14 Bilateral thalamic lesions are often associated with vascular causes, most commonly arterial occlusions (basilar artery, i.e., “top of the basilar syndrome”) or deep venous occlusion. Top of the basilar syndrome can be associated with bilateral or unilateral lesions. Bilateral paramedian thalamic infarcts have also been described due to occlusion of an unpaired thalamic perforating artery. Cerebral venous thrombosis can involve the superficial cortical veins, the dural sinuses, and/or the deep venous system (basal vein [of Rosenthal], internal cerebral veins, and vein of Galen). Deep cerebral venous thrombosis is the least common type of cerebral venous thrombosis. It is important to consider deep venous thrombosis as the etiology of bilateral acute thalamic lesions. The lesions seen in venous thrombosis may be reversible, and not progress to infarcts. Deep venous thrombosis should especially be considered if the patient is a young woman. Imaging features can help to differentiate deep venous thrombosis from arterial causes of bilateral thalamic lesions (Table 14.1).
Bilateral Thalamic Lesions
| Deep Venous Thrombosis | Arterial Infarct | |
|---|---|---|
| Generalized Edema | Yes | No |
| Areas Affected | Bilateral symmetric thalami, basal ganglia, and corona radiata | Midbrain, thalami, occipital lobes, and posterior fossa |
| Hemorrhages | Yes; tends to spread from center to periphery; may be multifocal | Less common and tends to begin at margins |
| Vessels | Dense veins (cord sign) and/or dural sinuses on non-contrast CT Venous sinus filling defects on enhanced CT/MRI or MRA |
