ABSTRACT OF THE WEEK

The veterinary journal
Volume 213 | Issue 0 (July 2016)

Natural history of canine paroxysmal movement disorders in Labrador retrievers and Jack Russell terriers.

Vet J. July 2016;213(0):33-7.

Mark Lowrie¹, Laurent Garosi²

¹ Dovecote Veterinary Hospital, 5 Delven Lane, Castle Donington, Derby DE74 2LJ, UK. Electronic address: m.l.lowrie.98@cantab.net.; ² Davies Veterinary Specialists, Manor Farm Business Park, Higham Gobion, Hitchin SG5 3HR, UK.

Abstract

Delineation of the typical disease progression in canine paroxysmal dyskinesia (PD) may assist in evaluating therapeutic agents during clinical trials. Our objective was to establish the natural disease course in a group of dogs diagnosed with PD that received no medication. Fifty-nine dogs (36 Labradors, 23 JRTs) with clinically confirmed PD and a follow-up of ≥3 years were retrospectively reviewed. Dogs with PD had a young onset, were triggered by startle or sudden movements, and had a male bias (75%) with the majority being entire sample population. Twenty-one dogs (36%) had at least one event comprising cluster episodes. Episode duration and frequency varied dramatically, even within an individual. Median follow-up was 7 years. No concurrent disease was identified in any dog that was investigated. The natural history was self-limiting with 32% entering remission and an improvement in 75%. Episodes reduced in terms of frequency and duration in Labradors and JRTs respectively. Remission was lower in dogs with cluster episodes than those without. These findings suggest that the diagnostic yield of advanced neuroimaging techniques in dogs with video footage and historical data supporting PD, without neurological deficits, is low. The presence of cluster episodes is of predictive value for the prognosis of canine PD. Future research should be cautious in reporting treatment response for PD without first considering the spontaneous remission rate and improvements in untreated dogs documented in this study.

Companion Notes

Retrospective report on paroxysmal movement disorders in Labrador retrievers and Jack Russell terriers in the UK

Introduction on paroxysmal dyskinesias (PD)

- PDs are group of hyperkinetic, paroxysmal movement disorders

- characterized by involuntary, sustained muscle contraction

- in canine medicine

- known causes include the following:

- genetic factors

- episodic falling syndrome in the Cavalier King Charles spaniel

- 1^st genetically mapped paroxysmal movement

- drug-induced factors

- phenobarbital reported to elicit dyskinesia in an epileptic chow

- dietary factors

- canine epileptoid cramping syndrome in the border terrier

- found a manifestation of gluten sensitivity

- in human medicine

- most commonly idiopathic or familial

- secondary or symptomatic dyskinesia also reported

(due to structural central nervous system lesions)

- multiple sclerosis

- head trauma

- cerebral palsy

- cerebrovascular accidents

- encephalitis

- current classification is based on precipitating factors for episodes

(each type of PD can have dystonia, chorea, athetosis, or a combination)

- paroxysmal kinesigenic dyskinesia (PKD): incited by sudden movements

- paroxysmal nonkinesigenic dyskinesia (PNKD): spontaneously at rest

- paroxysmal exertion-induced dyskinesia (PED): precipitated by fatigue

- paroxysmal hypnogenic dyskinesia (PHD): occurs during sleep

- definitions of clinical signs that incorporate the term ‘dyskinesia’.

- chorea: abrupt, unsustained contraction of different muscle groups

- athetosis: prolonged, slow contraction of trunk muscles

- resulting in bending and writhing of body (cannot maintain stable posture)

- choreoathetosis: involuntary movements involving chorea and athetosis

- ballism: abrupt contraction of limb muscles (often unilateral)

- results in flailing movement of the limb

- dystonia: sustained, involuntary contraction of a group of muscles

- resulting in abnormal postures

Study design

- study population: dogs seen at 2 private referral clinics in the UK from 01/05-01/15

- 59 dogs with clinically confirmed PD and a follow-up of ≥ 3 years

- 36 Labrador retrievers

- 23 Jack Russell terriers

- inclusion criteria

- video evidence of at least one typical episode

- assessment by a board-certified neurologist

- at least a 6-month history of PD

- dogs that had received treatment were excluded from analysis

- procedure: records retrospectively reviewed

Results (median followup: 7 years)

- history & signalment (53 owners kept a diary of each observed episode)

- median age episode onset

- Labradors: 2.25 years with a range of 9 months to 10 years 8 months

- JRTs: 4 years 8 months with a range of 1-8 years

- male (most intact), 75% (29 Labs were male and 15 JRTs were male)

- had at least one event comprising cluster episodes, 21 dogs

- 19 Labradors and 2 JRTs

- no concurrent disease identified in any dog investigated

- median duration of clinical signs in all dogs at presentation: 9 months

- clinical signs

- triggers always occurred at home

- JRTs, after extremes of temperature, 19 of the 23 dogs

- Labs

- after sudden movements or being startled, 21 of the 36 dogs

- with excitement, 9

- highly variable episode duration and frequency, even within individuals

- median frequency at presentation:

- Labs: 1 episode every 3 weeks

- with a range of every 6 months to 12/month

- JRTs: 1 episode per month

- with a range of 1 every 6 months to 2 per month

- similar duration of episodes in the 2 breeds

- ~ 13 Labs at presentation had a duration of 2-5 minutes

- ~ 11 Labs at presentation had a duration of 5-10 minutes

- many owners reported stress or variation in daily routine an inciting factor

- in both breeds

- CBC and biochemistry: unremarkable

- elevated creatine kinase, 3 dogs (all Labradors)

- CSF analysis, normal in the 48 dogs tested

- MRI of the brain, normal in the 48 dogs tested

- outcome

- self-limiting disorder

- 32% gained remission

- remission rate lower in dogs with cluster episodes than those without

- 75% had an improvement

- frequency and duration of episodes at followup

- decreased in 25 of the 36 Labradors

- progressed, 5 Labradors

- static, 6 Labradors at follow-up

- decreased in 19 of 23 JRTs

- progressed, 2 of 23 JRTs

- static, 2 of 23 JRTs

“PD, with video correlation, normal inter-ictal findings and normal neurological examination, is unlikely to yield abnormal findings when performing screening diagnostic procedures.”

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