What types of epilepsy typically have their onset in teenagers?

Types of Epilepsy with Onset in Teenage Years

The primary epilepsy syndromes with onset during adolescence are juvenile myoclonic epilepsy (JME), juvenile absence epilepsy, and epilepsy with generalized tonic-clonic seizures on awakening—all forms of idiopathic generalized epilepsy that share genetic underpinnings and overlapping clinical features. 1, 2

Juvenile Myoclonic Epilepsy (JME)

JME is the most recognizable and common epilepsy syndrome beginning in teenage years, affecting approximately 7% of adolescent and adult epilepsy patients. 3

Key Clinical Features

• Onset occurs between 6 and 22 years of age, most typically around puberty 4, 5
• The hallmark is bilateral myoclonic jerks without loss of consciousness, occurring predominantly after awakening from sleep or during evening relaxation periods 3, 4
• Most patients (the majority) also experience generalized tonic-clonic seizures (GTCSs), and approximately one-third have absence seizures 3, 5
• The typical presentation is a first GTCS in a teenager, with retrospective history revealing morning myoclonic jerks that preceded the GTCS by months or years 4

Precipitating Factors

• Sleep deprivation is the most common seizure trigger, followed by fatigue, sudden awakening, and alcohol consumption 3, 6
• Photic stimulation can trigger seizures in the EEG laboratory, though this is less commonly recognized in daily life 4

Diagnostic Considerations

• There is typically a diagnostic delay averaging 3.5 years because myoclonic jerks may not be recognized as seizures until a GTCS occurs 6
• Routine awake EEGs are abnormal in only 73% of cases and may show misleading findings in 7% 6
• Sleep EEGs are abnormal in 100% of JME cases, showing the characteristic 4-6 Hz polyspike and wave pattern, with discharge rates increasing significantly during the sleep-to-awakening transition phase 3, 6
• MRI is rarely indicated in neurologically normal patients with JME because positive intracranial findings occur in only 2% of low-risk patients, given the genetic basis of generalized epilepsies 7, 8

Juvenile Absence Epilepsy

This syndrome presents with absence seizures beginning in adolescence, distinguishing it from childhood absence epilepsy which starts earlier. 2

• Patients have absences without myoclonic seizures, though many may also develop GTCSs 2
• The syndrome shares genetic underpinnings and clinical overlap with JME, with 26% of adolescent-onset idiopathic generalized epilepsy patients showing features of both syndromes 2

Epilepsy with GTCS on Awakening

This syndrome is characterized by GTCSs occurring specifically after awakening or during evening relaxation, without myoclonic or absence seizures. 2

• This is not a distinct syndromic entity in many cases, as only 10% of adolescent-onset idiopathic generalized epilepsy patients have this seizure pattern alone 2
• The boundaries between this syndrome and JME are indistinct, suggesting underlying genetic relationships 2

Important Clinical Pitfalls

Phenotypic Overlap

• The three adolescent-onset idiopathic generalized epilepsy syndromes share substantial clinical features and have indistinct boundaries, with many patients showing characteristics of multiple syndromes 2
• Approximately 7% of patients with adolescent-onset idiopathic generalized epilepsy cannot be classified into current ILAE syndromic categories 2

Atypical Presentations

• Atypical presentations of JME are common and frequently lead to misdiagnosis 5
• A first GTCS in a teenager should be considered JME until proven otherwise, prompting specific questioning about morning myoclonic jerks 4

Focal Epilepsies in Adolescence

• While less common than idiopathic generalized epilepsies, focal epilepsies can also begin in teenage years and require different diagnostic and treatment approaches 8
• Focal seizures show considerably higher positive neuroimaging yields (approximately 50% on CT) compared to generalized seizures (6%), making recognition of any focal features critical 7, 8
• Focal epilepsies demonstrate significantly higher drug resistance rates (~30% fail two antiepileptic drugs) and may require earlier surgical evaluation 8