Chromosome 22. Merlin (schwannomin). Bilateral vestibular schwannoma. The young adult who slowly loses hearing in both ears, then their balance. Here is the whole disease, broken into pieces that stick.
Autosomal DominantChromosome 22q12Merlin / SchwannominBilateral CN VIII
A 23-year-old presents with two years of progressive hearing loss in both ears, ringing that never stops, and unsteadiness when walking in the dark. Audiogram shows bilateral sensorineural hearing loss. MRI of the brain with contrast reveals enhancing masses at both cerebellopontine angles, extending into the internal acoustic meatus.
What is the most likely underlying diagnosis?
Neurofibromatosis Type 1
Neurofibromatosis Type 2
Tuberous sclerosis
Von Hippel-Lindau
Sporadic acoustic neuroma
Bilateral vestibular schwannoma in a young adult = NF2 until proven otherwise.
A single, one-sided acoustic neuroma in an older adult is usually sporadic and stays sporadic. The second the lesion is on both sides, the diagnosis flips. NF1 grows neurofibromas on peripheral nerves and Lisch nodules in the iris, not bilateral CN VIII masses. Tuberous sclerosis makes cortical tubers and rhabdomyomas. VHL makes hemangioblastomas and renal cell carcinoma.
The gene lives on chromosome 22. The protein it codes for is merlin (also called schwannomin), a tumor suppressor that normally tells Schwann cells when to stop dividing. Lose merlin, the Schwann cells lose their brakes, and they pile up wherever a nerve sheath exists, most ruthlessly on the eighth cranial nerve.
The Clue Stack
Five fingerprints. See any of these in a stem, the answer is NF2.
Clue 01 · The Headliner
Bilateral CN VIII masses
Vestibular schwannoma on both sides. Hearing fades in both ears, the room starts spinning. Sporadic schwannoma is one-sided. Two sides equals NF2.
Clue 02 · The Protein
Merlin / Schwannomin
A tumor suppressor that brakes Schwann cell growth. Two names, one protein. If the stem mentions either, you are in NF2 land.
Clue 03 · The Address
Chromosome 22
Autosomal dominant. 22q12. The mnemonic shortcut: NF2, chromosome 22, two schwannomas. NF1 lives on 17. Do not flip these.
Clue 04 · The Skin
Cafe au lait, but quiet
A few cafe au lait spots show up, but no axillary freckling, no Lisch nodules, no cutaneous neurofibromas. The skin is a footnote, not the story.
Clue 05 · The Bonus Tumors
Meningioma + ependymoma
Often multiple meningiomas. Ependymomas in the spinal cord. Juvenile cataracts too: a young adult with cataracts and any of the above is NF2.
If a young adult drops three of these tumor types in one chart, the diagnosis is not coincidence. MISME is the radiologist way of saying NF2 in five letters.
Lock it in
NF 2·CN 8
Two and eight, every time. 2 from NF2, 8 from the cranial nerve it owns. Add it up: 2 + 2 = 4 + 4 = 8. Or just remember the equation.
Where it grows: CN VIII at the cerebellopontine angle
The eighth nerve runs from the brainstem out through a bony tunnel called the internal acoustic meatus. The schwannoma starts inside that tunnel and grows out into the cerebellopontine angle, the corner between cerebellum and pons. Tap each label to see what it does.
Axial slice · tap anything labeled to see what it does
Tap a structure on the diagram to read about it.
Why the eighth nerve? CN VIII is wrapped in a thick Schwann-cell sheath as it runs through the internal acoustic meatus. Schwann cells need merlin to know when to stop dividing. Lose merlin (NF2), and the cells stack up in that tiny bony tunnel until they push out into the CPA. Classic radiology shape: ice cream on a cone, the round CPA mass connected to a narrow stem inside the meatus.
Bilateral = NF2
Coronal view, looking at the brainstem from the front. One mass on each side, both eating into the eighth nerve. This is the single image that closes the diagnosis.
Coronal · Front view
Two masses. Two ears fading. One diagnosis.
Sporadic acoustic neuroma is unilateral and usually presents in older adults. Bilateral in a young adult is NF2 until the geneticist says otherwise.
Histology: Antoni A vs Antoni B
Two areas, one tumor. Compact spindle cells in palisades on one side (Antoni A, with Verocay bodies in the middle of the palisade), loose myxoid on the other (Antoni B). The real H and E sits next to a schematic so you can match what your eye sees to what the textbook is naming.
Real H&E · Antoni A
Compact spindle cells, palisading nuclei
Tightly packed, elongated cells. The nuclei line up in rows facing each other across an anuclear core. Those rows of nuclei plus the pink core in between are called Verocay bodies.
Wikimedia Commons · CC BY-SA
Schematic · A and B side by side
Two zones, one tumor
A: spindle cells in two opposing rows, pink core in between = Verocay body. B: same tumor, but the cells lose their formation, drift apart, and sit in a loose myxoid pool.
What stains positive? Schwannomas (and the cells they came from) are stuffed with S-100 protein. If the stem says "diffusely S-100 positive nerve sheath tumor" in someone with bilateral CN VIII masses, that is the histology confirming what the MRI already told you.
Board trap
Verocay bodies look like nuclear palisades on either side of an eosinophilic (pink) core. Do not confuse with the Schiller-Duval bodies of yolk sac tumor (those are glomeruloid structures with a central vessel, completely different organ) or pseudorosettes of ependymoma. Same word "palisading" appears in glioblastoma necrosis, but there the palisades surround dead tissue, not a Verocay core.
NF1 vs NF2
Same family name, completely different disease. Mix these up on test day and the question is over. Lock the four-line difference and move on.
NF1
NF2
Chromosome
17q11.2
22q12
Gene product
Neurofibromin (Ras-GAP brake)
Merlin (a.k.a. schwannomin)
Hallmark tumor
Cutaneous neurofibromas, optic glioma
Bilateral vestibular schwannoma
Other tumors
Pheochromocytoma, MPNST
Multiple meningiomas, spinal ependymoma
Skin
6+ cafe au lait, axillary freckling, neurofibromas everywhere
A few cafe au lait, no axillary freckling, no cutaneous neurofibromas
The number trick: NF1 → chromosome 17 (1+7 = something, just learn it as "1 then 7"). NF2 → chromosome 22 ("2 and 2") → cranial nerve 8 (the two from NF2 plus the two twos of chromosome 22, or just 2+2+2+2 = 8). Whatever number-trick clicks for you, use it. The exam never asks "is it NF1 or NF2" without a clue that flags one or the other.
The classic swap
Cafe au lait + axillary freckling + Lisch nodules = NF1. Bilateral hearing loss + meningioma + juvenile cataract = NF2. The skin question never goes to NF2. The hearing question never goes to NF1.
Test Yourself
Five clinical vignettes. Read the stem, hunt the clue, pick bottom-up. Explanations break down every wrong choice, not just the right one.
Medically reviewed by Kaitlyn Cocuzzo, MD and Fatima Ali, DO · Last updated July 1, 2026 at 10:03 PM ET
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