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Clinicoradiological Profile of Superficial Middle Cerebral Vein Thrombosis
Neeharika L Mathukumalli, Ravivarma Dandu, Meena A Kanikannan, Subhash Kaul
Department of Neurology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India
Department of Neurology, Nizam's Institute of Medical Sciences, Hyderabad - 500 082, Telangana
Source of Support: None, Conflict of Interest: None
Background: The diagnosis of isolated cortical vein thrombosis (ICVT) involving superficial middle cerebral vein (SMCV) remains challenging even in the present era of modern MRI protocols.
Objective: The purpose of this study is to review the clinical and radiological characteristics of SMCV thrombosis in our hospital.
Methods: Chart review of cases of SMCV thrombosis admitted in a tertiary care university hospital in South India during a 1-year period from September 2015 to August 2016.
Results: Five SMCV thrombosis patients were identified and presented with focal seizures. Neuroimaging showed edema (with or without hemorrhage) of cortex and white matter of inferior frontal gyrus, temporal pole, superior temporal gyrus, insular cortex, and external capsule. The thrombosis of SMCV was demonstrated by Spin echo T1-weighted, GRE-weighted axial, and postcontrast T1-weighted images in coronal and sagittal planes, with a slice thickness of <3 mm. Four received anticoagulation and all improved rapidly and completely.
Conclusion: SMCV thrombosis should be considered in patients having recent onset seizures in appropriate setting based on MRI evidence of parenchymal edema and/or hemorrhage in the perisylvian region along with evidence of thrombosed vein in that region. Appropriate imaging sequences help in confirmation of diagnosis.
Keywords: Herpes encephalitis, isolated cortical vein thrombosis, isolated cortical vein thrombosis, perisylvian edema, perisylvian hemorrhage, superficial middle cerebral vein, superficial middle cerebral vein
Key Messages: Thrombosis of SMCV should be considered in all patients with focal seizures having the MRI evidence of edema and/or hemorrhage in the perisylvian region. We recommend Spin echo T1-weighted and GRE-weighted axial images with a slice thickness of <3 mm in the plain study to demonstrate the thrombus in this vein. Postcontrast T1-weighted imaging with <3 mm slice thickness in coronal and sagittal plane or 3D T1 acquisition with steady-state sequences would be optimal for better visualization of the thrombus in SMCV.
Superficial middle cerebral vein (SMCV) thrombosis is a rarely reported form of isolated cortical vein thrombosis (ICVT).,,, Predisposing conditions for SMCV thrombosis include hyperhomocysteinemia, alcoholism, anemia, polycythemia, vasculitis, antiphospholipid antibody syndrome, postpartum status, oral contraceptive pills (OCP), and other thrombogenic drugs, infections such as HIV, syphilis, bacterial meningitis, and procoagulant states.,, These patients usually present with seizures, focal motor, and sensory deficits. Symptoms and signs of intracranial hypertension are not commonly encountered in contrast to dural sinus thrombosis., SMCV thrombosis is diagnosed by identification of the thrombosed vein which is usually depicted as the hyperintense signal on T1 and T2-weighted imaging and hypointense signal on T2* weighted gradient echo sequences. Demonstration of filling defects within the lumen of the vein on postcontrast T1-weighted imaging is a more direct method of documenting thrombosis. In about half of patients, SMCV receives small veins draining the perisylvian regions of frontal, temporal, and parietal lobes and runs along the Sylvian fissure to terminate in the sphenoparietal sinus located along the lesser wing of sphenoid (sphenoparietal type of SMCV). Alternatively, it can drain into the cavernous sinus, pterygoid plexus, superior petrosal sinus or the transverse sinus. The small caliber of the vein in relation to the slice thickness employed in MRI, slow luminal flow and its complex course contribute to the difficulty of visualization of this vessel on T1 and T2-weighted images as well as on noncontrast MR venography. Thrombosis of the SMCV has been reported in very few individual case reports in the past.,,, The purpose of this case series is to report the clinical and radiological features of SMCV thrombosis seen in a university hospital in one year.
| » Methods|| |
Twenty patients of ICVT admitted between September 2015 and August 2016 in the Nizam's Institute of Medical Sciences, a tertiary care referral center in Hyderabad, South India were identified. Amongst these, five patients were diagnosed to have SMCV thrombosis. All data pertaining to the clinical presentation, predisposing conditions, neuroimaging, treatment, and the outcome was noted from their case records for analysis.
| » Results|| |
The age of five patients of SMCV thrombosis ranged from 17–33 years with a median of 26 years; four were male. All of them presented with focal seizures. None had a headache or papilloedema. Two patients suffered neurological deficits, one had right sensory-motor hemiparesis and the other had Wernicke's aphasia. Four of them were diagnosed in the first week of illness and one was diagnosed 20 days later after the follow-up scan. Hyperhomocysteinemia was the most common predisposing factor in our patients. All five patients had SMCV thrombosis on the left side with other additional findings [Figure 1], [Figure 2], [Figure 3], [Figure 4]. All patients had cerebral parenchymal involvement in perisylvian regions of the left insula, frontal, and temporal lobes. Two of them had hemorrhagic venous infarcts. One patient with hemorrhagic venous infarct had a mass effect [Figure 2], not requiring a decompressive craniectomy. The thrombosed SMCV was identified in all the cases by isointense or hyperintense signal on T1-weighted image, hypointense, or hyperintense signal on T2-weighted image depending on the age of the clot [Figure 1], blooming on gradient recalled echo (GRE) and filling defect in the lumen of the vessel on postcontrast 3D T1 images. The clinical and neuroimaging characters of our patients are summarized in [Table 1].
|Figure 1: (Case 1): Axial MRI images 4 days after onset of symptoms (a-d) showing acute thrombus in left SPS and SMCV that was hypointense on T- weighted images (a), isointense on T1-weighted images, (b) and showed blooming on GRE images, (c). Edema in the temporal polar region was apparent. Axial postcontrast T1-weighted image, (d) revealed nonenhancing thrombus as a filling defect within the vein. Follow up MRI performed 12 days after onset of symptoms revealed subacute thrombus that is hyperintense on T2, (e) and T1, (f) weighted images|
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|Figure 2: (Case 2): T2-weighted axial MRI (a and b) showed large venous infarct in the frontal, temporal, and insular regions. Hyperintense thrombus was seen within the left SPS, (c) and left SMCV, (d) on precontrast T1-weighted images, with nonenhancement of these veins on postcontrast T1-weighted image (e). Postcontrast T1 image at 3-month follow-up (f) revealed recanalization of the occluded vein|
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|Figure 3: (Case 3) Hyperintense thrombus within the SMCV was apparent on the coronal precontrast T1-weighted image (a). Coronal postcontrast T1-weighted image (b) and axial 3D T1-weighted image (c) revealed nonenhancing thrombus as a filling defect within the vein|
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|Figure 4: (Case 4): Thrombus was seen within the left SMCV on precontrast T1-weighted image (a) as long cord sign which was not enhancing on postcontrast T1-weighted image (b)|
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|Table 1: Clinical and Neuroimaging characters of patients with SMCV thrombosis|
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Three patients were treated with anticoagulant therapy while the patient whose pathology was diagnosed retrospectively did not receive anticoagulation. All of them improved rapidly and completely with symptomatic treatment with or without anticoagulation.
| » Discussion|| |
The SMCV is an important component of the superficial cerebral venous system located along the lateral aspect of the cerebral hemisphere. It receives small veins draining the perisylvian regions of frontal, temporal, and parietal lobes. Thus, it participates in the venous drainage of functionally eloquent regions such as the inferior frontal gyrus (Broca's area), frontal, and parietal opercula. SMCV runs along the Sylvian fissure and terminates in the sphenoparietal sinus located along the lesser wing of the sphenoid in 46–54% of cases (sphenoparietal type of SMCV) [Figure 5]. Alternately, it can drain into the cavernous sinus, pterygoid plexus, superior petrosal sinus, or transverse sinus. In 10% of cases, the SMCV can be absent (underdeveloped type); where the venous drainage of superficial Sylvian areas is into the superior sagittal sinus or into the transverse sinus. Thrombosis of the SMCV has been reported earlier in literature in only four reports.,,, Through this paper, we report four additional cases in an effort to alert the treating physicians about the possibility of SMCV thrombosis in the presence of characteristic parenchymal brain lesions.
|Figure 5: (a) Sagittal image of the brain, depicting the anatomical course of the superficial middle cerebral vein (SMCV) within the Sylvian fissure and its anastomoses with the vein of Trolard (Trol) and vein of Labbe (Labbe). (b) Volume rendered reconstruction of the skull base, depicting the SMCV draining through the sphenoparietal sinus (SphPS) into the cavernous sinus (Cav). Venous drainage pathways of the cavernous sinus through the superior ophthalmic vein (SOV), superior petrosal sinus (SPS) and inferior petrosal sinus (IPS) are also seen|
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The diagnostic difficulty in SMCV thrombosis is due to nonspecific clinical presentation and the absence of clinical features of raised intracranial pressure. In the previously published case reports of SMCV thrombosis, headache was seen in two patients and seizure in 3,,, while focal seizures were the presenting symptoms of all the patients in our series. Three of them were found to have a mild left temporal headache when enquired retrospectively. None of our patients had papilloedema or other signs of raised ICP. The median age of our patients (26 years) was lesser when compared to that in the previously published literature (38.39 years). Ranjodh et al. in their case series of ICVT also had patient population of a median age of 25 years, suggesting that ICVT is commonly seen in young people <40 years of age. Predisposing conditions for ICVT are the same as those for dural sinus thrombosis. Hyperhomocysteinemia was the predisposing factor in three of our five patients.
All our patients had parenchymal involvement in perisylvian regions of the left insula, frontal and temporal lobes. The parenchymal abnormality consisted of edema (with or without hemorrhage) involving the cortex and white matter in the inferior frontal gyrus, temporal pole, superior temporal gyrus, insular cortex, external capsule, and extreme capsule. One patient had extensive edema extending into frontal, temporal, and parietal lobes. The distribution of these parenchymal changes is consistent with the venous drainage territory of SMCV. In the four previous reports of SMCV thrombosis, three patients did not have any parenchymal changes, while one patient had a hemorrhagic infarction in the left frontal operculum.,,, Parenchymal edema and hemorrhages in the perisylvian region may be seen in a host of other common conditions presenting with seizure and headache; such as post-traumatic cerebral contusion, subacute arterial infarct with hemorrhagic transformation, herpes encephalitis, and high-grade glioma. In a recent report, Yu et al. have described four cases of ICVT where the parenchymal lesions were mistaken as gliomas as is the case with one of our patients. This patient's MRI brain at presentation showed white matter signal changes with a central hemorrhagic focus in the left inferior frontal gyrus and external capsule, which was interpreted as a hemorrhagic neoplasm. Follow-up MRI after 20 days, when the patient was evaluated with MR spectroscopy, revealed resolution of the parenchymal lesion. The presence of the thrombus in the SMCV was identified on a retrospective review of the initial MR images. Thus, the high index of clinical suspicion of SMCV thrombosis is required in patients presenting with focal seizures or headache and MRI revealing such parenchymal changes. Interestingly, SMCV thrombosis occurred on the left side in all our 5 cases as has also been reported in other reports, the cause of which is not clear.,,,
In our patients, the suspicion of SMCV thrombosis was raised by a hyperintense signal within the vein on T1-weighted images, a feature commonly seen in the subacute stage of cortical venous thrombosis. Venous thrombus in other stages is more difficult to identify. In the acute stage (0–5 days), the signal intensity of thrombus mimics a normal flow state (isointense on T1 and hypointense on T2-weighted images). Chronic thrombus can show significant variability in signal intensity and may mimic the signal intensity of very slowly moving oxygenated blood.
T2* weighted gradient echo and postcontrast T1-weighted imaging enabled us to confirm the presence of thrombosis in our cases. Echoplanar susceptibility-weighted images, T2* weighted gradient echo and postcontrast 3D T1-weighted imaging have been described as the most accurate techniques for the depiction of ICVT., Gradient echo sequences elegantly depict the increased susceptibility effect of paramagnetic hemoglobin breakdown products in acute and subacute stages of thrombus., However, susceptibility artifacts from the skull base can sometimes hamper the visualization of the SMCV on GRE imaging. We could demonstrate filling defects within the lumen of the vein on postcontrast T1-weighted imaging suggesting thrombosis. However, normal enhancement of the vein on postcontrast images does not necessarily imply patency; as delay in image acquisition after gadolinium administration can increase the thrombus enhancement to a level that simulates patency. Moreover, the thrombus itself can enhance which is presumably secondary to intrinsic vascularization  as well as to slow flow in dural and intrathrombus collateral channels. Another potential pitfall in contrast-enhanced T1 sequence is the obscuring effect coming from intrinsic hyperintensity of the subacute thrombus that can prevent its appreciation as a filling defect. These pitfalls of contrast-enhanced T1 imaging in the identification of cortical venous thrombosis may also hinder the diagnosis of SMCV thrombosis. We recommend Spin echo T1-weighted and GRE-weighted axial images with a slice thickness of <3 mm in the plain study to demonstrate the T1 shortening and susceptibility effect produced by the thrombus. Postcontrast T1-weighed imaging with < 3 mm slice thickness in coronal and sagittal plane or 3D T1 acquisition with steady-state sequences would be optimal to demonstrate the thrombus as a filling defect within the SMCV.
All our five patients improved rapidly and completely after the diagnosis though only four of them received anticoagulation. This is in concordance with the published literature suggesting a good outcome for ICVT.,, There are no definitive guidelines for anticoagulation in ICVT. It seems prudent to apply the therapeutic guidelines of CVT to ICVT until such guidelines evolve.
| » Conclusion|| |
Thrombosis of SMCV should be considered in all patients with focal seizures having the MRI evidence of edema and/or hemorrhage in the perisylvian region. A high index of clinical suspicion and optimized MRI protocols may aid in diagnosis. We recommend Spin echo T1-weighted and GRE-weighted axial images with a slice thickness of <3 mm in the plain study to demonstrate the thrombus in this vein. Postcontrast T1-weighted imaging with <3 mm slice thickness in coronal and sagittal plane or 3D T1 acquisition with steady-state sequences would be optimal for better visualization of the thrombus in SMCV.
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