With the advances in pediatric neuroscience, pediatric EEG has become an important investigation. In my article I had discussed interpretational of common neurological disorders.
Major Frequence Ranges of Rhythms :
Electrical activity from the brain consists primarily of rhythms and these rhythms are named according to their frequency in cycles per second (C/sec), also called Hertz Hz).
- Delta refers to all rhythms less than 4 c/sec
- Theta is between 4 to <8 c/sec
- Alpha is between 8 to 13 c/sec.
- Beta is> 13 c/sec.
Normal Background Rhythms-Introduction
Usually, there is one dominant frequency that is called the ‘background rhythm’.
1. Background rhythm in wake
In infants = 4 to 5 c/sec. (Delta and Theta waves)
In children = 5 to 8 c/sec. (Theta)
In adults = 8 to 10 c/sec. (Alpha)
2. Background rhythm is sleep
In light sleep = 5 to 6 c/sec. (Theta)
In deep sleep = 2 to 3 c/sec. (Delta)
(A) Abnormal Patterns – Introduction:
Abnormal patterns are mainly divided into two types:
1. Slow waves and
2. Spikes (or-sharp waves)
Also, depression of normal rhythm’s may be abnormal.
(I) Slow Waves:
Slow waves are rhythms appearing especially during wakefulness that are slower than in the normal. Abnormal slow waves appear when the brain cells are damaged.
(II) Paroxysms: Spikes (Sharp Waves):
The spike (or Sharp wave) is a suddenly appearing electrical explosion that looks like a spike of large nail, spikes are <70 m sec and sharp wave 70 to 200 m sec in duration. These two patterns signify an epileptogenic region of the brain.
(III) Depression of normal Rhythms – Decreased amplitude of any normal rhythms.
Diffuse slow - suggestive of metabolic, toxic, infectious etiologies.
Focal slow-very slow - space occupying lesion.
B) Summary of Abnormal EEG Patterns and associated clinical conditions:
SHARP PAROXYSMALACTIVITY-NEONATAL:
- Multi focal spikes – (non specific) Seizures.
- Repetitive spike-Clonic seizure
- Slow delta discharge-tonic seizure
POST NATAL:
- Hypsarrhythmias-Infantile spasms.
- Slow (1 to 2/sec.) spike and wave-Lennox-Gastaut syndrome (tonic seizure)
- 3.3/sec.spike and wave complex-absence (Multiple spike-generalized tonic clonic seizure)
- Occipital spikes – Visual perceptual disorders
- Centro temporal sharp waves-benign epilepsy of childhood.
- Periodic Lateralized epileptiform discharge – Cerebrovascular emboli and also epilepsia partialis continua, meta static to mores.
- Temporal sharp waves
| Posterior |
Mid temporal |
Anterior |
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| Seizures |
Navigate Symptoms & Seizures |
P Psychomotor & generalized |
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Tonic clonic seizures |
© META BOLIC, INFECTONS AND TOXIC ETIOLOGIES:
These are diffuse slow waves, decreased frequency of back ground rhythm.
(D) VASCULAR:
- Carotid-Frontal and temporal slow waves
- Vertibrobasilar-Temporal and occipital show waves and low amplitude
- Haemorrhage-SharrJwaves or spikes with slow waves
- Space occupying lesion-highly localized abnormal slow waves.
(E) MENTAL & LEARNING DISABVITIES:
Occipital slow waves and extreme spindles.
(F) SENILITY:
Decreased frequency-of back ground rhythm and temporal slow waves on the left side of brain.
