References
Tremor syndromes in dogs and cats: an update
Abstract
Tremor syndromes in dogs and cats might include tremors and twitches. Tremors are movement disorders that resemble involuntary rhythmic oscillatory sinusoidal movements of a body part. Twitches are caused by peripheral nerve hyperexcitability and they have variable frequency and amplitude. When twitches are manifested as generalised fasciculations they can mimic tremors. Tremors and twitches are common presenting complaints of dogs and cats in daily veterinary practice, and the clinician should be aware of them and their most common underlying aetiologies. Thorough tremor and twitch assessment is imperative to help the clinician come to a more specific conclusion regarding the nature and origin of these clinical signs. History, occurrence, localisation, direction, distractibility, intentionality, observation of tremor during stances, weight-bearing lifting test, auscultation and palpation of the trembling part and conscious electromyography are important parts of a thorough clinical assessment of tremors and twitches. Further studies are necessary to better characterise yet unknown tremor syndromes in dogs and cats.
Tremor syndromes are movement disorders that have been rarely investigated in veterinary neurology of dogs and cats. Tremors are involuntary, rhythmic oscillatory movements of a body part with symmetric velocity in both directions of movement (such as sinusoidal movements) around a joint axis (Cerda-Gonzalez et al, 2021). Tremors can be classified by their age of onset, distribution, frequency of occurrence, activating conditions and frequency (Hz) (Cerda-Gonzalez et al, 2021).
Classification of tremors based on activation pattern has been adopted from human neurology and recently applied in veterinary medicine (Lowrie and Garosi, 2016a; Cerda-Gonzalez et al, 2021):
Twitches caused by peripheral nerve hyperexcitability can mimic tremors (Lowrie and Garosi, 2016a; Cerda-Gonzalez et al, 2021).
Orthostatic tremor is a rare tremor that predominantly affects the limbs, exclusively while standing with pathognomonic high-frequency muscle discharges (>12 Hz) on conscious electromyography (Liatis et al, 2022a). Its pathophysiology is unknown, but a central oscillator, located in the brainstem in the cerebellum, has been hypothesised to generate orthostatic tremors and it is considered a neurodegenerative disease (Benito-León and Domingo-Santos, 2016; Schöberl et al, 2017). It was first reported in Great Danes (Garosi et al, 2005) and it is a disease of purebred giant or large breed dogs that usually occurs over 4 months of age or between 9 months and 2 years old (Liatis et al, 2022a). In 62% of dogs, tremors can progress in intensity or expand to the thoracic limbs, trunk and head and a genetic predisposition has been suspected (Liatis et al, 2022a).
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