Tonic-Clonic Seizure Etiology and Diagnosis

Primary Etiologic Categories

The European Society of Cardiology recommends differentiating between tonic-clonic seizures and syncope based on key distinguishing features, including prolonged movements and loss of consciousness in seizures, whereas in syncope, any tonic-clonic movements are brief and start after loss of consciousness 1, 5
Genetic conditions, such as 22q11.2 deletion syndrome, have a lifetime prevalence of epilepsy of 5-7%, with both generalized tonic-clonic seizures and focal seizures with dyscognitive features occurring 2

Hypocalcemia can trigger seizures at any age, even in patients with no prior history of hypocalcemia or seizures, particularly in conditions like 22q11.2 deletion syndrome where underlying parathyroid dysfunction predisposes to hypocalcemia throughout life 2, 3
Hyponatremia and other electrolyte disturbances are common seizure precipitants, especially in elderly patients, with hypoglycemia, hypomagnesemia, and renal dysfunction also lowering seizure threshold 3

Cortical malformations, such as polymicrogyria, periventricular nodular heterotopia, and cortical dysplasia, can cause seizures, including tonic-clonic types, with brain imaging with MRI indicated when structural abnormalities are suspected 2

Fever, cerebral ischemia, hypoxia, and surgical procedures can trigger seizures, with infection, particularly with aspiration pneumonia, representing an acute symptomatic seizure trigger 2, 3
Medications, including antipsychotics, can lower seizure threshold, with non-compliance with antiepileptic medications being a major precipitant of breakthrough seizures in patients with established epilepsy 2, 3

Status epilepticus is defined as seizure activity lasting more than 5 minutes or recurrent seizures without return to baseline, with mortality rates of 5-22% if untreated 3
The American Heart Association and European Society of Cardiology recommend immediate return to clearheadedness and absence of prolonged post-ictal confusion as key distinguishing features of syncope from seizures 1, 5