Table 1 Clinical characteristics of episodic disorders
Discriminator | Syncope | Narcolepsy/Cataplexy | Neuromuscular weakness | Paroxysmal behaviour changes (compulsive disorder) | Vestibular attack | Paroxysmal Dyskinesia | Idiopathic head tremor | Seizure |
|---|---|---|---|---|---|---|---|---|
Clinical status between episodes | Normal or arrhythmia, pulse deficits, heart murmur, cyanosis, abnormal lung auscultation | Altered sleep/wake cycle, normal clinical examination | Normal or generalised weakness, muscle atrophy, pain, decreased reflexes | Normal | Normal | Normal | Normal | Normal or forebrain signs |
Precipitating event or trigger | Exercise, excitement | Excitement, eating | Activity, exercise | Behavioural triggers (e.g., fear) | None | None or activity, exercise, excitement, stress | None or stress, fatigue, overstimulation | None or flashing lights, anxiety, stress |
Pre-event changes | None | None | None | None | None | None | None | Pre-ictal signs may be observed including: anxiety, restlessness, increased affection, contact-seeking, withdrawal, hiding, aggressiveness, and vocalization |
Event description | Brief, sudden collapse and rapid recovery | Sudden collapse | Stiff, stilted gait prior to collapse | Pacing, barking, licking, chasing imaginary objects or tail, chewing objects | Head tilt, nystagmus, vestibular ataxia, collapse towards side of head tilt | Dystonia, chorea, ballismus, athetosis, tremors, impaired posture, inability to stand or walk | Vertical or horizontal rhythmic head movement | Depending on seizure focus, focal or generalized, tonic-clonic movements most common |
Level of consciousness | Reduced to absent | Normal if only cataplexy. Absent (asleep) in narcolepsy | Normal | Normal | Normal or disorientated | Normal | Normal | Often impaired |
Autonomic signs | Possible abnormalities of heart rate and rhythm | None | None | None | None | None | None | Possible: hypersalivation, defaecation, urination |
Muscle tone | Flaccid (all body) | Flaccid (all body) | Often flaccid (can appear spastic with certain myopathies) | Normal | Unilateral decrease in extensor muscle tone | Hypertonicity (focal or generalised) | Normal | Typically increased: tonic (hypertonicity) or alternating tonic-clonic movements |
Lateralising signs | No | No | No | No | Yes | Possible | No | Possible |
Duration | Seconds | Seconds to minutes | Minutes to hours | Minutes to hours | Seconds to hours | Seconds to hours | Seconds to hours | Seconds to minutes or > 5 min in case of status epilepticus |
Post-episodic changes | None | None | None | None | None | None or tiredness | None, tiredness, or restlessness | Post-ictal signs frequently occur including: disorientation, aggressive behaviour, restlessness, pacing, lethargy, deep sleep, hunger, thirst, ataxia, proprioceptive deficits, and blindness |
Further comments | May be accompanied by cough, increased respiratory noise | Often occurs in young purebred dogs. | May be accompanied by dysphagia, dysphonia, regurgitation, dyspnoea | History of anxiety disorder | Subtle signs of vestibular disease might persist | Interaction with the owner can alleviate or interrupt the episode. Consider breed specific disorders and age at onset. | Episodes can be interrupted by the owner | Facial muscles often involved during the ictus |