Which of the following is NOT a paranasal sinus?

Appeared in: NHM UP Staff Nurse-2023 shift 1st

Explanation

The sigmoid sinus is a dural venous sinus, which is a channel for blood drainage from the brain, not an air-filled paranasal sinus.
Paranasal sinuses (Ethmoid, Maxillary, Sphenoid, Frontal) are air-filled spaces connected to the nasal cavity.
The sigmoid sinus is part of the brain's venous system, draining blood towards the internal jugular vein, and is fundamentally different in structure and function from paranasal sinuses.

Option B: The ethmoid sinus is one of the four primary paranasal sinuses, consisting of multiple small air cells located between the eyes.
Option C: The maxillary sinus is the largest of the paranasal sinuses, located in the cheekbones (maxilla).
Option D: The sphenoid sinus is a paranasal sinus located deep within the skull in the sphenoid bone.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy of Paranasal and Dural Venous Sinuses as background academic context rather than a clinical decision trigger.
Understanding the distinction between paranasal and venous sinuses is crucial for diagnosing conditions like sinusitis (inflammation of paranasal sinuses) and dural sinus thrombosis (a blood clot in a venous sinus), which have vastly different symptoms and treatments.
A nurse assessing a patient with facial pain, pressure, and nasal discharge would suspect sinusitis, involving the paranasal sinuses. In contrast, a patient with a severe headache, neurological deficits, or seizures might be evaluated for dural venous sinus thrombosis.
What if? If a patient with mastoiditis (infection of the mastoid bone behind the ear) develops a severe headache and neurological symptoms, a nurse should be alert for the potential spread of infection to the adjacent sigmoid sinus, causing septic thrombosis—a life-threatening emergency.

How to Approach the Question

First, identify the core subject of the question, which is the anatomy of the 'paranasal sinus'.
Note the negative keyword 'NOT'. This means you are looking for the option that does not fit the definition of a paranasal sinus.
Mentally recall or list the four pairs of paranasal sinuses: Frontal, Maxillary, Ethmoid, and Sphenoid.
Evaluate each option against your list: 'Ethmoid', 'Maxillary', and 'Sphenoid' are all on the list of paranasal sinuses.
Recognize that 'Sigmoid' is not on the list. Recall that the sigmoid sinus is a dural venous sinus related to blood drainage in the brain.
Therefore, the sigmoid sinus is the correct answer as it is NOT a paranasal sinus.

Concept Tested & Keywords

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E6 Anatomy Applied Ashalatha 4e p. 92-94

E6 Medicine Harrison 22e Part 1 p. 1182-1184

Practise the full NHM UP Staff Nurse-2023 shift 1st

Attempt every question from this paper in a timed mock, then review the full solution for each one.