Workup/Staging Flashcards
What tests are performed on physical exam for pts with CPA lesions?
Rinne test (mastoid bone, air conduction > bone conduction) and Weber test (occiput, vibratory sound louder on good side) to confirm sensorineural hearing loss; also need to check for other CN deficits (CN VII, hypesthesia, corneal twitching)
What CN is being tested when a pt is asked to tighten the ant neck muscles?
CN VII (innervates platysma muscle) can often be affected with large AN lesions.
Why are pts with CPA lesions often asked to march in place with their eyes closed on physical exam?
When the vestibular nerve is affected, pts will often veer to the side of the lesion.
What is the best initial screening test for ANs, and what does it usually show?
Audiometry (asymmetric sensorineural loss, more prominent at ↑ frequencies) is the best screening tool for ANs.
What is the avg growth rate per yr for ANs?
∼1 mm/yr. Growth rates range from 0.5–2.5 mm/yr (slow-growing lesions) to ≥2.5 mm/yr (fast-growing lesions).
What % of ANs are stable (shrink/do not grow)?
∼20%–40% of ANs are considered stable.
Is the size of the tumor at presentation predictive of the tumor’s growth rate?
No. Tumor size is generally not predictive of the tumor’s growth rate.
Does AN tumor size correlate with hearing loss?
Usually not. The location of the tumor (i.e., intracanalicular vs. not intracanalicular) is more predictive. Pts with tumor growth rate ≤2.5 mm/yr have higher hearing preservation than those with higher tumor growth. (Sughrue ME et al., J Neurosurg 2010)
What do brainstem auditory evoked potentials typically show in pts with ANs?
A delay of conduction time on the affected side is seen with auditory evoked potentials.
What imaging study is typically performed for ANs?
Thin-slice (1–1.5 mm) MRI with gadolinium. MRI can detect tumors as small as 1–2 mm in diameter. If NF is suspected, neuraxis MRI is performed. If pt cannot undergo MRI, high-resolution CT scan +/− contrast is the alternative.
To what is the “ice cream cone” appearance of ANs on MRI due?
This AN appearance is d/t enhancing lesions in the canal (cone) and CPA (ice cream).
