Dr. Manoj Rathi *
Aashirwad Children Hospital,
Mudholkar Peth, Amravati *
|Major Frequency Range 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 PAROXYSMAL ACTIVITY-NEONATAL:
- Multi focal spikes - (non-specific) seizures
- Repetitive spike - Clonic seizure
- Slow delta discharge - Tonic seizure
- 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
|| Mid temporal
||Navigate Symptoms & Seizures
||P Psychomotor & generalized
||Tonic clonic seizures|
(C) METABOLIC, INFECTONS AND TOXIC ETIOLOGIES:
These are diffuse slow waves, decreased frequency of background rhythm.
- Carotid - Frontal and temporal slow waves
- Vertibrobasilar - Temporal and occipital show waves and low amplitude
- Haemorrhage-Sharr J-waves or spikes with slow waves
- Space occupying lesion - highly localized abnormal slow waves
(E) MENTAL & LEARNING DISABILITIES:
Occipital slow waves and extreme spindles
Decreased frequency of back ground rhythm and temporal slow waves on the left side of brain.
|How to Cite URL :|
|Rathi M D.. Available From : http://www.pediatriconcall.com/fordoctor/ Conference_abstracts/report.aspx?reportid=443|