Advanced Sigmoid Sinus Quiz

Q1. Why can infection in the mastoid region spread to the sigmoid sinus?

• The sinus lies inside the tympanic membrane
• The sinus is an artery within the mastoid cavity
• The sinus opens into the external acoustic meatus
• The sinus lies close to the mastoid air cell system

Q2. What anatomical process defines sigmoid sinus thrombosis?

• Formation of an obstructing thrombus within the sigmoid dural venous sinus
• Occlusion of the carotid canal by bone
• Compression of the cochlear nerve only
• Rupture of the middle cerebral artery

Q3. What is a direct hemodynamic consequence of occluding the sigmoid sinus?

• Isolated obstruction of scalp arteries
• Loss of basilar arterial inflow
• Impaired venous outflow with increased upstream venous pressure
• Immediate cessation of cerebrospinal fluid production

Q4. Why can injury to a dominant sigmoid sinus have greater consequences than injury to a smaller contralateral sinus?

• It supplies more arterial blood to the pons
• It contains additional cranial nerves
• It may carry a larger proportion of intracranial venous drainage
• It directly becomes the internal carotid artery

Q5. What is meant by a high-riding jugular bulb?

• The sigmoid sinus crosses above the frontal lobe
• The superior jugular bulb extends unusually high within the temporal bone
• The jugular bulb becomes an arterial structure
• The internal jugular vein enters the orbit

Q6. Why can the amount of bone over the sigmoid sinus vary during mastoidectomy?

• The sigmoid sinus is absent in most adults
• The sinus normally lies inside the tympanic cavity
• Sinus position and mastoid anatomy vary between individuals
• The temporal bone has a fixed thickness in all people

Q7. How can the mastoid emissary vein participate in intracranial spread of infection?

• It normally closes permanently after birth
• It provides a valveless extracranial connection to the sigmoid sinus
• It carries arterial blood from the sigmoid sinus to the scalp
• It connects only intracranial arteries

Q8. Why may an opened sigmoid sinus bleed persistently during surgery?

• Its wall contains a cardiac muscle pump
• Its dural walls help keep the venous channel open
• It connects directly to the left ventricle
• Its pressure equals systemic arterial pressure

Q9. Which relationship makes the sigmoid sinus an important landmark in posterolateral skull base surgery?

• It occupies the mandibular canal
• It crosses the cribriform plate
• It traverses the optic canal
• It follows the posterolateral skull base toward the jugular foramen

Q10. Which statement best integrates the anatomy of the sigmoid sinus?

• It drains the neck directly into the superior sagittal sinus
• It continues the transverse sinus through the posterior cranial fossa and becomes the internal jugular vein
• It is an artery connecting the carotid and vertebral circulations
• It is a lymphatic channel passing through the temporal bone