The cavernous sinus is a collection of veins in a cavity located at the base of the brain behind the eye sockets. Veins containing blood from the face and brain, and a few cranial nerves, pass through this cavity. Cavernous sinus thrombosis occurs when a blood clot forms in this space.
Cavernous sinus thrombosis often follows infection with Staphylococcus aureus or other microbes. When infections occur in the center of the face, there is a risk that they can spread to the cavernous sinus. Non-infectious causes include surgery, pregnancy, and trauma. Anyone who is at elevated risk for blood clots is more likely to develop cavernous sinus thrombosis.
Some of the infections that can cause septic cavernous sinus thrombosis include adjacent infections, like cellulitis or an abscess in the mouth or bridge of the nose, and bacterial nasal infections. Sinusitis is the most common cause. Other risks include cellulitis around the eyes, tonsillitis, pharyngitis, ear infections, and dental infections.
When a cavernous sinus thrombosis occurs, drainage from the veins in the face decreases, leading to swelling of the affected area. In addition to causing noticeable symptoms like swelling, particularly around the eyes, this inflammation also causes compression of the cranial nerves that pass through the cavernous sinus.
The third, fourth, and sixth cranial nerves and branches of the fifth cranial nerve are commonly affected by cavernous sinus thrombosis. Each cranial nerve plays a different role in the face.
The third cranial nerve or oculomotor nerve controls the pupil and most of the muscles around the eyes. The fourth (trochlear nerve) and sixth (abducens nerve) cranial nerves control outward, inward, and downward eye movements. The ophthalmic and maxillary branches of the fifth cranial nerve communicate sensory information from the upper and middle parts of the face. Compression of these nerves causes severe headaches, facial pain, bulging eyes, and diminished sensation in the face.
Other symptoms of cavernous sinus thrombosis include fever, elevated heart rate, low blood pressure, and altered mental state. Eye symptoms appear in 90 percent of cases due to the involvement of the cranial nerves. Blindness can result in as many as 15 percent of cases. Symptoms may start right away or slowly progress over a few days, starting with one eye and spreading to the other.
Septic cavernous venous thrombosis can cause significant complications in the nervous system and lungs if the infection spreads. If the infection from the cavernous sinus spreads into the brain, it can lead to a brain abscess, meningitis, or a collection of pus called brain empyema. If it gets into the lungs, it can cause pneumonia, emboli, or pulmonary empyema. The infection may also spread to the pituitary gland and decrease the secretion of pituitary hormones.
Cavernous sinus thrombosis is very rare and is often misdiagnosed. Any patient presenting with cellulitis around the eyes should be screened for cavernous venous thrombosis, especially if they present with mental status changes or eye involvement and had recently an ear, sinus, or tooth infection. The best diagnostic tool for cavernous sinus thrombosis is an MRI, though a CT scan is also helpful. If symptoms indicate that the cause is septic and that the infection has spread, a lumbar puncture and blood cultures may be necessary.
The primary treatment for cavernous sinus thrombosis is high doses of IV antibiotics. If there is no improvement within 24 hours, a surgeon may have to drain the nasal sinus. When the cranial nerves are affected, the doctor may prescribe corticosteroids, and when the pituitary gland is involved, patients often require supplemental hormones.
Cavernous sinus thrombosis is often life-threatening, even with prompt treatment. About 30 percent of affected people do not survive. About half of patients with both cavernous sinus thrombosis and infection in the sphenoid sinuses on either side of the nose die. Of those who survive, about 30 percent have serious side effects, including impaired eye movement, stroke, or long term problems with the pituitary glands.
Risk factors like cancer, chemotherapy, steroid use, and uncontrolled diabetes raise a person's risk for cavernous sinus thrombosis and serious complications. The biggest risk factors are acute sinusitis, facial, and eye infections. Women on hormone replacement therapy or those who are pregnant or post-partum also face an elevated risk. Other risk factors include obesity, dehydration, and sickle cell disease.
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