Carotid-cavernous junction.

Carotid-cavernous fistula is a pathological fistula that occurs as a result of damage to the internal carotid artery at the point where it passes through the cavernous sinus.

The most common cause of the formation of carotid-cavernous fistula is craniocerebral trauma, less often - infectious processes, developmental anomalies of the internal carotid artery.

An arteriovenous fistula is an abnormal connection between an artery and a vein. The blood in the affected vein becomes "arterial", the venous pressure increases, and the drainage function of the vein is impaired in volume and direction. A carotid-cavernous fistula is such a connection between the carotid artery and the cavernous sinus. When arterial blood is directed forward into the ophthalmic veins, the ocular symptoms are determined by venous and arterial stasis around the eyes and orbit, increased pressure in the episcleral veins, and decreased arterial flow to the cranial nerves within the cavernous sinus.

The classification of carotid-cavernous anastomosis is based on: etiology (spontaneous and traumatic), hemodynamics (high and low blood flow), anatomy (direct or indirect).

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Symptoms of carotid-cavernous fistula

Symptoms directly related to carotid-cavernous junction:

• aneurysmal noise (train noise);
• pulsating exophthalmos;
• dilation and pulsation of the veins of the face and cranial vault;
• phenomena of blood stagnation in the eyeball, swelling of the conjunctiva (chemosis);
• varicose veins, blood stasis and retinal vessels;
• increased intraocular pressure;
• impaired mobility of the eyeball;
• diplopia;
• drooping of the upper eyelid (ptosis).

Secondary symptoms caused by the duration of existing congestion in the cavernous sinus, orbit and venous system of the brain, a. carotis interna

• atrophy of retrobulbar tissue;
• hemorrhage into the retrobulbar tissue;
• corneal ulcers;
• clouding of the transparent media of the eye;
• panophthalmitis;
• thrombophlebitis of the veins of the orbit and acute glaucoma;
• optic nerve atrophy and blindness;
• bleeding from the vessels of the eyeball, nosebleeds;
• atrophy of adjacent areas of bone tissue;
• complications that depend on the disruption of cerebral circulation (psychosis, dementia, etc.).

Symptoms caused not by the fistula itself, but by the reasons that led to its appearance:

• optic nerve damage;
• damage to the oculomotor nerves;
• trigeminal nerve injury;
• general cerebral symptoms associated with the consequences of trauma to the skull and brain.

In the clinical picture of carotid-cavernous fistula, 3 periods are distinguished:

1. Acute (a fistula is formed and the main symptoms appear).
2. Compensation period (the increase in symptoms stops and they partially undergo reverse development).
3. The period of sub- and decompensation (there is a slow or rapid increase in phenomena that can lead to loss of vision, fatal bleeding, cerebral circulatory failure and mental disorders),

Direct carotid-cavernous anastomosis

This type occurs in 70-90% of cases and is a direct communication between the carotid artery and the cavernous sinus with high blood flow velocity due to a defect in the wall of the intracavernous portion of the carotid artery and as a result of the following reasons.

• Trauma (75% of cases): Basal skull fracture may result in a rupture in the intracavernous portion of the internal carotid artery with sudden and dramatic development of symptoms and signs.
• Spontaneous rupture of an intracavernous carotid aneurysm or atherosclerotic plaque. The risk group is hypertensive postmenopausal women. The blood flow velocity in spontaneous anastomosis is lower than in traumatic anastomosis, and the symptoms are less pronounced.

Symptoms of direct carotid-cavernous fistula

Manifestations may appear days or weeks after a head injury with the classic triad: pulsating exophthalmos, conjunctival chemosis, and tinnitus.

Signs usually appear on the side of the anastomosis, but can be bilateral and even contralateral due to the connection between the blood flows of both cavernous sinuses through the midline.

1. changes from the anterior segment
   • Ptosis and chemosis.
   • Pulsatile exophthalmos with noise and flutter that disappear when the ipsilateral carotid artery in the neck is compressed. There may also be a tinnitus.
   • Increased intraocular pressure due to increased pressure in the episcleral veins and congestion in the orbit.
   • Ischemia of the anterior segment of the eye is manifested by edema of the corneal epithelium, the presence of cells and flair in the moisture, atrophy of the iris, the development of cataracts and rubeosis of the iris.
2. ophthalmoplegia is observed in 60-70% of cases due to damage to the oculomotor nerve during trauma, intracavernous aneurysm of the carotid artery or the anastomosis itself. The VI nerve is most often affected due to its free location inside the cavernous sinus. The III and IV nerves are localized in the lateral wall of the sinus and are damaged less often. Blood-soaked and edematous extraocular muscles also contribute to limited mobility; c) congestion of the optic disc, dilated veins and intraretinal hemorrhages are visible on the fundus due to venous stasis and impaired blood flow in the retina. Preretinal hemorrhages and vitreous hemorrhages are rare.

Special research methods. CT and MRI show a protruding superior orbital vein and diffuse thickening of the extraocular muscles. Accurate diagnostics are based on angiography with isolated injection of contrast agent into the internal and external carotid arteries and into the spinal blood flow system.

The prognosis is poor: 90% of patients experience significant vision loss.

• Immediate loss of vision can occur if the optic nerve is damaged at the time of injury;
• Delayed vision loss may occur due to various complications: exposure keratopathy, secondary glaucoma, central retinal vein occlusion, anterior segment ischemia, or ischemic neuropathy.

Treatment of direct carotid-cavernous fistula

In most cases, carotid-cavernous fistula is not life-threatening. The eye is most severely affected. Surgical intervention is indicated if the fistula does not close spontaneously as a result of cavernous sinus thrombosis. Post-traumatic fistula closes less frequently than spontaneously occurring fistula due to higher blood flow velocity.

1. Indications: secondary glaucoma, diplopia, intolerable noise or headache, severe exophthalmos with keratopathy and anterior segment ischemia.
2. Interventional radiology: use of a temporary balloon to occlude the foramen. The balloon is inserted into the cavernous sinus through the foramen in the internal carotid artery (arterial route) or through the inferior petrosal sinus or superior ophthalmic vein (venous route).

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Indirect carotid-cavernous fistula

In indirect carotid-cavernous fistula (dural shunt), the intracavernous portion of the internal carotid artery is intact. Arterial blood enters the cavernous sinus indirectly, but through the meningeal branches of the external and internal carotid arteries. Due to the weak blood flow, clinical signs are expressed to a lesser extent than with direct fistula, so the condition may be incorrectly assessed or not noticed at all.

Types of indirect carotid-cavernous fistula

• Between the meningeal branches of the internal carotid artery and the cavernous sinus.
• Between the meningeal branches of the external carotid artery and the cavernous sinus.
• Between the meningeal branches of both (external and internal) carotid arteries and the cavernous sinus.

Causes of indirect carotid-cavernous fistula

• a congenital developmental anomaly in which the appearance of symptoms is associated with intracranial vascular thrombosis;
• spontaneous rupture that can occur with minor trauma or stress, especially in hypertensive patients.

It manifests itself as gradual reddening of one or both eyes due to conjunctival vessels becoming overfilled with blood.

Symptoms of indirect carotid-cavernous anastomosis

• Dilated conjunctival and episcleral vessels.
• Increased pulsation of the eyeball, best seen with applanation tonometry.
• Increased intraocular pressure.
• Mild exophthalmos usually associated with a soft murmur.
• Ophthalmoplegia, most often due to paralysis of the sixth pair of cranial nerves.
• The fundus picture may be normal or characterized by moderate venous dilation.

Differential diagnosis includes chronic conjunctivitis, thyroid eye disease, glaucoma of other etiologies, and arteriovenous anomalies of orbital development, which may have a similar picture to dural shunts.

Treatment involves the use of 'interventional radiology' to occlude feeding vessels, although some patients recover spontaneously.

Treatment of carotid-cavernous fistula

Destructive interventions:

• ligation of the carotid arteries on the neck, superior ophthalmic vein;
• exclusion of the internal carotid artery above and below the level of the anastomosis: clipping in the cranial cavity and ligation on the neck;
• application of clips to the internal carotid artery with subsequent embolization of the anastomosis;
• direct interventions on the anastomosis (sinus tamponade or application of clips on the anastomosis).

Reconstructive interventions:

• Brooks' anastomosis embolization;
• occlusion of the anastomosis with a balloon catheter using the F. Sorbtsiya method;
• embolization using coils
• embolization with spinal embolizing composites;
• embolization (spiral embolization mixtures).

What is the prognosis for carotid-cavernous junction?

Carotid-cavernous fistula has a relatively unfavorable prognosis. Recovery from spontaneous fistula thrombosis occurs only in 5-10% of cases, 10-15% of patients die from intracranial and nasal bleeding, and 50-60% become disabled due to loss of vision and mental disorders.