Transverse sinus stenosis (TSS) is defined by the narrowing of one or both transverse sinuses, which are large drainage channels located within the head. This narrowing restricts the normal outflow of blood from the brain, causing blood to back up and potentially increasing pressure inside the skull.
The Role of the Transverse Sinuses
The transverse sinuses are a pair of major veins situated within the dura mater, the tough outer membrane covering the brain. They collect the majority of the blood that has circulated through the brain tissue, channeling deoxygenated blood toward the internal jugular veins in the neck.
These sinuses also play a role in the reabsorption of cerebrospinal fluid (CSF). CSF is a clear fluid that cushions the brain and spinal cord and must be constantly produced and reabsorbed to maintain normal intracranial pressure. When the sinuses narrow, they impede this dual drainage process of both blood and CSF. This obstruction raises pressure within the veins and surrounding tissues, contributing to the associated symptoms.
Recognizing the Symptoms of Stenosis
The symptoms experienced by people with transverse sinus stenosis relate directly to the buildup of pressure within the head. One distinctive complaint is pulsatile tinnitus, a rhythmic whooshing sound heard in the ear that is synchronous with the heartbeat. This sound is caused by the turbulent flow of blood through the narrowed sinus segment, which is positioned close to the inner ear. Pulsatile tinnitus is frequently unilateral, occurring on the side of the most affected sinus.
Another common manifestation is chronic headache, which can often resemble a tension headache or a migraine. These headaches are persistent and may not respond well to standard pain medication. The increased intracranial pressure (ICP) can also affect the optic nerves, leading to transient visual obscurations. These temporary episodes may involve a momentary darkening of vision, double vision, or other fleeting visual disturbances. In some cases, TSS is associated with Idiopathic Intracranial Hypertension (IIH), a condition characterized by high intracranial pressure.
Diagnostic Procedures and Pressure Measurement
Confirming the presence of transverse sinus stenosis involves a combination of imaging and pressure measurement studies. Non-invasive imaging techniques are used first to visualize the vascular anatomy of the brain. Magnetic Resonance Venography (MRV) and Computed Tomography Venography (CTV) are specialized scans that create detailed images of the venous sinuses, allowing physicians to identify and measure the degree of narrowing. Stenosis is often defined radiographically as a reduction in vessel diameter greater than 50%.
To determine the functional impact of the stenosis, a lumbar puncture (spinal tap) may be performed to measure the opening pressure of the CSF. An elevated opening pressure, typically above 25 centimeters of water in an adult, helps confirm high intracranial pressure. The gold standard for confirming a functionally significant stenosis involves an invasive procedure called venous manometry. During this catheter-based procedure, a specialized wire is inserted into the vein to directly measure the pressure on both sides of the narrowed segment. A pressure difference, or gradient, greater than 8 mmHg across the stenosis is considered abnormal and an indication for treatment.
Treatment Approaches for Transverse Sinus Stenosis
Treatment for symptomatic transverse sinus stenosis is focused on alleviating the high pressure and restoring normal flow. Initial management often involves medical therapy, especially when the condition is associated with high intracranial pressure. Medications such as acetazolamide are commonly prescribed to reduce the production of cerebrospinal fluid, thereby lowering the overall fluid volume and pressure inside the skull. This medical approach aims to relieve headaches and protect vision.
When medical management fails to control severe symptoms, or if there is a threat of progressive vision loss, interventional procedures become an option. The primary intervention is venous stenting, a minimally invasive procedure performed in a cath lab. A small, metal mesh tube called a stent is guided through the blood vessels and deployed to physically widen the narrowed segment of the transverse sinus. This mechanical widening immediately reduces the pressure gradient across the stenosis, which can normalize intracranial pressure and resolve symptoms like pulsatile tinnitus and vision problems. Follow-up studies after stenting often show significant improvement in headache, visual symptoms, and papilledema, which is swelling of the optic nerve.