Optic Neuropathy Due to Compression by an Ectatic Internal Carotid Artery Within the Orbital Apex.

ABSTRACT: Neurovascular compression is a rare but potentially treatable cause of optic neuropathy. Although incidental contact of the cisternal optic nerve and internal carotid artery (ICA) is common, compressive optic neuropathy occurring within the orbital apex has not been comprehensively described. We report a case of intra-orbital and intracanalicular optic nerve compression due to an ectatic ICA in a patient with congenital absence of the contralateral ICA. This report describes the complementary roles of advanced neuroimaging and neuro-ophthalmologic examination in rendering the diagnosis.

Balloon-backstop technique: Preserving physiologic venous drainage during transvenous coil embolization of sigmoid sinus dural arteriovenous fistulas.

Dural arteriovenous fistulas can lead to catastrophic intracranial hemorrhage if left untreated. Transvenous embolization can cure arteriovenous fistulas, but preserving normal venous structures can be challenging. Inadvertent embolization of a functioning vein can result in catastrophic venous infarction or hemorrhage. Here, we report a case using balloon-assistance to facilitate preservation of the superior petrosal sinus during transvenous embolization of a sigmoid sinus dural arteriovenous fistula.

MRI and MR angiography evaluation of pulsatile tinnitus: A focused, physiology-based protocol.

BACKGROUND AND PURPOSE: Pulsatile tinnitus (PT) is the subjective sensation of a pulse-synchronous sound, most often due to a cerebrovascular etiology. PT can severely impact quality of life and may indicate a life-threatening process, yet a timely and accurate diagnosis can often lead to effective treatment. Clinical assessment with a history and physical examination can often suggest a diagnosis for PT, but is rarely definitive. Therefore, PT should be evaluated with a comprehensive and targeted radiographic imaging protocol. MR imaging provides a safe and effective means to evaluate PT. Specific MR sequences may be used to highlight different elements of cerebrovascular anatomy and physiology. However, routine MR evaluation of PT must comply with economic and practical constraints, while effectively capturing both common and rarer, life-threatening etiologies of PT. METHODS: In this state-of-the-art review, we describe our institutional MR protocol for evaluating PT. RESULTS: This protocol includes the following dedicated sequences: time-of-flight magnetic resonance angiography; arterial spin labeling; spoiled gradient recalled acquisition in the steady state; time-resolved imaging of contrast kinetics; diffusion weighted imaging, and 3-dimensional fluid-attenuated inversion recovery. CONCLUSIONS: We describe the physiologic and clinical rationale for including each MR sequence in a comprehensive PT imaging protocol, and detail the role of MR within the broader evaluation of PT, from clinical presentation to treatment.

The Effect of Extracranial-to-Intracranial Bypass on Cerebral Vasoreactivity: A 4D Flow MRI Pilot Study.

BACKGROUND AND PURPOSE: Extracranial-to-intracranial (EC-IC) surgical bypass improves cerebral blood flow (CBF) and cerebrovascular vasoreactivity (CVR) for patients with carotid occlusion. Bypass graft patency and contribution of the graft to the postoperative increase in CVR are challenging to assess. To assess the effectiveness of 4D flow magnetic resonance imaging (MRI) to evaluate bypass graft patency and flow augmentation through the superficial temporal artery (STA) before and after EC-IC bypass. METHODS: Three consecutive patients undergoing EC-IC bypass for carotid occlusion were evaluated pre- and postoperatively using CVR testing with pre- and poststimulus 4D flow-MRI for assessment of the bypass graft and intracranial vasculature. RESULTS: Preoperatively, 2 patients (patients 1 and 3) did not augment flow through either native STA. The third, who had evidence of extensive native EC-IC collateralization on digital subtraction angiography (DSA), did augment flow through the STA preoperatively (CVR = 1). Postoperatively, all patients demonstrated CVR > 1 on the side of bypass. The patient who had CVR > 1 preoperatively demonstrated the greatest increase in resting postoperative graft flow (from 40 to 130 mL/minute), but the smallest CVR, with a poststimulus graft flow of 160 mL/minute (CVR = 1.2). The 2 patients who did not demonstrate augmentation of graft flow preoperatively augmented postoperatively from 10 to 20 mL/minute (CVR = 2.0) and 10-80 mL/minute (CVR = 8.0), respectively. Intracranial flow was simultaneously interrogated. Two patients demonstrated mild reductions in resting flow velocities in all interrogated vessels immediately following bypass. The patient who underwent CVR testing on postoperative day 48 demonstrated a stable or increased flow rate in most intracranial vessels. CONCLUSION: Four-dimensional flow MRI allows for noninvasive, simultaneous interrogation of the intra- and extracranial arterial vasculature during CVR testing, and reveals unique paradigms in cerebrovascular physiology. Observing these flow patterns may aid in improved patient selection and more detailed postoperative evaluation for patients undergoing EC-IC bypass.

18F-FDG Uptake in Subcutaneous Fat Preceding Clinical Diagnosis of Human Immunodeficiency Virus-Associated Lipodystrophy.

A 62-year-old man with human immunodeficiency virus (HIV) on long-standing highly active antiretroviral therapy presented for F-FDG PET/CT evaluation of a pulmonary nodule. The examination showed unusual radiotracer distribution accumulating in the subcutaneous and visceral fat with low cerebral and skeletal muscle uptake. Imaging features were consistent with HIV-associated lipodystrophy, an unsuspected diagnosis that was later confirmed on physical examination. Recognition of HIV-associated lipodystrophy by the nuclear medicine physician is critical as altered biodistribution may affect diagnostic yield or be mistaken for infectious pathology.