasmosis.
      • Inflammatory: immune-mediated, eg Aleutian disease Aleutian disease induced encephalomyelitis.
      • Toxic: metronidazole.
    • Vestibular:
      • Infectious: canine distemper virus Canine distemper, otitis media/interna Otitis (rare in ferrets), often associated with upper respiratory disease. Common organisms include Streptococcus pneumoniae, Streptococcus zooepidemicus, Staphylococcus aureus and Bordetella bronchiseptica, although fungi and yeasts may be involved. These organisms can also be associated with space-occupying abscesses within the brain:
        • Infectious causes:
          • Botulism caused by Clostridium botulinum.
          • Listeriosis caused by Listeria monocytogenes
        • Fungal:
          • Blastomycosis Blastomyces dermatitidis leading to granulomatous meningoencephalitis.
          • Cryptococcosis Cryptococcosis caused by Cryptococcus neoformans – rare.
      • Toxoplasmosis.
      • Neoplastic.
      • Trauma.
      • Inflammatory: immune-mediated Aleutian disease Aleutian disease induced meningoencephalomyelitis.
    • Miscellaneous, ie other conditions that mimic true neurological ataxia:
      • Respiratory dysfunction.
      • Cardiac dysfunction.
      • Drugs: acepromazine, antihistamines, antiepileptics.
      • Intoxication:
        • Pyrethrin/organophosphate poisoning.
        • Lead toxicity.
      • Limb fractures Fractures/luxations.

Predisposing factors

General

  • Depends on underlying cause.

Specific

  • Trauma: poor supervision of young children handling small pets.
  • Immunosuppression and stress.
  • Lack of vaccination against rabies Rabies and canine distemper virus Canine distemper in ferrets in endemic areas.
  • Ingestion of contaminated raw meat and cat feces (Toxoplasma gondii).

Pathophysiology

  • Sensory (proprioceptive) ataxia:
    • Gradual compression of the spinal cord causes proprioceptive deficits to be shown first as these pathways are located more superficially within the spinal cord, plus their large axons are more vulnerable to compression.
    • Weakness often noted together with this due to early upper motor neuron involvement.
    • Can have reduced awareness of limb placement with resultant toe scuffing, standing on the dorsum of paws and crossing of limbs.
    • Can localize deficit to the affected region of the spinal cord.
  • Cerebellar ataxia:
    • Cerebellum regulates and coordinates motor activity and controls posture.
    • Normal proprioception (as these ascending pathways are intact) and no weakness as the upper motor neurons are not affected.
    • Difficulties in motor activity performance, eg with rate, range and force of movement, but strength and proprioception are not affected.
  • Vestibular ataxia:
    • Can be central or peripheral.
    • Caused by damage to vestibular nerve, inner ear or brainstem nuclei.
    • Loss of balance: leaning, tilting, falling or rolling to the side of the lesion. Often head tilt or circling, usually to the side of the lesion.
    • May see nystagmus.
    • Rare in ferrets.

Timecourse

  • Dependent on underlying cause.
  • May be acute or chronic, and progressive or static.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed Papers

Other sources of information

  • Huynh M & Piazza S (2021) Musculoskeletal and Neurologic Diseases. In: Ferrets, Rabbits and Rodents Clinical Medicine and Surgery. 4th edn. Eds: Quesenberry, K E, Orcutt C J, Mans C & Carpenter J W. Elsevier. pp 117-130.
  • Johnson-Delaney C A (2018) Disorders of the Musculoskeletal System. In: Ferret Medicine and Surgery. Ed: Johnson-Delaney C A. CRC Press. pp 259-271.
  • Oglesbee B L (2006) Ataxia (Ferret). In: Blackwell’s Five-Minute Veterinary Consult: Small Mammal. Wiley-Blackwell. pp 58-59.

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