Tuesday, 7 January 2014

Understanding cervical arterial dysfunction (CAD) for clinicians

The publication of the succinctly titled;

‘International framework for examination of the cervical region for potential of Cervical Arterial Dysfunction prior to Orthopaedic Manual Therapy intervention’ (Rushton, et al 2013)

... has highlighted the need for manual therapy clinicians to be cognisant with cervical arterial dysfunction (CAD)

BUT what is that? … and what does it mean to clinicians?

Let us start ... by dealing with what it is NOT
Dissection of an artery
  1. Cervical arterial dysfunction is NOT cervical arterial dissection! That may seem obvious to some, but both acronyms are now in common usage and therefore some confusion may arise. The term dissection is specific to dissection events (see image) and therefore narrow. Cervical arterial dysfunction is a broader term which is all-encompassing of a range of pathologies which may affect the cervico-cranial vasculature. 
  2. CAD is NOT vertebro-basilar insufficiency (VBI). However, it does incorporate it - as one of the component parts of a wider system based approach to thinking about haemodynamics and ischaemia
  3. Above all, CAD is NOT (in isolation) dissection of the vertebral artery. That would simply be a continuation of the narrow thought process which lead us to believe that a single test i.e. the vertebral artery test, could somehow allow us to decide whether cervical manipulation was ‘safe’ or not! That outdated concept has thankfully been de-bunked once and for all, as we move closer to science based practice.

So what is cervical arterial dysfunction then…?

CAD is a consideration of ALL of the potential arterial dysfunctions, which may present to, or ensue from a manual therapy intervention.
CAD is simply a way of thinking about an age old problem in a different way, and more importantly asking ourselves different questions about this familiar problem – linked to RISK and cervical spine management. The emphasis has moved firmly away from just ‘manipulation’, into a consideration of movement per se. This clearly widens the thinking into a consideration of ASSESSMENT (which incorporates movement) as well as intervention, which may incorporate ANY form of manual therapy or exercise prescription. This is then combined with a consideration of ALL of the potential structures and vascular 'dysfunctions'. Thinking is no longer constrained by one structure or pathology.

So why the shift from VBI and vertebral artery dissection …?

Well first of all, there is a lot more to the cervical vasculature than the vertebro-basilar system and there is a lot more to the range of pathologies than just dissection. Dissection or damage to the intimal wall of a vessel is a commonly cited vascular ‘injury’ thought to be associated with cervical spine manipulation in particular. However, an understanding of the basic science of haemodynamics allows us to incorporate many more conditions and pathologies into the paradigm. 

There are a range of reasons why blood vessels may be compromised in the cervico-cranial region, from pre-existing underlying anatomical anomalies, vasospasm, atherosclerotic disease, through to arteritis (i.e. temporal). All of these may lead in different ways, to potential ischaemia which may manifest and a variety of ways, ranging from PAIN, through to blindness, stroke or at worst death.

 Some direction for clinicians:
  • Develop an understanding that there is more to cervical spine risk assessment than a consideration of ‘VBI’ or dissection of the vertebral artery.
  • Consider a ‘systems based’ approach, incorporating the whole cervical vascular system, including the carotid vasculature (and branches) and the whole range of potential pathologies (NOT just dissection).
  • Develop awareness, that whilst commonly cited vascular risk factors have not been shown to be associated with dissection pathologies, they are strongly correlated with atherosclerosis, hypertension and stroke … This is ‘system based thinking’.
  • Develop increased awareness that neck pain and headache may be the early signs of pre-existing vascular dysfunction.
  • Develop an index of suspicion for cervico-cranial vascular pathology, particularly in cases of acute trauma or non-resolving/worsening conditions.
  • Enhance subjective/objective examination by including vascular risk factors such as hypertension, and procedures such as blood pressure, cranial nerve testing and eye examination.
  • Consider carefully the ORDER of your examination in the presence of potential vascular ‘red flags’.
  • Expand manual therapy teaching and practice to include haemodynamic principals and their relationship to movement, handling, anatomy and biomechanics.

Despite all this … when all is said and done, the 64m dollar question still seems to be … Should clinicians perform a ‘vertebral artery test’?

Answer … If they believe it is clinically indicated AND if they understand that its sensitivity and specificity is very poor AND if they don’t use it as their sole decision making point … Then it is just ONE of the things they may wish to incorporate into a balanced vascular assessment.

Note - that cranial nerve and blood pressure testing are additional objective measures to incorporate into the physical examination. Both feature prominently in the IFOMPT framework.

For a more detailed description of this paradigm change see:
A ‘system based’ approach to risk assessment of the cervical spine prior to manual therapy (Taylor & Kerry 2010) http://www.sciencedirect.com/science/article/pii/S1746068910000532

‘International framework for examination of the cervical region for potential of Cervical Arterial Dysfunction prior to Orthopaedic Manual Therapy intervention’ (Rushton, et al 2013)