Venous sinus stenosis (VSS) refers to a narrowing of the large veins inside the head that collect and drain blood from the brain. These channels, known as the dural venous sinuses, function as the brain’s primary drainage system, returning deoxygenated blood to the heart. When this narrowing occurs, it can impede the outflow of blood and cerebrospinal fluid (CSF), potentially causing a buildup of pressure within the skull. While the presence of VSS alone may not always cause symptoms, it frequently becomes a significant medical concern when it leads to a specific condition of high pressure inside the head.
Understanding Venous Sinus Stenosis
The cerebral venous sinuses are a network of vessels located within the layers of the dura mater, the tough membrane surrounding the brain. Stenosis most commonly affects the transverse and sigmoid sinuses, which guide blood flow toward the internal jugular veins in the neck. The narrowing physically restricts the path of venous blood, creating resistance and slowing the overall drainage of the brain.
This restriction can be categorized into two main types based on its cause. Intrinsic stenosis arises from something physically inside the vessel, such as enlarged arachnoid granulations—small, valve-like structures that normally help absorb CSF into the bloodstream. If these granulations become enlarged, they protrude into the sinus and physically block blood flow.
Alternatively, extrinsic stenosis involves compression from outside the vessel wall, which can cause the sinus to collapse against the skull. Factors like tumors, inflammation, or even abnormally high pressure within the skull itself can press on the venous sinus, causing the narrowing.
The Link to Intracranial Pressure
The primary danger associated with venous sinus stenosis stems from its direct connection to elevated pressure inside the skull, a condition termed Intracranial Hypertension (IH). Since the venous sinuses drain both blood and cerebrospinal fluid, their obstruction causes a backup, much like a pinched hose, leading to a rise in fluid pressure within the skull.
When VSS is present alongside this pressure elevation without another identifiable cause, it is often diagnosed as Idiopathic Intracranial Hypertension (IIH), historically known as pseudotumor cerebri. The most serious long-term risk of this elevated pressure involves the visual system.
Increased pressure is transmitted to the optic nerve, causing it to swell at the back of the eye, a condition called papilledema. If this swelling is not resolved, the prolonged compression of the optic nerve can cause irreversible damage, leading to permanent vision loss or even blindness. This potential for permanent visual impairment makes addressing VSS and its resulting high pressure paramount.
Recognizing Common Symptoms
One of the most distinctive and common complaints is pulsatile tinnitus, which is the perception of a rhythmic whooshing or buzzing sound in the ear that is synchronous with the patient’s heartbeat. This symptom results from turbulent blood flow as it rushes through the narrowed sinus segment near the inner ear.
Severe headaches are another frequent symptom, often described as throbbing or generalized, and they may be worse in the mornings or when bending over due to temporary increases in intracranial pressure. Some patients also report transient vision changes, such as brief episodes of dimming, blurring, or temporary graying out of the visual field, reflecting the stress the elevated pressure places on the optic nerve.
Treatment and Management Options
Managing venous sinus stenosis and the associated intracranial hypertension typically involves a two-pronged approach: medical management and, if necessary, interventional procedures. The initial medical strategy focuses on lowering the elevated cerebrospinal fluid pressure using pharmaceutical interventions. Diuretics, such as acetazolamide, are commonly prescribed to decrease the production of CSF, thereby reducing the volume of fluid within the skull.
If medical therapy fails to control symptoms or if there is a threat of progressive vision loss, interventional management is considered. The most common procedure is venous sinus stenting, which is a minimally invasive technique. A small, metallic mesh tube, or stent, is placed through a catheter into the narrowed segment of the venous sinus.
The stent mechanically props open the vessel wall, restoring normal blood flow. This restoration of outflow directly reduces the intracranial pressure, which can alleviate symptoms like headaches and halt the progression of papilledema. In cases where stenting is not suitable or has been ineffective, alternative procedures, such as shunting, may be considered to divert excess CSF away from the brain to another body cavity.