5. The cavernous sinus

Question 1

what are the cavernous venous sinuses

Answer 1

pair of dural venous sinuses located laterally to body of sphenoid

Question 2

where does the cavernous venous sinus receive blood from

Answer 2

• superior and inferior ophthalmic veins
• middle superficial cerebral veins
• sphenoparietal sinus

Question 3

describe the boundaries of the cavernous sinus

Answer 3

• roof: tentorium cerebelli (attached to anterior and middle clinoid processes)
• floor: greater wing of sphenoid
• anterior wall: superior orbital fissure (medial end)
• posterior wall: petrous apex
• medial wall: body of sphenoid
• lateral wall: dura mater of middle cranial fossa

Question 4

name 2 structures running in the middle of the sinus

Answer 4

1. internal carotid a.

2. abducens n. (CN VI)

Question 5

name 4 nerves running along the lateral sinus walls

Answer 5

1. occulomotor n. (CN III)
2. trochlear n. (CN IV)
3. ophthalmic n. (CN Va)
4. maxillary n. (CN Vb)

Question 6

how can infection in the danger zone of the face spread to the cavernous sinus

Answer 6

via the valveless facial vein which is connected to the cavernous sinus by superior ophthalmic vein - blood can reverse direction and flow into sinus

Question 7

other than infection, how does the facial vein pose a risk to the cavernous sinus

Answer 7

blood clot may travel from facial vein, via superior ophthalmic vein, to sinus, causing cavernous sinus thrombosis

Question 8

describe and explain the signs/symptoms of cavernous sinus thrombosis

Answer 8

1. severe pain in eye and ant. forehead
   - sensory info. from ophthalmic n. (CN Va)
2. complete ophthalmoplegia
   - dysfunction of occulomotor n. (CN III), trochlear n. (CN IV) and abducens n. (CN VI)
3. dilated unreactive pupils
   - compression of CN III parasympathetic fibres - loss of sphincter pupillae function
4. ptosis
   - occulomotor n. (CN III) dysfunction (+/- sympathetics)
   - oedema of upper eyelid
5. exopthalmos & periorbital oedema
   - venous block, e.g. of ophthalmic vv.