A 9-month-old intact female Yorkshire terrier presented with recurring episodes of limb cramping, initially suspected to be partial seizures. These episodes, which began six months prior, gradually increased in frequency and duration. Despite a comprehensive diagnostic workup, including neurological examinations, blood tests, abdominal imaging (radiography and ultrasonography), and advanced imaging like CT angiography and MRI, no underlying cause was identified. Based on the characteristic clinical signs and the failure to detect other pathologies, a diagnosis of Canine Epileptoid Cramping Syndrome (CECS), a form of paroxysmal dyskinesia, was suspected. A trial therapy involving a specific prescription diet (Science Diet k/d) led to a dramatic reduction in clinical signs, confirming the CECS diagnosis. This case marks the first reported instance of CECS in a Yorkshire terrier.
Understanding Muscle Cramping and Hypertonicity Syndromes
Muscle cramps are defined as prolonged, involuntary, forceful, and painful muscle contractions that can last from seconds to minutes. They are often accompanied by palpable muscle knotting and abnormal joint bending. This phenomenon is linked to repetitive firing of motor units, producing a distinct electrical activity known as “cramp discharge.” In veterinary medicine, muscle cramping is typically associated with hyperactivity of the peripheral nerve terminals or the central nervous system, rather than primary muscle disease. While human medicine commonly links muscle cramping to neurological disorders, electrolyte imbalances, and metabolic conditions, its presentation in animals is less frequently documented due to their inability to verbally express pain.
Hypertonicity syndromes, characterized by sudden, reversible episodes of limb stiffness, potential cramping, and muscle rippling, have been observed in dogs. Initially identified in Scottish terriers as “Scottie cramps,” similar conditions have since been noted in other breeds like Cavalier King Charles spaniels, springer spaniels, and wheaten terriers. The term “canine epileptoid cramping syndrome” (CECS) was later introduced for Border terriers exhibiting these paroxysmal cramping or hypertonicity episodes. Despite ongoing research, CECS remains relatively rare in veterinary literature.
Clinical Presentation and Diagnostic Process
The 9-month-old Yorkshire terrier in this report exhibited episodic seizure-like limb cramping. These episodes occurred up to four times daily, with each episode lasting over 30 minutes. Crucially, the dog remained conscious and responsive during these episodes, and all neurological functions, including gait, were normal between episodes. The primary clinical signs involved hypertonic muscle tone, sustained involuntary contractions, and painful bending of the affected joints, consistent with cramping syndrome.
A thorough diagnostic investigation was undertaken. Physical examination revealed a normal body condition score. Routine blood work, including a complete blood count, serum biochemistry, and electrolyte analysis, yielded normal results. Pre- and postprandial bile acid concentrations were also within the normal range, and liver function tests were unremarkable. Neurological examination provided no significant findings. To exclude central nervous system or vascular abnormalities, advanced imaging, including brain magnetic resonance imaging (MRI) and angiographic computed tomography (CT), was performed. These tests ruled out brain disease and portosystemic shunts.
Diagnosis and Therapeutic Intervention
Following the exclusion of other potential causes, CECS was suspected. As a therapeutic trial, the dog was placed on a prescription diet, Science Diet k/d, known for its protein restriction. This dietary intervention resulted in a dramatic improvement, with a significant reduction in the frequency and severity of the cramping episodes. No recurrence of symptoms has been observed for 13 months post-treatment. Based on this positive response to diet therapy, the patient was diagnosed with CECS.
Understanding Canine Epileptoid Cramping Syndrome (CECS)
CECS, sometimes referred to as Spike’s disease, is a paroxysmal hypertonicity syndrome primarily recognized in Border terriers, but its spectrum of clinical signs aligns with other previously described hypertonicity disorders. These syndromes are characterized by involuntary movements, sudden onset, and a return to normal motor function between episodes, without neurological deficits. Affected dogs may display gait abnormalities, muscle hypertonicity, limb rigidity, and even collapse. In severe instances, intestinal cramping can occur, indicated by audible borborygmi and abdominal pain.
While dogs remain conscious during CECS episodes, distinguishing them from partial seizures can be challenging. Key differentiating factors include the nature of the movement, episode duration, and the absence of autonomic signs like urination, defecation, or hypersalivation, which are common in seizures. The age of onset typically ranges from 4 months to 6 years. Episode frequency varies greatly, from daily to monthly, and episodes themselves can last from seconds to minutes, though longer durations are possible.
The exact cause of CECS is not fully understood, but a hereditary component is suspected, and genetic research is ongoing. Metabolic diseases and hepatic microvascular dysplasia have been considered as potential contributing factors. In some cases, elevated bile acid levels may suggest hepatic microvascular dysplasia, although this was not observed in the current case. Diet therapy, often involving a low-protein or hypoallergenic diet, has shown promise in managing CECS, alongside medications like diazepam. Channelopathies, ion-channel abnormalities, are another differential diagnosis, but these are typically associated with muscle weakness rather than rigidity, as seen in this case.
Conclusion and Future Directions
This case highlights the diagnostic challenges posed by CECS, particularly its similarity to partial seizures in dogs. The inability of animals to communicate pain further complicates recognition. Veterinarians should consider CECS in cases presenting with seizure-like episodes, and a trial diet therapy can be a valuable initial management strategy. The successful outcome in this Yorkshire terrier broadens the known breed predisposition for CECS, underscoring the need for further genetic research across diverse breeds to better understand and manage this condition.
Acknowledgments
This work was supported by Chungnam National University in the form of research funds.
