Key messages

• Transcranial laser therapy (low-level light therapy applied to the head) does not reduce the number of people who die or have moderate to severe disability at 90 days after ischaemic stroke (where blood flow to the brain is blocked by a blood clot).

• The existing studies provide insufficient evidence to support the routine use of transcranial laser therapy in people with ischaemic stroke.

What is ischaemic stroke, and how is it treated?

An ischaemic stroke happens when a blood clot blocks an artery in the brain, cutting off blood flow and killing brain cells. Someone having an ischaemic stroke might feel confused, weak, or have trouble talking or moving.

Currently, the main treatments for ischaemic stroke include medicine injected into a vein to dissolve blood clots, and surgery to remove blood clots from brain vessels. Both these options are known as reperfusion therapies: treatments that aim to reopen the blocked blood vessels and restore the blood supply to the brain tissue.

Why is this review important?

The extent of brain injury following ischaemic stroke depends on how long the brain is deprived of oxygen, because brain cells can only survive without oxygen for a limited time. Therefore, reperfusion therapies should be given as early as possible. However, some people who receive reperfusion therapies still have severe disability and may even die. This calls for the exploration of novel treatments.

Transcranial laser therapy is also known as photobiomodulation, low-level light therapy, or near-infrared laser therapy. This noninvasive technology transmits laser energy through the scalp and skull to stimulate healing in the brain. It is considered a promising treatment for improving outcomes after ischaemic stroke.

What did we want to find out?

We wanted to know whether transcranial laser therapy could help to reduce disability and death in people with ischaemic stroke, and whether it was associated with harms.

What did we do?

We searched for studies that compared transcranial laser therapy with sham (fake) therapy or no therapy in people who had had an ischaemic stroke, with or without usual treatment in both groups. We assessed the quality of the included studies, compared and summarised their results, and rated our confidence in the findings.

What did we find?

We included four studies with 1420 people who had had an ischaemic stroke. The included studies were published between 2007 and 2014 and took place in different hospitals in Europe, North America, South America, Asia, or more than one of these continents. Participants were mostly men (59.6%), with an average age of 68.3 years. All were included in the studies within 24 hours after having stroke symptoms.

Compared with sham treatment, transcranial laser therapy results in little to no difference in the number of people with moderate to severe disability or death at 90 days after ischaemic stroke. Transcranial laser therapy may have little to no effect on death rate and improvement of stroke severity, and probably has little to no effect on harms. However, it may reduce serious harms slightly.

What are the limitations of the evidence?

The included studies were generally small and took place at least 10 years ago. There were inconsistencies in the findings between studies, which limited our ability to draw conclusions. One study did not clarify whether the people measuring the outcome knew which group the participants belonged to, which could have influenced how they recorded or interpreted the results relating to moderate to severe disability, improvement of stroke severity, and serious harms.

How up to date is this evidence?

The evidence is current to August 2024.