Medial Strabismus in Dogs: A Neurological Insight

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Questions and Answers

What neurological sign is highlighted as a localizing indicator in the described cases?

  • Esotropia (correct)
  • Ataxia
  • Hemiplegia
  • Strabismus

Which imaging technique revealed the ischemic infarction in the dogs?

  • Ultrasound
  • Computed Tomography (CT)
  • Magnetic Resonance Imaging (MRI)
  • Diffusion-weighted Imaging (DWI) (correct)

What is medial strabismus also known as?

  • Diplopia
  • Esotropia (correct)
  • Exotropia
  • Hyperopia

What kind of infarction was identified in the dogs presented in the cases?

<p>Lacunar infarction (D)</p> Signup and view all the answers

Which animal was diagnosed with medial strabismus in the case report?

<p>A 7-year-old male neutered Border Collie (A)</p> Signup and view all the answers

What did the computed tomography of the thorax and abdomen reveal?

<p>No significant findings (D)</p> Signup and view all the answers

What neurological condition was associated with the medial strabismus in both dogs?

<p>Vestibular ataxia (D)</p> Signup and view all the answers

What neurological signs were observed in the dog during the examination?

<p>Marked right head tilt and vestibular ataxia (C)</p> Signup and view all the answers

What was suggested by the multiple electrode aggregometry analysis?

<p>Increased platelet activation (B)</p> Signup and view all the answers

What type of brain imaging was used to identify thalamic lesions in the dogs?

<p>Magnetic resonance imaging (MRI) (A)</p> Signup and view all the answers

Which medication was used for antinausea treatment in the dog?

<p>Ondansetron (C), Maropitant (D)</p> Signup and view all the answers

What condition was the 7-year-old male neutered Border Collie initially evaluated for?

<p>Vestibular ataxia (B)</p> Signup and view all the answers

Which cranial nerve's motor nucleus is affected leading to medial strabismus?

<p>Oculomotor nerve (C)</p> Signup and view all the answers

What does restricted diffusion in imaging typically indicate?

<p>Ischemic changes (C)</p> Signup and view all the answers

What was the outcome for the dog after 7 days of supportive care?

<p>The dog was discharged with resolution of episodic head tremor (A)</p> Signup and view all the answers

What was the main cause of the observed symptoms in the dogs?

<p>Thalamic ischemic infarction (D)</p> Signup and view all the answers

Which artery's territory is associated with the identified ischemic infarct?

<p>Caudal perforating artery (B)</p> Signup and view all the answers

What additional condition was suggested by the neuroanatomical localization in the dog?

<p>Thalamic involvement (B)</p> Signup and view all the answers

What additional symptom was present in both dogs besides medial strabismus?

<p>Nonambulatory tetraparesis (D)</p> Signup and view all the answers

What were the results of the venous blood gas analysis and thyroid profile?

<p>Showed mild hypercholesterolemia (D)</p> Signup and view all the answers

What is a rare consequence of a thalamic ischemic infarction as mentioned in the case report?

<p>Pseudoabducens paralysis (D)</p> Signup and view all the answers

What is pseudoabducens paralysis mainly characterized by?

<p>Increased convergence activity to the eye (A)</p> Signup and view all the answers

Which area is primarily affected by a paramedian thalamic lesion resulting in esotropia?

<p>Oculomotor nerve nucleus (C)</p> Signup and view all the answers

Which condition has NOT been reported to cause esotropia in dogs?

<p>Increased intraocular pressure (A)</p> Signup and view all the answers

What consequence can a thalamic infarct produce regarding strabismus in dogs?

<p>Medial strabismus (esotropia) in the contralateral eye (A)</p> Signup and view all the answers

Which of the following neurological signs is commonly associated with midbrain-thalamic ischemic infarcts in dogs?

<p>Ipsilateral mydriasis (D)</p> Signup and view all the answers

Which of the following describes thalamic esotropia in dogs?

<p>Esotropia secondary to contralateral thalamic infarcts (C)</p> Signup and view all the answers

Which statement regarding pseudoabducens palsy in humans is correct?

<p>It can be either ipsilateral or contralateral to the infarct (D)</p> Signup and view all the answers

What is a key sign that can be manifested due to a dorsal midbrain lesion?

<p>Convergence-retraction nystagmus (D)</p> Signup and view all the answers

Flashcards

Medial strabismus (esotropia)

A condition where the eye turns inward towards the nose.

Paramedian thalamic ischemic infarction

A stroke-like event affecting a specific part of the thalamus, reducing blood flow.

Contralateral

On the opposite side of the body (or brain).

Pseudoabducens paralysis

A condition mimicking abducens nerve paralysis, though not directly caused by it.

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Vestibular ataxia

Loss of balance and coordination resulting from damage to the vestibular system.

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Magnetic resonance imaging (MRI)

A medical imaging technique that uses magnetic fields and radio waves to visualize internal structures in the brain.

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Lacunar ischemic infarct

A small area of brain damage due to a lack of blood flow.

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Descending inhibitory pathways

Neural pathways that transmit signals to suppress inappropriate motor signals.

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Oculomotor nerve

A cranial nerve that controls eye movement.

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Medial Rectus muscle

Eye muscle that pulls the eye in towards the nose.

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Esotropia

A condition where the eye turns inwards.

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Paramedian thalamic ischemic infarct

Stroke in a specific part of the thalamus, reducing blood supply.

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Contralateral

Opposite side of the body (or brain).

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Vestibular ataxia

Loss of balance from damage to the vestibular system.

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Lacunar ischemic infarct

Small area of brain damage due to reduced blood flow.

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Pseudoabducens paralysis

Failure of eye movement outward (abduction), not due to a problem with the abducens nerve, but likely from increased convergence signals.

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Esotropia

Eyes turning inward (cross-eyed).

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Paramedian thalamic lesion

Damage to a specific area in the thalamus that disrupts pathways controlling eye movement.

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Contralateral thalamic infarct

Stroke affecting the thalamus on the opposite side of the brain from the affected area.

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Descending inhibitory convergence pathways

Brain pathways that reduce the tendency for the eyes to turn inward.

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Motor nucleus of oculomotor nerve

Part of the brain that controls eye muscles.

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Thalamic esotropia

Cross-eyed condition caused by a thalamic stroke or injury.

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Right head tilt

A neurological sign where the head is tilted to the right, often indicative of vestibular system impairment

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Nonambulatory tetraparesis

The inability to walk on all four legs, due to weakness in all four limbs, often a neurological sign.

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Vestibular ataxia

Loss of balance and coordination related to inner ear (vestibular system) damage.

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Right esotropia

The eye turns inwards, specifically toward the nose on the right side.

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Suspected upward gaze palsy

Inability to look upwards adequately, suspected as a disorder

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Episodic head tremor

Head shaking that happens occasionally and isn't constant

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Central vestibular system lesion

Damage to the part of the vestibular system in the brain.

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Thalamic involvement

Damage or dysfunction affecting the thalamus.

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Hypercholesterolemia

High cholesterol levels in the blood.

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Increased C-reactive protein

Elevated levels of C-reactive protein, suggesting inflammation or infection.

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Study Notes

Medial Strabismus in Dogs

  • Rare neurological sign: Medial strabismus (esotropia) at rest is a rare consequence of a contralateral paramedian thalamic ischemic infarction.
  • Not previously linked to thalamic lesions: While esotropia has been linked to abducens neuropathy or extraocular myopathy in dogs, this report is the first to associate it with thalamic lesions.
  • Two dogs presented with symptoms: Two dogs (a Border Collie and a mixed breed dog) had peracute non-progressive vestibular ataxia.
  • Signs in dogs: Neurological examination revealed right esotropia, nonambulatory tetraparesis, head tilt, vestibular ataxia, and nystagmus.
  • Brain lesions identified: Magnetic resonance imaging (MRI) localized lesions to the left paramedian thalamic lacunar ischemic infarction in both dogs.
  • Mechanism of esotropia: Interruption of descending inhibitory pathways (crossing in the subthalamic region), that control the contralateral motor nucleus of the oculomotor nerve leads to medial rectus muscle hypertonicity and hence esotropia.
  • Important diagnostic sign: Esotropia can be a localized sign in dogs with thalamic infarctions.
  • Treatment: Supportive care, including IV fluids, antiemetic medications, and physiotherapy, were administered to both dogs.
  • Recovery: Both dogs recovered and were discharged, with the head tremor resolving completely in the first dog nine days later.

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