ISSN 2398-2985      

Ataxia

6guinea pig
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 guinea pigs. 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:
      • Electrolyte imbalances, eg sepsis, GI foreign bodies.
      • Anemia, eg chronic renal failure, leukemia Leukemia, hyperestrogenism.
    • Neurological - spinal cord:
      • Neoplastic: primary, multiple myeloma, secondary, eg lymphoma affecting the vertebral body.
      • Trauma (common in guinea pigs): fracture Fractures overview, luxation, intervertebral disk herniation.
      • Vascular: hematomelia due to hyperestrogenism.
      • Infectious: diskospondylitis (rare), myelitis (rare). Lymphocytic choriomeningitis virus (LCMV) in guinea pigs - meningitis and hindlimb paralysis:
        •  Zoonotic.
        • Encephalitozoon cuniculi infections.
    • Cerebellar:
      • Neoplastic.
      • Infections: bacterial meningitis/encephalitis, LCMV, toxoplasmosis.
      • Inflammatory: immune-mediated.
      • Toxic: metronidazole.
    • Vestibular:
      • Infectious: otitis media/interna Otitis externa/media/interna (very common in guinea pigs), 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.
      • Toxoplasmosis.
      • Neoplastic.
      • Trauma.
      • Toxic: use of high doses of metoclopramide Metoclopramide in guinea pigs.
    • 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 overview/luxations.
      • Hypovitaminosis C Vitamin C deficiency.

Predisposing factors

General

  • Depends on underlying cause.

Specific

  • Trauma: poor supervision of young children handling small pets.
  • Immunosuppression and stress, eg from overcrowding and poor ventilation may predispose guinea pigs to upper respiratory infection with spread to the middle and inner ear.
  • Hypovitaminosis C Vitamin C deficiency in guinea pigs due to poor diet.

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.

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.
  • Oglesbee B L (2006) Ataxia (Guinea Pig). In: Blackwell’s Five-Minute Veterinary Consult: Small Mammal. Wiley-Blackwell, USA. pp 236-239.

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