A 51-year-old man was admitted for transient aphasia and dizziness. During the 10 years prior to admission, he had slowly progressive cognitive decline with increasing disorientation, slowness of thought, and inability to cope with multiple tasks at work. The patient also had hearing loss, balance difficulties, and decreased sense of smell for several months. His medical history was notable for a recent diagnosis of vitamin B12 deficiency, history of smoking, and alcohol use. He also had a remote history of C2 fracture 33 years prior due to a motor vehicle accident—as a consequence, the patient was paralyzed for 2 days and in cervical traction for 4 months with complete recovery. At presentation, his neurologic examination revealed slowness of speech, mixed aphasia, apraxia, broad-based gait, mild ataxia, and hyperreflexia with bilateral extensor plantar responses. An electroencephalogram showed left temporal slowing. Initial magnetic resonance imaging showed cerebellar atrophy and T2 hypointesity along the surface of the brain (including the spinal cord, brainstem, cerebellum, and cerebrum) most prominent on susceptibility sequences consistent with meningeal siderosis (Figure 1). Magnetic resonance imaging of the spine showed prominent venous engorgement involving the ventral aspect of the brainstem and cervical cord with no intrinsic cord abnormalities (Figure 2). The patient started taking phenytoin for suspicion of focal left temporal seizures and nimodipine for prophylaxis for vasospasm, and he did not have any further episodes of aphasia. A lumbar puncture showed opening pressure of 10 mm Hg; xanthochromia; total protein, 0.107 g/dL (to convert to grams per liter, multiply by 10.0); glucose, 84 mg/dL (to convert to millimoles per liter, multiply by 0.0555); white blood cell count, 2 to 3/cm3 (100% neutrophils); and red blood cell count, 383/cm3, which did not clear. Gram stain and culture did not reveal any infection. Cerebral and spinal angiograms were then performed and showed no angiographic evidence of arterial venous malformation, fistula, or aneurysm. However, there was bilateral venous occlusion at the level of the jugular bulbs (Figure 3, A and B). Below the jugular bulbs, there was an extensive venous collateral network in the neck that included engorged anterior and posterior spinal veins (Figure 3, C and D). The patient had a tagged (Tc-99M) red blood cell study that did not reveal a source of active bleeding. A chest computed tomogram did not show any evidence of malignancy or superior vena cava syndrome. A repeated lumbar puncture 2 weeks later showed pressure within the reference range; protein, 0.98 g/dL; glucose, 90 mg/dL; and no xanthochromia. Results of laboratory evaluation were normal including negative anti–Purkinje cell, antineuronal nuclear, lupus anticoagulant, anticardiolipin antibodies, and activated protein C resistance screening. The homocysteine level was slightly elevated at 1.93 mg/L (to convert to micromoles per liter, multiply by 7.397). No active source of bleeding was found, and the patient was discharged while taking phenytoin and nimodipine. Owing to the chronicity of the jugular vein thrombosis and the extensive venous collateralization, no specific treatment was recommended. He continued to be neurologically stable without recurrence of seizures during 8 months of follow-up.