Cranial venous outflow obstruction, also referred to as impaired cranial venous outflow, impaired cerebral venous outflow, cerebral venous impairment is a

vascular disorder Vascular disease is a class of diseases of the vessels of the circulatory system in the body, including blood vessels – the arteries and veins, and the lymphatic vessels. Vascular disease is a subgroup of cardiovascular disease. Disorders in thi ...

that involves the impairment of venous drainage from the

cerebral veins In human anatomy, the cerebral veins are veins in the cerebral circulation which drain blood from the cerebrum of the human brain. They are divisible into ''external'' (superficial cerebral veins) and ''internal'' ( internal cerebral veins) grou ...

of the

human brain The human brain is the central organ (anatomy), organ of the nervous system, and with the spinal cord, comprises the central nervous system. It consists of the cerebrum, the brainstem and the cerebellum. The brain controls most of the activi ...

. The cause of cranial venous outflow obstruction is not fully understood. It is believed to be associated with various factors including

anatomical Anatomy () is the branch of morphology concerned with the study of the internal structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old scien ...

abnormalities,

thrombosis Thrombosis () is the formation of a Thrombus, blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thrombocytes) and fib ...

, posture, and increased

intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adu ...

. The obstruction can occur in any part of the venous system involved in draining blood from the brain, like vertebral venous system (VVS) or cerebral venous sinus (CVS), but it is most commonly seen in the

dural venous sinuses The dural venous sinuses (also called dural sinuses, cerebral sinuses, or cranial sinuses) are venous sinuses (channels) found between the periosteal and meningeal layers of dura mater in the brain. They receive blood from the cerebral veins, ...

Signs and symptoms

Impaired cranial venous outflow can lead to increased venous pressure, decreased

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

(CSF) absorption, brain cortex hypoperfusion, brain edema, blood–brain barrier (BBB) disruption, inflammatory reactions, hemorrhagic complications, and increased intracranial pressure. Which can result in a variety of neurological symptoms, such as pseudotumor cerebri,

chronic fatigue syndrome Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a disabling Chronic condition, chronic illness. People with ME/CFS experience profound fatigue that does not go away with rest, as well as sleep issues and problems with memory ...

, different types of headaches, visual disturbances,

pulsatile tinnitus Tinnitus is a condition when a person hears a ringing sound or a different variety of sound when no corresponding external sound is present and other people cannot hear it. Nearly everyone experiences faint "normal tinnitus" in a completely ...

and various

neurodegenerative disease A neurodegenerative disease is caused by the progressive loss of neurons, in the process known as neurodegeneration. Neuronal damage may also ultimately result in their death. Neurodegenerative diseases include amyotrophic lateral sclerosis, mul ...

Pathophysiology

The pathophysiology of cranial venous outflow obstruction involves the disruption of normal venous drainage from the brain. Cerebral veins play a crucial role in draining brain interstitial fluid (ISF), and their significance has been linked in various neurological conditions. It can be caused by extrinsic or intrinsic anomalies.

Extrinsic

Extrinsic anomalies are structural changes near the

Internal Jugular Vein The internal jugular vein is a paired jugular vein that collects blood from the brain and the superficial parts of the face and neck. This vein runs in the carotid sheath with the common carotid artery and vagus nerve. It begins in the posteri ...

(IJV) that can cause venous outflow obstruction. These changes can be due to bone pressure, artery pressure, enlarged

lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that includ ...

s, or an enlarged

thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by ...

. These factors can squeeze the vein wall and block the blood flow. This blockage can range from a local narrowing (

stenosis Stenosis () is the abnormal narrowing of a blood vessel or other tubular organ or structure such as foramina and canals. It is also sometimes called a stricture (as in urethral stricture). ''Stricture'' as a term is usually used when narrowing ...

) to a complete blockage (occlusion). Different parts of the IJV can be affected by different factors. The upper part of the IJV is often squeezed by the side parts of the neck bones at the vertebral C1 segment and by the styloid processes. The middle and lower parts of the IJV are more often squeezed by the nearby carotid artery, lymph nodes, and unusual muscles. Among all these factors, bone pressure is the most common, causing about 40% of extrinsic anomalies. A recent study showed that 41.9% of IJV narrowing in a Chinese group was due to external pressure.

Intrinsic

Intrinsic anomalies are changes within the IJV itself. These can include blood clots (thrombi), abnormalities in the vessel wall, and malformed venous valves. IJV thrombosis is rare and has only been mentioned in a few case reports. Defects inside the vein (flaps, webs, septa, membranes, and malformed valves) can hinder normal blood flow from the brain. This can result in changes in blood flow, including backflow (reflux), reduced flow, or no flow entirely. Doppler and intravascular ultrasound are effective tools for seeing malformed valves. There are many types of malformed valves, including fused, elongated, ectopic, accessory leaflet-containing, inverted, and double valves.

Management

Management of cranial venous outflow obstruction involves treating the underlying cause, if identifiable, and managing the symptoms. This can include medication to reduce intracranial pressure, anticoagulation therapy to prevent thrombosis, and in some cases, surgical intervention to restore normal venous drainage.

Epidemiology

The epidemiology of cranial venous outflow obstruction is not well-studied, and the condition is likely underdiagnosed due to the nonspecific nature of its symptoms. However, it is known to affect individuals of all ages, with a higher prevalence in females and individuals with anatomical venous disorders (varicose veins), certain risk factors such as obesity and thrombophilic disorders and sedentary lifestyle.

Types

Styloidogenic jugular venous compression syndrome

Styloidogenic jugular venous compression syndrome (SJVCS) shares symptoms with idiopathic

intracranial hypertension Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury (mmHg) and at rest, is normally 7–15 mmHg for a supine adult. ...

(IIH). Patients with SJVCS experience compression of venous outflow on both sides due to bone structures. It occurs due to compression of the internal jugular vein (IJV) between the C1 vertebrae transverse process and the

temporal styloid process The temporal styloid process is a slender bony process of the temporal bone extending downward and forward from the undersurface of the temporal bone just below the ear. The styloid process gives attachments to several muscles, and ligaments. Str ...

. Treatments like venous stenting and styloidectomy have shown positive results.

Diagnostics

Diagnostics of this pathology might include advanced MR venography, direct microcatheter

venography Venography (also called phlebography or ascending phlebography) is a procedure in which an X-ray of the veins, a venogram, is taken after a special dye is injected into the bone marrow or veins. The dye has to be injected constantly via a cathete ...

with manometry, 3D catheter

angiographic Angiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and the heart chambers. Modern angiography is perform ...

studies, three-dimensional rotational venography (3D-RV), cone-beam rotational angiography (3D-RA), also CT venography or MRI scans with contrast with would potentially show obstruction.

References

{{Reflist Vascular diseases