Pathognomonic EEG Patterns

Epilepsy Syndromes

• Epilepsy syndrome: a group of signs or symptoms that help identify a unique medical condition, characterized by specific signs or symptoms, type of seizure(s), age when seizures start, and pattern on EEG.
• Types of epilepsy syndromes:
  • Symptomatic/Encephalopathic
  • Progressive and Infantile Myoclonic Epilepsies
  • Focal
  • Idiopathic
  • Febrile Seizure

Infantile Spasms and West Syndrome

• Infantile Spasms: flexor, extensor, lightning, or nods—most are mixed, onset 4-8 months, peak 5 mo.
• West Syndrome: triad of infantile spasms, hypsarrhythmia, and developmental delay, onset 4-7 months, always before 1 year old, boys>girls.
• Etiology: 75-85% symptomatic, 15-25% asymptomatic, underlying conditions include genetic, metabolic, congenital infection, and neonatal infection.
• Treatment: steroids, vigabatrin, ketogenic diet, zonisamide, vitamin B6, prognosis partly based on early treatment, but typically poor.

Lennox-Gastaut Syndrome

• Triad: multiple seizures types, cognitive dysfunction, and slow GSW (1.5-2 Hz) on EEG.
• Onset: 1-8 years, typically 3-5 yr, 10-25% cases preceded by infantile spasms.
• Causes: 70-78% structural/metabolic, 30-22% unknown, family history of epilepsy in 3-30%.
• Prognosis: overall refractory to ASDs and poor prognosis.

Severe Myoclonic Epilepsy of Infancy (SMEI)

• Prolonged febrile seizures in the 1st year of life, seizure-free period followed by myoclonic seizures at 1-4 yr old.
• Normal early development, then later deterioration, pyramidal signs and ataxia.
• EEG: slow SW, polyspike-and-wave, 70-80% mutation in SCN1A.

Myoclonic Astatic Epilepsy (MAE) or Doose Syndrome

• Type of generalized epilepsy, onset 1-5 years old.
• EEG: 2-3 Hz gen SW, polyspike and 4-7 Hz central/vertex rhythmic theta activity.
• MRI: normal, associated with SCN1A mutation, boys>girls (2:1).
• Prognosis: typically poor with severe intellectual disability, ataxia, poor motor function, dysarthria, and poor language development.

Epileptic Encephalopathy with Continuous Spike and Wave During Sleep (CSWS)

• Epileptiform activity occupying >85% of NREM sleep, 2 syndromes: Landau-Kleffner Syndrome (LKS) and CSWS.
• Landau-Kleffner Syndrome: typically age 3-10 y, sudden or gradual aphasia, verbal auditory agnosia, 2/3rd have seizures, ADHD.
• CSWS: global regression in cognition and behavior, majority of patients have seizures, may have identifiable pathology.

Panayiotopolous Syndrome (Early Childhood Onset “Occipital” Epilepsy)

• Seizures: behavioral agitation, headache, autonomic symptoms, and motor (hemi-clonic or GTC), prolonged and nocturnal (2/3).
• Interictal EEG: occipital spikes in sleep (classic), 85% have boys, frequent absence seizures (pyknolepsy).

Absence Epilepsy

• Not fully understood, abnormal oscillatory rhythms are believed to develop in thalamocortical pathways.
• Treatment: ethosuxamide, lamotrigine, valproic acid, double-blinded RCT compared the 3 and found ethosuxamide provides the best combo of seizure control and fewest attentional side effects.

Juvenile Absence Epilepsy

• Onset 10-17 years old, less frequent absence seizures, more associated with GTCs, less severe impairment in consciousness.

Juvenile Myoclonic Epilepsy

• Onset 12-18 years old, seizures upon awakening in AM or after nap, triggers: sleep deprivation, stress, fatigue, and alcohol.
• EEG: interictal high amplitude, generalized 4-6 Hz polyspike and wave, 30% have photosensitivity, 40-50% with family history.

Genetic Epilepsy and Febrile Seizures Plus (GEFS+)

• FS after 6 yr old OR occurrence of other seizure types, almost any type of seizure can occur, associated mutations SCN1A, SCN1B, GABRG2.

Epilepsy Disorders with Pathognomonic EEG Patterns

• Pathognomonic: of a sign or symptom, specifically characteristic or indicative of a particular disease or condition.
• Types of pathognomonic EEG patterns:
  • Periodic
  • Rhythmic
  • Other

Crutzfeldt-Jakob Disease (CJD)

• Rapidly progressive, invariably fatal neurodegenerative disorder, EEG: generalized periodic discharges, myoclonic jerks, and variations do occur.

Subacute Sclerosing Panencephalitis (SSPE)

• Progressive neurological disorder, EEG: generalized periodic discharges of longer interval than CJD, bilaterally synchronous, high-amplitude spike or slow-wave bursts.

Herpes Encephalitis

• Rare neurological disorder, EEG: lateralized periodic discharges (LPDs), bihemspheric independent discharges (BiPDs) are sometimes seen.

Anti-NMDA Receptor Encephalitis

• Autoimmune encephalitis, EEG: extreme delta brush, often seen with more prolonged illness.

Angelman Syndrome

• Neurodevelopmental disorder, EEG: notched delta, small interstitial deletion between 15q11 and 15q13, maternally derived.

Epilepsy Syndromes

• Epilepsy syndrome: a group of signs or symptoms that help identify a unique medical condition, characterized by specific signs or symptoms, type of seizure(s), age when seizures start, and pattern on EEG.
• Types of epilepsy syndromes:
  • Symptomatic/Encephalopathic
  • Progressive and Infantile Myoclonic Epilepsies
  • Focal
  • Idiopathic
  • Febrile Seizure

Infantile Spasms and West Syndrome

• Infantile Spasms: flexor, extensor, lightning, or nods—most are mixed, onset 4-8 months, peak 5 mo.
• West Syndrome: triad of infantile spasms, hypsarrhythmia, and developmental delay, onset 4-7 months, always before 1 year old, boys>girls.
• Etiology: 75-85% symptomatic, 15-25% asymptomatic, underlying conditions include genetic, metabolic, congenital infection, and neonatal infection.
• Treatment: steroids, vigabatrin, ketogenic diet, zonisamide, vitamin B6, prognosis partly based on early treatment, but typically poor.

Lennox-Gastaut Syndrome

• Triad: multiple seizures types, cognitive dysfunction, and slow GSW (1.5-2 Hz) on EEG.
• Onset: 1-8 years, typically 3-5 yr, 10-25% cases preceded by infantile spasms.
• Causes: 70-78% structural/metabolic, 30-22% unknown, family history of epilepsy in 3-30%.
• Prognosis: overall refractory to ASDs and poor prognosis.

Severe Myoclonic Epilepsy of Infancy (SMEI)

• Prolonged febrile seizures in the 1st year of life, seizure-free period followed by myoclonic seizures at 1-4 yr old.
• Normal early development, then later deterioration, pyramidal signs and ataxia.
• EEG: slow SW, polyspike-and-wave, 70-80% mutation in SCN1A.

Myoclonic Astatic Epilepsy (MAE) or Doose Syndrome

• Type of generalized epilepsy, onset 1-5 years old.
• EEG: 2-3 Hz gen SW, polyspike and 4-7 Hz central/vertex rhythmic theta activity.
• MRI: normal, associated with SCN1A mutation, boys>girls (2:1).
• Prognosis: typically poor with severe intellectual disability, ataxia, poor motor function, dysarthria, and poor language development.

Epileptic Encephalopathy with Continuous Spike and Wave During Sleep (CSWS)

• Epileptiform activity occupying >85% of NREM sleep, 2 syndromes: Landau-Kleffner Syndrome (LKS) and CSWS.
• Landau-Kleffner Syndrome: typically age 3-10 y, sudden or gradual aphasia, verbal auditory agnosia, 2/3rd have seizures, ADHD.
• CSWS: global regression in cognition and behavior, majority of patients have seizures, may have identifiable pathology.

Panayiotopolous Syndrome (Early Childhood Onset “Occipital” Epilepsy)

• Seizures: behavioral agitation, headache, autonomic symptoms, and motor (hemi-clonic or GTC), prolonged and nocturnal (2/3).
• Interictal EEG: occipital spikes in sleep (classic), 85% have boys, frequent absence seizures (pyknolepsy).

Absence Epilepsy

• Not fully understood, abnormal oscillatory rhythms are believed to develop in thalamocortical pathways.
• Treatment: ethosuxamide, lamotrigine, valproic acid, double-blinded RCT compared the 3 and found ethosuxamide provides the best combo of seizure control and fewest attentional side effects.

Juvenile Absence Epilepsy

• Onset 10-17 years old, less frequent absence seizures, more associated with GTCs, less severe impairment in consciousness.

Juvenile Myoclonic Epilepsy

• Onset 12-18 years old, seizures upon awakening in AM or after nap, triggers: sleep deprivation, stress, fatigue, and alcohol.
• EEG: interictal high amplitude, generalized 4-6 Hz polyspike and wave, 30% have photosensitivity, 40-50% with family history.

Genetic Epilepsy and Febrile Seizures Plus (GEFS+)

• FS after 6 yr old OR occurrence of other seizure types, almost any type of seizure can occur, associated mutations SCN1A, SCN1B, GABRG2.

Epilepsy Disorders with Pathognomonic EEG Patterns

• Pathognomonic: of a sign or symptom, specifically characteristic or indicative of a particular disease or condition.
• Types of pathognomonic EEG patterns:
  • Periodic
  • Rhythmic
  • Other

Crutzfeldt-Jakob Disease (CJD)

• Rapidly progressive, invariably fatal neurodegenerative disorder, EEG: generalized periodic discharges, myoclonic jerks, and variations do occur.

Subacute Sclerosing Panencephalitis (SSPE)

• Progressive neurological disorder, EEG: generalized periodic discharges of longer interval than CJD, bilaterally synchronous, high-amplitude spike or slow-wave bursts.

Herpes Encephalitis

• Rare neurological disorder, EEG: lateralized periodic discharges (LPDs), bihemspheric independent discharges (BiPDs) are sometimes seen.

Anti-NMDA Receptor Encephalitis

• Autoimmune encephalitis, EEG: extreme delta brush, often seen with more prolonged illness.

Angelman Syndrome

• Neurodevelopmental disorder, EEG: notched delta, small interstitial deletion between 15q11 and 15q13, maternally derived.