Imaging spectrum of hypoxic-ischemic brain injury in adults

Transcription

1 Imaging spectrum of hypoxic-ischemic brain injury in adults Poster No.: C-0935 Congress: ECR 2017 Type: Educational Exhibit Authors: S. Benítez Rivero, E. Alventosa Fernández, M. Fernandez del Castillo Ascanio, C. González González, S. Paz Maya, V. Martin Garcia, Y. El Khatib Ghzal, D. Eiroa Gutiérrez, V. Vázquez Sánchez; Santa Cruz de Tenerife/ES Keywords: Acute, Computer Applications-Detection, diagnosis, MR, CT, Neuroradiology brain, Ischemia / Infarction DOI: /ecr2017/C-0935 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 22

2 Learning objectives The purposes of our educational exhibit are to describe the specific imaging manifestations of hypoxic-ischemic brain injury in adults and to be familiar with the different imaging patterns of this condition. Background Hypoxic-ischemic brain injury (HII) results from a global insult due to a profound loss of cerebral blood supply or hypoxia despite adequate perfusion. A wide variety of causes can lead to interruption of cerebral blood flow. While in children brain hipoxia is often the consequence of asphyxial events, HII in adults is usually secondary to cardiac arrest or cerebrovascular disease. Imaging findings are highly variable and depend on a number of factors, including severity and duration of the insult, type and size of the affected region, type and timing of the imaging studies and are closely related to brain maturity, such that the findings will differ depending on patient's age. The critical duration of hypoxia to induce permanent brain damage remains controversial, but it is estimated at 4 or 5 min of complete arrest of cerebral circulation. Almost invariably, the consequence is a bilateral and symmetric brain damage. A characteristic of HII is the so-called selective vulnerability, cortical and deep gray matter are more frequently affected because neurons are more vulnerable to hypoxia than oligodendroglia or astrocytes. Regarding the topographical distribution of the lesions, phylogenetically, older neurons (gray nuclei of the brainstem, the globus pallidus and thalamus) are more resistant than newer portions, such as the caudate and putamen. The neocortex and Purkinje cells are also usually more vulnerable to HII. It is also frequent to observe a gradient of neuronal involvement, with the occipitoparietal cortex being more severely affected than the frontal and temporal lobes. Findings and procedure details We retrospectively collected several cases of HII assessed at our institution, focussing in the different imaging patterns that may be observed. Clinical diagnosis of HII is obvious due to the sequence of events leading to such a situation. Neuroimaging plays a major role not only in diagnosing the severity of damage but also helps in prognostication. Page 2 of 22

3 Computed tomography (CT) is generally the initial imaging study performed when brain injury is suspected and often the single imaging modality performed in the setting of HII. Abnormalities in the acute and subacute phases are usually seen only in severe cases and are nonspecific. The typical findings that may be found in this phase in the brain CT include: Diffuse cerebral edema with sulci effacement, ventricular narrowing and decreased subarachnoid cisterns ( Fig. 1 on page 13 Fig. 2 on page 14). Page 3 of 22

4 Fig. 1: A 60-year-old male, victim of cardiac arrest. Early unenhanced CT examination shows diffuse cerebral edema, with sulci effacement, ventricular narrowing and loss of normal gray-white differentiation. References: - Santa Cruz de Tenerife/ES Page 4 of 22

5 Loss of normal gray-white differentiation due to increased water content in the cortical gray matter that decreases its attenuation values (Fig. 1 on page 13). Decreased basal ganglia attenuation due to edema (Fig. 2 on page 14). Page 5 of 22

6 Fig. 2: A 30-year-old female, victim of traffic accident and cardiorespiratory arrest. Early unenhanced CT examination shows decreased caudate and putamen attenuation, as well as diffuse cerebral edema with sulci effacement. References: - Santa Cruz de Tenerife/ES Decreased gray matter attenuation in watershed areas bilaterally distributed, being the occipitoparietal region the most vulnerable and the first to experience a critical reduction of oxygen supply. Pseudosubarachnoid haemorrhage: it is a pseudolesion in which basal cisterns, tentorium cerebelli and falx cerebri appear hyperdense relative to the ischaemic brain parenchyma. This is a synergistic result of distention of the superficial venous structures secondary to the elevated intracranial pressure and severe brain edema manifesting as hypoattenuated brain parenchyma. On unenhanced CT, attenuation coefficients in these cases vary from 29 to 33 Hounsfield Units (HU), values that are lower than those seen in patients with subarachnoid haemorrhage (60-70 HU). Pseudosubarachnoid haemorrhage may develop within 3 days following resuscitation in approximately 20% of patients. This indicates severe brain damage and suggests a poor prognosis (Fig. 3 on page 16). Page 6 of 22

7 Fig. 3: A 48-year-old male with autolytic attempt and cardiorespiratory arrest. Early unenhanced CT examination shows diffuse high attenuation involving cerebellar tentorium, falx cerebri and middle cerebral arteries, relative to the ischaemic hypodense brain parenchyma. References: - Santa Cruz de Tenerife/ES Reversal sign: it is reversal of the normal CT attenuation of grey and white matter. It has been proposed that this finding is due to the distention of deep Page 7 of 22

8 medullary veins secondary to partial obstruction of venous outflow from the elevated intracranial pressure caused by diffuse edema. The result is that the cerebral white matter is of higher attenuation than the cortical gray matter (Fig. 4 on page 17 Fig. 5 on page 18 Fig. 6 on page 19). Fig. 4: A 48-year-old male with myocardial infarction and cardiac arrest. Early unenhanced CT examination shows a reversal sign, with higher Page 8 of 22

9 attenuation of cerebral white matter compared to the cortical gray matter. Also note the decreased basal ganglia attenuation. References: - Santa Cruz de Tenerife/ES Fig. 5: A 45-year-old male with myocardial infarction and cardiac arrest. Early unenhanced CT examination shows a reversal sign. Note the gradient Page 9 of 22

10 of neuronal involvement, with the occipitoparietal cortex being more severely affected than the temporal and frontal cortices. References: - Santa Cruz de Tenerife/ES Fig. 6: An 18-year-old female with history of drowning and cardiorespiratory arrest. Early enhanced CT examination, with coronal (A) and sagittal (B) reconstructions, shows a reversal sign, with a more severe impairment of occipitoparietal cortex. References: - Santa Cruz de Tenerife/ES White cerebellum sign: some authors consider this sign as part of the reversal sign. It consists in a diffuse oedema and hypoattenuation of the cerebral hemispheres with sparing of the cerebellum and brainstem, giving the appearance of high attenuation of the cerebellum and brainstem compared to the cerebral hemispheres. It has been proposed that this finding is due to the redistribution of blood to the posterior circulation that occurs during anoxic events (Fig. 7 on page 19). Page 10 of 22

11 Fig. 7: A 60-year-old male with cardiac arrest of unknown etiology. Early unenhanced CT examination shows the white cerebellum sign, representing a diffuse edema and hypoattenuation of the cerebral hemispheres with Page 11 of 22

12 sparing of the cerebellum and brainstem. It can also be visualized the reversal sign. References: - Santa Cruz de Tenerife/ES Although the reversal sign and the white cerebellum sign are more typical in children, they may be discovered in adults and indicate poor outcome. In the late subacute phase the following findings may be observed: Delayed leucoencephalopathy: this is an uncommon syndrome that affects % of patients who have suffered hypoxic events, usually occurring weeks after the hypoxic-ischemic event and progressing over a period of months. It is seen most commonly in association with carbon monoxide intoxication. The physiopathology of this phenomenon is still unclear. It is characterized by extensive cerebral hemispheric noninflammatory demyelination, usually affecting deep white matter without neuronal or axonal involvement. Clinically, it is characterized by a period of relative stability or even improvement, followed by an acute neurologic decline, usually 2-3 weeks after the initial insult. Patients may experience delirium, personality changes, intellectual impairment, movement disorders, or, rarely, seizures. Approximately 75% of patients experience a complete or nearcomplete recovery over the next 6-12 months. In the remaining patients, there may be residual dementia. Rarely this condition can progress to death. Selective enhancement of the cortex and basal ganglia on contrast-enhaced CT secondary to blood-brain barrier breakdown. In the chronic phase, CT findings are mainly related to atrophic changes. After aproximately 6 weeks, gliosis and expansion of extracellular spaces are observed, as well as cortical and cerebellar atrophy and basal ganglia retraction. Magnetic resonance (MR) imaging is more sensitive than CT in assessing brain damage in HII. Diffusion-weighted MR imaging (DWI) is the earliest imaging modality to become positive because of the presence of cytotoxic edema, usually within the first few hours after a hypoxic-ischemic event. Imaging may demonstrate increased signal intensity in the cerebellar hemispheres, basal ganglia or cerebral cortex. The thalami, brainstem or hippocampi may also be involved. Findings on T1 and T2-weighted images usually become apparent in the early subacute phase (24 hours-2 days). In the late subacute phase, postanoxic leukoencephalopathy and contrast enhancement could be observed. In the chronic phase, atrophic changes predominate over tissue signal changes. In this last stage, T2-weighted images may demonstrate some residual hyperintensity in the basal ganglia and T1-weighted images may show cortical necrosis. Page 12 of 22

13 MR spectroscopy has also become a valuable tool in the evaluation of HII. MR spectroscopy is perhaps more sensitive to injury and more indicative of the severity of injury in the first 24 hours after a hypoxic-ischemic episode, when conventional and diffusion-weighted MR imaging may yield false-negative findings or lead to significant underestimation of the extent of injury. MR spectroscopy will demonstrate substantial lactate elevation within the first 12 to 24 hours and is the best prognostic factor in the early stage. In the late stage, N-acetyl-aspartate is the preferred prognostic indicator. The optimal regions for determining the abnormalities associated with hypoxic injury include the occipital cortex, the basal ganglia and watershed zones. In conclusion, MR spectroscopy and diffusion-weighted MR imaging are the most sensitive imaging modalities for detecting HII in the acute period. Some findings, such as the extent of lesions on DWI and presence of a lactate peak and depleted N-acetyl aspartate peak on MR spectroscopy, seem to have prognostic value. As aforementioned, unenhanced head CT is the initial screening test of choice when HII is suspected. If the study is positive, no additional imaging is usually necessary. If the CT is negative further evaluation with MR imaging should be considered, given the relative low sensitivity of brain CT for detecting injury in the acute phase. Imaging repetition in the subacute phase may be helpful in determining the final extent of damage due to delayed tissue injury. Images for this section: Page 13 of 22

14 Fig. 1: A 60-year-old male, victim of cardiac arrest. Early unenhanced CT examination shows diffuse cerebral edema, with sulci effacement, ventricular narrowing and loss of normal gray-white differentiation. - Santa Cruz de Tenerife/ES Page 14 of 22

15 Fig. 2: A 30-year-old female, victim of traffic accident and cardiorespiratory arrest. Early unenhanced CT examination shows decreased caudate and putamen attenuation, as well as diffuse cerebral edema with sulci effacement. Page 15 of 22

16 - Santa Cruz de Tenerife/ES Fig. 3: A 48-year-old male with autolytic attempt and cardiorespiratory arrest. Early unenhanced CT examination shows diffuse high attenuation involving cerebellar tentorium, falx cerebri and middle cerebral arteries, relative to the ischaemic hypodense brain parenchyma. Page 16 of 22

17 - Santa Cruz de Tenerife/ES Fig. 4: A 48-year-old male with myocardial infarction and cardiac arrest. Early unenhanced CT examination shows a reversal sign, with higher attenuation of cerebral white matter compared to the cortical gray matter. Also note the decreased basal ganglia attenuation. Page 17 of 22

18 - Santa Cruz de Tenerife/ES Fig. 5: A 45-year-old male with myocardial infarction and cardiac arrest. Early unenhanced CT examination shows a reversal sign. Note the gradient of neuronal involvement, with the occipitoparietal cortex being more severely affected than the temporal and frontal cortices. Page 18 of 22

19 - Santa Cruz de Tenerife/ES Fig. 6: An 18-year-old female with history of drowning and cardiorespiratory arrest. Early enhanced CT examination, with coronal (A) and sagittal (B) reconstructions, shows a reversal sign, with a more severe impairment of occipitoparietal cortex. - Santa Cruz de Tenerife/ES Page 19 of 22

20 Fig. 7: A 60-year-old male with cardiac arrest of unknown etiology. Early unenhanced CT examination shows the white cerebellum sign, representing a diffuse edema and Page 20 of 22

21 hypoattenuation of the cerebral hemispheres with sparing of the cerebellum and brainstem. It can also be visualized the reversal sign. - Santa Cruz de Tenerife/ES Page 21 of 22

22 Conclusion Imaging plays an important role in the diagnosis of hypoxic-ischemic brain injury, helping to guide management in the acute phase and providing valuable information about longterm outcome. Early imaging findings can be subtle and easily overlooked. Thus, it is essential to be familiar with the different patterns of injury and to focus attention on the most vulnerable brain areas. Personal information References Benjamin Y. Huang, Mauricio Castillo. Hypoxic-Ischemic Brain Injury: Imaging Findings from Birth to Adulthood. RadioGraphics 2008;28: Leonardo Guilhermino Gutierrez, Álex Rovira, Luiz Antonio Pezzi Portela, Claudia da Costa Leite, Leandro Tavares Lucato. CT and MR in nonneonatal hypoxic-ischemic encephalopathy: radiological findings with pathophysiological correlations. Neuroradiology 2010;52: Lara A. Brandão, Cristiana Caires. Hypoxic-Ischemic Injuries: The Role of Magnetic Resonance Spectroscopy. Neuroimag Clin N Am 2013;23: Amogh N. Hegde, Suyash Mohan, Narayan Lath, C.C. Tchoyoson Lim. Differential Diagnosis for Bilateral Abnormalities of the Basal Ganglia and Thalamus. RadioGraphics 2011; 31:5-30. H. Yuzawa, S. Higano, S. Mugikura, A. Umetsu, T. Murata, A. Nakagawa, A. Koyama, S. Takahashi. Pseudo-Subarachnoid Hemorrhage Found in Patients with Postresuscitation Encephalopathy: Characteristics of CT Findings and Clinical Importance. Am J Neuroradiol 2008;29: Ana Castrillo-Sanz, Amelia Mendoza-Rodríguez. Reversal sign. Rev Neurol 2014;58: Col V.K. Maurya, Brig R. Ravikumar, Gp Capt Mukul Bhatia, Surg Lt Cdr Roma Rai. Hypoxic-Ischemic brain injury in an adult: Magnetic Resonance Imaging findings. Medical Journal Armed Forces India 2016;72: Page 22 of 22