Structural peculiarity of the anatomy of cerebral veins and venous sinuses is their lack of vascular valves and tunica muscularis. Bidirectional venous flow is permitted due to the lack of one-way valves, which usually pose a structural advantage for collateral drainage when any major veins are compressed or occluded. Also, there are multiple confluences in the entire cerebral venous system which give greater flexibility for collateral venous drainage. Lack of muscle layer in the venous sinuses and cerebral veins enables increased compliance for the volume of venous flow. Lastly, venous sinuses are located within the thick and tough dura mater, so that they are protected when the intracranial pressure is elevated. Various prognoses in CVT patients may be explained by the above anatomic characteristics.

Superficial veins in the hemisphere usually drain venous blood to superior sagittal sinuses, which have large intravenous lumen with slow flow. The confluence of superficial cerebral veins and superior sagittal sinus may cause turbulence in the sinus. Also, fibrous septa in the inferior angle may also interfere with lamina venous flow. Both of the above may be underlying conditions for higher proportion of CVT in superior sagittal sinus or adjacent venous structures. Additionally, the intracranial venous system also receives venous drainage from the diploic vein, meningeal vein, and emissary veins, which drains blood from extracranial anatomic structures. Due to the drainage from extracranial structures, infective organisms from the face and scalp or chronic otitis media may spread into the intracranial venous system and cause CVT.

Risk factors associated with CVT are multiple (Table 16.1) [3]. Most of the associated factors are linked to the classic Virchow triad, including stasis of blood, changes in the vessel wall, and changes in the composition of the blood. The structural characteristics of the cerebral venous system discussed in the previous section may attribute to the stasis of blood inside of the venous system. Risk factors for CVT are usually prothrombotic conditions, including genetic or acquired, oral contraceptives, puerperium and pregnancy, infection, and malignancy. Subjects with predisposing genetic prothrombotic conditions may become more susceptible to CVT when exposed to any of the acquired causes, including oral contraceptives or puerperium. The most frequent genetic thrombophilias are G20210A prothrombin and factor V Leiden mutations, followed by protein C, S, and antithrombin III deficiencies. But the prevalence of genetic prothrombotic conditions may differ according to the ethnic groups of patients, so stroke physicians should use their caution before ordering a genetic test. Hyperhomocysteinemia is a risk factor for venous thrombosis, but the role of MTHFR/C677T mutation is under controversy. Anticardiolipin antibodies are found in 6% of CVT cases. According to the largest study of CVT patients, ISCVT, 34% of CVT patients had an inherited or acquired prothrombotic condition.

The most frequent risk factors in young women are oral contraceptive use and pregnancy/puerperium. During pregnancy and for 6–8 weeks after birth, women are at increased risk of venous thromboembolic events, such as deep venous thrombosis. Hypercoagulability worsens after delivery as a result of volume depletion and trauma. Additional risk factors are infection and instrumental delivery or cesarean section during the puerperium. CVT has also been reported in association with hormone replacement therapy, the day-after pill, and in vitro fertilization. The additional risk for CVT from oral contraceptive use and pregnancy/puerperium may be augmented for young women with inherited thrombophilic conditions.

Other conditions associated with CVT are local or systemic infections including mastoiditis, sinusitis, or meningitis and medical conditions including cancer, iron deficiency anemia, thrombotic thrombocytopenic purpura, nephrotic syndrome, and systemic lupus erythematosus.

The clinical presentation of CVT is highly variable and its mode of onset may be acute or subacute. Headache is the most frequent symptom of CVT, usually the initial one and may be the sole manifestation of CVT, found in more than 90% of afflicted cases. The most frequent type of headache is the intracranial hypertension type, a severe, generalized headache of progressive onset, worsening with Valsalva maneuvers and when lying down. However, focal and nonspecific headache found in the neck or posterior cranium may be associated with CVT. Also, isolated headache without focal neurological findings or papilledema occurs in up to 25% of patients with CVT. ISCVT study reported higher frequency of headache in women with oral contraceptive use or pregnancy/puerperium [5].