ISSN 2398-2985      

Ataxia

Jreptile
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 reptiles. 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 (especially in reptiles). 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:
      • Hypoglycemia Hypoglycemia.
      • Electrolyte imbalances, eg sepsis, GI foreign bodies.
      • Anemia Anemia, eg chronic renal failure, leukemia, hyperestrogenism.
      • Hypocalcemia/hypovitaminosis D (MBD) Metabolic bone disease.
      • Hypovitaminosis B1 in garter snakes.
    • Neurological - spinal cord:
      • Neoplastic: primary, multiple myeloma, secondary, eg lymphoma affecting the vertebral body.
      • Trauma: fracture, luxation Joint/limb luxation/subluxation, intervertebral disk herniation.
      • Vascular: hematomelia due to hyperestrogenism.
      • Infectious: diskospondylitis (rare), myelitis (rare):
        • Zoonotic.
        • Osteomyelitis of the spinal column is common in snakes – Gram-negative bacteria, eg Aeromonas, Pseudomonas spp commonly isolated. Salmonella and Streptococcus have also been isolated on blood culture from affected snakes.
    • Cerebellar:
      • Neoplastic.
      • Inflammatory: immune-mediated.
      • Toxic: metronidazole Metronidazole.
    • Vestibular:
      • Infectious: 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. Otitis media common in aquatic chelonians.
      • Atadenovirus in Bearded dragons Bearded dragons, Ferlavirus Ferlavirus infection (paramyxovirus) in snakes, Sunshine virus Sunshinevirus infection (paramyxovirus unrelated to ferlavirus) in snakes, inclusion body disease Inclusion body disease in snakes, and West Nile Virus in reptiles.
      • Neoplastic.
      • Trauma.
      • Toxic: metronidazole Metronidazole, eg in snakes.
    • Miscellaneous, ie other conditions that mimic true neurological ataxia:
      • Respiratory dysfunction.
      • Cardiac dysfunction.
      • Drugs: acepromazine, antihistamines, antiepileptics.
      • Intoxication:
        • Pyrethrin/organophosphate poisoning, eg reptile mite treatments.
        • Lead toxicity.
        • Ivermectin use in Chelonia.
      • Limb fractures/luxations.
      • Hypo- or hyperthermia in reptiles Hypothermia

Predisposing factors

General

  • Depends on underlying cause.

Specific

  • Trauma: poor supervision of young children handling small pets.
  • Immunosuppression and stress.

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.
    • Often seen as intention tremors and exaggerated limb movements in reptiles.
  • 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

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Treatment

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Prevention

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Outcomes

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Further Reading

Publications

Refereed Papers

Other sources of information

  • Girling S J (2019) Neurology. In: BSAVA Manual of Reptiles. 3rd edn. Eds: Girling S J & Raiti P. BSAVA, UK. pp 353-364.
  • Platt S R (2019) Neurology. In: Mader’s Reptile and Amphibian Medicine and Surgery. Eds: Divers S J & Stahl S J. pp 805-826.
  • Baron H & Phalen D N (2018) Diseases of the Nervous System. In: Reptile Medicine and Surgery in Clinical Practice. Eds: Doneley B, Monks D, Johnson R & Carmel B. Wiley Blackwell, USA. pp 331-344.

Can’t find what you’re looking for?

We have an ever growing content library on Vetlexicon so if you ever find we haven't covered something that you need please fill in the form below and let us know!

 
 
 
 

To show you are not a Bot please can you enter the number showing adjacent to this field

 Security code