Current Trends in the Imaging of Diffuse Axonal Injury

Transcription

1 September 2009 Current Trends in the Imaging of Diffuse Axonal Injury University of Texas Medical School in San Antonio Harvard Medical School Beth Israel Deaconess Medical Center

2 Outline Introduction to Traumatic Brain Injury Our Patient: MC Diffuse Axonal Injury (DAI) Imaging Modalities for Diffuse Axonal Injury Summary Acknowledgements References

3 Introduction to Traumatic Brain Injury (TBI) Defined as damage to the brain from an external mechanical force. Examples of such forces include rapid acceleration or deceleration motions, impact injuries, or penetration by a projectile Incidence: /100, /100,000 12% of all U.S. hospital admissions are TBI- related Meythaler, J. M. (2001). "Current concepts: diffuse axonal injury-associated traumatic brain injury." Archives of physical medicine and rehabilitation 82(10):

4 Our Patient: MC CC: Traumatic Brain Injury HPI: 23 y/o M with unknown medical history transferred from an outside hospital s/p high speed (~100mph) motorcycle vs. bus accident. Pt was helmeted. In the field, GCS 3. Negative tox screen. GCS- Glasgow Coma Score

5 On Admission- Patient MC: CT Imaging Axial non contrast CT imaging showing hyperdensity (green box) in left frontal lobe consistent with a hemorrhagic contusion. No other signs of hemorrhage were seen acutely. Images from PACS, BIDMC

6 3 Days Later- Patient MC : MRI T2 Flair Areas of Hemorrhage Axial T2 weighted Flair MR imaging showing hyperintense signal in the right and left grey-white matter interface and splenium of the corpus callosum Images from PACS, BIDMC Axial T2 weighted Flair MR Imaging showing hyperintense signal in the right posterior limb of the internal capsule and a left frontal lobe contusion

7 3 Days Later- Patient MC : MRI T2 Flair Axial T2 weighted Flair MR imaging showing hyperintense signal in the corpus callosum Images from PACS, BIDMC

8 3 Days Later- Patient MC : MR Susceptibility Weighted Imaging Areas of Hemorrhage Axial SW MR imaging showing hypo-intense signal in the right and left grey-white matter interface and a left frontal lobe contusion Images from PACS, BIDMC Axial SW MR imaging showing hypo- intense lesions in the right grey-white matter interface and splenium; ; left frontal lobe contusion

9 3 Days Later- Patient MC : MR Susceptibility Weighted Imaging Axial T2 weighted SW MR imaging showing hypo-intense signal in the corpus callosum Axial T2 weighted SW MR imaging showing hypo-intense signal in the corpus callosum Images from PACS, BIDMC

10 Diffuse Axonal Injury Biomechanics, Pathogenesis, Stages of Damage, and Long-term Consequences

11 Diffuse Axonal Injury (DAI) Severe head trauma can produce diffuse axonal injury characterized by punctate hemorrhagic or non-hemorrhagic lesions primarily in white matter tracts Common sites: Parasagittal white matter, grey-white matter junctions of the cerebral cortex, corpus callosum, and brainstem Occurs in 40-50% of patients hospitalized for TBI Affects more than 2 million people every year Meythaler, J. M. (2001). "Current concepts: diffuse axonal injury-associated traumatic brain injury." Archives of physical medicine and rehabilitation 82(10):

12 DAI and its Long-Term Consequences 26,000 deaths/yr are due to DAI 20,000-45,000 surviving patients/yr suffer neurobehavioral or physical impairments Average hospital cost per patient: $117,000 Direct health care costs: $25 billion/year Meythaler, J. M. (2001). "Current concepts: diffuse axonal injury-associated traumatic brain injury." Archives of physical medicine and rehabilitation 82(10):

13 Biomechanics of DAI Commonly referred to as a shear force injury Rapid head motions produce inertial forces which cause rotational acceleration of the brain leading to shearing and strain of axons Rapid stretch of an axon leads to damage to the neuron s s cytoskeleton. Axonal transport continues until local inflammation causes further cytoskeleton breakdown

14 Pathogenesis of Microscopic Axonal Changes Brain Injury Influx of Na + and Ca 2+ through respective channels Axonal Swelling Axonal cytoskeleton damage Accumulation of axonal transport proteins within swellings Increased cytoskeleton damage + protein accumulation = axon disconnection Axon disconnection leads to irreversible damage Pathologic Feature: Bulb formation

15 Histopathology of DAI Below: Silver stain of the same area indicating the axonal terminal bulbs. Top: Low power view of hematoxylin- eosin stain demonstrating DAI and petechial hemorrhages Images from: Meythaler, J. M. (2001). "Current concepts: diffuse axonal injury-associated traumatic brain injury." Archives of physical medicine and rehabilitation 82(10):

16 Stages of DAI Stage I II Areas Affected - parasagittal regions of the frontal lobes - periventricular temporal lobes - internal and external capsules - cerebellum Stage I areas + corpus callosum III Stage I + Stage II areas + dorsolateral quadrants of the rostral brain stem Adams, J. H. (1989). "Diffuse axonal injury in head injury: definition, diagnosis and grading." Histopathology 15(1):

17 Imaging Modalities for Diffuse Axonal Injury

18 Imaging of DAI: CT CT imaging is first line for any neurotrauma Benefits Widely available in most hospitals in the US Comparatively inexpensive Good, quick test for injuries that require immediate surgical attention Drawbacks Initially 50-80% of pts with DAI will have normal CT scans Less sensitivity for detecting DAI Toyama, Y. (2005). "CT for acute stage of closed head injury." Radiation medicine 23(5):

19 Examples of DAI on CT Imaging: Companion Patient TC HPI: 22 y/o F being found down in the road, entangled with her bicycle, unresponsive, unhelmeted,, pupils unequal. Initial CGS was 4 upon arrival to ED.

20 Companion Patient TC: Axial Non-Contrast CT Imaging Areas of Hemorrhage Soft Tissue Edema Images from PACS, BIDMC

21 Companion Patient TC: Axial Non-Contrast CT Imaging Areas of Hemorrhage Soft Tissue Edema Images from PACS, BIDMC

22 Companion Patient TC: Axial Non-Contrast CT Imaging Areas of Hemorrhage Images from PACS, BIDMC

23 More Examples: Non-Contrast CT Imaging showing Hemorrhagic DAI Lesions Black arrows: areas of hemorrhagic foci Left Image from: Provenzale, J. (2007). "CT and MR imaging of acute cranial trauma." Emergency radiology 14(1): Right Image from: Toyama, Y. (2005). "CT for acute stage of closed head injury." Radiation medicine 23(5):

24 Imaging of DAI: MRI MRI has greater sensitivity in detecting DAI Commonly used techniques include Flair, DWI, and GRE, and SWI* Kinoshita et al.- DWI sensitivity in detecting DAI is comparable to Flair Tong et al.- Number of hemorrhagic DAI lesions seen on SWI was 6 times greater than that on conventional T2* weighted 2D GRE imaging and the volume of hemorrhage was approx 2 fold greater * Flair- Fluid Attenuated Inversion Recovery DWI- Diffusion weighted Imaging GRE- Gradient Recalled Echo SWI- Susceptibility Weighted Imaging

25 T2 MR Imaging of DAI Sagittal T2-weighted MR image showing hyper-intense signal within the corpus callosum (white arrows) Image from: Provenzale, J. (2007). "CT and MR imaging of acute cranial trauma." Emergency radiology 14(1): 1-12.

26 MR Flair: Conspicuity of DAI Lesions MR FLAIR image showing hyper-intense lesion in the left splenium MR FLAIR image showing hyper-intense lesion in the left frontal grey-white matter interface Images from: Kinoshita, T. (2005). "Conspicuity of diffuse axonal injury lesions on diffusionweighted MR imaging." European journal of radiology 56(1): 5-11.

27 MR DWI: Conspicuity of DAI Lesions MR DWI Gx image showing high-intensity lesion in the splenium MR DWI Gz image showing highintensity lesion in the left frontal grey-white matter interface Images from: Kinoshita, T. (2005). "Conspicuity of diffuse axonal injury lesions on diffusionweighted MR imaging." European journal of radiology 56(1): 5-11.

28 More Lesions are seen on Susceptibility Imaging: Comparing T2 and SWI A) Axial T2 MRI B) Axial Susceptibility-weighted MRI Small hemorrhagic shearing injuries in the left frontal subcortical white matter (Black arrows) Image from: Tong, K. A., S. Ashwal, et al. (2008). "Susceptibility-weighted MR imaging: a review of clinical applications in children." AJNR. American journal of neuroradiology 29(1): 9-17.

29 More Lesions are seen on Susceptibility Imaging: Comparing T2 and SWI C) Axial T2 MRI D) Axial Susceptibility-weighted MRI Hemorrhagic shearing foci (open arrows) ) in the left frontal white matter, right subinsular region, and left splenium Image from: Tong, K. A., S. Ashwal, et al. (2008). "Susceptibility-weighted MR imaging: a review of clinical applications in children." AJNR. American journal of neuroradiology 29(1): 9-17.

30 The Emergence of MRI Diffusion Tensor Tractography (DTT) DTT is rapidly becoming another modality to look for DAI in the acute phase Modality can characterize white matter integrity by measuring fractional anisotropy (FA) Fractional anisotropy is the degree of alignment of the underlying nerve fibers (ratio: 0 to 1) Wang, J. Y., B. Khamid, et al. (2008). "Diffusion tensor tractography of traumatic diffuse axonal injury." Archives of neurology 65(5):

31 Using DTT for Long-Term DAI Skoglund et al. Follow-up 22 y/o F with closed head injury. Comparison images of Axial T2 and DTT at 6 days post-injury and 18 months post-injury Results: In follow-up imaging, conventional MRI showed no pathology. However, in DTT imaging, FA values had improved but did not normalize. Conclusion: MR-DTT may be more sensitive to DAI than conventional MR imaging. Skoglund, T. S. (2008). "Long-term follow-up of a patient with traumatic brain injury using diffusion tensor imaging." Acta radiologica (Stockholm, Sweden : 1987) 49(1):

32 Results: Long-Term DAI Follow-up with DTT a) 6 days post injury- Axial T2 MR image showing hyper-intense lesion in left pons b) 18 months post injury- Axial T2 MR image showing no lesion c) 6 days post injury- Axial DTT image showing decreased blue intensity d) 18 months post injury- Axial DTT image showing moderately improved blue intensity Images from: Skoglund, T. S. (2008). "Long-term follow-up of a patient with traumatic brain injury using diffusion tensor imaging." Acta radiologica (Stockholm, Sweden : 1987) 49(1):

33 Fractional Anisotropy in Long-Term DAI Follow-up FA values on left side improve 18 months post- injury but do not normalize to right-sided values Key: dx Patient s s right side sin Patient s s left side Graph from: Skoglund, T. S. (2008). "Long-term follow-up of a patient with traumatic brain injury using diffusion tensor imaging." Acta radiologica (Stockholm, Sweden : 1987) 49(1):

34 Summary Diffuse Axonal Injury is caused by traumatic brain injury and can be characterized by punctate hemorrhagic or non-hemorrhagic lesions primarily in white matter tracts MRI is now the imaging of choice for detecting DAI. SWI and DWI are the best techniques DTT holds promising results as an imaging modality for the acute and long-term follow-up of DAI patients

35 Acknowledgements Special thanks to Dr. Rafeeque Bhadelia for help with this index case and presentation Dr. Rivka Colen Dr. Gillian Lierberman

36 References Adams, J. H. (1989). "Diffuse axonal injury in head injury: definition, diagnosis and grading." Histopathology 15(1): Kinoshita, T. (2005). "Conspicuity of diffuse axonal injury lesions on diffusion-weighted MR imaging." European journal of radiology 56(1): Meythaler, J. M. (2001). "Current concepts: diffuse axonal injury-associated traumatic brain injury." Archives of physical medicine and rehabilitation 82(10): Provenzale, J. (2007). "CT and MR imaging of acute cranial trauma." Emergency radiology 14(1): Skoglund, T. S. (2008). "Long-term follow-up of a patient with traumatic brain injury using diffusion tensor imaging." Acta radiologica (Stockholm, Sweden : 1987) 49(1): Smith, D. H. (2003). "Diffuse axonal injury in head trauma." The Journal of head trauma rehabilitation 18(4): Tong, K. A., S. Ashwal, et al. (2008). "Susceptibility-weighted MR imaging: a review of clinical applications in children." AJNR. American journal of neuroradiology 29(1): Toyama, Y. (2005). "CT for acute stage of closed head injury." Radiation medicine 23(5): Wang, J. Y., B. Khamid, et al. (2008). "Diffusion tensor tractography of traumatic diffuse axonal injury." Archives of neurology 65(5):