Case of the Week

Section Editors: Matylda Machnowska¹and Anvita Pauranik²
¹University of Toronto, Toronto, Ontario, Canada
²BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada

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May 27, 2021

Basal Meningitis with Isolated Unilateral Basal Vein of Rosenthal Thrombosis

Background:
- Cerebral venous thrombosis refers to thrombotic occlusion of 1 or more intracranial venous channels, including dural venous thrombosis, cortical vein thrombosis, and deep cerebral vein thrombosis.
- The basal veins, also known as the veins of Rosenthal (BVR), are paired, paramedian veins which originate on the posterior aspect of the frontal lobes and run posteriorly and medially. Embryologically, the BVR is not one of the original pial veins but is rather a secondary vessel formed by longitudinal anastomoses of 3 primitive veins during development: the telencephalic, diencephalic, and mesencephalic veins. In the early embryonic stage, these primitive veins drain into the tentorial sinuses. Later, many channels draining into the tentorial sinus usually spontaneously obliterate with a secondarily posteromedial and superior drainage of the BVR into the Galenic venous system via the anastomotic channels.
- It may have a plexiform configuration, with multiple small channels rather than a single vessel. The medial afferent branches that contribute to the anterior venous circle include the septal veins, callosal veins, anterior cerebral veins, chiasmatic veins, and olfactory veins near the midline. The lateral afferents include the inferior striate veins, insular veins, and uncal veins.
- Its drainage territory encompasses the orbital surface of the frontal lobe, the insula and mesial temporal lobe structures, the hypothalamus, parts of the striatum and thalamus, and the midbrain.
- A gamut of factors like pregnancy, oral contraceptives, protein C and S alterations, malignancy, dehydration, and malnutrition can cause cerebral venous sinus thrombosis. In this case, the patient was severely dehydrated.
Clinical Presentation:
- Headache (75%) and vomiting constitute the majority of presenting symptoms of cerebral venous sinus thrombosis. Seizures (37%) and motor and sensory deficit (34%) are other presenting symptoms. Multiple cranial nerve palsy has been reported in 12% of cases.
- Venous infarct secondary to basal vein of Rosenthal thrombosis involving the thalamic region presents with symptoms of thalamic stroke like contralateral hemisensory loss, hemiparesis and hemiataxia, and pain syndromes that are more common after right thalamic lesions.
Key Diagnostic Features:
- Hyperintensity (sometimes stripe-shaped or punctiform) on T1- and T2-weighted imaging instead of normal flow voids in the venous sinus is the important evidence of venous sinus thrombosis.
- Absence of the basal vein in magnetic resonance venography and postcontrast images
- Basal vein thrombosis leads to venous infarct in a typical location corresponding to its territory of drainage, namely, the ipsilateral cerebral peduncle and hippocampal gyrus.
- Hemorrhagic venous infarct manifests as a diffusion-restricting area of T2/FLAIR heterogeneous hyperintensity with extensive internal areas of blooming on susceptibility-weighted imaging.
Differential Diagnoses:
- Arterial infarctions: These appear as low-density areas on NCCT conforming to arterial territories along with a hyperdense thrombus in the artery supplying the particular area. CT angiography may reveal the site of occlusion in the artery as filling defects. MRI shows areas of restricted diffusion in the acute stage along with loss of flow void in the affected artery.
- Tumors such as gliomas: Hemorrhagic venous infarcts can be mistaken for high-grade gliomas because areas of necrosis and hemorrhage can be present in high-grade gliomas. However, extensive perilesional edema, mass effect, and ring enhancement are typical of high-grade gliomas. These lesions show an increase in choline and creatine levels on spectroscopy with a decrease in NAA levels.
- Tumefactive demyelinating lesion: Tumefactive demyelination appears as a large, hypoattenuating lesion with ill-defined ring enhancement, central necrosis, perilesional edema, and minimal mass effect on CT. Postcontrast T1 images show a typical open-ring type of enhancement where the incomplete portion of the ring is on the gray matter side of the lesion.
- Hemorrhagic encephalitis: A history of upper respiratory infection prior to presenting neurologic symptoms may be present in about 50% of cases. These are large tumefactive lesions which involve the white matter and spare the cortex. They have associated punctate hemorrhages and extensive mass effect and surrounding edema. Basal ganglia and thalami are other possible sites of involvement.
Treatment:
- The mainstay of treatment is anticoagulation (intravenous heparin or subcutaneous low-molecular-weight heparin), thrombolysis (systemic or local). The therapy usually starts with injectable LMWH and is then switched over to oral warfarin.
- Symptomatic treatment includes antiepileptic therapy, lowering intracranial pressure, and decompressive craniectomy.
- Mechanical thrombectomy may be considered alone or in combination with pharmacologic thrombolysis in refractory cases.