JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
of consciousness may range from coma or stupor to delirium, with coma being a poor prognostic factor for morbidity and mortality. 1, 10 In a multicenter, prospective, observational study thirty nine percent of patients had seizure at presentation and seven percent had a seizure within two weeks of presentation. 12 Overall, the most common presenting symptom is headache, which can be the only presenting symptom of CVT. 1, 13-14
DISCUSSION
Pathogenesis
The pathophysiology of CVT is not completely understood. However, coagulation derangements secondary to pro- inflammatory conditions such as infections and trauma have been implicated in the pathogenesis. Vascular endothelial cells are directly altered in pro-inflammatory events resulting in endothelial dysfunction. 4 Tissue factor (TF), expressed by dysfunctional endothelial cells and damaged tissues, acts as an activator of the coagulation pathway. 4, 5 Inflammatory pathways mediated by complements and cytokines can also trigger and propagate the coagulation cascade. IL-1 andTNF-α are cytokines that have been shown to mediate coagulation by inducing TF expression. 4-6 It is thought that the interplay between these mechanisms may contribute to the establishment of a hypercoagulable state and consequently thrombus formation in the presence of pro-inflammatory stressors. Occlusion of cerebral venous structures results in obstruction of flow, decreased cerebrospinal fluid absorption, and increased intracranial pressure. Increased venous pressure leads to blood-brain barrier (BBB) dysfunction. 7 Extravasation of blood plasma secondary to BBB disruption causes cerebral edema. Cytotoxic edema from intracellular shift of water has been proposed as part of the pathological mechanism of CVT. 8 Histological findings from rat models of CVT have revealed neuronal shrinkage and necrosis, cellular infiltration, capillary collapse, intravascular fibrin aggregation, and hemorrhages. 7,9 Parenchymal involvement accounts for many of the clinical features of the disease.
Diagnosis
Given the nonspecific clinical presentations in patients with CVT, neuroimaging is essential.
Non-contrast CT of the head is an early imaging modality employed to rule out other acute or subacute cerebral causes. Head CT, however, may be normal in approximately 20% of CVT cases. 15 Features of CVT include the dense triangle sign and cord sign seen on nonenhanced CT and the empty delta sign seen on contrasted CT. 14, 16 Indirect signs of CVT on CT consist of cerebral edema and hemorrhages and mass defects. 14 CT venography can be useful in confirming a diagnosis of CVT and is comparable to magnetic resonance (MR) venography. In addition to good visualization of the cerebral venous system, the advantages of CT venography include cost effectiveness and the availability and rapidity of CT scan in hospital settings. Similar to MR venography, CT venography is also limited by anatomic variability. 17 When available, MRI with MR venography remains the current standard for CVT diagnosis. Variations in blood flow and blood breakdown products produce signal changes on MRI. 15 Initially, thrombus formation is visualized as area of isointensity and hypointensity in T1- and T2- weighted images, respectively. Over time, the thrombus becomes hyperintense on both T1- and T2- weighted images. 18-20 MR venography can demonstrate absence of flow in occluded sinus and vessels, and contrast-enhanced MR venography can further differentiate venous thrombosis from normal anatomic variants such as a hypoplastic sinus. 14-15 Conventional cerebral angiography is invasiveandnotcommonly used for diagnosing CVT as CT and MR venography are safer diagnostic options. In the event that MR and CT venography are inconclusive, conventional cerebral angiography may be performed as it offers superior spatial resolution of the cerebral arteriovenous circulation. 21-22
Presentation
Patients with CVT may have variable clinical presentations, and onset can be subacute, acute or chronic. Factors that affect the spectrum of clinical manifestations and course include extent and duration of venous thrombosis, territories of the involved vessels, establishment of venous collaterals, presence of parenchymal lesions (i.e. cerebral edema, cerebral hemorrhage), gender, and age. 1, 10 The three major presenting syndromes of CVT are isolated intracranial hypertension syndrome, focal cerebral syndrome (including cavernous sinus syndrome) and encephalopathy. 11 Isolated intracranial hypertension syndrome consists of headache, vomiting and/or papilledema. 1 Focal cerebral syndrome consists of focal motor and sensory deficits. Paresis is the most frequent focal deficit associated with CVT. 1 Ocular manifestations are the dominant signs and symptoms seen incavernous sinus syndrome. Cranial nerves III and IV, aswell as the ophthalmic and maxillary branches of cranial nerve V, are locatedalong the lateralwall of thecavernous sinus. Cranial nerve VI and the internal carotid artery are located medially within the cavernous sinus. Given the anatomic relationships, thrombosis of the cavernous sinus can result in ophthalmoplegia, chemosis, periorbital swelling, proptosis, Horner’s syndrome, diplopia and decreased visual acuity. Patients with CVT may also present with encephalopathy, multifocal deficits and seizures. Altered level
Management and Treatment
Once CVT is confirmed, treatment should be implemented as early as possible. Treatment should focus on addressing the underlying cause, prompt anticoagulation, and controlling seizures and intracranial hypertension. In CVT patients with known or suspected infection, appropriate antibiotics should be administered. Surgical drainage of associated infectious fluid collections is recommended. 21 Anticoagulation is considered a cornerstone in the treatment of acute and subacute CVT. The goal of anticoagulation therapy is to reestablish blood flow, prevent subsequent venous
34 J La State Med Soc VOL 169 MARCH/APRIL 2017
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