Review Cerebral Blood Flow in Orthostatic Intolerance, 2025, Muhammad Shahzeb Khan, MD, MSC et al

[Mij]

Abstract
Cerebral blood flow (CBF) is vital for delivering oxygen and nutrients to the brain. Many forms of orthostatic intolerance (OI) involve impaired regulation of CBF in the upright posture, which results in disabling symptoms that decrease quality of life.

Because CBF is not easy to measure, rises in heart rate or drops in blood pressure are used as proxies for abnormal CBF. These result in diagnoses such as postural orthostatic tachycardia syndrome and orthostatic hypotension.

However, in many other OI syndromes such as myalgic encephalomyelitis/chronic fatigue syndrome and long COVID, heart rate and blood pressure are frequently normal despite significant drops in CBF. This often leads to the incorrect conclusion that there is nothing hemodynamically abnormal in these patients and thus no explanation or treatment is needed. There is a need to measure CBF, as orthostatic hypoperfusion is the shared pathophysiology for all forms of OI.

In this review, we examine the literature studying CBF dysfunction in various syndromes with OI and evaluate methods of measuring CBF including transcranial Doppler ultrasound, extracranial cerebral blood flow ultrasound, near infrared spectroscopy, and wearable devices.
LINK

 

[Utsikt]

Are the CBF measuring methods mentioned here valid?

 

[SNT Gatchaman]

Duke/Cornell/Vanderbilt/Karachi/Calgary team.

That's a good review article that describes the techniques: transcranial Doppler US, extracranial Dopper US, and wearables monitoring external carotid artery. NIRS has more limited discussion, being found to be less accurate than the ultrasound techniques. It will be a useful starting point for some mechanistic and technical aspects for a fact sheet on OI, although its reference list is probably mostly already on S4ME.

It's good to see this article in a major cardiovascular journal (Journal of the American Heart Association) and there are some very helpful contextual comments, such as —

OI has been labeled an epidemic since the mid-1990s and yet is still not well understood.

Given the insensitivity of current biomarkers including heart rate and BP for evaluating OI in ME/CFS, many with orthostatic symptoms are misdiagnosed as healthy. CBF monitoring is vital for proper and compassionate care.

It can be argued that the ME/CFS and OCHOS populations are effectively the same population and that they are both severely misdiagnosed as being “objectively normal” if CBF is not monitored.

Without monitoring a proxy for CBF, many of these patients would be labeled as objectively normal, and their symptoms could be incorrectly attributed to psychological causes.

The lack of proper diagnosis of OI stems from the unmet need to provide bedside CBF evaluation.

Because of the poor sensitivity of diagnostic criteria relying on heart rate and BP such as that of POTS and OH, we recommend the incorporation of CBF monitoring as the core diagnostic criteria of cerebral autoregulatory abnormality.

 

[Utsikt]

That’s very good! My cardiologist said I don’t need more treatments because my BP is fine. I tried to tell him about reduced bloodflow to the brain and he wouldn’t listen. Said the body adjusted that on its own.
He’s a nice guy, so he might be concinced to check CBF is they have the equipment.

 

[Dolphin]

ME Research UK:

Continuing on with our recent theme of orthostatic intolerance (symptoms when assuming an upright posture) in ME/CFS

- A review (https://bit.ly/3WQh9PS) highlighted that approximately half of patients who meet symptomatic criteria for orthostatic intolerance do not meet the heart rate and blood pressure thresholds required for a diagnosis of postural orthostatic tachycardia syndrome (PoTS; a specific form of orthostatic intolerance marked by a persistent heart rate increase). Yet this group likely has abnormalities in cerebral (brain) blood flow.

The authors mention that without assessing cerebral blood flow during testing, these patients may be deemed "objectively normal," which increases the risk of their symptoms being misdiagnosed.

The researchers emphasise that cerebral blood flow is a crucial biomarker for orthostatic intolerance. However, they note that standardised CBF monitoring techniques must be established before a "unified diagnostic criteria can be defined and recommended".

Read more: https://bit.ly/4gxWtTK

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