Download CT Perfusion for Brain Death Confirmation

Neuroimaging in Brain Death:
CT Perfusion in comparison with
other ancillary imaging tests
Dr. Derek MacDonald, Dr. Jai Shankar
Poster #: eP-39
Control #: 2304
Disclosures
• None
Purpose of Brain Death Confirmation
• The goal is timely resolution
• Unnecessary/ harmful treatment for patient; closure for families
• Expedite organ transplantation (prerequisite)
• Reduce costs
• Brain death etiology
• Adults – TBI, SAH
• Children – Abuse, MVC’s, Asphyxia
• Definition has progressed from 1959 coma dépassé
• “irreversible coma” – lost consciousness, brainstem reflexes, respiration, flat EEG’s
Brain Death (BD) in Canada
• In Canada, 2 physicians must determine
• Deep unresponsive coma with established etiology, absence of reversible conditions
• Absent brainstem reflexes (gag/ cough, bilateral absence of corneal response, pupillary
response to light, vestibulo-ocular response)
• Absent respiratory effort based on apnea test
• Absent confounding factors
• Ancillary testing often required due to…
• Unresuscitated shock, hypothermia (<34⁰ in Canada), severe metabolic abnormalities/
disorders, peripheral nerve or muscle dysfunction, complex spinal reflexes
• Drugs (EtOH, barbiturates, sedatives, neuromuscular blockade agents)
• High cervical spine injury, craniofacial trauma
• Failed apnea test
Ancillary Testing
• Various modalities (cerebral blood flow or bioelectrical activity):
•
•
•
•
•
•
•
EEG
Cerebral angiography*
Nuclear Med*
Transcranial Doppler
CTA
MRA
CTP – particular utility in brainstem evaluation
• Clinical judgement is deciding factor
L Vert
Cerebral Angiography in BD
• Gold standard, 1st used CBF modality
• 4 vessel angiogram; anterior & posterior
circulation evaluation
• No intracerebral filling detected at level of entry
into the skull of carotid or vertebral artery
• External carotid filling
• Invasive, availability, costly, contrast,
requires expertise
32 F, woke with large L MCA territory stroke
L CCA
Nuclear Medicine in BD
• Gold standard, radionuclide angiography
(Tc99m HMPAO)
• Isotope injection 30 min after
reconstitution
• Immediate, 30-60 min, 2 hr delay images
• “hollow skull/ empty light bulb” sign
= no uptake
• Associated time delay, availability
• May not be detecting brainstem activity
59 F, TBI. Pedestrian hit by
sideview mirror of truck
Electroencephalogram
Transcranial Doppler
Ultrasonography
• EEG in BD demonstrates loss of
bioelectrical activity
• Bilateral insonation of intracerebral
(including vertebral/ basilar)
arteries
• Used for BD confirmation since
1959
• Absent flow, reversed diastolic flow,
small systolic spikes
• Non-invasive, portable
• Non-invasive, portable
• No longer recommended
• Electrical interference
• Unable to detect deep cerebral or
brainstem function
• Operator-dependent/ technical
expertise
MR Angiography in BD
• Intracranial arterial flow voids
• No contrast required
23 M, punched in head, fell & hit head
• Availability, cost, associated
time delay, life-sustaining
equipment in MR zone
Non-enhanced CT in BD
• Loss of grey-white differentiation, edema
• Cannot assess intracranial flow
• Contrast-enhanced acquisition too
delayed compared to CT angiography
• 5 minutes with CECT versus 12-16 seconds
with CTA
• Slow diffusion causing late opacification not
representative of viable brain
47 F, Anoxic injury after found unresponsive
19 M, TBI. Gunshot, no exit wound
CT Angiography in BD
• Quickly replacing all modalities
• Fast, non-invasive, available
• Protocol variation
• Large vessel perfusion
• Demonstrate absence of
intracranial flow, but presence of
extracranial flow
• Non-opacification is a late
phenomenon
5 days & a frontal craniectomy later
CT Perfusion in BD
• Brainstem evaluation – ‘absence of brainstem reflexes/ function’
• Small vessel perfusion
• Absence of intracranial flow, but presence of extracranial flow
• Availability, timely, but currently post-processing data variation
• CTP advantage
• other ancillary tests demonstrate only global absence of CBF
• research has demonstrated the utility of CTP in BD
• brainstem activity can be measured by CTP (functional data)
• Can detect severe hypoperfusion (2%, 1.2 ml/100g/min) from absence (0%)
• Normal CBF 50-60
• < 35 cessation of neuronal protein synthesis, < 20 synaptic transmission modified
• < 10 = irreversible damage and neuronal death
CTP
• Small vessel perfusion (arterioles, capillaries, venules)
• TTP (MTT) = time it takes for blood to perfuse through tissue (seconds)
• CBF = blood flow rate (ml/ 100 g/ min)
• CBV = blood flow volume (ml/ 100 g)
• Technique
• 9.6 cm coverage (“shuttle mode”), 80 kV, 100mAs, 128 x 0.6 mm collimation
• Total scan time 110 seconds, start delay 5 seconds (DLP 2220 mGy-cm)
• Total contrast 40 ml Isovue-370, rate 5 ml/s, saline flush 40 ml
• Perfusion analysis performed if intracranial arteries seen on source images
• Color-coded perfusion maps for TTP (MTT), CBF, and CBV
23 F Diffuse hypoxic injury post cardiac arrest
CBF
CBV
25 M, TBI.
Fell out of
vehicle at
25km/hr
2013 Study (Shankar & Vandorpe)
• 11 patients clinically suspected of brain death
• CTP
• CTA derived from CTP data for anatomic information
• All 11 showed no or matched decrease in CBF and CBV
• 100% sensitivity
• 9 showed none
• 2 showed brainstem death, but residual flow to rest of brain
• Later declared BD
• Early declaration of brain death possible with CTP (timely resolution)
Purpose of Current Study
• Was CTP useful locally for confirming brain death?
• If brain death was confirmed:
• When did withdrawal of life-sustaining care occur?
• Was it because of brain death confirmation?
Materials and Methods
• Data from brain-death confirmation studies past 10 years
• 49 patients
• Imaging studies
• CTP, CTA, CT Head, Nuc Med, cerebral angiogram, MR
• “brain death, neurological determination of death, NDD”
• CTP
• # cases
• Brain death Y/N
• Withdrawal of life-sustaining care
Results
• Pt demographics
• Age range: 16 – 74, mean - 43
• Gender: 19 F, 30 M
• Diagnosis
•
•
•
•
•
•
Anoxic injury – 18
TBI - 15
SAH – 9
ICH – 7 (three also SAH)
Stroke – 2
Meningitis - 1
Modalities
Modality
#
Brain Dead
on Imaging
Not Brain Dead
on Imaging
CTP (2011)
22
12
10
CTA
20
14
6
Nuc Med
15
13
2
Angiogram
2
2
-
MR
1
1
-
CT Head
2
-
-
CTP Results
Modality
#
Brain Dead
on Imaging
Clinically BD
Not Brain Dead
on Imaging
Not Clinically BD
CTP
22
12
12
10
10
CTA
20
14
16
6
4
Nuc Med
15
13
13
2
2
• Nuc Med: 100% sensitivity, specificity, PPV, NPV
• CTA: 87.5% sens, 100% spec, 100% PPV, 67% NPV
• CTP: 100% sens, spec, PPV, NPV
• CTP demonstrated BD for 2 patients for which CTA did not
• CTP demonstrated not BD for 1 patient, clinical decision was reevaluated and reversed
• Further analysis of withdrawal of life-sustaining care (22 patients)
Limitations & Future Applications
• Small number of cases
• Difficult to further study when families/ clinicians not keen to have patient undergo
multiple imaging modalities
• No children included
• CTP results may require collaborative expert opinion in BD determination
• Multimodal evaluation of brain death
• Collaborative efforts amongst centers
• CTP in Trauma?
• Added time, cost, & contrast BUT potential timely resolution & cost reduction
Conclusions
1) Multiple imaging modalities used to assess for brain death when
clinical picture unclear
• Cerebral angiogram, nuclear medicine studies are gold standard
• CTA, CTP evolving to become preferred tests
2) CTP useful ancillary tool in brain(stem) death confirmation
• Extracranial flow must be seen
3) Clinical judgement is deciding factor if faced with discrepant results
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