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MRI Internal Auditory Canals (IAC) With and Without Contrast

MR+ ContrastHead & Neck

Indications

Sensorineural hearing loss (asymmetric)
Tinnitus
Vertigo
Suspected vestibular schwannoma / CPA mass
Facial nerve palsy

Patient prep

MRI safety screening
IV access for contrast
Head coil
Stress importance of stillness (thin slices)

Contrast

Agentgadolinium-based

RouteIV

Dose0.1 mmol/kg

TimingPost-contrast thin T1 through IAC/CPA

Technique

High-resolution thin-section imaging of IAC, CPA, and cochlea/labyrinth
Heavily T2-weighted 3D sequence (CISS/FIESTA/DRIVE) for cranial nerves and endolymph
Small FOV (~16-18 cm) targeted to posterior fossa
Whole-brain screening T2/FLAIR usually included

Series / Sequences

#	Series / Sequence	Plane	Weighting / Recon	Thickness	Notes
1	Ax 3D heavily T2 (CISS/FIESTA)	axial	T2 (3D)	0.5-1 mm	Cranial nerves VII/VIII, membranous labyrinth
2	Ax T2 FSE whole brain	axial	T2	4-5 mm	Screening
3	Ax FLAIR	axial	FLAIR	4-5 mm	Brain screening; labyrinthitis
4	Ax T1 pre IAC	axial	T1	2-3 mm	Thin through IAC
5	Ax T1 post fat-sat	axial	T1 +C FS	2-3 mm	Enhancing schwannoma/neuritis
6	Cor T1 post fat-sat	coronal	T1 +C FS	2-3 mm

Key points

3D CISS/FIESTA depicts the nerve bundle within CSF and detects small intracanalicular schwannomas.
Some sites screen with non-contrast 3D T2 alone for hearing loss; contrast adds sensitivity/specificity.
Post-contrast fat-sat improves conspicuity of small enhancing lesions.
Evaluate labyrinth on FLAIR for labyrinthitis/hemorrhage.

References

• ACR-ASNR Practice Parameter for MRI of the Head
• Radiopaedia: IAM/IAC MRI protocol link
• ACR Appropriateness Criteria: Hearing Loss and/or Vertigo

Source: Researched — verify against your institution

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Reference template — verify and adapt to your scanner, vendor and institution before clinical use. Not a substitute for clinical judgment.