Transverse sinus stenosis (TSS) is the narrowing of one or both transverse sinuses, large veins located within the protective layers of the brain. This constriction impedes the normal flow of blood and cerebrospinal fluid (CSF) out of the skull. While sometimes an incidental finding, TSS is frequently associated with Idiopathic Intracranial Hypertension (IIH), a disorder characterized by unexplained elevated pressure inside the skull. TSS is observed in a vast majority of patients diagnosed with IIH, and this anatomical blockage is thought to be a major contributing factor to the symptoms of elevated intracranial pressure.
The Role of the Transverse Sinus and Venous Outflow
The transverse sinuses are part of the dural venous sinus system, a network of channels that collects deoxygenated blood from the brain and drains it toward the heart. They receive blood from major vessels, including the superior sagittal sinus, before emptying into the sigmoid sinuses and eventually the internal jugular veins.
Beyond blood drainage, this venous system plays a role in CSF circulation. CSF, which cushions the brain and spinal cord, is continuously produced and absorbed, with a significant portion returning to the bloodstream through specialized structures called arachnoid granulations that project into the dural sinuses. When the transverse sinus narrows, it creates a bottleneck effect, slowing venous outflow and causing blood to back up. This venous hypertension increases the pressure within the dural sinuses, which reduces the pressure gradient needed for CSF to be effectively reabsorbed.
The physical narrowing can arise from two primary mechanisms, often occurring together in patients with IIH. Intrinsic stenosis is caused by structures inside the sinus, such as enlarged arachnoid granulations that physically obstruct flow. Extrinsic stenosis occurs when the transverse sinus is compressed from the outside, such as the collapse of the flexible vein wall against the rigid skull due to chronic elevated intracranial pressure. The presence of stenosis is directly linked to the pathology of impaired venous and CSF drainage.
Common Symptoms Resulting from Stenosis
The symptoms of transverse sinus stenosis result directly from the elevated intracranial pressure (ICP) and venous hypertension. The most common complaint is a chronic daily headache, often described as dull and generalized. Headaches frequently worsen in the morning or with activities that increase head pressure, such as bending over or coughing.
A highly specific symptom associated with TSS is pulsatile tinnitus, the perception of a rhythmic sound in the ear synchronous with the patient’s heartbeat. This symptom is reported in an estimated 55% to 60% of patients with IIH. The stenosis causes blood flow to become turbulent as it rushes through the constricted vessel, generating a “whooshing” sound heard by the patient.
Vision changes are a major concern because sustained high ICP can threaten eyesight by causing swelling of the optic nerve head, known as papilledema. Patients may experience transient visual obscurations—temporary blackouts or dimming of vision—often triggered by changes in position. Untreated papilledema can lead to permanent damage to the optic nerve fibers and result in irreversible peripheral vision loss. Less common symptoms include double vision caused by pressure on cranial nerves.
Diagnostic Procedures
Evaluation for TSS and associated intracranial hypertension begins with a thorough clinical assessment, including a detailed history of headaches, tinnitus, and visual disturbances. A comprehensive ophthalmological examination checks for the presence and severity of papilledema, a significant indicator of elevated ICP. These findings guide subsequent diagnostic steps.
Neuroimaging confirms the structural abnormality and rules out other causes of elevated ICP. Magnetic Resonance Venography (MRV) and Computed Tomography Venography (CTV) are the preferred non-invasive modalities used to visualize the venous anatomy and confirm stenosis. MRV is highly sensitive and can identify TSS in approximately 94% of patients diagnosed with IIH, showing a significant reduction in the sinus diameter, often bilaterally.
The definitive diagnostic step for confirming intracranial hypertension is a lumbar puncture (spinal tap). During this procedure, a needle is inserted to measure the cerebrospinal fluid (CSF) opening pressure. An opening pressure greater than 250 mm of water in an adult confirms the diagnosis of IIH, provided other neurological pathology is absent. In some cases, invasive catheter venography is performed to directly measure the pressure gradient across the narrowed segment; a gradient greater than 8 mm Hg is considered hemodynamically significant.
Management and Treatment Options
Management of TSS associated with intracranial hypertension typically follows a tiered approach, starting with medical therapy. The primary medication is acetazolamide, a carbonic anhydrase inhibitor that reduces the production rate of cerebrospinal fluid. By decreasing CSF volume, this drug lowers the overall pressure inside the skull, alleviating symptoms like headache and reducing papilledema.
Interventional procedures are considered for patients whose symptoms, particularly vision loss, do not improve with maximum medical therapy or for those who cannot tolerate medication. Venous sinus stenting is an endovascular procedure designed to physically open the narrowed transverse sinus and restore normal venous outflow. A small mesh tube (stent) is guided into the narrowed segment and expanded to hold the vessel open, immediately reducing the pressure gradient across the stenosis.
Stenting has demonstrated efficacy, showing improvement or resolution of chronic headaches in approximately 80% of patients and resolution of papilledema in about 90% of cases. The goal is to normalize cerebral venous pressure, which reduces intracranial pressure and safeguards vision. Weight management is also an important measure, as a reduction in body weight can significantly contribute to the long-term control of intracranial pressure.