Brain death: Radiologic signs of a non-radiologic diagnosis

Ancillary tests for brain death

Background

Ancillary tests are often used in the determination of death by neurologic criteria (DNC), especially when the clinical examination is inconclusive. DNC is widely accepted, as defined by the comprehensive report of the World Brain Death Project. However, there are several medical, legal, religious, ethical, and social controversies. Accordingly, "premature" and "delayed" diagnoses of brain death attract these issues.

Methods

Depending upon the availability and experience of the managing medical teams, various ancillary tests are employed for an early and supplementary diagnosis of brain death.

Results

We describe the practicality, test performance, and utility of some of the commonly employed ancillary tests for the diagnosis of brain death in clinical practice, along with their case examples.

Conclusion

Brain death is a clinical diagnosis determined by history, physical examination, and adherence to recommended criteria. All ancillary investigations are used as supplementary tests with variable accuracy parameters. These ancillary tests often facilitate an early and "timely" diagnosis of brain death.

Brain death in children: is computed tomography angiography reliable as an ancillary test?

BACKGROUND

The diagnosis of brain death is primarily clinical. Sometimes ancillary tests are needed.

OBJECTIVE

This study compared sensitivity and interobserver agreement of the 10-, 7- and 4-point CT angiography scoring systems for the diagnosis of brain death in children.

MATERIALS AND METHODS

CT angiography examinations of 50 pediatric patients with a clinical diagnosis of brain death were evaluated according to 10-, 7- and 4-point scoring systems. Images were evaluated by two radiologists who considered the vessel opacification first in the arterial phase (A₀-V₅₀) and then in the venous phase (A₀-V₅₀). We evaluated interobserver agreement for the assessment of vessel opacification and diagnosis of brain death. We compared the differences among brain death diagnoses between children with craniotomy-craniectomy defects, open fontanelles and preserved bone integrity. We subdivided children into two groups according to age: ≤ 2 years and > 2 years. We calculated sensitivities according to age groups.

RESULTS

Using the clinical exam as the reference standard, we found sensitivities for 10-, 7- and 4-point scoring systems to be 70%, 88% and 92% in the A₀-V₅₀ method and 40%, 82% and 82% in the A₅₀-V₅₀ method, respectively. Percentage agreement between readers was 78% for the 7-point scale using the A₀-V₅₀ method and more than 90% for other scoring systems for both the A₀-V₅₀ method and the A₅₀-V₅₀ method. The sensitivity was much lower in children with open anterior fontanelles compared to the groups with preserved bone integrity and with a craniotomy-craniectomy defect.

CONCLUSION

Just as in adult age groups, in children the 4-point scale appears to be more sensitive than the 10- and 7-point scales for CT angiography-based assessment of brain death. Because the scoring systems have similar sensitivities, they could be used as ancillary tests in pediatric cases.

AC, da Cruz Jr. LCH. The role of neuroimaging in the determination of brain death

Brain death is the irreversible cessation of all brain function. Although protocols for its determination vary among countries, the concept of brain death is widely accepted, despite ethical and religious issues. The pathophysiology of brain death is related to hypoxia and ischemia in the setting of extensive brain injury. It is also related to the effects of brain edema, which increases intracranial pressure, leading to cerebral circulatory arrest. Although the diagnosis of brain death is based on clinical parameters, the use of neuroimaging to demonstrate diffuse brain injury as the cause of coma prior to definitive clinical examination is a prerequisite. Brain computed tomography (CT) and magnetic resonance imaging (MRI) demonstrate diffuse edema, as well as ventricular and sulcal effacement, together with brain herniation. Angiography (by CT or MRI) demonstrates the absence of intracranial arterial and venous flow. In some countries, electroencephalography, cerebral digital subtraction angiography, transcranial Doppler ultrasound, or scintigraphy/single-photon emission CT are currently used for the definitive diagnosis of brain death. Although the definition of brain death relies on clinical features, radiologists could play an important role in the early recognition of global hypoxic-ischemic injury and the absence of cerebral vascular perfusion.

Possible additional MRI markers for critical brain swelling with increased intracranial pressure in children?

A retrospective study was performed evaluating the volume and T2/T1 signal intensity of orbital fat in five children diagnosed with severe global brain swelling and confirmed cessation of cerebral perfusion. Imaging showed a volume increase (five of five) and a heterogeneous T2-hypointensity of orbital fat (four of five). This preliminary study suggests that swelling and T2-hypointensity of orbital fat may be a marker of global brain swelling and/or increased intracranial pressure.

Acute cerebral compression caused by an epidural hematoma associated with cryptococcosis in a dog

OBJECTIVE

To describe acute cerebral compression caused by an epidural hematoma (EDH) in a dog with cryptococcal infection.

CASE SUMMARY

An 18-month-old neutered male Neapolitan Mastiff was found comatose with no preceding clinical signs apart from a mild forelimb lameness. A CT scan of the head revealed a lesion within the right caudal nasal cavity that traversed the cribriform plate in addition to a right epidural lesion resulting in compression of the right cerebrum. Assessment of brain death was made based on the presence of coma, apnea, and absence of brain stem reflexes and included assessment of the vestibulo-ocular reflex. Postmortem identified a large EDH causing marked compression of the right frontal lobe. A nasal biopsy cultured Cryptococcus gattii.

NEW OR UNIQUE INFORMATION PROVIDED

EDH formation in a dog secondary to cryptococcosis has not been previously reported. This is also the first time a caloric vestibulo-ocular reflex assessment has been reported in a dog.

Computed tomography angiography scoring systems and the role of skull defects in the confirmation of brain death

To assess and compare all current computed tomography angiography (CTA) scoring systems for the diagnostic workup of brain death (BD) to digital subtraction angiography (DSA) and clinical tests. Fifty-two patients with a clinical suspicion of BD underwent CTA and subsequently DSA. The diagnostic performance of all current CTA scoring systems was compared to that of DSA, in all patients with a suspicion of BD. A comparison to clinical tests was made only in DSA-positive for BD patients (n = 49), since in DSA-negative BD patients (n = 3) clinical tests were not performed. Further subgroup analysis was performed in relation to skull defects (SDs) stratification. Statistical analysis was conducted by applying statistics-contingency tables, Cochran's-Q test and McNemar's test. The CTA -10, and -7- and all 4-point scoring systems, showed overall sensitivities of 81,6%, 87.8% and 95.9% respectively and 100% specificity, when compared to DSA. In patients with a clinical verification of BD, the CTA -10 and -7-point scoring systems were significantly inferior to clinical tests (p = 0.004 and p = 0.031), while the 4-point scoring systems showed no such difference (p = 0.5). All 4-point scoring systems showed 100% sensitivity in patients with a minor SD or no SD. In patients with a major SD, all CTA scoring systems (- 10, - 7- and all 4-point) were less sensitive (62.5%, 62.5% and 75% respectively). The presence of a major SD was associated with an 8 × relative risk for false negative results in all 4-point scoring systems. CTA showed excellent diagnostic performance in patients with a suspicion of BD. The 4-point CTA scoring systems are the most sensitive for the diagnosis of BD, although in patients with a major SD patient, the role of CTA is ambiguous.

Cerebral venous steal equation for intracranial segmental perfusion pressure predicts and quantifies reversible intracranial to extracranial flow diversion

Cerebral perfusion is determined by segmental perfusion pressure for the intracranial compartment (SPP), which is lower than cerebral perfusion pressure (CPP) because of extracranial stenosis. We used the Thevenin model of Starling resistors to represent the intra-extra-cranial compartments, with outflow pressures ICP and Pe, to express SPP = Pd–ICP = FFR*CPP–Ge(1 − FFR)(ICP–Pe). Here Pd is intracranial inflow pressure in the circle of Willis, ICP—intracranial pressure; FFR = Pd/Pa is fractional flow reserve (Pd scaled to the systemic pressure Pa), Ge—relative extracranial conductance. The second term (cerebral venous steal) decreases SPP when FFR < 1 and ICP > Pe. We verified the SPP equation in a bench of fluid flow through the collapsible tubes. We estimated Pd, measuring pressure in the intra-extracranial collateral (supraorbital artery) in a volunteer. To manipulate extracranial outflow pressure Pe, we inflated the infraorbital cuff, which led to the Pd increase and directional Doppler flow signal reversal in the supraorbital artery. SPP equation accounts for the hemodynamic effect of inflow stenosis and intra-extracranial flow diversion, and is a more precise perfusion pressure target than CPP for the intracranial compartment. Manipulation of intra-extracranial pressure gradient ICP–Pe can augment intracranial inflow pressure (Pd) and reverse intra-extracranial steal.

Teleneurology-Enabled Determination of Death by Neurologic Criteria After Cardiac Arrest or Severe Neurologic Injury

OBJECTIVE

To determine whether providing teleneurology (TN) consultations aiding in determination of death by neurologic criteria (DNC) to a bedside intensivist is feasible and whether timely access and expert input increase the quality of the DNC examination and identification of potential organ donors, we reviewed retrospective data related to outcomes of such consultations.

METHODS

Between November 2017 and March 2019, TN consults were requested for sequential comatose patients in the intensive care unit (ICU). We recorded patients' demographic information, causes leading to coma or suspected DNC, and the results of TN consultations. We obtained data on the number of referrals to the organ bank and number of organ donors.

RESULTS

Ninety-nine consults were performed with a median time from request to start of the consult of 20.2 minutes (interquartile range 5.4-65.3 minutes). Eighty consults were requested for determination of prognosis, whereas 19 consults were requested for supervision of the DNC examination. In 1 of 80 (1.2%) prognostication consults, the patient was determined by the neurologist to require assessment of DNC and was found to meet DNC criteria; determination of DNC occurred in 11 of the 19 (57.9%) consultations for a supervised DNC examination. In a comparison of the pre-TN (94 months) and post-TN (17 months) periods, there was 2.56-fold increase in the proportion of patients meeting DNC criteria who were medically suitable for donation (pre-TN 8.9% vs post-TN 21.1%, p = 0.02) and a 2.12-fold increase in the proportion of donors (pre-TN 6.14% vs post-TN 13.1%, p = 0.14).

CONCLUSIONS

It is feasible to perform TN consultations for patients with severe neurologic damage and to allow expert supervision for DNC examination. Having a teleneurologist as part of the ICU assessment team helped differentiate severe neurologic deficits from DNC and was associated with increase in organ donation.

Ancillary Testing for Determination of Death by Neurologic Criteria Around the World

OBJECTIVE

We sought to identify similarities and differences in the diagnostic requirements for ancillary testing for determination of brain death/death by neurologic criteria (BD/DNC) around the world.

METHODS

We reviewed diagnostic requirements for ancillary testing for BD/DNC in 78 unique official national BD/DNC protocols obtained from contacts worldwide between January 2018 and April 2019.

RESULTS

Details provided on the performance and interpretation of ancillary tests for determination of BD/DNC were variably provided and inconsistent. Approximately half of all protocols that included each ancillary test provided details about study performance: 63% of protocols that included conventional cerebral angiography, 55% of protocols that included electroencephalography, 50% of protocols that included somatosensory evoked potentials, 48% of protocols that included transcranial Doppler ultrasonography, 43% of protocols that included nuclear medicine flow study and 41% of protocols that included brainstem auditory evoked potentials. Similarly, about half of all protocols that included each ancillary test provided details about study interpretation: 66% of protocols that included electroencephalography, 59% of protocols that included brainstem auditory evoked potentials, 56% of protocols that included somatosensory evoked potentials, 55% of protocols that included transcranial Doppler ultrasonography, 52% of protocols that included conventional cerebral angiography and 49% of protocols that included nuclear medicine flow study.

INTERPRETATION

Diagnostic requirements for ancillary testing in BD/DNC determination vary around the world. We hope that the World Brain Death Project will improve worldwide consensus on the diagnostic requirements for ancillary testing in BD/DNC, both for performance and interpretation.