JME

Juvenile Myoclonic Epilepsy (JME) is a well-defined genetic generalized epilepsy syndrome. It is characterized by a triad of seizure types and is considered a lifelong condition, requiring long-term management.

Presentation and Clinical Features

• Age of Onset: JME typically begins in adolescence, with an age of onset between 10 and 20 years. It affects both sexes, but is slightly more common in girls.

• Seizure Types: The diagnosis of JME requires the presence of myoclonic jerks. In addition, most patients also have generalised tonic-clonic seizures (GTCS) and about one-third have absence seizures.

• Myoclonic Jerks: These are the most characteristic feature. They consist of sudden, brief, muscle jerks, most often affecting the upper limbs. They are most prominent in the morning, shortly after waking. Patients may describe “clumsiness” or “dropping things,” such as a toothbrush or a plate, especially when they are tired or stressed.

• Generalised Tonic-Clonic Seizures (GTCS): These are also very common, occurring in over 90% of patients. They often happen after a period of sleep deprivation or excessive alcohol consumption.

• Absence Seizures: About 30% of patients with JME also experience brief absence seizures, similar to those seen in other generalised epilepsy syndromes.

• Triggers: The seizures in JME are highly sensitive to sleep deprivation, fatigue, stress, and alcohol consumption. Photosensitivity (seizures triggered by flashing or flickering lights) is also a common feature.

• Cognition: Cognitive development and intellect are typically normal.

Investigation

• Diagnosis: The diagnosis is primarily based on a detailed clinical history. Asking about specific triggers like sleep deprivation and morning myoclonic jerks is crucial.

• EEG: The EEG is key for confirming the diagnosis. It shows generalised 4-6 Hz polyspike-and-wave discharges on a normal background. These discharges are strongly provoked by sleep deprivation and can often be triggered by photic stimulation (flashing lights) during the recording.

• Neuroimaging: Routine brain imaging (MRI) is not required for a typical presentation, as JME is a functional disorder, not a structural one. MRI should only be considered if there are atypical features or the EEG is not classic for JME.

Management

• Lifelong Condition: JME is considered a lifelong condition. Patients should be counselled that they will likely need to continue medication indefinitely, as withdrawal almost always leads to a recurrence of seizures.

• Medication Choice: Treatment aims to control all three seizure types.

  • Valproate is the most effective drug for controlling all seizure types in JME. However, due to its teratogenic potential and other side effects, it should be used with extreme caution in women of childbearing age.

  • Levetiracetam is now considered a first-line alternative to valproate, especially for women, due to its broad-spectrum efficacy, good tolerability, and a more favorable side-effect profile.

  • Lamotrigine is effective for GTCS and absences but is often less effective for myoclonic jerks.

  • Topiramate and Zonisamide are also effective but have a higher risk of cognitive side effects.

  • Ethosuximide and Carbamazepine are generally not used as they are not effective against all seizure types in JME (Ethosuximide is for absences only, Carbamazepine can worsen myoclonic seizures).

• Non-Pharmacological Management: Patients should be educated on the importance of maintaining a regular sleep schedule, avoiding alcohol, and managing stress to prevent seizures.

• Prognosis: The prognosis for seizure control with medication is excellent, but patients are at high risk of relapse if they stop their medication.