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|LETTER TO EDITOR
|Year : 2014 | Volume
| Issue : 5 | Page : 565-567
Spontaneous thrombosis of a cerebral arteriovenous malformation
Roopesh V. R. Kumar, Venkatesh S Madhugiri, AS Ramesh, A Sathiaprabhu
Department of Neurosurgery, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India
|Date of Submission||28-Sep-2014|
|Date of Decision||28-Sep-2014|
|Date of Acceptance||28-Sep-2014|
|Date of Web Publication||12-Nov-2014|
Roopesh V. R. Kumar
Department of Neurosurgery, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Kumar RV, Madhugiri VS, Ramesh A S, Sathiaprabhu A. Spontaneous thrombosis of a cerebral arteriovenous malformation. Neurol India 2014;62:565-7
Spontaneous thrombosis of cerebral arteriovenous malformations (AVM) is exceedingly rare  and only 29 such cases have been reported in the literature. ,,,, We report one such case.
A 25-year-old female presented with headache, vomiting and generalized tonic-clonic seizures. She was drowsy but arousable and confused, and had no obvious motor or sensory deficits. Computed tomography (CT) of brain revealed a right frontal lobe hematoma with surrounding edema. [Figure 1]a She was managed conservatively and was referred to our institute after 1 week. CT angiogram (CTA) [Figure 1]b-d revealed a right frontal arteriovenous malformation (AVM) with a compact nidus supplied by an enlarged and tortuous frontopolar branch of the right anterior cerebral artery (ACA). A single large vein draining into the superior sagittal sinus was noted. She was scheduled for a digital subtraction angiogram (DSA) after 6 weeks, to be followed by definitive management. Four-vessel DSA done (7 weeks after ictus) revealed no opacification of the nidus of the AVM; the arterial feeder ended abruptly. [Figure 2]a, b CT angiogram confirmed these findings and demonstrated a filling defect in the dilated draining vein. [Figure 2]c, d MRI brain showed gliosis in the region of the nidus and T1 hyperintense signals within the draining vein [Figure 2]e, f. These features were confirmative of spontaneous thrombosis of the AVM. She underwent further evaluation to look for a hypercoagulable state. She was not on oral contraceptives. Protein C, protein S, antithrombin III, antiphospholipid antibodies and homocysteine levels were all within normal limits, and anti-DNA antibodies were negative. She was discharged on anti-epileptic drug and advised follow up DSA after 6 months.
|Figure 1: Initial imaging study. (a) Sagittal reconstruction of a CT image showing the frontal lobe hematoma. (b) Sagittal reconstruction of a CT angiogram image, showing the nidus of the AVM and a venous varix near the sagittal sinus. (c) Coronal view of the AVM nidus. (d) Magnified view of the single large draining vein with a venous varix|
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|Figure 2: Follow-up imaging studies. (a) DSA, AP view showing no opacification of the nidus on right ICA injection. (b) DSA, lateral view. The nidus is not seen. (c) Sagittal and (d) Coronal views on a CT angiogram. Neither the nidus nor the large venous varix is seen. (e) Axial T1 and f - T2 sagittal MRI images showing gliosis in the region of the nidus|
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Spontaneous thrombosis of an AVM is a very rare event and occurs in <1% of all AVMs. ,,, Review of the reported cases suggests that the period from diagnosis to thrombosis ranges between 3 and 252 months.  In this patient, the thrombosis occurred within 6 weeks; the shortest reported time till date. The mean age of these patients was 40 years, most had lesions in the parietal lobe.  In 70% of the reported cases (n = 29), the occlusion occurred after symptomatic intra-cerebral or subarachnoid hemorrhage. ,, Thus, suggesting the possibility that the hematoma might compress the draining vein resulting in nidus thrombosis. ,, Alternatively, vasospasm of the feeding artery due to hemorrhage could result in a gradual thrombosis of the nidus.
The factors common to all the lesions that underwent spontaneous thrombosis were: A single draining vein (most common), hypercoagulable state, solitary arterial feeder (possibility of embolic occlusion) and small nidus (<6 cm). In some instances, the excised thrombosed AVM was analyzed; histopathology revealed fibromuscular cushions within the feeder vessels.  This could have been caused by turbulent flow in a tortuous, elongated vessel resulting in fibromuscular cushions with subsequent stasis, ischemia and thrombosis of the nidus. In one case, a thrombosed AVM recanalized after 31 months, requiring microsurgical excision. 
Spontaneous thrombosis does occur in the natural history of AVM, though exceedingly rare. Owing to the rarity of this occurrence, there is no definite evidence pointing to the exact pathogenesis of thrombosis. Patients should be followed up for remote possibility of recanalization.
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[Figure 1], [Figure 2]