Neuroanatomy: dural venous sinuses: practice question

A Anatomy question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Anatomy · Neuroanatomy: dural venous sinuses

Sample item

A child with chronic otitis media has spiking fever, tenderness over the mastoid and a thrombus in the sigmoid sinus on MRI venography. Why does mastoid infection extend so readily to this sinus?

AThe sinus passes through the middle ear cavityBThe sinus lies in the petrous apex next to the tympanic roofCThe sinus lies in a groove on the inner surface of the mastoid, separated from the air cells by a thin plate of boneDThe sinus drains the mastoid air cells directly through the stylomastoid foramen

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. The sinus lies in a groove on the inner surface of the mastoid, separated from the air cells by a thin plate of bone

The sigmoid sinus continues the transverse sinus and lies in a groove on the inner surface of the mastoid part of the temporal bone. It is separated from mastoid air cells only by a thin bony plate, so infection can erode through it. The sinus then continues as the internal jugular vein through the jugular foramen.

Option by option

A. The sinus passes through the middle ear cavity
The sinus does not pass through the middle ear.
B. The sinus lies in the petrous apex next to the tympanic roof
The petrous apex relates to the inferior petrosal and abducens nerve, not to the sigmoid sinus.
C. The sinus lies in a groove on the inner surface of the mastoid, separated from the air cells by a thin plate of bone (correct)
Correct. The thin bony relation explains the spread.
D. The sinus drains the mastoid air cells directly through the stylomastoid foramen
The stylomastoid foramen transmits the facial nerve, not a sinus.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is C, The sinus lies in a groove on the inner surface of the mastoid, separated from the air cells by a thin plate of bone. The sigmoid sinus continues the transverse sinus and lies in a groove on the inner surface of the mastoid part of the temporal bone.

Why is "The sinus passes through the middle ear cavity" not the answer?

The sinus does not pass through the middle ear.

Why is "The sinus lies in the petrous apex next to the tympanic roof" not the answer?

The petrous apex relates to the inferior petrosal and abducens nerve, not to the sigmoid sinus.

Why is "The sinus drains the mastoid air cells directly through the stylomast…" not the answer?

The stylomastoid foramen transmits the facial nerve, not a sinus.

What concept does this question test?

It tests Neuroanatomy: dural venous sinuses in Anatomy. It is separated from mastoid air cells only by a thin bony plate, so infection can erode through it. The sinus then continues as the internal jugular vein through the jugular foramen.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Neuroanatomy: dural venous sinuses?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.