Contributed by Janna Neltner, MD and Craig Horbinski, MD, PhD
Department of Pathology, University of Kentucky, Lexington, KY 40536
The patient was a 29 year old Caucasian female with a past medical history of poorly controlled hypertension and diabetes mellitus who presented with a one week history of marked confusion and ataxia. She was brought to the hospital by local authorities who found her wandering in a nearby creek, completely disoriented with regards to where she was or how she had gotten there.
Upon admission, she was found to have a urinary tract infection (Citrobacter sp.) and possible pneumonia, for which Levaquin and Zosyn were initiated. Initial imaging of her head showed multifocal white matter changes suggestive of multiple sclerosis or infarcts (not shown). High dose steroids were initiated, yet her mental status continued to decline. She became febrile (up to 105oF), though blood and CSF microbial cultures were repeatedly negative. Other pertinent negative lab values included: anti-nuclear antibodies, C- and P-ANCAs, Rocky Mountain Spotted Fever IgM and IgG, Ehrlichia chaffeensis IgM and IgG, West Nile Virus IgM, HIV, and fungal serologies.
A repeat MRI showed marked progression of the white matter lesions within the bilateral anterior frontal lobes, corpus callosum, and basal ganglia (Figs. 1 [FLAIR] and 2 [T2]). Magnetic resonance angiography showed severe attenuation of the supraclinoid internal carotid arteries (ICAs), with absence of flow-related signal within the M1 segments of the middle cerebral arteries (MCAs) and the proximal anterior cerebral arteries (ACAs) bilaterally (Fig. 3, short and long arrows, respectively). Unfortunately the patient continued to decline and expired fifteen days after her initial presentation. An autopsy was requested by the family for the purposes of determining the etiology of her decline.
At autopsy, the brain weighed 1250 grams. There was marked occlusion of both ICAs extending into the proximal MCA and ACA branches bilaterally (Fig. 4 [right ICA] and Fig. 5 [left ICA]). Other vessels, including the basilar and vertebral arteries, were unremarkable. No aneurysms or hemorrhage was present. Consistent with the aforementioned premortem imaging, there was marked softening and edema within the bilateral ACA distribution with some extension into bilateral MCA territories, with involvement of the bilateral anterior medial frontal and parietal lobes, basal ganglia, thalami, and corpus callosum. There was also tonsillar herniation with associated Duret hemorrhages within the pons and medulla (not shown).
Microscopically there was striking intimal proliferation of MCA/ACA/ICA intima with medial thinning (Figs. 6, 7, 8). Trichrome stains highlight the undulating intact internal elastic lamina (IEL), which was thickened and rarely showed focal splitting (Figs. 9, 10). No atherosclerotic plaques or inflammation was seen. The softened areas in the cerebrum showed edema, "dead red" neurons, and early neutrophil infiltration, but no macrophages, neovascularization, or reactive gliosis (not shown). What is the diagnosis?