Sleep Spindles
Posted on
February 17, 2023
Let's learn all the facts about a brain pattern called
Sleep Spindles
!
Sleep Spindles
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EEG Sample Credit: The Learning EEG (learningeeg.com)
Sleep spindles happen intermittently and stage II sleep (N2) is marked by sleep spindles and K complexes and can persist into slow wave sleep.
Sleep spindles have a frequency of 12-14Hz, with a low amplitude, occurring in the central head region in a fusiform morphology. They arise from the reticular nucleus of the thalamus. Normally sleep spindles are symmetrical and synchronous aside from newborns, developing post term at approximately 2 months of age. Many EEG patterns are asynchronous in preterm newborns. Sleep spindles are typically asynchronous until 1- 2 years of age. They can also appear exaggerated in children.
The absence of spindles, or an asymmetry of their formation or frequency, should be considered abnormal. Oftentimes focal features do not present themselves in an awake EEG but appear in sleep and are depressed. On the other spectrum extreme high voltage over 200μV spindles that are generalized with an anterior dominance and a fast activity such as continuous sleep spindles (extreme spindles) are likely indicating brain damage.
Persistent and totally asynchronous activities including sleep spindles have been noted in patients with Aicardi’s syndrome. Clinically, the Aicardi’s syndrome is characterized by flexion spasms (infantile spasm), chorioretinal abnormalities, and agenesis of corpus callosum, seen exclusively in girls. People with Aicardi syndrome have absent or underdeveloped tissue connecting the left and right halves of the brain (agenesis or dysgenesis of the corpus collosum). They have seizures beginning in infancy (infantile spasms), which tend to progress to recurrent seizures (epilepsy) that can be difficult to treat. Affected individuals also have chorioretinal lacunae, which are defects in the light-sensitive tissue at the back of the eye (retina).
People with Aicardi syndrome often have additional brain abnormalities, including asymmetry between the two sides of the brain, brain folds and grooves that are small in size or reduced in number, cysts, and enlargement of the fluid-filled cavities (ventricles) near the center of the brain. Some have an unusually small head (microcephaly). Most affected individuals have moderate to severe developmental delay and intellectual disability, although some people with this disorder have milder disability.
Another example of asynchronous sleep patterns (spindle, vertex sharp waves, and K complex) may be seen in patients with obstructive hydrocephalus.
