eMedicine Specialties > Neurology > Seizures and Epilepsy
Epilepsy, Juvenile Myoclonic: Differential Diagnoses & Workup
Updated: Nov 29, 2007
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Differential Diagnoses
Absence Seizures
Benign Childhood Epilepsy
Frontal Lobe Epilepsy
Tonic-Clonic Seizures
Other Problems to Be Considered
Epilepsy with generalized tonic-clonic seizures on awakening
Nocturnal generalized tonic-clonic seizures
Myoclonic absence epilepsy
Myoclonus
Partial seizures with secondary generalization
Progressive myoclonic epilepsies
Workup
Imaging Studies
- Neuroimaging studies are typically normal in JME. Many clinicians believe that, in the presence of an adequate supportive history, EEG abnormalities, normal intelligence, and normal neurologic findings, neuroimaging studies are unnecessary. However, the clinical scenario might not be as clear as the classical description.
- MRIs of the brain are usually unremarkable. This observation reflects the fact that JME is an idiopathic generalized epilepsy and not caused by conditions such as brain tumors or encephalitis.
- Some patients with brain MRIs, particularly if the MRIs are high definition, or high Telsa studies, have shown minor abnormalities of cortical development.
Other Tests
- Study of choice to confirm the clinical diagnosis is sleep-deprived EEG with activation procedures (ie, hyperventilation, photic stimulation). A normal study does not rule out epilepsy or JME. Typical EEG abnormalities are highly supportive of the clinical diagnosis (see Media file 1).
- The typical interictal EEG abnormality consists of a generalized 4- to 6-Hz spike or polyspike and slow-wave discharges lasting 1-20 seconds (see Media file 1). Usually, 1-3 spikes precede each slow wave. When absence seizures are also present, 3-Hz spike-and-wave activity may be seen in addition to the polyspike-and-wave pattern.
- The ictal EEG associated with myoclonic jerks typically reveals 10- to 16-Hz polyspike discharges. These may be preceded by spike and wave activity and are often followed by 1- to 3-Hz slow waves. The number of spikes is typically 5-20 and tends to be proportionately correlated with the clinical intensity of the seizure. These epileptic discharges may briefly persist, even after clinical activity has ceased.
- Absence seizures of JME may be associated with ictal EEG patterns consisting of 3-Hz spike-and-wave activity. Sometimes, these are preceded by 4- to 6-Hz polyspike-and-wave discharges, which slow to 3 Hz as the patient loses consciousness.
- Background activity of the EEG is normal in JME. Hyperventilation and photic stimulation often facilitate the appearance of epileptiform discharges. Photic stimulation frequently precipitates spike-and-wave patterns. This occurs in approximately 30% of patients with JME, compared with 18% of patients with childhood absence epilepsy, 13% of patients with epileptic seizures on awakening, and 7.5% of patients with juvenile absence epilepsy.
- Ictal and interictal polyspike-and-wave discharges are not pathognomonic of JME; they may be seen in other primary generalized epilepsies as well as in myoclonic epilepsies of early childhood.
- In addition to generalized epileptiform discharges, focal abnormalities may be found in 20-55% of patients with JME. These include focal slow waves, generalized discharges that evolve from a focal onset, and focal spikes or spike-and-wave discharges. Ignorance of these changes may lead to one's mistakenly ruling out the syndrome. The etiology of these focal abnormalities is unclear. A possible explanation is structural changes in the cerebral cortex secondary to recurrent seizures or head injury; another is fluctuation in the refractoriness of the cortex to the influence of a spike/wave generator.
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Differential Diagnoses & Workup: Epilepsy, Juvenile Myoclonic |
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| Follow-up: Epilepsy, Juvenile Myoclonic |
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References
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Further Reading
Keywords
JME, idiopathic generalized epileptic syndrome, myoclonic jerks, generalized tonic-clonic seizures, GTCSs, absence seizures
Differential Diagnoses & Workup: Epilepsy, Juvenile Myoclonic