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Head Trauma Part 1
 

Head Trauma Part 1

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Rathachai Kaewlai

Rathachai Kaewlai

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    Head Trauma Part 1 Head Trauma Part 1 Presentation Transcript

    • Imaging of Head Trauma Part 1: Introduction Rathachai Kaewlai, MD Specialized in Body Imaging and Emergency Radiology rathachai@gmail.com December 2006 The author is willing to receive any input, comments and corrections, Please do not hesitate to contact at the email address provided above. 1 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Outline • When to do brain imaging in trauma setting? • What imaging is appropriate? • Advantage and disadvantage of each imaging modality • Review of important cranial CT anatomy 2 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Introduction • Significance of craniocerebral injuries – Common cause of hospital admission following trauma – High morbidity and mortality particularly in adolescent and young adults • Concepts 1. Brain is contained within the skull which is a rigid and inelastic container, so only small increases in volume can be tolerated (Intracranial volume = Brain + CSF + Blood volume) 2. Cerebral perfusion pressure (CPP) in injured areas is pressure-passive flow (no autoregulation, cerebral blood flow dependent on blood pressure) 3 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Introduction • Traumatic brain injury: 2 categories 1. Primary injury – Initial injury to the brain as a result of direct trauma – Example: hematoma, diffuse axonal injury, contusion 2. Secondary injury – Subsequent injury to the brain after the initial insult – Result from systemic hypotension, hypoxia, elevated intracranial pressure (ICP) or biochemical insults 4 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • When to Do Imaging and What to Do? • Minor or mild acute closed head injury (GCS > 13) – Without risk factors or neurologic deficit head CT without contrast can be performed also known to be low yield (see next page) – With risk factors or neurologic deficit head CT without contrast most appropriate and should be performed, brain MRI reserved for problem solving – Children < 2 years old head CT without contrast most appropriate and should be performed According to American College of Radiology (ACR) Appropriateness Criteria 5 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • When to Do Imaging and What to Do? • Indications for CT in patients with minor head injury – Haydel MJ et al. Indications for CT in patients with minor head injury. N Engl J Med 2000;343:100-5. • 520 patients with minor head injury who had a normal Glasgow Coma Scale and normal findings on a brief neurologic examination underwent CT scans: 36 patients (6.9%) had positive scans • All patients with positive scans had one of the clinical findings: short-term memory deficity, drug or alcohol intoxication, physical evidence of trauma above clavicles, age > 60 yr, seizure, headache, vomiting, or coagulopathy 6 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • When to Do Imaging and What to Do? • Indications for CT in patients with minor head injury – Haydel MJ et al. Indications for CT in patients with minor head injury. N Engl J Med 2000;343:100-5. • Results were tested in another 909 patients; using at least one of the clinical findings above, the sensitivity of seven clinical findings was 100%. • CT abnormalities in 93 patients with positive CT scans: cerebral contusion (none had surgery), subdural hematoma (6% had surgery), subarachnoid hemorrhage (none had surgery), epidural hematoma (22% had surgery), depressed skull fracture (20% had surgery) 7 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • When to Do Imaging and What to Do? • Moderate or severe acute closed head injury – Head CT without contrast most appropriate and should be performed – X-ray and/or CT of cervical spine also appropriate and recommended – MRI reserved for problem solving • Rule out caroid or vertebral artery dissection – MRI with MRA, or CT with CTA of the head and neck most appropriate – Cerebral angiography reserved for problem solving According to American College of Radiology (ACR) Appropriateness Criteria 8 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • When to Do Imaging and What to Do? • Penetrating injury, stable, neurologically intact – Head CT without contrast most appropriate and should be performed – Skull x-ray also appropriate if calvarium is the site of injury – C spine x-ray or CT appropriate if neck or C-spine is the site of injury – CTA of head and neck if vascular injury suspected • Skull fracture – Head CT without contrast most appropriate and should be performed – CTA of head and neck if vascular injury suspected According to American College of Radiology (ACR) Appropriateness Criteria 9 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Skull Radiography • 1/3 of patients with severe brain injury don’t have fracture • Role of skull radiography in acute head injury – Calvarial fractures • Linear fracture that is ‘in plane’ with axial CT scan can be missed. Scout image of head CT, or CT reformation is useful – Penetrating injuries • Provide rapid assessment of degree of foreign body penetration, e.g. stab wounds – Radiopaque foreign bodies • Example: patients with gunshot wounds to the head (to screen for retained intracranial bullet fragments) 10 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Computed Tomography (CT) • Advantages – High sensitivity for demonstrating mass effect, ventricular size and configuration, bone injury, acute hemorrhage regardless of location – Widespread availability, rapid scanning, compatibility with other medical and life support devices • Limitations – Insensitivity to detect small and nonhemorrhagic lesions such as contusion, particularly when adjacent to bony surfaces, diffuse axonal injury – Relatively insensitive to detect early brain edema, hypoxic- ischemic encephalopathy (HIE) 11 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Computed Tomography (CT) • Role of CT in acute head injury – Patients with moderate-risk or high-risk for intracranial injury should undergo early noncontrast CT to look for… • Intracerebral hematoma • Midline shift • Increased intracranial pressure – Patients with low-risk for intracranial injury: clinical selection for CT is still problematic • CT may be able to triage this patient group to admission, surgery or discharge • CT may lower the cost of hospital admission for observation • Trade-off with greater use of CT in emergency setting 12 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Computed Tomography (CT) • Repeat head CT – Required for clinical or neurologic deterioration, especially within 72 hours after trauma – Detection of delayed hematoma, hypoxic-ischemic lesions and cerebral edema • Pediatric patients – Lower threshold for doing a CT scan • Clinical criteria for scanning is less reliable, particularly in children less than 2 years – CT order needs to be balanced with risk of radiation exposure 13 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Magnetic Resonance Imaging (MRI) • Advantages – Sensitive for detection of diffuse axonal injury or contusion with susceptibility sequence (T2 gradient echo), distinguish different ages of blood – Useful for screening of vascular lesions such as thromboses, pseudoaneurysms, or dissection • Limitations – Insensitive for subarachnoid hemorrhage, air and fracture – Certain absolute contraindications, e.g. pacemaker – Limited availability in acute setting, longer imaging time (than CT), incompatibility with some medical devices 14 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Magnetic Resonance Imaging (MRI) • Role of MRI in acute head injury – Problem solving tool when CT is inconclusive or high clinical suspicion • Diffuse axonal injury: CT is less sensitive than MRI. For example, patients with severe head injury but normal CT • Brain contusion – Vascular examinations of the brain and neck • Suspicion of dissection, aneurysm or thrombosis • CT angiography also has a competitive role as MR angiography 15 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Brain CT: Normal Anatomy • Make sure to look at all 3 different window displays on one brain CT exam. Brain window Subdural window Bone window 16 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • 3 1 3 Make sure the first image include the foramen magnum (red circle), 1 otherwise you will miss (impending) tonsillar herniation 2 1 = cervicomedullary junction 2 = CSF space (should be dark) 3 = Cerebellar tonsils (tonsils are not midline structures) 17 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • 5 = Pons (usually not clearly seen due to ‘beam hardening artifact’ from bony skull base) 6 = Middle cerebellar peduncle (structure that connects pons and cerebellar hemispheres) 7 = Cerebellar hemisphere 8 = Forth ventricle (CSF cavity behind the brainstem, slit-like appearance when normal) 5 6 7 8 18 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • 7 = Cerebellum 9 = Midbrain (heart-shaped structure normally surrounded by CSF. Effacement of CSF may suggest early brain herniation) 10 = Temporal lobe 11 = Temporal horn of lateral 13 ventricle (Look for earliest hydrocephalus here. Normally slit-like, or curvilinear) 10 12 = Uncus (Most medial portion of 12 temporal lobes; uncal herniation is called when uncus displaces medially and obliterates 11 9 the CSF space on the side of midbrain) 13 = CSF cistern (Not seeing CSF around midbrain may be abnormal; that’s what 7 radiologists call ‘effacement of the cistern’ as a sign of cerebral herniation. Also a place to look for subarachnoid hemorrhage) 19 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • 14 = Anterior falx (Know where it is, so 14 you can draw a ‘midline’ to see if there is ‘midline shift’ or not) 15 = Posterior falx 16 = Basal ganglia (Lateral to the frontal horn of lateral ventricle) 17 = Thalamus (lateral to the third ventricle which is very narrow here) 18 16 18 = Sylvian fissure (CSF space dividing frontal from temporal lobes. Look for subarachnoid hemorrhage here) 17 Red line = Cerebral convexity (Look for extra-axial hemorrhage here, better seen in ‘subdural window’) • Intra-axial = any pathology ‘in’ the brain parenchyma • Extra-axial = any pathology ‘not in the parenchyma’ e.g. subarachnoid, subdural and epidural pathology 15 20 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • 19 = Lateral ventricle 20 = Septum pellucidum (midline structure dividing right and left lateral ventricles; helps in measuring degree of midline shift) 19 20 21 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • 2 = CSF space (Look for subarachnoid hemorrhage here) 2 22 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Red lines = Temporomandibular joint (socket) 21 = Condyle of mandible (ball; should sit in the socket. Missing fracture or dislocation in this region will cause patients’ long term disability) 21 22 = Mastoid air cells (should be filled with air density, otherwise fracture of the skull base should be suspected) 22 23 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • 23 = Sphenoid sinus (Look for fluid or blood density, air-fluid level which may represent skull base fracture) 23 24 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Checklist for Trauma Brain CT  Have 3 different windows to look for different pathology (brain, subdural and bone windows)  First image includes foramen magnum  Look first for the pathology that needs emergent Rx  Hydrocephalus  Look for primary pathology (hemorrhage in different compartments, depressed skull fracture)  Look for secondary pathology (brain herniation, midline shift)  Look at the mastoid and sphenoid sinuses for hemorrhage which implies skull base fractures  Always look at scout CT image for fracture ‘in plane’ with axial scans  Look at temporomandibular joints for fracture and/or dislocation 25 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • Traumatic brain pathology will be continued on ‘Part 2’ 26 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD
    • • The information provided in this presentation… – Does not represent the official statements or views of the Thai Association of Emergency Medicine. – Is intended to be used as educational purposes only. – Is designed to assist emergency practitioners in providing appropriate radiologic care for patients. – Is flexible and not intended, nor should they be used to establish a legal standard of care. 27 Emergency Radiology: Imaging of Head Trauma Rathachai Kaewlai, MD