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early myoclonic encephalopathy

Description

Early myoclonic encephalopathy (EME) is a rare and severe form of epilepsy that affects infants, typically within the first three months of life [1]. It is characterized by:

  • Erratic or fragmentary myoclonus: Sudden, brief muscle contractions that can be focal or generalized [2].
  • Focal seizures: Seizures that affect a specific part of the body, such as one arm or leg [3].
  • Late tonic spasms: A type of seizure characterized by stiffening of the muscles [4].
  • Suppression-burst pattern (SB) in EEG: An abnormal brain wave pattern seen on electroencephalogram (EEG) that is often associated with EME [5].

EME is considered a developmental and epileptic encephalopathy (DEE), which means it is a condition where the epilepsy is closely linked to the development of the brain [6]. Children with EME often have delayed development, intellectual disability, and drug-resistant seizures [7].

It's worth noting that EME is now included as part of the Early infantile developmental and epileptic encephalopathy (EIDEE) under the 2022 ILAE (International League Against Epilepsy) syndrome classification [8].

Additional Characteristics

  • Focal seizures
  • Erratic or fragmentary myoclonus
  • Late tonic spasms
  • Suppression-burst pattern (SB) in EEG

Signs and Symptoms

Early myoclonic encephalopathy (EME) is a rare and severe form of epilepsy that affects infants and young children. The signs and symptoms of EME can vary, but they often include:

  • Fragmentary myoclonus: This is the most characteristic feature of EME, where small, brief muscle contractions occur randomly throughout the body.
  • Frequent seizures: Children with EME may experience frequent seizures, which can be triggered by various factors such as fever, stress, or certain medications.
  • Poor suckling reflexes: Infants with EME may have difficulty sucking and feeding due to poor coordination of their muscles.
  • Hypotonia: This refers to low muscle tone, which can cause the child's limbs to feel floppy or weak.
  • Generalized tonic spasms: These are seizures that affect the entire body, causing a stiffening of the muscles.
  • Myoclonic seizures: These are brief, sudden jerks or contractions of the muscles.

These symptoms often appear in the first few months of life and can be severe enough to cause developmental delays or intellectual disability. It's essential for parents and caregivers to seek medical attention immediately if they notice any unusual muscle movements or other signs of EME in their child.

References:

  • [4] Early myoclonic encephalopathy (EME) is characterized by fragmentary myoclonic jerks or violent myoclonic spasms, which generally occur in the neonatal period ...
  • [6] Neonates have poor suckling reflexes, hypotonia and manifest with generalized and symmetrical tonic spasms that can appear in clusters or singly and can last ...
  • [8] Myoclonic seizures are characterized by rapid, jerklike movements that can affect the face, limbs, or axial musculature.
  • [9] Myoclonic seizures are brief, sudden jerking of muscles.

Diagnostic Tests

Diagnostic Tests for Early Myoclonic Encephalopathy (EME)

Early myoclonic encephalopathy (EME) is a rare and severe form of epilepsy that affects infants. Diagnosing EME can be challenging, but several diagnostic tests can help confirm the condition.

  • Electroencephalogram (EEG): An EEG is the most important test in making a diagnosis of EME. It records electrical activity within the brain and can show characteristic patterns such as suppression-bursts [4][5]. An EEG can be performed on infants as young as a few weeks old.
  • Magnetic Resonance Imaging (MRI): MRI scans, preferably at least 1.5-Tesla strength, are recommended to rule out other conditions that may cause similar symptoms [7].
  • Computed Tomography (CT) imaging: CT imaging may be useful in specific cases, such as when calcification is suspected [7].

Other diagnostic tests may include:

  • Genetic testing: Testing for STXBP1 mutations may be considered in infants with EME-like symptoms [13].
  • Clinical evaluation: A thorough clinical evaluation by a specialist, including a review of the infant's medical history and physical examination, can help identify potential causes of EME.

It is essential to note that no single test can definitively diagnose EME. A combination of these tests, along with a comprehensive clinical evaluation, can help confirm the diagnosis [14].

References:

[4] Dec 27, 2022 — The most important part of diagnosing EME is electroencephalography (EEG), which is an electrical recording of brain activity. [5] Feb 28, 2019 — An electroencephalogram (EEG) test is the best method for diagnosing early myoclonic encephalopathy. [7] Jul 26, 2022 — MRI, preferably at least 1.5-Tesla strength, is recommended. [13] Early myoclonic encephalopathy presents within the first 3 months of age and mostly within the neonatal period. The prenatal onset is known. ... Testing for STXBP1 mutations may be considered in infants with ... [14] Clinical resource with information about Early myoclonic encephalopathy and its clinical features, available genetic tests from US and labs around the world and links to practice guidelines and authoritative resources like GeneReviews...

Additional Diagnostic Tests

  • Clinical evaluation
  • Magnetic Resonance Imaging (MRI)
  • Genetic testing
  • Electroencephalogram (EEG)
  • Computed Tomography (CT) imaging

Treatment

Differential Diagnosis

Early myoclonic encephalopathy (EME) is a rare epileptic syndrome characterized by frequent intractable seizures that begin ≤3 months of age [6]. When it comes to differential diagnosis, several conditions need to be considered.

Key Differential Diagnoses:

  • Ohtahara Syndrome: This condition shares similarities with EME in terms of clinical presentation, prognosis, and electroencephalographic signature. However, Ohtahara syndrome is typically distinguished from EME based on specific clinical and etiologic criteria [14].
  • Early Infantile Developmental and Epileptic Encephalopathy Syndrome (EIDEE): This syndrome also presents with frequent drug-resistant seizures that begin ≤3 months of age, similar to EME. However, the exact differential diagnosis between these two conditions can be challenging [6].
  • Myoclonus: Myoclonus is a movement disorder characterized by sudden, brief, shock-like jerks. In some cases, myoclonus can be a symptom of EME or other epileptic encephalopathies [10].

Other Conditions to Consider:

  • Neonatal Seizures: Neonatal seizures can present with similar symptoms to EME, including erratic and fragmentary myoclonias.
  • Absence Seizures: Absence seizures are another type of seizure disorder that may be considered in the differential diagnosis of EME.
  • Myoclonic Status Epilepticus: This condition is characterized by severe mental retardation and continuous abnormal movements, which can be similar to the symptoms seen in EME.

Important Considerations:

  • EEG Results: EEG results play a crucial role in diagnosing EME. The suppression-burst pattern (SB) in EEG is often seen in EME [11].
  • Clinical Presentation: The clinical presentation of EME, including erratic and fragmentary myoclonias, partial seizures, and late tonic spasms, should be carefully considered when making a differential diagnosis.

In conclusion, the differential diagnosis of early myoclonic encephalopathy involves considering several conditions, including Ohtahara syndrome, early infantile developmental and epileptic encephalopathy syndrome (EIDEE), myoclonus, neonatal seizures, absence seizures, and myoclonic status epilepticus. A thorough evaluation of EEG results and clinical presentation is essential for accurate diagnosis.

References:

[6] Early-infantile developmental and epileptic encephalopathy syndrome (EIDEE) is a rare condition characterized by frequent drug-resistant seizures that begin ≤3 months of age. [10] Myoclonus is a movement disorder characterized by sudden, brief, shock-like jerks. [11] Early myoclonic encephalopathy (EME) is a rare epileptic syndrome characterized by erratic and fragmentary myoclonias, partial seizures, and late tonic spasms. [14] Ohtahara syndrome and early myoclonic encephalopathy are the earliest presenting of the epileptic encephalopathies.

Additional Differential Diagnoses

Additional Information

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