Convergence-Retraction Pulses in a Dog With Ischaemic Encephalomyelopathy

Liatis, T. , Furtado, R., Mantis, P. and Cherubini, G.B. (2019) Convergence-Retraction Pulses in a Dog With Ischaemic Encephalomyelopathy. 5th British Veterinary Neurology Society (BVNS) Annual Meeting, Birmngham, UK, 3 Apr 2019.

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Abstract

Convergence-retraction pulses (or “nystagmus) are a highly localizing saccadic abnormality of the dorsal midbrain syndrome in humans and dogs. Ischaemic encephalomyelopathy attributed to presumptive fibrocartilaginous embolism (FCE) has been reported in human, dog and lamb, whilst FCE encephalopathy was reported recently in a cat. The aim of this study is to report the clinical and imaging findings of a rare case of ischaemic encephalomyelopathy due to presumptive FCE with manifestation of convergence-retraction pulses and an excellent outcome. A 6.5-year-old client-owned male neutered Trailhound was admitted for hyperacute non-progressive non-painful left-sided hemiparesis developed during exercise. Physical examination revealed obesity and bilateral conjunctival hyperaemia. Neurological examination revealed non-painful left-sided poorly-ambulatory hemiparesis; decreased left-sided postural reactions and left thoracic limb spontaneous knuckling; thoracic limbs hyporeflexia; and no evidence of spinal pain. Neuroanatomical localisation was consistent with C6-T2 myelopathy. Haematology revealed stress-leukogram, whilst serum biochemistry revealed mild stress-hyperglycaemia, hypotriglyceridemia and mildly decreased alkaline phosphatase. The patient underwent a low-field magnetic resonance imaging (MRI) of the C1-T2 spinal segments which revealed a focal intramedullary lesion at C6-C7 spinal segments compatible with FCE. On the second day of hospitalisation, the patient suddenly developed “nystagmus”. Neurological examination revealed spontaneous-and-positional convergence-retraction pulses accompanied by synchronous blinking, mydriasis and upward gaze palsy (Collier’s sign) bilaterally. Ambulation and postural reactions were unchanged. The neuroanatomical localisation now was consistent with an additional dorsal midbrain syndrome. MRI of the brain revealed a focal, poorly-marginated, left-lateralized, hyperintense lesion on T2-weighted and fluid fluid-attenuated inversion recovery (FLAIR) sequences, at the level of the rostral midbrain. In transverse images, this lesion was visible adjacent to the midline (left-sided) and lateral to the rostral part of the mesencephalic aqueduct. This area was hyperintense on diffuse-weighting imaging (DWI) sequence, but did not suppress on apparent diffusion coefficient (ADC) mapping or uptake contrast. These findings were compatible with an ischaemic infarct in the rostral aspect of the dorsal midbrain. Cisternal cerebellomedullary cerebrospinal fluid (CSF) analysis revealed albuminocytological dissociation, with occasional monocytes, rare neutrophils and small lymphocytes. The finding of neutrophils in the absence of pleocytosis could be associated with cerebrovascular accident. Oscillometric arterial blood pressure revealed an average of 147/93 (mean106) mmHg. Ophthalmological examination, ophthalmoscopy, endocrine profile (TT4, TSH, basal cortisol, ACTH stimulation test), coagulation profile (BMBT, PT, APTT, D-dimers), ANA serology, extended infectious agents panel (blood serology and CSF PCR), urinalysis, urine culture, abdominal ultrasound and thoracic computed tomography were all unremarkable. Consequently, ischaemic encephalomyelopathy due to presumptive multifocal FCE was diagnosed. The dog was kept hospitalised for one week while received physiotherapy. At the time of discharge, the dog was ambulatory hemiparetic with normal haematology. On a three-week follow-up the dog was normal. The “nystagmus” was reported to have resolved within two weeks from onset. This is a rare report of a dog with multiple simultaneous central nervous system ischaemic infarctions which manifested convergence-retraction pulses and had an excellent outcome. This neuro-ophthalmological sign should be considered as a guide to localise precisely. FCE should be considered in the differential diagnoses for a dog with ischaemic encephalomyelopathy.

Item Type:Conference or Workshop Item
Additional Information:Oral Abstract.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Liatis, Dr Theophanes
Authors: Liatis, T., Furtado, R., Mantis, P., and Cherubini, G.B.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine

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