Thrombosis of the Internal Cerebral Vein Associated with Transient Unilateral Thalamic Edema: A Case Report and Review of the Literature

Clinical Course

In contrast to dural sinus thrombosis, DICVT more often leads to death or major long-term sequelae (2). Patients with DICVT tend to present with a short history of rapidly declining consciousness (2). The prognosis of this entity, however, is not necessarily poor (7).

Clinical manifestation of DICVT can be both complex and nonspecific. They can cover a wide range of symptoms from headache, nausea, and vomiting to focal neurologic deficits, hemiparesis, aphasia, seizures, coma, and death. Of the 24 patients reported in the literature (Table), 13 presented with mild symptoms, five with neurologic deficits or seizures, and five with decline of consciousness or coma. In one patient, clinical symptoms were not communicated (8). Of the 13 patients with mild symptoms, four recovered completely, six had persistent deficits, and three died. In the five patients with focal neurologic symptoms, three recovered almost completely, and one died. One patient was unreported (9). Finally, of the five patients with impairment of consciousness or coma, three died and one had persistent deficits. In the case of one patient, there is no information of clinical outcome.

In contrast, the outcome seems to be much more favorable in unilateral DICVT. In the two cases reported in the literature, both patients had neuropsychological deficits, and one of them presented with hemiparesis. At follow-up, one patient recovered completely (6), and the second patient had a mild persistent deficit (5). Our patient with unilateral ICV thrombosis also presented with mild clinical symptoms (headache, short-term amnesia, and discrete hemiparesis) and recovered completely in 3 weeks.

Radiologic Findings

In most cases of DICVT, the thalamus is affected bilaterally (Table). Additional cerebral structures adjacent to the thalami such as the basal ganglia and the mesencephalon are affected in one-third of patients.

CT findings in deep venous thrombosis are bilateral hypoattenuation of the thalami (and, in some cases, the basal ganglia and adjacent white matter), whereas the venous structures, such as the thalamostriate vein, ICV, vein of Rosenthal, vein of Galen, straight sinus, and confluens sinuum are hyperattenuated (8, 10, 11). Hydrocephalus may occur as a consequence of edema and swelling of both thalami (2, 12). In cases of hemorrhagic transformation, scattered areas of hyperattenuation (usually unilateral) may be seen.

Ischemia and vasogenic edema due to thrombosis of the deep veins appear hyperintense on T2-weighted images and hypointense on T1-weighted images, although if hemorrhage has occurred, these areas appear hyperintense on T1-weighted images. The actual thrombus in a deep vein appears as an area of hyperintensity on T1-weighted images, and the area fails to enhance after administration of Gd-DTPA.

Phase-contrast MR angiography shows deep venous thrombosis as absent flow signal intensity in the deep venous system (1, 2, 6, 13). Time-of-flight MR angiography may be more difficult to interpret, because the high signal intensity of the thrombus can be mistaken as flow, although there is usually a difference in the degree of hyperintensity between flow signal intensity and thrombus.

The differential diagnoses of unilateral thalamic lesions include vascular lesions, mainly arterial thalamic infarctions (3), and tumors such as germinomas (14–17), gliomas (18), neurocytomas (19), and cavernous hemangiomas (20, 21). Particular imaging techniques and attention to specific features may be helpful in establishing the correct diagnosis. Arterial infarction can present with hyperintensity on T2-weighted images and hypointensity on T1-weighted images, similar to venous edema or venous infarction. Both entities can be differentiated by using diffusion-weighted imaging. Whereas arterial infarction with cytotoxic edema is characterized by restricted diffusion (22), venous edema with its vasogenic edema is characterized by increased diffusion (22). In venous infarction, cytotoxic edema adds to the existing vasogenic edema leading to patchy areas of restricted and increased diffusion (22). Cavernomas are usually easily identified by a typical hypointense ring on T2- and T2*-weighted images (21). Tumors such as gliomas, neurocytomas, and germinomas have all been reported to occur in the thalamus (16, 17, 19, 23). These lesions can present as masses with compression of adjacent structures. Imaging changes found on MR and CT images, however, are not specific. Neurocytomas may contain areas of calcifications (19). Germinomas usually enhance (15) and can be characterized by elevated levels of human chorionic gonadotropin in serum and CSF (14, 15). Spectroscopy shows an increase in the choline peak in gliomas (24, 25). Perfusion imaging does not reveal significant changes in regional cerebral blood volume and mean transit time in low-grade gliomas but these decrease in the presence of high-grade gliomas (25, 26).

Arriving at the diagnosis of unilateral ICV thrombosis in our patient was not straightforward. The gradual onset of signs and symptoms in our patient made an infarction of arterial origin unlikely. A neoplastic lesion was therefore suspected at first; however, the finding on MR images and particularly the delineation of a thrombus in the ICV suggested the diagnosis of unilateral venous hypertension leading to a vasogenic edema, which could not be differentiated from an infarction. The entire resolution of all pathologic changes and the absence of subsequent defects on follow-up examinations suggest that the signal intensity changes represent pure vasogenic edema rather than definite infarction.

In contrast to this excellent outcome, patients with more extensive involvement of deep cerebral structures typically present with more severe clinical symptoms, especially when bilateral thalamic swelling induces occlusion of the third ventricle and internal hydrocephalus (27). In 12 of the 24 patients reported with DICVT (Table), signal intensity changes were limited to one thalamus (n=2) or to both thalami (n=10). Of those 12 patients, five recovered from all symptoms, and seven had residual neurologic deficits. When the changes extended beyond the thalami and included the basal ganglia (n=6), only one patient recovered completely and two patients died. A further extension beyond these structures into the mesencephalon or pons was fatal (n=2) (Table). In four patients, the clinical outcome and the location of the lesion were not specified. All patients with fatal outcome presented with either severe initial clinical symptoms or pathologic imaging findings extending beyond both thalami to adjacent structures.

The difficulty in diagnosing unilateral thrombosis of a deep cerebral vein is that bilateral deep vein thrombosis is so common and unilateral thrombosis is so rare. Remaining alert to the possibility of unilateral ICV thrombosis combined with visualization of a thrombus in the ICV on CT or MR images should establish the correct diagnosis.