Overview

Juvenile myoclonic epilepsy (JME) is an idiopathic, hereditary, and generalized form of epilepsy, accounting for approximately 5%-10% of all epilepsy cases. JME typically manifests between the ages of 12 and 18 years. It is characterized by the presence of absence seizures (20-40%), myoclonic seizures (100%), and generalized tonic-clonic (GTC) seizures (85-90%).

Clinical Features

• Myoclonic Seizures: Defining feature of JME, required for diagnosis. These seizures are short, bilateral jerking motions of the arms and legs, typically occurring 30 minutes to an hour after waking up without loss of consciousness.
• Absence Seizures: Often the first type to appear, usually occurring 3 to 5 years before the onset of myoclonic or GTC seizures, as early as 5 to 6 years old.
• GTC Seizures: Typically develop many months after myoclonic seizures begin.
• Triggers: Sleep loss, alcohol consumption, mental stress, worry, and exhaustion. Approximately 30-40% of JME patients are photosensitive, often with an earlier onset of seizures.
• Psychiatric Disorders: Increased prevalence of anxiety, mood disorders, and personality disorders (Trinka E et al., 2006).

EEG Findings

• Interictal EEG: Abnormal in most JME patients, showing diffuse, symmetric, bilateral 4 to 6 Hz polyspike and wave discharges with fronto-central predominance.
• Ictal EEG: Shows 10-16 Hz polyspike discharges with myoclonic jerks, spikes correlating with myoclonic jerks.
• Additional Findings: GTC seizures show low voltage fast activity with spike and wave discharges, and absence seizures show generalized 3 Hz spike and wave discharges.

MRI Findings

Quantitative MRI studies have reported focal or regional abnormalities in the subcortical and cortical grey matter, particularly the thalamus and frontal cortex (Tae WS et al., 2008; Kim JH, 2017).

Genetics

• Family History: Positive in approximately 50% of cases.
• Inheritance: Multifactorial mechanism suspected.
• Identified Genes: CACNB4, CASR, GABRA1, GABRD, and Myoclonin1/EFHC1.
• SNP Alleles: BRD2, Cx-36, ME2, and microdeletions in 15q13.3, 15q11.2, and 16p13.11 contribute to JME risk (Delgado-Escueta AV et al., 2013).

Differential Diagnosis

Includes childhood or juvenile absence epilepsy, eyelid myoclonia with absences, progressive myoclonic epilepsy, photosensitive occipital epilepsy, epilepsy with grand mal seizures upon awakening, hypnagogic myoclonus (hypnic jerk), and non-epileptic seizures.

Treatment and Management

• Monotherapy: Valproic acid is the drug of choice. Other options include levetiracetam, lamotrigine, topiramate, and zonisamide (Mantoan & Walker, 2011).
• Cautions: Lamotrigine can worsen myoclonic seizures but controls other seizure types. Carbamazepine, oxcarbazepine, phenytoin, vigabatrin, tiagabine, gabapentin, pregabalin, and primidone are contraindicated.
• Combination Therapy: Required for intractable cases, with Vagal nerve stimulation (VNS) as an option.
• Lifelong Treatment: Necessary with antiepileptic drugs (AEDs). Avoidance of triggers like alcohol, fatigue, stress, sleep deprivation, and flashing lights is important.

References

1. Trinka E, et al. "Psychiatric comorbidity in juvenile myoclonic epilepsy." Epilepsia, 2006. doi: 10.1111/j.1528-1167.2006.00828.x.
2. Tae WS, et al. "Cortical thickness abnormality in juvenile myoclonic epilepsy." J Neurol, 2008. doi: 10.1007/s00415-008-0745-6.
3. Kim JH. "Grey and White Matter Alterations in Juvenile Myoclonic Epilepsy: A Comprehensive Review." J Epilepsy Res, 2017. doi: 10.14581/jer.17013.
4. Delgado-Escueta AV, et al. "The quest for juvenile myoclonic epilepsy genes." Epilepsy Behav, 2013. doi: 10.1016/j.yebeh.2012.06.033.
5. Mantoan L, Walker M. "Treatment options in juvenile myoclonic epilepsy." Curr Treat Options Neurol, 2011. doi: 10.1007/s11940-011-0131-z.