[2][3][4] Typically it first presents between the ages of 12 and 18 with myoclonic seizures (brief, involuntary, single or multiple episodes of muscle contractions caused by abnormal excessive or synchronous neuronal activity in the brain).
[10] Common triggers for JME seizures include lack of sleep, alcohol consumption, emotional stress, anxiety, and fatigue.
A notable portion (30%–40%) of JME patients exhibit photosensitivity, whereby flashing lights from sources like sunlight, TV screens, and computers can provoke seizures.
Patients typically present to medical providers following their first generalized tonic–clonic seizure, by which time they have often had myoclonus for several years.
The first generalized tonic–clonic seizure usually occurs in the context of a particular provoking factor, such as sleep deprivation, stress or alcohol consumption.
[15] Other potential provoking factors include "praxis induction" which is the precipitation of seizures or epileptiform discharges in the context of a complex cognitive tasks.
[16] Patients with JME tend to perform worse on neuropsychological assessments in multiple cognitive domains and are also more likely to have psychiatric comorbidities such as depression and anxiety when compared to control populations.
[22] More recently, variants in intestinal cell kinase, which is encoded by a gene at chromosomal locus 6p12, were found to be associated with JME.
This is characterized by ataxia and lethargic behavior at early stages of development followed within days by the onset of focal motor seizures and episodes of behavioral immobility correlated with patterns of cortical spike and wave discharges on electroencephalography (EEG)[31] A premature-termination mutation, R482X, was identified in a patient with JME while an additional missense mutation C104F was identified in a German family with generalized epilepsy and praxis-induced seizures.
[32] The R482X mutation causes increased current amplitudes and an accelerated fast time constant of inactivation.
This mutation affects GABAergic transmission by altering the surface expression of the receptor as well as reducing the channel opening duration.
[10] The primary diagnosis for JME is a good knowledge of patient history and the neurologist's familiarity with the myoclonic jerks, which are the hallmark of the syndrome.
Both magnetic resonance imaging (MRI) and computer tomography (CT) scans generally appear normal in JME patients.
However a number of quantitative MRI studies have reported focal or regional abnormalities of the subcortical and cortical grey matter, particularly the thalamus and frontal cortex, in JME patients.
[41][12] Due to valproic acid's high incidence of fetal malformations,[42][41] women of child-bearing age may be started on alternative medications such as lamotrigine or levetiracetam.
The first citation of JME was made in 1857 when Théodore Herpin described a 13-year-old boy with myoclonic jerks, which progressed to tonic–clonic seizures three months later.