doppler ultrasound screening of vertebral arteries
TRANSCRIPT
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DOPPLER ULTRASOUND SCREENING OF VERTEBRAL
ARTERIES
Michael HaynesB.Sc.,B.App.Sc.(Chiro).,PhD.
Michael HaynesB.Sc.,B.App.Sc.(Chiro).,PhD.
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INTRODUCTIONPART 1
Background - Basic & clinical science Post-manipulation Stroke• Mechanism• Link• Incidence
PART 2 Doppler ultrasound - rationale & -------------------------- application
Provocational Tests• Validity?
Doppler Ultrasound• Validity/Reliability• Clinical practicality
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PART 1: BACKGROUND
Post manipulation stroke
Mechanism
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Vertebral A approx 48x Int Carotid A post-manipulation strokes
Subclavian artery
Posterior inferior cerebellar arteries (PICA)
Vertebral artery--(VA)
Basilar artery
Carotid artery
Internal carotid…artery (ICA)
Lateral Modified from Cunninghams
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Vertebrobasilar territory
PONSMIDBRAIN
MEDULLA Cerebellum
Occipital lobeBrain stemCerebellar peduncles
superiormiddle
inferior
Cerebralpeduncle
Mid sagittal
Base of brain
Lateral
Cranial nerve nuclei - mainly pons & medulla
V
Dorsal brainstem
Posterior
VIII
Thalamus
Posterior circulation
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Post manipulation stroke
First reported 1934
Mostly no particular syndrome due to variability in -----circulation circ (Frisoni et al, 1990)
Most common syndrome - Postero-lateral medullary-------- -(Wallenburg). PICA First described 1895, same year chiropractic began. (Terrett, 1996)
Most serious syndrome - “Locked in” (Cerebro-medullary - ( ( (rare) bBasilar A spinal disconnection).
First described in “ The Count of Monte Cristo” (re: M. Noitier de ---Villaforte) by Alexandre Dumas, 1844.
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Post manipulation stroke patients
Typically:
- are relatively young, healthy adults
- have little or no risk factors for stroke
- cannot be identified as being at risk from --their history or by standard clinical --examination, including X-ray BUT new ----- --techniques such as Doppler may have -------potential to assist.
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Infarctedarea
PICA
Anterior view of PICA, & brain-stem bent backwards
X section of Medulla
Vertebral A Dorso-lateral medulla
PICAVertebral A
Oclusion of PICA
VIII
Inf. Cerebellar.peduncle
Spinal tract of trigeminal nerve
Lateralmedulla
PICA TerritoryPosterior inferior cerebellarar A. most common VA branch in post manipulation cases
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Post-manipulation Stroke - MRI X section
Anterior
Posterior
Right cerebellar infarction
Sir Charles Gairdner Hospital
Perth, Western Australia
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Arterial dissectionMost commonly identified cause opost manipulation stroke
4 vessel Arteriography:“gold standard” Dx
Sir Charles Gairdner Hospital
Perth, Western Australia
Lateral
Postero-lateral
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Intimal disruption Arterial dissection ---- ICAs 2x VAs
ICA
Thrombus embolus occlusion (may stenose) (carried downstream) (of branch)
Blood tracking under intima
Bloodtracking under intima
Blood flow Thrombus
Intima
Artery wall
Can be delayed
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VA Dissectionsmall large
Intima disrupted Thrombus
Lumen
Clinical presentation- posterior territory stroke: most common - very severe sharp, first time felt, unilateral -neck/head pain (poor indicator by itself)-- prior to onset of neurological deficit: very common- may heal without stroke developing
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• Minor intimal disruption
• Thrombus due to hyper-…coagualability & stenosis
• Vasospasm
Other possible mechanisms
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Summary - Mechanisms
Most common : artery - Vertebral A
branch - PICA
syndrome - Wallenburg: 3Ds And 3Ns
identified cause - arterial dissection BUT
other causes may be important
Dissections 1. Aetiology - intrinsic weakness of arterial wall
Arteriopathies: FMH? Collagen defects?
- Mechanical stresses?
2. Risk factors? - Current OCP use?, Migraine?
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Post manipulation stroke
Link with manipulation
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Stroke & Manipulation Link
Close timing between manipulation & stroke -63% immediate (Terrett, 1996)∴ Unlikely that all cases coincidental Later onset could be due to delayed thrombus propogation or embolism
Cadaveric studies suggesting stresses to Vertebral A during neck motion. (Selecki,1969)
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Stroke & Manipulation Link
Case control studies
• Stroke (dissection/occlusion) in patients …. < 45 yo attended chiropractors for neck ….complaint. ,, ,,(Rothwell et al, 2001)
Limitations - confounding factors
• Stroke (dissection) in patients who had neck ---manipulation (Smith et al, 2003)
Limitation - selection bias ?
Link unproven BUT high index of suspicion
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Strokes coincidental with manipulation?-Due to weak arterial wall only?
Spontaneous dissections similar to minor trauma eg manipulation cases (Mas et al, 1987)
BUT Major difference-
Spontaneous cases ICAs 2x VAs --------Manipulation cases VAs 48x ICAs
Stretch on VAs: Neck manipulation < cervical ROMs (Symons et al, 2002)
BUT Extremely poor experiment design eg: Wrong testing locations, No full rotation manip
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Causes VA stenosis/stress morethan other cervical motions.
Most -cervical rotation at C1/2
- motion at C1/2 is rotation
C1/2 >>Lower Cervical:
Rotational stenosis &Minor trauma (eg manipulation)-dissections
Contralateral >> Ipsilateral
Effects of cervical rotation
Symons et al tested here - wrong side & location!
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Effects of cervical rotation
C1/2 rotation (>35o) = rotational stenosis --(MRA studies by Dumas et al, 1996)
Full Rotational manipulation likely riskProposed Definition : Head rotated passively = or >--------------------end range
Chiropractors do use full rotational techniques - BUT uncommon in Perth (Haynes, 1996)
BUT most post manipulation strokes in Perth-involved rotation (Heye et al, 1995)
Symons et al needed to check for full rotational -manipulation but didn’t.
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BIOMECHANICAL STUDIES VA ROTATIONAL STENOSIS
METHOD : Duplex US only studies : 20 participants
MRA & Doppler studies : 13 participants
Cadaveric studies : 1 specimen
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VA Cadaveric StudiesNeutral Contralateral rotation Ipsilateral rotation
C1/2 curves straightening, no stretch Adding slack
Compression
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Colour US duplex scan upper cervical VA - Neutral
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Colour US duplex scan upper cervical VA - Rotation
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MRA 3D VIEWS
QuickTime™ and aCinepak decompressor
are needed to see this picture.
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MRA Studies of VAs
Neutral
Rotation Contralateral
Note straightening of C1/2 curves,no stretch, no compression
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VAs usually well designed for neck rotation
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• 60% reduction lumen cross sectional area -Doppler
• Causes jetting effect at site without affecting blood flow, (like putting a finger over the end of a hose that is turned on)
OR just major decrease
VA Rotational Stenosis (Marked)
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Marked rotational stenosis
VA Doppler spectral waveforms
Neutral
Full contralateral rotation
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MODELLING STUDIES
1. Compression or kinking precedes stretch induced by -----..rotation.
2. Stretching insufficient to cause Doppler signals to be -- -markedly affected.3. Effect of C1/C2 rotation offset by: a) curves in VA --------------------------------------b) lateral flexion C1/C24. Increasing intramural pressure decreases compression
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CLINICAL RELEVANCE
Cervical movement usually causes little stress to VAs, so manipulation unlikely to cause injury.
Rotational stenosis due to faulty biomechanics eg inadequate VA curves & C1/C2 lat flexion.May risk of injury from manipulation.
Detecting this indicates compression & ∴early warning prior to injurious stretch.
Repeated compression may weaken artery similar to popliteal artery entrapment syndrome. FMHpredilection for VA at C1/2 ?
Doppler findings are affected by blood pressure - needs measuring in case hypertension masks stenosis
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Marked Rotational StenosisHealthy participants
5% VAs (n=280) - Doppler (Haynes, 1996) ii 7% VAs (n=79) - arteriography (Faris et al, 1963)
TIA vertebrobasilar patients33% VAs (n=60) - Doppler (Arnetoli et al, 1989)
56% VAs (n=64) - MRA (Weintraub & Khoury, 1995)
Independent risk factor for VB stroke…………………………...
TIA patients0.5% ICAs (n=1638) - arteriography (Opala & Arkuszewski, ‘89)
VAs >> ICAsMay explain why VAs >> ICAs in post manip stroke
-----------despite ICAs >> VAs in arterial dissectionsT
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Summary - Link
Growing body of clinical & biomechanical circumstantial evidence suggests that neck manipulation may at least trigger some cases of stroke, due to increased stress to VA. No evidence which contradicts this.
2 case control studies provide more direct evidence, but have limitations - inconclusive. BUT high index of suspicion. Clinically wise to accept link - for safety of patients.
VA design & C1/2 biomechanics generally protect from injury. Abnormalities can cause stress, indicated by rotational stenosis - needs to be screened prior neck manipulation.
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Post manipulation stroke
Incidence
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Incidence
Accurate rate unavailable - probably impossible to determine due to rarity (Rothwell et al ,2001)
Great difficulty retrieving all cases.
Note: true incidence of stroke in general not obtained until last 10-15 years.
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Incidence Estimates
1/100,000 - (Australia): Haynes, 1994, 2006
- (USA): Dabbs & Lauretti, 1995
- (Canada): Rothwell et al, 2001
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Comparative safety
Medical iatrogenesis alarming statistics very serious problem.
USA preventable hospital deaths (annual rate = 120,000) equivalent to a jumbo jet crash every day!
Available data suggests that cervical manipulation is relatively safe, no evidence to the contrary, & growing evidence that it is effective.
Neck manipulation is appropriate for most
chiropractic patients BUT not all.
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Incidence of post- manipulation stroke Summary
- Precise incidence is unknown.
- Generally accepted that most severe casesrare - so cervical manipulation is safe in-the vast majority of cases.
- Is probably more common than many------ --chiropractors realize.
- Not so rare as to excuse chiropractors --- -from using reasonable, best evidence--- -----approach to reduce risk, especially since -- -stroke is so so serious.