Blue boxes

Question 1

Why could a fracture of the pterion be life threatening?

Answer 1

Because it overlies the frontal branches of the middle meningeal vessels

• the pterion is two fingers breadth posterior to the frontal process of the zygomatic bone
• a hard blow to the side of the head may fracture the thin bones forming the pterion
• this would produce a rupture of the frontal branch of the middle meningeal artery or vein crossing the pterion
• this would result in a hematoma which would put pressure on the underlying cerebral cortex
• untreated middle meningeal vessel hemorrhage may cause death in a few hours

Question 2

Because of what connections could an infection of the face spread to the cavernous sinus and pterygoid venous plexus?

Answer 2

The facial vein make connections with the cavernous sinus through the superior ophthalmic vein, and the pterygoid venous plexus through the inferior ophthalmic and deep facial veins

• blood from the medial angle of the eye, nose, and lips usually drains inferiorly through the facial vein, especially when a person is erect
• because facial vein has no valves blood may pass through it in the opposite direction
• this leads to thrombophlebitis of the facial vein-inflammation of the facial vein with secondary thrombus (clot) formation-pieces of this infected clot may extend into the intracranial venous system and produce thrombophlebitis of the cavernous sinus
• caused by squeezing pimples
• “danger triangle”

Question 3

What is tectontorial herniation?

Answer 3

• tentorial notch is the opening in the tentorium cerebella for the brainstem, which is slightly larger than is necessary to accommodate the midbrain
• so things like tumors in the supratentorial compartment, produce increased intracranial pressure and may cause part of the adjacent temporal lobe of the brain to herniate through the tectontorial notch
• during this herniation, the temporal lobe may be lacerated by the tough tentorium cerebelli and the oculomotor nerve (CN III) may be stretched, compressed, or both
• oculomotor lesions may produce paralysis of the extrinsic eye muscles

Question 4

Explain bulging of Diaphragma sellae

Answer 4

• Pituitary tumors may extend superiorly through the aperture in the diaphragma sell, or cause it to bulge
• tumors often expand the diaphragm sellae producing disturbances in endocrine function

Question 5

How are occlusion of cerebral veins and dual venous sinuses formed?

Answer 5

• may result from thrombi, thrombophlebitis (venous inflammation), or tumors
• the dural venous sinuses most frequently thromboses are the transverse, cavernous, and superior sagittal sinuses
• the facial veins make clinically important connections with the cavernous sinus through the superior ophthalmic veins
• Cavernous sinus thrombosis usually results from infections in the orbit, nasal sinuses, and superior part of the face
• this may spread to more than one sinus
• septic thrombosis of the cavernous sinus often results in the development of acute meningitis

Question 6

Explain metastasis of tumor cells to dural venous sinuses

Answer 6

• the basilar and occipital sinuses communicate through the foramen magnum with the internal vertebral venous plexus
• because these venous channels are valveless, compression of the thorax, abdomen or pelvis (as occurs with heavy coughing), may force venous blood from these regions into the internal vertebral venous system and from it into the dural venous sinuses
• as a result, pus in abscess and tumor cells in these regions may spread to the vertebrae and brain

Question 7

What occurs because of fractures of the cranial base?

Answer 7

• the internal carotid artery may be torn, producing an arteriovenous fistula within the cavernous sinus
• arterial blood rushes into the cavernous sinus, enlarging it and forcing retrograde blood flow into its venous tributaries, especially ophthalmic veins
• the eyeball protrudes and the conductive becomes engorged

Question 8

what is the dural origin of headaches?

Answer 8

• the dura is sensitive to pain, especially where it is related to the dural venous sinuses and meningeal arteries
• pulling on arteries at the cranial base or veins near the vertex, where they pierce the dura, causes pain
• distension of the scalp or meningeal vessels is believed to be one cause of headache

Question 9

What is leptomeningitis?

Answer 9

• an inflammation of the leptomeninges (arachnoid and pia) resulting from pathogenic microorganisms
• the infection and inflammation are usually confined to the subarachnoid space and the arachnoid-pie
• the bacteria may enter the subarachnoid space through the blood or spread from an infection of the heart, lungs
• microorganisms may also enter the subarachnoid space from a compound of cranial fracture or a fracture of the nasal sinuses