When are episodes of loss of consciousness life-threatening?

Abstract

Episodic loss of consciousness is common in the paediatric population. While the majority of cases are due to benign conditions, lifethreatening causes must be promptly identified. The present paper presents a case of recurrent loss of consciousness associated with convulsive activity and subsequent cardiac arrest due to a rare inherited ion channel disease known as Brugada syndrome. The case highlights the challenges of distinguishing epilepsy from convulsive syncope and the potentially disastrous consequences of an undiagnosed cardiac etiology. The most important paediatric causes of paroxysmal loss of consciousness and their salient features are reviewed. Clinical features suggesting a cardiac cause are emphasized because early recognition of these cases is critical. T here are many causes of brief episodes of loss of consciousness (LOC), but most are benign. Identifying the few patients with an ominous cause is challenging. Syncope is often misdiagnosed as epilepsy, leading to unnecessary and ineffective treatment -an unsatisfactory, but not dangerous, error. More concerning is misdiagnosis of a cardiac cause of LOC, which may be fatal with the next attack. We present a case of paroxysmal LOC that illustrates the clinical features that should alert the clinician to potentially life-threatening cardiac conditions. CASE PRESENTATIONA 15-year-old boy experienced a sudden LOC while standing. Without warning, he fell down, and was unconscious with tonic limb extension for 5 min. He was described as pale, but he recovered quickly without residual drowsiness. Head computed tomography was normal.One week later, during sleep, he had tonic limb extension, LOC and gasping respirations. Epilepsy was diagnosed and carbamazepine started. Frequent events continued and he was admitted to hospital. On day 2, sudden LOC occurred with tonic stiffening and eye deviation, quickly followed by cardiac arrest. He was successfully resuscitated with multiple defibrillations, and an amiodarone load was given for atrial fibrillation. He was then transported to a tertiary care children's hospital.His initial electrocardiogram (ECG) showed a prolonged QT interval (QTc=0.49), which was believed to be secondary to amiodarone; two follow-up ECGs were normal. An echocardiogram, interictal electroencephalogram (EEG) and brain magnetic resonance imaging scan were normal.Previous normal cognitive and physical development was documented. The patient had no history of shortness of breath, chest pain, palpitations or syncope. There was no family history of epilepsy, syncope, arrhythmia or sudden death. On examination, he was alert and oriented to person but initially disoriented to time and place. By day 3, he had recovered completely with normal cardiac and neurological examinations.An ECG from the day of his initial event was reviewed and showed ST segment elevation of V1 to V3 and right bundle branch block (RBBB) -a pattern consistent with Brugada syndrome. Holter monitoring showed incomplete RBBB, nondiagnostic T-wave changes and frequent prem...

Modes of onset of epilepsy and differential diagnosis

“…A child who presents with a collapse during exercise, including swimming without premonitory symptoms, may well have cardiac syncope from a cardiac arrhythmia (Brna et al, 2006). There may be generalized stiffening as in vasodepressor syncope.…”

Pediatric syncope: pearls and pitfalls in history taking

“…Tonic posturing is “probably universal” when syncope lasts long enough to produce a flat EEG [ 46 ]. A breath-holding spell is a good example, often accompanied by intense opisthotonic stiffening caused by profound but brief cerebral hypoxia [ 46 , 51 ]. The “slow-flat-slow” pattern sequence is independent of syncopal mechanisms.…”

“…46) A breathholding spell is a good example, often accompanied by intense opisthotonic stiffening caused by profound but brief cerebral hypoxia. 46,51) The "slowflatslow" pattern sequence is independent of syncopal mechanisms. However, mild forms of syncope may present as iso lated background slowing without EEG flattening.…”