Print version ISSN 0004-282X
Arq. Neuro-Psiquiatr. vol.66 no.2a São Paulo June 2008
Dural arteriovenous fistula presenting as thalamic dementia
Demência talâmica secundária a fistula arteriovenosa dural
Mariangela Barbi GonçalvesI; Orlando Maia JrII; Jorge Luiz Amorim CorreaIII; Sávio Boechat Primo de SiqueiraIV; Daniel de Holanda ChristophIV; José Alberto LandeiroV
IMédica Residente do Serviço de Neurocirurgia do HFAG, Mestre em Neurociências pela Universidade Federal do Estado do Rio de Janeiro, Brasil (UNIRIO) - Serviço de Neurocirurgia do Hospital de Força Aérea do Galeão, Rio de Janeiro RJ, Brasil (HFAG)
IINeurocirurgião Endovascular do Serviço de Neurocirurgia do HFAG - Serviço de Neurocirurgia do Hospital de Força Aérea do Galeão, Rio de Janeiro RJ, Brasil (HFAG)
IIIMédico Assistente do Serviço de Neurocirurgia do HFAG - Serviço de Neurocirurgia do Hospital de Força Aérea do Galeão, Rio de Janeiro RJ, Brasil (HFAG)
IVMédico Residente do Serviço de Neurocirurgia do HFAG - Serviço de Neurocirurgia do Hospital de Força Aérea do Galeão, Rio de Janeiro RJ, Brasil (HFAG)
VChefe do Serviço de Neurocirurgia do HFAG, Professor Adjunto da Disciplina de Neurocirurgia da Universidade Federal Fluminense, Brasil (UFF) - Serviço de Neurocirurgia do Hospital de Força Aérea do Galeão, Rio de Janeiro RJ, Brasil (HFAG)
Dementia implies the decline of intellectual abilities or cognitive function. It is also characterized by behavioral abnormalities and changes in personality1. One unusual cause of dementia, characterized mainly by amnestic syndrome, apathy, speech and language disturbances, hypersomnia, vigilance disorder and vertical gaze palsy, is due to thalamic lesion that led to the term "thalamic dementia"2-4. This is related to the known thalamic connections with cortical nucleus concerned with memory process, cognition and behavior, the thalamo-fronto-limbic loops5,6. Intracranial dural arteriovenous fistula (AVF) with venous drainage into internal cerebral veins and consequently venous hypertension is uncommon and may be associated with thalamic injury. Dural AVF consists of abnormal shunting of blood between the meningeal branches or rarely cortical branches of the external, internal carotid or vertebral arteries, and the venous system, embedded in the dural leaflets of a venous sinus to form the nidus7-10. Capillary beds usually interposed are lacking7. Intracranial dural AVF represent approximately 10% to 15% of all intracranial vascular malformations8,9,11-13.
Since the posterior fossa dural AVF and subsequent venous hypertension is important to be considered in the different diagnosis of thalamic lesions14, we report an unique case of thalamic dementia associated with venous hypertension in the bilateral thalamus due to a dural AVF that was successfully treated by endovascular procedures.
A 43-year-old man, air professional, coursing political science master, presented subacute onset of apathy and memory deficit. Initially, the symptoms were stress misdiagnosed. Nevertheless, his symptoms worsened progressively. On admission, the patient was awake but confuse in time. There was neither headache, neither visual impairment nor vomits. The thorough neurological examination revealed critical sense mild compromised and amnesia, predominately of recent events. No significant medical history was related.
The optic fundi were normal. There was no signal of intracranial hypertension, and the neurological symptoms were restricted to cognitive dysfunction. The blood pressure was normal. Thus, investigation of another cause of dementia began. The laboratories exams such as endocrinology and inflammatory tests, syphilis antibody and complex B vitamin dosage were normal. No infection preceding the onset of symptom was related. A computed tomography (CT) scan of the brain was compatible with a major arachnoid cyst, that involved the right frontal and temporal lobes, with little shift of midline and osseous remodeling.
Magnetic resonance image (MRI) showed FLAIR-high signal lesions in both thalamic areas (Fig 1A), with no alterations on diffusion or perfusion sequences. Cerebral angiography (Fig 2A) showed a tentorial dural AVF, type IIa+IIb according to the Cognard classification and type II according to the Borden classification, fed by the meningo tentorial branches of the right internal carotid artery and meningeal branches of the occipital artery of the right external carotid artery (Fig 3A). Retrograde flow through the basal cortical veins, the internal cerebral veins and the vein of Galen with straight sinus arterialization was evident (Fig 2B).
Accordingly, the diagnosis of bithalamic venous infarction secondary to increased deep venous pressure around the basal ganglia and consequently difficult of venous drainage due to arteriovenous fistula was done.
Considering the cerebral angiography findings, endovascular embolization was performed as treatment. By means of selective arterial microcatheterism, ultra flow microcatheter was navigated into the right occipital artery and into as many arteries supplying the tentorial dural AVF as possible (Fig 3B). The dural AVF was then completely occluded with a liquid adhesive embolic agent (Onyxtm - MTI) via the right external carotid artery approach (Fig 4A). Post-embolization angiography revealed angiographic occlusion, with marked devascularization of the dural AVF (Fig 4B). The tentorial draining veins immediately reopened, and the flow through deep cerebral venous systems was restored. There was no thrombosis of venous system, but venous congestion.
Three months after the interventional therapy, MRI showed absence of FLAIR-high signal thalamic lesions (Fig 1B). Clinical evaluation revealed a completely improvement of memory and cognitive status. The patient also returned to work and study.
Approval was obtained from the hospital's Ethics Committee and the patient's informed consent for publication of this case report.
Progressive dementia caused by venous congestion in bilateral thalamic areas associated with dural AVF is rare14. The so-called thalamic dementia, when secondary to an intracranial dural AVF as in our patient is considered a reversible dementia as symptoms recover after interventional therapy4,14.
Dural AVF can be presented through multiple clinical symptoms depending on the location, size of the lesion, flow, and venous drainage of the dural AVF7,15,16. Memory or behavior impairment may occur, as shows our patient, due to retrograde flow into the tentorial veins leading to venous hypertension, which can result in cerebral edema and associated neurological deficits due to bilateral thalamic lesions15,16.
Venous congestion in the thalamus of our patient may have been caused by tentorial venous reflux to the straight sinus, vein of Galen and consequently to the internal cerebral veins and the basal vein. The thalamic veins from the superior and medial portions of the thalamus drain into the internal cerebral or great veins, and those from the inferior and lateral portions of the thalamus drain into the basal vein or its tributaries17. So the drainage of the fistula to the thalamus produces a decrease in the arteriovenous pressure gradient and ischemia8. This is explained by chronic passive congestion following retrograde increase in venous pressure toward the thalamic venous drainage territory4,14. If venous thrombosis were the primary disease we should not expect normal sinus blood flow immediately after the occlusion of the dural AVF.
In the setting of subacute cognitive deficit, the diagnosis of deep cerebral vein thrombosis must be considered when neuroimage exams show bilateral thalamic changes. Accordingly, the patient was submitted to a cerebral angiography, gold standard for evaluation of dural AVF9, via transarterial approach. This angiography demonstrated tentorial dural AVF fed by the right internal (meningo tentorial branches) and external carotid artery (occipital artery) and drained by the straight sinus and the internal cerebral veins. The straight sinus originates behind the splenium of the corpus callosum at the union of the inferior sagittal sinus and the great vein. It continues posteriorly and downward in the junction of the tentorium and falx. It may drain into either transverse sinus, but most commonly drains predominantly into the left transverse sinus17. Those angiographic findings were correlated with our patient clinical presentation of the tentorial dural AVF and confirm that the thalamic symptoms were related to the venous character and depended on the territory of the draining veins of the dural AVF.
In this case, with arterialization of the straight sinus that becomes dysplastic, increment of venous pressures can promote the formation of venous aneurysms, thereby augmenting the potential for intracranial hemorrhage7,18. On the basis of researchers' findings, it is now generally accepted that the venous drainage prototype of dural AVF is the most predictive factor that predispose to the risk of these aggressive dural AVF symptoms, with focal neurologic deficits or hemorrhage12.
Although several classification systems have been developed to enable prediction of dural AVF risks with the purpose of better decision about treatment, those devised by Cognard et al.12 and Borden et al.19 are the most commonly used11. This case, type IIa+IIb according to the Cognard classification and type II according to the Borden classification, was at risk to present potentially devastating venous hypertension due to high flow dural AVF drainage into a sinus with insufficient antegrade venous drainage and reflux.
Pathophysiologic mechanism of the thalamic dementia of this patient is venous hypertension of the thalamus. Retrograde arterial flow into the venous system promotes high pressure that is thought to be a significant cause of venous congestion8.
There is a general agreement that embolization have become the first-line treatment8,15. Venous drainage is the most important factor in directing the treatment, witch goal is complete occlusion15. In that case the strategy of embolization is to catheterize and embolize the origin of the fistula until it is obliterated20, as we have done.
Bilateral thalamic lesions have a poorer neurobehavioral prognosis than unilateral one. Persistent dementia and severe amnesia often occurs rather than improvement of cognitive and behavioral functions21. Nevertheless, our patient postoperative neurological evaluation revealed an improvement of memory and cognitive status, that is probably correlated to functional outcome of venous better than arterial infarctions22. The improvement in clinical symptoms and MRI findings would propose that the thalamic lesions reveal venous hypertension, differing from infarction16.
Bilateral lesions of the thalamus characteristically present with specific neurological and neuropsychological patterns, like mood and behavior changes and memory dysfunction2,6. Impairment of the thalamus caused by venous hypertension must be differentiating from infarction as the cause of the neurological symptoms. In such cases, while venous occlusion involves anticoagulation treatment, which might lay the patient with dural AVF at considerable complications risk. As a result, the association between thalamic dementia and dural AVF should be considered. Interventional therapy can lead to angiographic occlusion and resolution of the symptoms.
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Received 11 December 2007. Accepted 27 February 2008.
Dra. Mariangela Barbi Gonçalves Rua Nina Rodrigues 72/602 - 22461-100 Rio de Janeiro RJ - Brasil. E-mail: firstname.lastname@example.org