CT Scan (Head/Orbits)

CT (computed tomography) scan uses X-rays to create detailed cross-sectional images of the head, brain, and eye sockets. It's faster than MRI and excellent for evaluating bone and detecting bleeding.

Why It's Ordered

• Rule out acute bleeding or stroke causing vision loss or double vision
• Evaluate orbital fractures
• See bony anatomy (sinuses, skull base)
• Quick assessment when MRI unavailable
• Detect optic disc drusen calcification (causes pseudo-disc edema)
• Evaluate for thyroid eye disease (proptosis, muscle enlargement)
• Chest CT to evaluate for thymoma in myasthenia gravis
• Look for Pancoast tumor in Horner syndrome

CT vs MRI

CT	MRI
Quick (5-10 minutes)	Longer (30-60 minutes)
Best for bone, bleeding	Best for soft tissue, nerves
Uses radiation	No radiation
Widely available	Less available
OK with most implants	Magnet concerns

What to Expect

Before the Scan

• Remove metal from head/neck area
• May receive IV contrast

During the Scan

• Lie on table that slides through ring
• Must hold still for best images
• Takes only a few minutes
• You'll hear whirring sounds

After the Scan

• Resume normal activities immediately
• Drink fluids if contrast was given

CT Angiography (CTA)

Special CT with IV contrast to see blood vessels:

• Evaluate for aneurysm (if third nerve palsy with pupil involvement)
• Assess arterial disease (carotid dissection in Horner syndrome)
• Look for venous sinus thrombosis (causing papilledema)

Contrast

Why It's Used

• Enhances blood vessels
• Shows inflammation
• Highlights tumors

Precautions

• Kidney function checked beforehand
• Allergies to contrast discussed
• Generally very safe

Related Tests

• MRI brain and orbits—better for soft tissue, optic nerve, demyelination
• OCT—detailed retinal and optic nerve imaging
• Visual field testing—functional assessment of vision loss