Bilateral Thalamic Lesions Caused by a Complex Intracranial Dural Arteriovenous Fistula: A Rare Case Report
Bilateral thalamic lesions are a rare but significant neurological condition that can arise from various etiologies, including metabolic processes, toxic exposures, infections, vascular lesions, and tumors. Among these, intracranial dural arteriovenous fistulas (dAVFs) are an exceedingly rare cause. This case report presents a unique instance of a complex intracranial dAVF that led to bilateral thalamic lesions and dementia-like symptoms in a 38-year-old male patient. The report details the patient’s clinical presentation, diagnostic imaging findings, therapeutic intervention, and post-treatment outcomes, providing valuable insights into the diagnosis and management of this rare condition.
Clinical Presentation
The patient, a 38-year-old man with a 10-year history of cigarette smoking, presented with a 5-day history of progressively worsening forgetfulness, headache, dizziness, and blurred vision. His medical history was otherwise unremarkable. On physical examination, his vital signs were normal, but a neurological examination revealed mild short-term memory impairment and sluggish reaction times. The remainder of the neurological examination was unremarkable.
Diagnostic Imaging
Initial brain magnetic resonance imaging (MRI) revealed symmetric bilateral thalamic lesions that appeared hypointense on T1-weighted images and hyperintense on fluid-attenuated inversion recovery (FLAIR) and T2-weighted sequences. No free diffusivity changes were observed. Despite two days of mannitol treatment to reduce intracranial pressure, the patient’s condition continued to deteriorate, with increased confusion and speech abnormalities. Further MRI imaging, including susceptibility-weighted imaging (SWI), revealed multiple microhemorrhagic lesions in the right thalamus.
Magnetic resonance angiography (MRA) and magnetic resonance venography (MRV) were subsequently performed. MRA visualized the straight sinus, Galen vein, and large, curved, abnormal vessels connected to the branches of the left posterior cerebral artery. MRV showed malformed blood vessels in the awning area, with the straight sinus presenting a thick proximal end, an uneven thick distal end, and a confluens sinuum variation. These findings raised the suspicion of a dAVF.
To confirm the diagnosis, digital subtraction angiography (DSA) was performed. DSA revealed a circuitous and complex dAVF in the left posterior thalamus, with multiple arterial feeders and involvement of the deep venous system. The arterial supply arose from branches of the left occipital artery, left posterior cerebral artery, and right middle meningeal artery. The meningeal branch of the left occipital artery was the primary contributor to the dAVF, with partial redirection into the straight sinus, Galen vein, intracerebral vein, and superior sagittal sinus. The branch of the left posterior cerebral artery was the secondary artery involved, draining into the straight sinus and cortical veins. The right middle meningeal artery was the least involved, primarily draining into the posterior sagittal sinus. These findings were consistent with a Cognard type IIa+b dAVF.
Therapeutic Intervention
Given the complexity of the dAVF and the patient’s deteriorating condition, interventional endovascular treatment was performed. The dAVF was successfully embolized at the Galen vein and the straight sinus using a liquid blood suppository and a transarterial approach via the left posterior cerebral and left occipital arteries. Post-treatment angiography confirmed the obliteration of the fistula.
Clinical Outcome
The patient’s health status began to improve during his hospitalization, and he was discharged to his home seven days after the procedure. Three months following the intervention, a clinical evaluation revealed a remarkable recovery, with significant improvement in his forgetfulness and confusion. Follow-up MRI showed the disappearance of the previously observed bilateral abnormal thalamic signals.
Discussion
Bilateral thalamic lesions can result from a wide range of etiologies, but dAVFs are an uncommon vascular cause. This case highlights the importance of considering dAVFs in the differential diagnosis of bilateral thalamic lesions, particularly when accompanied by dementia-like symptoms. The patient’s presentation of memory deficits and confusion was attributed to the retrograde flow of the fistula into the straight sinus and Galen vein, leading to thalamic edema and functional deficits.
The classification of dAVFs is well-documented, with the revised Cognard classification system being widely used. In this case, the dAVF was classified as Cognard type IIa+b, characterized by retrograde venous drainage into the deep venous system. This classification is significant as it correlates with the clinical severity and risk of neurological deficits, underscoring the need for prompt intervention.
The diagnostic workup for dAVFs typically involves a combination of MRI, MRA, MRV, and DSA. While MRI can reveal thalamic abnormalities, MRA and MRV are crucial for visualizing dilated draining veins and malformed vessels. DSA remains the gold standard for confirming the diagnosis and delineating the arterial supply and venous drainage of the fistula.
Treatment options for dAVFs include endovascular embolization, surgical intervention, and, in some cases, radiosurgery. Endovascular treatment has become increasingly favored due to its minimally invasive nature and high success rates. However, complex dAVFs often require multiple embolization sessions and carry a risk of recurrence. In this case, the patient was successfully treated with a single endovascular embolization procedure, resulting in complete obliteration of the fistula and significant clinical improvement.
Conclusion
This case report underscores the importance of considering dAVFs as a potential vascular etiology in patients presenting with bilateral thalamic lesions and dementia-like symptoms. The use of advanced imaging techniques, including MRI, MRA, MRV, and DSA, is essential for accurate diagnosis and treatment planning. Endovascular embolization is an effective therapeutic option, particularly for complex dAVFs, but close follow-up is necessary to monitor for potential recurrence. The successful outcome in this case highlights the critical role of early diagnosis and intervention in improving patient prognosis.
doi.org/10.1097/CM9.0000000000001115
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