Educational Objectives_16_

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					     How to Read a Head CT




    (or “How I learned to stop worrying
     and love computed tomography”)
                        Andrew D. Perron, MD, FACEP
1
    Andrew D. Perron, MD, FACEP
     EM Residency Program Director

    Department of Emergency Medicine
          Maine Medical Center
              Portland, ME

                     Andrew D. Perron, MD, FACEP
2
                    Head CT
    • Has assumed a critical role in the daily
      practice of Emergency Medicine for
      evaluating intracranial emergencies. (e.g.
      Trauma, Stroke, SAH, ICH).
    • Most practitioners have limited experience
      with interpretation.
    • In many situations, the Emergency
      Physician must initially interpret and act
      on the CT without specialist assistance.

                            Andrew D. Perron, MD, FACEP
3
                  Head CT
    • Most EM training programs have no
      formalized training process to meet
      this need.
    • Many Emergency Physicians are
      uncomfortable interpreting CTs.
    • Studies have shown that EPs have a
      significant “miss rate” on cranial
      CT interpretation.

                         Andrew D. Perron, MD, FACEP
4
                  Head CT
    • In medical school, we are taught a
      systematic technique to interpret
      ECGs (rate, rhythm, axis, etc.) so that
      all aspects are reviewed, and no
      findings are missed.




                          Andrew D. Perron, MD, FACEP
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                  Head CT
    • The intent of this session is to
      introduce a similar systematic
      method of cranial CT interpretation,
      based on the mnemonic…




                         Andrew D. Perron, MD, FACEP
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            Head CT




    “Blood Can Be Very Bad”
                Andrew D. Perron, MD, FACEP
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        Blood Can Be Very Bad

    • Blood
    • Cisterns
    • Brain
    • Ventricles
    • Bone
                    Andrew D. Perron, MD, FACEP
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        Blood Can Be Very Bad

    • Blood
    • Cisterns
    • Brain
    • Ventricles
    • Bone
                    Andrew D. Perron, MD, FACEP
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         Blood Can Be Very Bad

     • Blood
     • Cisterns
     • Brain
     • Ventricles
     • Bone
                     Andrew D. Perron, MD, FACEP
10
         Blood Can Be Very Bad

     • Blood
     • Cisterns
     • Brain
     • Ventricles
     • Bone
                     Andrew D. Perron, MD, FACEP
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         Blood Can Be Very Bad

     • Blood
     • Cisterns
     • Brain
     • Ventricles
     • Bone
                     Andrew D. Perron, MD, FACEP
12
               CT Scan Basics
     • A CT image is a computer-generated
       picture based on multiple x-ray
       exposures taken around the periphery
       of the subject.
     • X-rays are passed through the subject,
       and a scanning device measures the
       transmitted radiation.
     • The denser the object, the more the
       beam is attenuated, and hence fewer x-
       rays make it to the sensor.
                           Andrew D. Perron, MD, FACEP
13
                CT Scan Basics
     • The denser the object, the whiter it is on CT
       – Bone is most dense = + 1000 Hounsfield U.
       – Air is the least dense = - 1000H Hounsfield U.




                               Andrew D. Perron, MD, FACEP
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        CT Scan Basics: Windowing




Focuses the spectrum of gray-scale used on a particular image.
                                  Andrew D. Perron, MD, FACEP
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2 Sheet Head CT
     Posterior Fossa
     •Brainstem
     •Cerebellum
     •Skull Base
       –Clinoids
       –Petrosal bone
       –Sphenoid bone
       –Sella turcica
       –Sinuses


                        Andrew D. Perron, MD, FACEP
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     CT Scan




         Andrew D. Perron, MD, FACEP
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CT Scan
Sagittal View




                C Circummesencephalic Cistern
     CT Diagnostics

      Where is the most sensitive area
         to examine the CT for
         increased ICP?
      A. Lateral Ventricles
      B. IVth ventricle
      C. Basilar Cisterns
      D. Gyral pattern
                          Andrew D. Perron, MD, FACEP
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     Cisterns




          Andrew D. Perron, MD, FACEP
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     CT Scan




         Andrew D. Perron, MD, FACEP
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     Brainstem Lateral View




                 Andrew D. Perron, MD, FACEP
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                         2nd Key Level
       2nd Key Level Sagittal View




     Circummesencephalic Cistern




                                   Andrew D. Perron, MD, FACEP
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     Cisterns at Cerebral Peduncles
                  Level




                     Andrew D. Perron, MD, FACEP
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     CT Scan




         Andrew D. Perron, MD, FACEP
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     Suprasellar Cistern




                Andrew D. Perron, MD, FACEP
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     CT Diagnostics

      Where is the most sensitive area
         to examine the CT for
         ventricular dilation?
      A. IIIrd ventricle
      B. IVth ventricle
      C. Temporal horns of lateral
         ventricles
                          Andrew D. Perron, MD, FACEP
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     CT Scan




         Andrew D. Perron, MD, FACEP
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      3rd Key Level Sagittal View




     Circummesencephalic Cistern




                                   Andrew D. Perron, MD, FACEP
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     Cisterns at High Mid-Brain Level




                      Andrew D. Perron, MD, FACEP
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CT Scan
     Ventricles




           Andrew D. Perron, MD, FACEP
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                  CSF Production
     • Produced in choroid plexus in the
       lateral ventricles  Foramen of Monroe
        IIIrd Ventricle  Acqueduct of
       Sylvius  IVth Ventricle 
       Lushka/Magendie
     • 0.5-1 cc/min
     • Adult CSF volume is approx. 150 cc’s.
     • Adult CSF production is approx. 500-
       700 cc’s per day.     Andrew D. Perron, MD, FACEP
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     CT Scans




37              Andrew D. Perron, MD, FACEP
     A Few Kid-Specific Thoughts




                    Andrew D. Perron, MD, FACEP
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                A Few Kid-Specific Thoughts
•    Premature Infants (30-34 weeks):
          Larger sylvian, basilar (circummesencephalic) cisterns.
          Larger subarachnoid spaces
          Thin cerebral cortex (Gray matter)
          Prominent white matter (with higher water content)
          Limited cortical gyral pattern
          Ventricles are variable: slit-like to well-developed
•    Term Infant (36-41 weeks):
          Small, slit-like lateral ventricles
          Continued white-matter prominence
          More prominent sulcal pattern
          Temporal horns unlikely to be seen
•    1st & 2nd years of Life:
          Marked growth of all lobes of the brain (proportionally greatest in frontal lobes)
          Wide variation in lateral ventricle size (3rd and 4th fairly constant)
          Temporal horns unlikely to be seen.


                                                      Andrew D. Perron, MD, FACEP
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     1 day   1 year               2 years




40                Andrew D. Perron, MD, FACEP
Trauma Pictures
                   B is for Blood
     • 1st decision: Is blood present?
     • 2nd decision: If so, where is it?
     • 3rd decision: If so, what effect is it
       having?




                             Andrew D. Perron, MD, FACEP
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     CT Diagnostics

      At what point does blood become
         isodense with brain?
      A. About 48 hours
      B. About 1 week
      C. About 2 weeks
      D. After 1 month

                        Andrew D. Perron, MD, FACEP
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           B is for Blood
     • Acute blood is bright white
       on CT (once it clots).


                             •Blood becomes isodense
                             at approximately 1 week.




     • Blood becomes
       hypodense at
44
       approximately 2 weeks.        Andrew D. Perron, MD, FACEP
           B is for Blood
     • Acute blood is bright white
       on CT (once it clots).


                             • Blood becomes isodense
                             at approximately 1 week.




     • Blood becomes
       hypodense at
       approximately 2 weeks.        Andrew D. Perron, MD, FACEP
45
           B is for Blood
     • Acute blood is bright white
       on CT (once it clots).


                             • Blood becomes isodense
                             at approximately 1 week.




     • Blood becomes
       hypodense at
       approximately 2 weeks.        Andrew D. Perron, MD, FACEP
46
               Epidural Hematoma
     • Lens shaped
     • Does not cross sutures
     • Classically described
       with injury to middle
       meningeal artery
     • Low mortality if treated
       prior to unconsciousness
       ( < 20%)

                              Andrew D. Perron, MD, FACEP
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     CT Scans




                Andrew D. Perron, MD, FACEP
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                   Subdural Hematoma
     • Typically falx or sickle-
       shaped.
     • Crosses sutures, but does
       not cross midline.
     • Acute subdural is a
       marker for severe head
       injury. (Mortality
       approaches 80%)
     • Chronic subdural usually
       slow venous bleed and
       well tolerated.           Andrew D. Perron, MD, FACEP
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     CT Scan




50       Andrew D. Perron, MD, FACEP
     Subarachnoid Hemorrhage




                 Andrew D. Perron, MD, FACEP
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        Subarachnoid Hemorrhage
     • Blood in the cisterns/cortical gyral
       surface
       – Aneurysms responsible for 75-80% of SAH
       – AVM’s responsible for 4-5%
       – Vasculitis accounts for small proportion
         (<1%)
       – No cause is found in 10-15%
       – 20% will have associated acute
         hydrocephalus
                            Andrew D. Perron, MD, FACEP
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     CT Diagnostics

      What is the sensitivity of CT for
         SAH?
      A. 100%
      B. 95%
      C. 80%
      D. Depends…I need a lot more
         information to answer.
                           Andrew D. Perron, MD, FACEP
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        CT Scan Sensitivity for SAH
     • 98-99% at 0-12 hours
     • 90-95% at 24 hours
     • 80% at 3 days
     • 50% at 1 week
     • 30% at 2 weeks
       Depends on generation of scanner and
        who is reading scan and how much
54      blood there is.     Andrew D. Perron, MD, FACEP
     CT Scan




55       Andrew D. Perron, MD, FACEP
     CT Scan




56       Andrew D. Perron, MD, FACEP
            Intraventricular/
     Intraparenchymal Hemorrhage




                    Andrew D. Perron, MD, FACEP
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     CT Scan




58       Andrew D. Perron, MD, FACEP
               C is for CISTERNS
               (Blood Can Be Very Bad)
     • 4 key cisterns
       – Circummesencephalic
       – Suprasellar
       – Quadrigeminal
       – Sylvian
                                   Circummesencephalic




                               Andrew D. Perron, MD, FACEP
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                       Cisterns
     • 2 Key questions to answer regarding
       cisterns:
       – Is there blood?
       – Are the cisterns open?




                                  Andrew D. Perron, MD, FACEP
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61   Andrew D. Perron, MD, FACEP
62   Andrew D. Perron, MD, FACEP
63   Andrew D. Perron, MD, FACEP
        B is for BRAIN
     (Blood Can Be Very Bad)




                  Andrew D. Perron, MD, FACEP
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65   Andrew D. Perron, MD, FACEP
     Tumor




66      Andrew D. Perron, MD, FACEP
     Atrophy




67        Andrew D. Perron, MD, FACEP
     CT Diagnostics

      What percentage of mass lesions
         will require IV contrast to be
         identified?
      A. 100%
      B. 50%
      C. 30-40%
      D. 10-20%
                          Andrew D. Perron, MD, FACEP
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     Abscess




69       Andrew D. Perron, MD, FACEP
     Hemorrhagic Contusion




70               Andrew D. Perron, MD, FACEP
71   Andrew D. Perron, MD, FACEP
     Mass Effect




72          Andrew D. Perron, MD, FACEP
     Stroke




73       Andrew D. Perron, MD, FACEP
     Intracranial Air




              Andrew D. Perron, MD, FACEP
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     Intracranial Air




75            Andrew D. Perron, MD, FACEP
     Intracranial Air




76            Andrew D. Perron, MD, FACEP
     V is for VENTRICLES
     (Blood Can Be Very Bad)




                  Andrew D. Perron, MD, FACEP
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78   Andrew D. Perron, MD, FACEP
79   Andrew D. Perron, MD, FACEP
     Ex-Vacuo Phenomenon




80             Andrew D. Perron, MD, FACEP
81   Andrew D. Perron, MD, FACEP
82   Andrew D. Perron, MD, FACEP
83   Andrew D. Perron, MD, FACEP
     BONE




84      Andrew D. Perron, MD, FACEP
85   Andrew D. Perron, MD, FACEP
86   Andrew D. Perron, MD, FACEP
87   Andrew D. Perron, MD, FACEP
88   Andrew D. Perron, MD, FACEP
         Blood Can Be Very Bad
If no blood is seen, all cisterns
are present and open, the brain
is symmetric with normal gray-
white differentiation, the
ventricles are symmetric without
dilation, and there is no fracture,
then there is no emergent
diagnosis from the CT scan.

                            Andrew D. Perron, MD, FACEP
89
RIP
                                         Questions
                                   www.ferne.org
                                  ferne@ferne.org

            Andrew D. Perron, MD, FACEP
                                perroa@mmc.org
                                 (207) 662-7015
 ferne_acep_2005_peds_perron_ich_bcbvb_fshow.ppt   1/24/2013 10:45 PM
                                                             Andrew D. Perron, MD, FACEP
91

				
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