As soon as a stroke strikes, neurons in the affected area, who are deprived of oxygen, begin to die; each second costs as many as 32,000 neurons, 230 million synapses, and 200 meters of axons. In terms of minutes, each passing minute costs 1.9 million neurons, 13.8 billion synapses, and 12 kilometres of axonal fibres1.

Stroke kills 32,000 neurons each passing second.

Saver J.L. (20051)

So, every second counts when a stroke hits; that is why “Time is Brain”. 

This image illustrates the importance of time in emergency stroke care.
Time matters when a stroke hits.

“Time is Brain”, but only as a general rule

As far back as 1993, Dr Camilo R. Gomez2 coined this exhortation – “Time is Brain” – in an editorial to the Journal of Stroke and Cerebrovascular Diseases.  


There is a caveat.

In 2018, Dr Gomez3 updated his “Time is Brain” slogan!


It is because the neurons and other brain cells’ dying speed is not linear. It depends on the affected person’s collateral system.

What does that mean?

We all have a backup blood supply mechanism, just in case. When the main supply route is blocked, our alternate support system gets activated. We still do not know how wide this mechanism operates. What we do know is that its spread varies from person to person.

In other words, the “Tims is Brain” slogan is still valid. We should act F.A.S.T. even the golden hour elapses.

The critical time of no return

How long a neuron can survive after a stroke?

I had this question when I began writing this post.

I found an answer.

As far back as 1981, Jones and a team of researchers have attempted to answer this question using monkeys. They found no irreversible damage when blood supply restores in 30 minutes (Jones et al. 19814).
Then, there was another significant finding!

When blood supply was not blocked – only reduced to 12, 18ml/100g/min (this is called mild-moderate ischemia) – even after 2 – 3 hours, the affected cells survived! That means only when the blood supply was reduced to less than 10-12ml/100g/min the damage was irreversible (Jones et al. 1981).

Within the first 3 – 8 days after a stroke, the affected area swells more than the volume of this area. Then, re-organisation and retraction remove the dead tissues resulting in an amount smaller than the pre-affected brain area within the next two weeks to 3 months time (Saver J.L. 2005).   

Would you like to add anything to this post? Please do.


  1. Saver J.L. (2005). Time is brain – quantified. Stroke. 2005;37:263–266.
  2. Gomez C.R. (1993). Time is Brain. J Stroke Cerebrovas Disc. 3(1):1-2. 
  3. Gomez. C.R. (2018). Time Is Brain: The Stroke Theory of RelativityJournal of Stroke and Cerebrovascular Diseases, 27 (8):2214-2227.
  4. Jones TH, Morawetz RB, Crowell RM, Marcoux FW, FitzGibbon SJ, DeGirolami U, et al.. Thresholds of focal cerebral ischemia in awake monkeys.J Neurosurg. 1981;54:773–782.

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