Outline
I. Current neuroimaging modalities, advantages, and limitations
A. Plain film skull radiography
1. Brief review of functional principles
2. Allows visualization of facial bones
3. May reveal orbital fractures/sinusitis
4. Can be used to screen for periocular metallic FB prior to MRI
5. Can be used to screen for intraocular FB when direct view impossible
B. Computed tomography (CT)
1. Brief review of functional principles
2. Allows good visualization of bone and muscle
3. Primary Indications
a) Globe/orbital foreign bodies
b) Acute head trauma/fractures (globe, orbit, brain)
c) Acute cerebral vascular accident
d) Suspected calcific and osseous lesions
e) Orbitopathy
f) Study tumor effects on bone (erosion/hyperostosis)
g) Preseptal cellulitis in children
h) MRI contraindications
4. Less effective compared to MRI in imaging soft tissue
5. More dental implant-induced artifact when compared to MRI
6. Iodinated CT contrast dye markedly more allergenic than MRI gadolinium
7. Ionizing radiation is reduced with newer scanners
C. Magnetic Resonance Imaging (MRI)
1. Brief review of functional principles
2. Provides high contrast/high resolution imaging of soft tissue
a) Surface coils decrease signal/noise ratio to improve image resolution
b) Fat suppression decreases signal from retro-orbital fat to improve
orbital structural evaluation
3. Useful for most all neurologic presentations, though CT may be more
advantageous in instances noted above (see CT indications)
4. Can easily run concurrent MRA sequence for vascular evaluation
5. Requires enhanced patient cooperation and longer scanning time than CT;
however requires less head positioning demands than CT
6. Contraindicated when metallic intraocular FB/metallic brain aneurysm
clip/pacemaker/other electronic devices are implanted within a patient
7. More expensive than CT scan (approximately double the cost)
8. Obese patients may not fit inside scanner; however newer scanners are being
constructed to eliminate this impediment
II. Requirements for appropriate ordering of neuroimaging
A. Must correctly identify which cases warrant neuro-imaging
1. General neurologic signs or symptoms (e.g. paresthesia, weakness, cognitive
dysfunction)
2. Specific types of headache
3. Specific types of vision loss
a) Orbital disease related
b) Visual pathway related
4. Neurologic or restrictive EOM abnormalities
5. Proptosis
B. Must determine which is the “best” initial test to order
1. Plain film skull radiography is primarily a screening tool
2. Computed tomography is good initial choice for:
a) Trauma (foreign body/fracture)
b) Acute CVA (rule out hemorrhagic CVA)
c) Orbitopathy (thyroid??)
d) Tumors that may cause bone erosion or hyperostosis
e) Tumors associated with calcification
f) Preseptal cellulitis in pediatric cases
g) MRI contraindicated
3. Magnetic resonance imaging
a) Useful for any disease associated with soft tissue abnormality
b) Useful for screening of cerebral vascular abnormalities (MRA)
c) Frequently used in conjunction with CT scan
4. Use of contrast agents
a) Useful for vascular, inflammatory, neoplastic disease processes: thus
frequently indicated for eyecare-related pathology
b) May not be necessary for orbital disease
c) Contraindicated in setting of acute head trauma
C. Must communicate specific information to radiologist to ensure appropriate study
1. Clinical findings supporting imaging***
2. Type of imaging desired
3. Areas of interest
4. With or without contrast
5. Planes of sectioning
6. Width of sections: CT and MRI have different capabilities
7. Allergy history
8. Claustrophobia and other cooperation issues
D. Determine where the test will be performed (know what options are available)
1. Privileges to order imaging
2. Ability to accommodate obese patients (open scanner availability)
3. Ability to accommodate claustrophobic patients
4. Effective Communication establishment
5. Continuity of care
III. Cursory Review of Normal Anatomy
A. Plain film skull radiography
1. Orbital rim evaluation
2. Maxillary sinus evaluation
B. Computed Tomography (CT)
1. Review several typical axial sections/identify normal structures
2. Review several typical coronal sections/identify normal structures
C. Magnetic Resonance Imaging (MRI)
1. Review several typical axial sections/identify normal structures
2. Review several typical coronal sections/identify normal structures
3. Review typical mid-sagittal section/identify normal structures
IV. Neuro-ophthalmic Case Presentations
A. History
B. Ocular Examination findings
C. Neuroimaging findings
1. Intraocular disease
2. Orbital foreign body
3. Orbital trauma
4. Orbital infection
5. Acute orbital inflammatory syndrome (orbital pseudotumor)
6. Orbital space-occupying lesion
7. Thyroid orbitopathy
8. Cavernous sinus disease
9. Chiasmal disease
10. Intracranial neoplastic disease
11. Intracranial vascular disease including;
a) ischemic disease
b) aneurysmal disease
12. Intracranial inflammatory disease
V. References
http://www.cid.ch/DAVID/Mainmenu.html
http://www.cid.ch/Indic/Aa-ac.html (Guide: What test and when to order radiology)
http://www.meddean.luc.edu/lumen/MedEd/GrossAnatomy/cross_section/vhphead/vhp
head.html
http://www.laurie.umdnj.edu/database/framedat.html
http://www.uhrad.com/mriarc.htm
http://www.med.harvard.edu/AANLIB/home.html
http://www.mdchoice.com/xray/xrx.asp
http://www.cc.emory.edu/ANATOMY/Radiology/Head_and_Neck/Head.html
http://radiology.bidmc.harvard.edu/default.htm
http://www.radiologyweb.com/
http://auntminnie.com/index.asp?Sec=log&Sub=reg&Pag=104&user=new
http://www.geocities.com/Hollywood/Highrise/1713/mfile.htmlhttp://www.netmedicine.com/
xray/ctscan/ct.htm
“Imaging” Ophthalmology Clinics, September 1998
“Ophthalmic Imaging and Diagnostics” Ophthalmology Clinics, September 1994
“MRI of the Eye and Orbit” DePotter, Shields, Shields. 1995 Lippincott
“Computed Tomography of the Eye and Orbit” Hammerschlag, Hesselink, Weber. 1983
Appleton-Century-Crofts
“MR/CT Atlas of Anatomy: CD-ROM” Keuper. 2002 Thieme
“Teaching Atlas of Brain Imaging” Fischbein, Dillon, Barkovich. 2000 Thieme