Muscle stiffness with concurrent naturally occurring hypercortisolism

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Naturally occurring or iatrogenic hypercortisolism can cause myopathic signs in addition to the more 'classical' signs of PuPd, polyphagia, bilateral symmetrical truncal hair loss, and excessive panting. Muscle atrophy and weakness are frequently seen contributing to the 'pot belly' appearance and exercise-induced weakness. Rarely, severe muscle stiffness (SMS) can develop with naturally occurring hypercortisolism. The pathophysiology is unclear. EMG in these dogs often reveals complex repetitive discharges which has led to this condition being labelled as a pseudomyotonia. Unlike myotonic discharges, there is no waxing and waning of these discharges. In this study, the authors evaluate signalment, presentation, treatments, and long-term outcomes of dogs with concurrent hypercortisolism and SMS. While muscle weakness usually resolves with hypercortisolism treatment, SMS does not. This was the case with the dog in the above video kindly provided by Drs Falzone, Gasparinetti, Della Camera from Diagnostica Piccoli Animali, Italy, showing you the severe SMS which can sometimes be associated with hypercortisolism.

Clinical features of muscle cramp in 14 dogs

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Muscle cramps (MC) are defined as prolonged, involuntary, painful muscle contraction, having acute onset and short duration, lasting from seconds to minutes. MC are considered the clinical manifestation of nerve hyper excitability and characterised by repetitive motor unit action potentials from the simultaneous contraction of a large number of motor units. One of the main differentials for MC is paroxysmal dyskinesia (PD) which presents with similar characteristics helping to differentiate from epileptic seizures such as not being associated with autonomic signs, impaired consciousness and abnormal postictal behaviour. Although PD are considered painless, this criteria may be difficult to ascertain in a dog not showing overt pain manifestation. In this series, the authors described 3 clinical patterns of MC depending on whether or not the cramps migrate to other limbs. The most common cause of muscle cramps was hypocalcemia in 79% of dogs with primary hypoparathyroidism being most commonly encountered. In two third of dogs, MC were triggered by prompting the dog to move as shown in the attached video which shows one of our old patients with MC caused by primary hypoparathyroidism

Paradoxical pseudomyotonia in English Springer and Cocker Spaniels

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The aim of this paper is to define and describe the clinical, diagnostic, and genetic features and disease course of paradoxical pseudomyotonia in 7 Spaniel dogs.

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All dogs were <24 months of age at onset. The episodes of myotonic‐like generalized muscle stiffness always occurred with exercise, and spontaneously resolved with rest in <45 seconds in all but 1 dog - see video above. Extreme outside temperatures seemed to considerably worsen episode frequency and severity in most dogs. Complete blood count, serum biochemistry including electrolytes, urinalysis, brain magnetic resonance imaging, cerebrospinal fluid analysis, electromyography, motor nerve conduction velocity, ECG, and echocardiography were unremarkable. Muscle biopsy samples showed moderate but nonspecific muscle atrophy. The episodes seemed to remain stable or decrease in severity and frequency in 6/7 dogs, and often could be decreased or prevented by avoiding the episode triggers.