Question 1: Vestibular Schwannoma
Stem: A 52-year-old woman presents with progressive, unilateral sensorineural hearing loss and tinnitus on the right. A contrast-enhanced MRI reveals an avidly enhancing 2 cm mass that is centered on the right internal auditory canal (IAC), expanding it, and extending into the cerebellopontine angle (CPA).
Question: What is the classic descriptive shape of this mass?
(A) “Dural tail” sign (B) “Ice-cream cone” appearance (C) “Salt-and-pepper” appearance (D) “Target” sign (E) “Whorled” appearance
Correct Answer: (B) “Ice-cream cone” appearance
Explanation:
- Why (B) is correct: A vestibular schwannoma (acoustic neuroma) arises from the 8th cranial nerve within the IAC. As it grows, the portion inside the bone (the IAC) stays narrow (the “cone”), while the portion protruding into the CPA expands (the “ice cream”).
- Why (A) is wrong: This is classic for a meningioma, which is the second most common CPA mass but is dural-based and does not usually expand the IAC.
- Why (C) is wrong: This refers to the flow voids and hemorrhage seen in paragangliomas (e.g., glomus jugulare).
- Why (D) is wrong: A “target sign” is seen in neurofibromas, not typically in vestibular schwannomas.
- Why (E) is wrong: This is a histological feature of meningiomas.
Key Points: Vestibular Schwannoma
- Most common CPA mass (80%).
- NF-2: Suspect if lesions are bilateral.
- Imaging: Intensely enhancing; expands the IAC.
Question 2: Cholesteatoma
Stem: A 35-year-old man with chronic ear discharge and conductive hearing loss undergoes a CT of the temporal bones. The images show a soft-tissue mass in Prussak’s space causing erosion of the scutum and displacement of the ossicles.
Question: What is the most likely diagnosis?
(A) Otosclerosis (B) Glomus tympanicum (C) Acquired cholesteatoma (D) Cholesterol granuloma (E) Facial nerve schwannoma
Correct Answer: (C) Acquired cholesteatoma
Explanation:
- Why (C) is correct: An acquired cholesteatoma (pars flaccida type) classically begins in Prussak’s space (lateral epitympanic space). The erosion of the scutum (the sharp bony spur of the lateral attic wall) is the earliest and most reliable sign.
- Why (A) is wrong: Otosclerosis causes bony demineralization around the oval window (fenestral) or cochlea (retrofenestral), not an erosive mass.
- Why (B) is wrong: Glomus tympanicum is a vascular red mass on the cochlear promontory, not in Prussak’s space.
- Why (D) is wrong: Cholesterol granulomas occur in the petrous apex and are bright on both T1 and T2 MRI.
- Why (E) is wrong: This arises from the facial nerve canal and would follow its course (e.g., geniculate ganglion).
Key Points: Cholesteatoma
- CT: Non-enhancing soft tissue + bony erosion.
- MRI: Shows restricted diffusion (non-echo planar DWI is the gold standard for recurrence).
Question 3: Thyroid Eye Disease
Stem: A 48-year-old woman presents with bilateral, painless proptosis. CT orbits show symmetric enlargement of the extraocular muscle bellies, but the tendinous insertions are spared.
Question: Which extraocular muscle is most commonly involved first in this condition?
(A) Superior rectus (B) Medial rectus (C) Lateral rectus (D) Inferior rectus (E) Superior oblique
Correct Answer: (D) Inferior rectus
Explanation:
- Why (D) is correct: In Thyroid Eye Disease (Grave’s orbitopathy), the order of muscle involvement follows the mnemonic I’M SLO (Inferior, Medial, Superior, Lateral, Obliques). The inferior rectus is the most common and earliest muscle affected.
- Why (A), (B), (C) are wrong: These are involved later than the inferior rectus.
- Why (E) is wrong: Oblique muscles are rarely involved in Grave’s.
Key Points: Thyroid Eye Disease
- Tendon Sparing: Key feature to distinguish from orbital pseudotumor.
- Clinical: Painless proptosis; strongly associated with smoking.
Question 4: Orbital Pseudotumor
Stem: A 40-year-old patient presents with painful proptosis. CT shows an ill-defined enhancing mass in the orbit that involves both the muscle belly and the tendinous insertion of the lateral rectus.
Question: What is the most likely diagnosis?
(A) Grave’s orbitopathy (B) Orbital pseudotumor (Idiopathic Orbital Inflammation) (C) Orbital lymphoma (D) Dermoid cyst (E) Optic nerve glioma
Correct Answer: (B) Orbital pseudotumor
Explanation:
- Why (B) is correct: Unlike Thyroid Eye Disease, orbital pseudotumor is painful and involves the tendons. It is a diagnosis of exclusion.
- Why (A) is wrong: Grave’s is painless and spares the tendons.
- Why (C) is wrong: Lymphoma is painless and classically “molds” to the shape of the globe without invading it.
- Why (D) is wrong: Dermoid cysts are well-circumscribed fat-containing masses, usually at the frontozygomatic suture.
- Why (E) is wrong: This involves fusiform enlargement of the optic nerve itself.
Key Points: Orbital Pseudotumor
- Treatment: Responds dramatically to steroids.
- Imaging: “Shaggy” appearance of the orbital fat; involves muscle + tendon.
Question 5: Allergic Fungal Rhinosinusitis (AFRS)
Stem: A 30-year-old with chronic sinusitis and nasal polyps has a CT scan showing complete opacification of the ethmoid sinuses with centrally hyperdense material. On MRI, this central material shows a signal void on T2-weighted images.
Question: The T2 signal void is primarily due to:
(A) Acute hemorrhage (B) Highly proteinaceous secretions and fungal elements (C) Dense calcification (D) Air within the sinus (E) An inverted papilloma
Correct Answer: (B) Highly proteinaceous secretions and fungal elements
Explanation:
- Why (B) is correct: Fungal mucin in AFRS is thick and contains high concentrations of manganese, magnesium, and iron, which causes the pathognomonic T2 signal void (appearing like air) on MRI.
- Why (A) is wrong: Hemorrhage signal changes over time but isn’t the classic cause of central signal void in chronic sinusitis.
- Why (C) is wrong: While the mucin is hyperdense on CT, it is not solid bone/calcification.
- Why (D) is wrong: While it looks like air, the sinus is actually full of dense mucin.
- Why (E) is wrong: Inverted papilloma is a tumor with a “cerebriform” pattern on MRI.
Key Points: AFRS
- CT: Hyperdense mucin + bony expansion/remodeling.
- MRI: T2 signal void in the center of the sinus.
Question 6: Inverted Papilloma
Stem: A 55-year-old man presents with unilateral nasal obstruction. CT shows a soft-tissue mass centered in the middle meatus with focal hyperostosis at its origin on the lateral nasal wall.
Question: This lesion has a 10% associated risk of which malignancy?
(A) Adenocarcinoma (B) Squamous cell carcinoma (SCC) (C) Esthesioneuroblastoma (D) Lymphoma (E) Melanoma
Correct Answer: (B) Squamous cell carcinoma (SCC)
Explanation:
- Why (B) is correct: Inverted papillomas are benign but locally aggressive tumors. Approximately 10% are associated with synchronous or metachronous SCC.
- Why (A), (C), (D), (E) are wrong: While these occur in the sinonasal tract, they are not specifically associated with inverted papillomas.
Key Points: Inverted Papilloma
- Origin: Lateral nasal wall (middle meatus).
- CT: Look for the bony “pedicle” (focal hyperostosis) at the site of origin.
- MRI: “Convoluted cerebriform pattern.”
Question 7: Juvenile Nasopharyngeal Angiofibroma (JNA)
Stem: A 16-year-old male presents with severe, recurrent epistaxis. CT shows a highly vascular mass in the nasopharynx that is causing anterior bowing of the posterior wall of the maxillary sinus.
Question: This “bowing” sign is known as:
(A) The “Antral sign” (B) The “Holman-Miller sign” (C) The “Thurman sign” (D) The “Pfeiffer sign” (E) The “Scimitar sign”
Correct Answer: (B) The “Holman-Miller sign”
Explanation:
- Why (B) is correct: The Holman-Miller sign is pathognomonic for JNA and represents the anterior displacement of the posterior maxillary sinus wall.
- Why (A) is wrong: Not a standard radiologic eponym for this.
- Why (C), (D) are wrong: Not associated with JNA.
- Why (E) is wrong: This refers to Scimitar Syndrome in the chest.
Key Points: JNA
- Demographic: Adolescent males only.
- Origin: Sphenopalatine foramen.
- Contraindication: Do not biopsy (massive hemorrhage risk).
Question 8: Otosclerosis
Stem: A 40-year-old woman with progressive conductive hearing loss shows a small focus of lucency at the fissula ante fenestram (anterior to the oval window) on a high-resolution CT.
Question: This is the most common location for which type of otosclerosis?
(A) Retrofenestral (B) Cochlear (C) Fenestral (D) Labyrinthine (E) Ossicular
Correct Answer: (C) Fenestral
Explanation:
- Why (C) is correct: Fenestral otosclerosis involves the oval window. The most common site is the fissula ante fenestram.
- Why (A), (B), (D) are wrong: Retrofenestral (or cochlear) otosclerosis is more severe, involving the otic capsule around the cochlea, and appears as a “double ring” sign.
- Why (E) is wrong: Otosclerosis affects the otic capsule, not the ossicles directly (though it can fix the stapes footplate).
Key Points: Otosclerosis
- Fenestral: Conductive hearing loss (oval window).
- Retrofenestral: Sensorineural hearing loss (otic capsule).
Question 9: Optic Nerve Sheath Meningioma
Stem: A 45-year-old woman presents with slow vision loss. Contrast-enhanced MRI of the orbits shows avid enhancement of the optic nerve sheath with a non-enhancing central nerve.
Question: This appearance is known as the:
(A) “Doughnut” sign (B) “Target” sign (C) “Tram-track” sign (D) “Bull’s eye” sign (E) “Halo” sign
Correct Answer: (C) “Tram-track” sign
Explanation:
- Why (C) is correct: On axial imaging, the enhancing sheath surrounding the dark nerve looks like parallel railroad tracks.
- Why (A) is wrong: This is the appearance on coronal imaging, but “tram-track” is the primary eponym.
- Why (B), (D), (E) are wrong: These refer to other pathologies (e.g., neurofibroma or liver lesions).
Key Points: Optic Nerve Sheath Meningioma
- Clinical: Slow, painless vision loss.
- Differential: Optic neuritis (nerve itself enhances, no mass).
Question 10: Glomus Jugulare
Stem: A patient presents with pulsatile tinnitus and a “moth-eaten” pattern of destruction at the jugular foramen. MRI shows a “salt-and-pepper” appearance within the mass.
Question: The “pepper” in the “salt-and-pepper” sign represents:
(A) Areas of slow flow (B) Subacute hemorrhage (C) High-flow vascular flow voids (D) Dense calcification (E) Fatty marrow
Correct Answer: (C) High-flow vascular flow voids
Explanation:
- Why (C) is correct: The “pepper” represents low-signal vascular flow voids from high-flow vessels.
- Why (B) is wrong: The “salt” represents high-signal foci of subacute hemorrhage.
- Why (D), (E) are wrong: These do not cause the classic glomus appearance on MRI.
Key Points: Glomus Jugulare
- Nerves: Can involve CN IX, X, XI.
- Pathology: A paraganglioma.
Question 11: Branchial Cleft Cyst
Stem: A 25-year-old presents with a painless mass at the angle of the mandible. CT shows a thin-walled cyst located lateral to the carotid space and anterior to the sternocleidomastoid muscle.
Question: From which branchial cleft does this most commonly arise?
(A) First (B) Second (C) Third (D) Fourth (E) Fifth
Correct Answer: (B) Second
Explanation:
- Why (B) is correct: Second branchial cleft cysts are the most common (95%) and occur at the level of the mandibular angle.
- Why (A) is wrong: First cleft cysts are around the parotid/ear.
- Why (C), (D) are wrong: These occur lower in the neck/chest and are rare.
Key Points: 2nd Branchial Cleft Cyst
- Beak Sign: A “beak” pointing between the internal and external carotid arteries is diagnostic.
Question 12: Thyroglossal Duct Cyst
Stem: A 10-year-old boy presents with a midline neck mass that moves upwards when he sticks his tongue out.
Question: What is the most common location for this lesion?
(A) Suprahyoid (B) Infrahyoid (C) Level of the hyoid bone (D) Within the tongue base (E) Suprasternal notch
Correct Answer: (B) Infrahyoid
Explanation:
- Why (B) is correct: While they can occur anywhere along the duct, 65% are infrahyoid.
- Why (A), (C) are wrong: Less common locations (Suprahyoid ~20%, Hyoid ~15%).
Key Points: Thyroglossal Duct Cyst
- Sistrunk Procedure: Surgical removal includes the mid-portion of the hyoid bone to prevent recurrence.
Question 13: Ranula
Stem: A patient presents with a soft-tissue swelling in the submandibular space. CT shows a cystic lesion “diving” from the sublingual space into the submandibular space by passing around the posterior border of the mylohyoid muscle.
Question: What is this lesion called?
(A) Simple ranula (B) Diving ranula (C) Dermoid cyst (D) Laryngocele (E) Retention cyst
Correct Answer: (B) Diving ranula
Explanation:
- Why (B) is correct: A diving (or plunging) ranula is a mucous retention cyst from the sublingual gland that herniates into the submandibular space.
- Why (A) is wrong: A simple ranula is confined to the sublingual space.
Key Points: Diving Ranula
- Sign: The “tail sign” (the portion of the cyst in the sublingual space) is diagnostic.
Question 14: Laryngocele
Stem: A trumpet player presents with a neck mass that increases in size with a Valsalva maneuver. CT shows an air-filled sac arising from the laryngeal ventricle and extending through the thyrohyoid membrane.
Question: What is the most important underlying condition to exclude in an adult with a secondary laryngocele?
(A) Laryngeal papillomatosis (B) Squamous cell carcinoma (SCC) (C) Reinke’s edema (D) Vocal cord paralysis (E) Amyloidosis
Correct Answer: (B) Squamous cell carcinoma (SCC)
Explanation:
- Why (B) is correct: An acquired laryngocele is often caused by a tumor (SCC) obstructing the laryngeal ventricle. Always look for a mass at the base of the laryngocele.
Key Points: Laryngocele
- Internal: Confined to the larynx.
- External: Protrudes through the thyrohyoid membrane into the neck.
Question 15: Sialolithiasis
Stem: A patient presents with pain and swelling of the submandibular gland that worsens during meals.
Question: Which salivary gland is the most common site for stone formation?
(A) Parotid gland (B) Sublingual gland (C) Submandibular gland (D) Minor salivary glands (E) Lacrimal gland
Correct Answer: (C) Submandibular gland
Explanation:
- Why (C) is correct: 80-90% of stones occur in the submandibular gland (Wharton’s duct) because the saliva is more alkaline, has higher calcium content, and must flow against gravity.
- Why (A) is wrong: Parotid stones (Stensen’s duct) are less common (~10-20%) and often radiolucent.
Key Points: Sialolithiasis
- CT: Best for detecting stones (90% of submandibular stones are radiopaque).
- Ultrasound: Good for dilated ducts and larger stones.
