The study by Martinelli and colleagues, mentioned earlier in the chapter, attributed 35 percent of cases of cerebral vein thrombosis in the context of oral contraceptive use to a mutation in the factor V or in the prothrombin gene. Averback, who reported seven cases of venous thrombosis in young adults, has emphasized the diversity of the clinical causes. Two of his patients had carcinoma of the breast and one had ulcerative colitis. A few cases will follow head injury or remain unexplained.
A stroke in a patient suffering from any one of these systemic conditions should suggest venous thrombosis, although in some instances—for example, postpartum strokes—arteries are occluded as often as veins. A slower evolution of the clinical stroke syndrome, the presence of multiple cerebral lesions not in arterial territories, and a convulsive and hemorrhagic character, favor venous over arterial thrombosis.
The reasons for these clinical features and their variability as well as the differences from ischemic brain damage caused by arterial occlusion become apparent in the discussions below. Stam has undertaken a review of this subject.
Cortical Vein Thrombosis (Superficial Thrombosis of Cortical Veins)
Certain syndromes occur with sufficient regularity that they suggest thrombosis of a particular vein or sinus. The signature features of isolated thrombosis of superficial cortical veins are the presence of large superficial (cortex and subjacent white matter) hemorrhagic infarctions and a marked tendency to focal seizures. Hemiparesis, incomplete hemianopia, and aphasia, any of which may fluctuate over days, are also characteristic according to Jacobs and colleagues. These variable syndromes reflect the inconstant location of the main surface veins. Thrombosis of the vein of Labbé causes infarction of the underlying superior temporal lobe, and occlusion of the vein of Trolard implicates the parietal cortex. A concern is the propagation of the clot into the larger draining veins or dural sinuses.
Quite often, in our experience, the focal deficit worsens immediately after a focal seizure. The intracranial pressure is not elevated, as it is when the dural venous sinuses are occluded. The diagnosis is made by careful examination of the MRV or by the venous phase of the conventional angiogram. Cortical vein thrombosis should be suspected in the situation of multiple hemorrhagic infarctions in one hemisphere without a source of embolism or atherothrombosis.
Sagittal and transverse (lateral) sinus thrombosis In the case of sagittal sinus thrombosis, intracranial hypertension with headache, vomiting, and papilledema may constitute the entire syndrome; this is the main consideration in the differential diagnosis of pseudotumor cerebri (see Chaps. 9, 12, and 29) or it may be conjoined with hemorrhagic infarction. Paraparesis, hemiparesis, fluctuating unilateral or bilateral sensory symptoms, or aphasia result only if the thrombosis propagates to surface veins. Focal or odd sensory or motor seizures occur on the same basis but are not as common as with cortical vein thrombosis.
The transverse sinuses are usually asymmetrical; slightly more than half of individuals have a dominant right vein and approximately a quarter are symmetrical. (The larger sinus corresponds to a smaller occipital lobe on that side—a petalia). Unilateral occlusion of the nondominant transverse sinus may not be symptomatic, whereas thrombosis of the dominant side generally gives the equivalent syndrome to blockage of the sagittal sinus. Increased intracranial pressure without ventricular dilatation occurs with thrombosis of the superior sagittal sinus, the main jugular vein, and the transverse sinus or the confluence of the sinuses.