<p><a href="https://emedicine.medscape.com/article/1140530-overview" rel="nofollow noreferrer">Medscape</a> defines <a href="https://emedicine.medscape.com/article/1140530-overview" rel="nofollow noreferrer">diffuse</a> as <strong>generalized</strong>, in the context of EEG. Generalized means activity recorded across large portions of the cortex. This opposes <strong>focal</strong> patterns, that occur locally. In turn this is reflected in generalized epilepsy and focal epilepsy. Generalized epilepsias are characterized by gross paroxysmal activity across the cortex, associated with a loss of consciousness. Focal epilepsy is localized in the cortex and stays restricted to one hemisphere and is not associated with a loss of consciousness.  </p>

<p><a href="https://www.ncbi.nlm.nih.gov/books/NBK390357/#_pt6_s1_" rel="nofollow noreferrer">Britton <em>et al</em>. (2016)</a> explain <strong>generalized and focal slowing</strong> in the EEG as follows: </p>

<blockquote>
  <p>The two main types of slowing are focal and generalized slowing. As
  previously discussed, generalized background slowing in the theta and
  delta frequency ranges is a normal finding on EEG when it represents
  developmental slowing [] or the evolution of drowsiness and sleep activity. However, when there is intermittent or persistent focal slowing seen consistently over one head region, or persistent, unvarying, and unreactive focal or generalized slow wave activity in a vigilant adult patient, this slow wave activity should be considered pathologic and indicates
  corresponding focal or generalized cerebral dysfunction or both.</p>
</blockquote>

<p><sub><strong>Reference</strong><br>
<strong>-</strong> <a href="https://www.ncbi.nlm.nih.gov/books/NBK390357/#_pt6_s1_" rel="nofollow noreferrer">Britton <em>et al</em>. The Abnormal EEG. In: St. Louis &amp; Frey (eds). <em>Electroencephalography (EEG): An Introductory Text and Atlas of Normal and Abnormal Findings in Adults, Children, and Infants</em>. Chicago: American Epilepsy Society; 2016</a></sub> </p>

CC BY-SA 4.0
2018-07-04T13:41:30.763Z
2018-07-04T13:41:30.763Z
AliceD
<p><a href="https://www.tnu.ethz.ch/fileadmin/user_upload/documents/Publications/2018/Horvath_Szucs_Csukly_Sakovics_Stefanics_2018.pdf" rel="nofollow noreferrer">Horvath <em>et al</em>. (2018)</a> mention that:</p>

<blockquote>
  <p>The disappearance of posterior dominant alpha rhythm and the diffuse
  slowing in AD (alzheimer disease) are easily detectable EEG signs for the experienced
  eyes.</p>
</blockquote>

<p>What does diffuse slowing mean in this context? I tried searching it up online but I only found papers that take its meaning for granted.</p>

<p><strong>Reference</strong><br>
1. <a href="https://www.tnu.ethz.ch/fileadmin/user_upload/documents/Publications/2018/Horvath_Szucs_Csukly_Sakovics_Stefanics_2018.pdf" rel="nofollow noreferrer">Horvath, A., Szucs, A., Csukly, G., Sakovics, A., Stefanics, G. and Kamondi, A., 2018. EEG and ERP biomarkers of Alzheimer's disease: a critical review. Frontiers in bioscience (Landmark edition), 23, pp.183-220</a></p>

<neuroscience><terminology><eeg><electrophysiology><alzheimer>
What does "diffuse slowing" mean in the context of EEG and Alzheimer's?
MattSt
# What does "diffuse slowing" mean in the context of EEG and Alzheimer's?

(Asked by: username_0 on 2018-07-04)

[Horvath *et al*. (2018)](https://www.tnu.ethz.ch/fileadmin/user_upload/documents/Publications/2018/Horvath_Szucs_Csukly_Sakovics_Stefanics_2018.pdf) mention that:

> The disappearance of posterior dominant alpha rhythm and the diffuse
> slowing in AD (alzheimer disease) are easily detectable EEG signs for the experienced
> eyes.

What does diffuse slowing mean in this context? I tried searching it up online but I only found papers that take its meaning for granted.

**Reference**  
1. [Horvath, A., Szucs, A., Csukly, G., Sakovics, A., Stefanics, G. and Kamondi, A., 2018. EEG and ERP biomarkers of Alzheimer's disease: a critical review. Frontiers in bioscience (Landmark edition), 23, pp.183-220](https://www.tnu.ethz.ch/fileadmin/user_upload/documents/Publications/2018/Horvath_Szucs_Csukly_Sakovics_Stefanics_2018.pdf)

**Tags:** neuroscience, terminology, eeg, electrophysiology, alzheimer


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## 1 answers

### Answer by username_1 on 2018-07-04. Score: 4 | Accepted answer

[Medscape](https://emedicine.medscape.com/article/1140530-overview) defines [diffuse](https://emedicine.medscape.com/article/1140530-overview) as **generalized**, in the context of EEG. Generalized means activity recorded across large portions of the cortex. This opposes **focal** patterns, that occur locally. In turn this is reflected in generalized epilepsy and focal epilepsy. Generalized epilepsias are characterized by gross paroxysmal activity across the cortex, associated with a loss of consciousness. Focal epilepsy is localized in the cortex and stays restricted to one hemisphere and is not associated with a loss of consciousness.

[Britton *et al*. (2016)](https://www.ncbi.nlm.nih.gov/books/NBK390357/#_pt6_s1_) explain **generalized and focal slowing** in the EEG as follows:

> The two main types of slowing are focal and generalized slowing. As
> previously discussed, generalized background slowing in the theta and
> delta frequency ranges is a normal finding on EEG when it represents
> developmental slowing [] or the evolution of drowsiness and sleep activity. However, when there is intermittent or persistent focal slowing seen consistently over one head region, or persistent, unvarying, and unreactive focal or generalized slow wave activity in a vigilant adult patient, this slow wave activity should be considered pathologic and indicates
> corresponding focal or generalized cerebral dysfunction or both.

**Reference**  
**-** [Britton *et al*. The Abnormal EEG. In: St. Louis & Frey (eds). *Electroencephalography (EEG): An Introductory Text and Atlas of Normal and Abnormal Findings in Adults, Children, and Infants*. Chicago: American Epilepsy Society; 2016](https://www.ncbi.nlm.nih.gov/books/NBK390357/#_pt6_s1_)


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