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RESIDENT & FELLOW SECTION Clinical Reasoning: Section Editor An unusual case of subacute Mitchell S.V. Elkind, MD, MS encephalopathy Neal Parikh, MD SECTION 1 revealed wide-based gait and lower extremity dysmet- Alexander E. Merkler, A 52-year-old previously healthy man presented with 8 ria. Relevant laboratory evaluation revealed only a MD months of progressive cognitive decline. He complained C-reactive protein of 1.79 (normal 0–0.99). Natalie T. Cheng, MD of months of confusion, fatigue, depression, hypersom- Brain MRI obtained in Morocco 2 months prior Hediyeh Baradaran, MD nolence, headaches, and, subsequently, urinary inconti- to presentation had demonstrated bilateral thalamic Halina White, MD nence and unsteady gait. His family reported that he T2 hyperintensities and patchy enhancement in the Dana Leifer, MD spoke of his deceased mother as if she were alive. His right medial temporal lobe, midbrain, and basal gan- executive deficits progressed, leading to termination of glia. A right thalamic biopsy obtained in Morocco his employment and a motor vehicle accident. He had revealed “inflammatory cells” without evidence Correspondence to was evaluated and treated in Morocco before presenting of malignancy. Dr. Leifer: to our institution for further care. [email protected] Questions for consideration: Mental status examination was notable for slowed mentation and dyscalculia but was otherwise normal. 1. How can thalamic injury cause encephalopathy? Motor, sensory, and deep tendon reflex examination 2. What is the differential diagnosis for bilateral tha- results were normal. Cerebellar and gait examination lamic MRI abnormalities? GO TO SECTION 2 From the Departments of Neurology (N.P., A.E.M., N.T.C., H.W., D.L.) and Radiology (H.B.), Weill Cornell Medical Center, New York, NY. Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article. © 2015 American Academy of Neurology e33 ª 2015 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. SECTION 2 2 are part of the reticular activating system, which is The thalamus is a major processing center for the involved in maintaining consciousness and arousal. brain that relays motor, sensory, cerebellar, as well Perturbations in these portions of the thalamus can as cognitive and limbic inputs. Information regarding cause confusion, depressed levels of alertness, and cognition and arousal is processed in the mediodorsal, coma. Lesions of other structures initially affected midline, and intralaminar thalamic nuclei. The latter on the patient’s MRI, such as the basal ganglia and medial temporal lobe, can produce similar symptoms; however, only bilateral thalamic injury was rede- Figure Pre-embolization and post-embolization neuroimaging monstrated on our own imaging. The differential diagnosis for thalamic lesions is broad. Etiologies for bilateral thalamic MRI abnormalities include neoplastic (glioma or lymphoma), heredi- tary, metabolic and toxic (Wernicke encephalopathy, osmotic myelinolysis, pantothenate kinase deficiency, Wilson disease, liver disease, hypoxic ischemic encephalopathy, carbon monoxide poisoning), infectious (West Nile virus or other flaviviruses, Creutzfeldt-Jakob disease, toxoplasmosis), inflammatory (neuro-Behçet disease), and vascular (occlusion at the top of the basilar artery, occlusion of an artery of Percheron, cerebral venous sinus thrombosis [CVST]).1 Clinical history, other imaging features, and laboratory analysis narrow thediagnosticpossibilities. Repeat MRI revealed microhemorrhage, T2 and fluid-attenuated inversion recovery signal abnormality (figure, A), and patchy postcontrast enhancement in the bilateral thalami. Additionally, our patient had already been treated with prednisone in Morocco with subsequent worsening. Based on the bilateral midline signal abnormalities with only patchy enhancement and lack of steroid responsiveness, we suspected a vascular etiology, specifically a straight sinus venous thrombosis, rather than a vasculitic, meningoencepha- litic, or neoplastic etiology. Magnetic resonance angiography results were normal; however, magnetic resonance venography showed prominent collateral veins along the left occipital lobe and nonvisualization (A) Right greater than left fluid-attenuated inversion recovery signal hyperintensity in the of the internal cerebral veins, distal vein of Galen, and thalami with patchy postcontrast enhancement (not shown) and microhemorrhage on gradi- ent echo imaging (not shown), consistent with subacute venous infarction. (B) Arrowheads at straight sinus (figure, B). expected sites of occluded vein of Galen and straight sinus. (C) Pre-embolization digital sub- Questions for consideration: traction angiogram (DSA) image after injection of the left common carotid artery demon- strates early filling of a venous varix (arrow) in the left perimesencephalic cistern, 1. What is the differential diagnosis for CVST? primarily supplied by small branches of the left middle meningeal artery, consistent with a dural arteriovenous fistula (dAVF). (D) Post-embolization DSA image after embolization of 2. What is the appropriate next step in diagnostic the dAVF with onyx with no evidence of residual vessel filling. evaluation? GO TO SECTION 3 e34 Neurology 84 February 10, 2015 ª 2015 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. SECTION 3 Angiography confirmed straight sinus thrombosis CVST is observed most commonly in patients with and revealed early filling of a venous varix supplied acquired or inherited hypercoagulability, high by small branches of the left middle meningeal artery estrogen states, cancer, and, uncommonly, head and dural branches of the left posterior cerebral artery, and neck infections.2 In our patient, nonvisualiza- which were consistent with a dAVF (figure, C). tion of the straight sinus was seen along with Questions for consideration: prominent collateral veins and thalamic ischemia or infarction. These findings suggested a dural 1. What interventions are indicated? arteriovenous fistula (dAVF) and prompted 2. What is the pathophysiologic relationship among angiography.3 thalamic injury, CVST, and dAVF? GO TO SECTION 4 Neurology 84 February 10, 2015 e35 ª 2015 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. SECTION 4 Ischemia in the context of a dAVF and CVST is We elected to treat the patient by embolization of the therefore a potentially treatable condition. Appropriate dAVF and with anticoagulation for venous thrombo- treatment is primarily endovascular embolization of the sis. Angiography demonstrated complete obliteration dAVF, which resulted in reversal of T2 signal abnor- of the dAVF at the end of embolization (figure, D). malities in our patient, along with anticoagulation for MRI was repeated 1 month later and showed nearly the CVST. Alternative treatments for dAVF include complete resolution of the thalamic T2 hyperinten- surgical intervention and stereotactic radiosurgery.3 sities. There was no change in the neurologic exam- Since thalamic injury attributed to both dAVF ination at that time; however, persistent CVST was and CVST may be reversible, and the 2 processes seen. The patient was subsequently lost to follow-up. require distinct treatments, it is imperative to con- sider CVST with associated dAVF in the differential DISCUSSION Dural arteriovenous fistulas are rare vas- diagnosis for bilateral thalamic MRI abnormalities. cular malformations in which meningeal arteries drain directly into dural venous sinuses, meningeal veins, or AUTHOR CONTRIBUTIONS subarachnoid veins.3 This type of vascular malformation Neal Parikh conceived and designed the study and drafted and revised the manuscript for intellectual content. Alexander E. Merkler conceived and is associated with various neurologic symptoms and def- designed the study and drafted and revised the manuscript for intellectual icits including tinnitus, dementia, seizures, parkinson- content. Natalie T. Cheng drafted and revised the manuscript for intel- ism, and cerebellar symptoms.3 When seen with cortical lectual content. Hediyeh Baradaran drafted and revised the manuscript 4 for intellectual content. Halina White conceived and designed the study venous drainage, they have a 30% hemorrhage risk. A and drafted and revised the manuscript for intellectual content. Dana retrospective analysis also found a 4.5% incidence of Leifer conceived and designed the study and drafted and revised the man- ischemic stroke in a cohort of 134 patients with dAVF; uscript for intellectual content. 5ofthe6patientswithstrokeshadvenousinfarctions.5 STUDY FUNDING Ischemic stroke was nonsignificantly more common in No targeted funding reported. patients who had CVST in addition to dAVF. Although CVST has been described in the setting of dAVF, there DISCLOSURE are no known reports of this combination as a cause of N. Parikh, A. Merkler, N. Cheng, H. Baradaran, and H. White report no bilateral thalamic injury and encephalopathy. disclosures. D. Leifer is supported by NIH grant R01 HL089521. He also Accumulating evidence suggests that this is a unique has received research support from NIH grants NS058728 and NS044378. Go to Neurology.org for full disclosures. vascular mechanism by which thalamic compromise results in subacute encephalopathy or rapidly progressive REFERENCES dementia. Three case reports describe patients

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