Lateral Sinus Thrombosis - Symptoms, Diagnosis, and Treatment

Introduction

The network of veins between the two layers of the dura mater that help drain the venous blood from the brain is called the dural venous sinus. It collects the deoxygenated blood from the skull and returns it to the heart for oxygenation. There are seven main dural venous sinuses between the dural layers: the periosteal or endosteal layer and the meningeal layer. They are listed below:

• Superior sagittal sinus.

• Inferior sagittal sinus.

• Cavernous sinus.

• Straight sinus.

• Transverse sinus.

• Sigmoid sinus.

• Superior petrosal sinus.

The most important sinus among the seven sinuses is the cavernous sinus. There are no valves in the dural venous sinuses, meaning the direction of blood flow can either be forward or backward. The backward flow can spread microbes and cancer cells to the other adjacent parts of the brain through which the venous drains. A dangerous triangular area on the face is marked by the inner corner of the eyes as the apex, the sides of the nose, and the upper lip as the base. It is where any infectious pathogen can travel from the face to the brain and cause a cavernous sinus infection. The infection will form a blood clot in the cavernous sinus called cavernous sinus thrombosis. The thrombus causes the sinus to swell and press on adjacent nerve structures.

What Is Sinus Thrombosis?

The formation of a blood clot is known as thrombosis. Hence, the formation of a thrombus in the venous sinuses of the brain cavity is called dural venous sinus thrombosis. Venous sinus thrombosis is of three types which are given as follows.

• Cavernous Sinus Thrombosis (CST): The most important and clinically significant sinus thrombosis occurring in the cavernous sinus is called cavernous sinus thrombosis. They can get infected through the dangerous area of the face, and the irregularity in their shape and location on the skull base makes them more vulnerable to infection. The infection can be from the ear or the upper teeth or due to trauma.

• Lateral Sinus Thrombosis (LST): The formation of a thrombus in the mastoid sinus is called lateral sinus thrombosis.

• Superior Sagittal Sinus Thrombosis: Superior sagittal sinus is the largest venous channel in the skull because many veins drain into the sinus. So, clot formation is rare because of its big size.

What Is Lateral Sinus Thrombosis?

Lateral sinus thrombosis is the blood clot formation in the sigmoid and transverse sinuses. It usually occurs as a complication of a middle ear infection called otitis media. The occurrence of complications is rare in recent times with the use of antibiotics for the treatment of otitis media. When antibiotics were not used for treating otitis media, lateral sinus thrombosis was the second most common fatal complication, with meningitis being the first. It is relatively rare but requires immediate treatment. The death percentage ranges from 5 % to 10 %. The anatomical location of mastoid air cells and the middle ear in the proximity of the dural venous sinuses makes it more susceptible to secondary infection during otitis media.

What Are the Signs and Symptoms of Lateral Sinus Thrombosis?

There are variations in the signs and symptoms because of different locations of clot formation.

They include the following:

• Chronic otitis media.

• Severe headache.

• Ear and neck pain.

• Fever (picket fence fever - temperature spikes in the afternoon or early evening and then comes down).

• Vomiting.

• Loss of sharpness in vision.

• Otorrhea (drainage of liquid from the ear).

• Papilledema (swelling of the optic nerve).

• Increased intracranial pressure.

• The typical clinical feature of lateral sinus thrombosis and reflex thrombosis in the mastoid emissary vein is Griesinger’s sign - edema and tenderness over the mastoid bone behind the ear.

• Neck swelling and tenderness if the thrombosis spreads to the internal jugular vein.

• Paralysis of the 9th, 10th, and 11th cranial nerve if thrombosis spreads to the jugular bulb.

What Is the Diagnosis of Lateral Sinus Thrombosis?

The diagnosis is made based on laboratory tests and radiology.

• Blood Tests: The number of red blood cells getting reduced or diminished hemoglobin concentration, called anemia, is present, and an elevated number of white blood cells called leukocytes are common laboratory findings.

• Blood Culture: The bacteria causing the infection was mainly beta-hemolytic streptococcus. But now, due to antibiotics, cultures show a mixed flora of microbes, including Bacteroides, Staphylococcus, Proteus, Pseudomonas, Enterobacteriaceae, and other species. The blood culture is often negative since ear infections are pre-treated by antibiotics.

• Computed Tomography (CT) Scan: This imaging technique is used to demonstrate the specific ‘delta sign’-dural enhancement around the sinus and abnormality in the opacification of the sinus cavity. The scan also helps in detecting the compilation that occurs in the brain.

• Magnetic Resonance Imaging (MRI) Scan: It is the choice of investigation for lateral venous thrombosis. The imaging method is more sensitive than CT and shows the location of sinus occlusion and the sequel of backflow of blood. In addition, Gadolinium-enhanced MRI gives the thrombus a vascular and bright appearance for the dural walls.

• Magnetic Resonance Venography: This type of MRI can detect the signals lost in the sinus and the absence of blood flow.

• Tobey-Ayer Test: It monitors cerebrospinal fluid pressure during a lumbar puncture. When the internal jugular vein is compressed, if there is no increase in CSF pressure on the affected side and an exaggerated response on the unaffected side suggests lateral sinus thrombosis.

What Is the Treatment for Lateral Sinus Thrombosis?

The different treatment options available are:

• Antibiotics: Broad-spectrum antibiotics are administered intravenously at the earliest. The use of antibiotics has brought down the percentage of complications.

• Myringotomy: It is a cut made on the tympanic membrane to drain pus.

• Mastoidectomy: It is an incision made on the lateral sinus of the mastoid to remove the clot. Local packing of the cavity is done.

• Anticoagulation Therapy: The effectiveness of anticoagulants (drugs that prevent the clotting of blood) is poorly understood. But they can be used to slow down the thrombus propagation and improve the neurological condition in patients with raised intracranial pressure.

• Internal Jugular Vein Ligation: This procedure involves removing the affected part of the event from the body. But it was done in older days to prevent septic emboli formation. But now, the surgery is performed infrequently.

What Are the Complications of Lateral Sinus Thrombosis?

The incidence of complications has reduced but is still present, which are:

• Meningitis (inflammation of membranes that cover the brain and spinal cord).

• An intracranial abscess (swelling filled with pus in the brain).

• Otitic hydrocephalus.

• Internal jugular vein thrombosis.

Conclusion

Ear infection leading to lateral sinus thrombosis has now become rare due to the implementation of antibiotics to treat infections, and it can prove to be fatal and dangerous if not treated appropriately. No improvement in symptoms, even with antibiotics, should raise suspicion and be investigated with MRI and venography to diagnose lateral sinus thrombosis. The treatment should be provided at the airline to prevent further complications.