Miscellaneous Clinical Nuclear Medicine Neuroimaging Studies
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This chapter consists of three sections. Section “Brain Death Scintigraphy” devotes to the brain perfusion imaging to help diagnose brain death, which is typically indicated by no appreciable perfusion to the entire brain parenchyma on dynamic, static, and/or SPECT imaging. In addition to the direct imaging evidence of brain death, a “hot nose sign” may or may not be observed as indirect evidence of brain death due to increased perfusion in the peripheral secondary to no perfusion to the brain (Donohoe et al. JNMT 40:198–203, 2012). Section “Spect Brain Perfusion Study of Chronic Lyme Encephalopathy” focuses on scintigraphy of chronic Lyme encephalopathy which is characterized by heterogeneity and multifocal/asymmetric cortical hypoperfusion and/or tubular-like cortical defects, while perfusion to the primary visual cortices and cerebella is often preserved (Logigian et al. J Infect Dis 180:377–383, 1999; Sumiya et al. J Nucl Med 38:1120–1122, 1997). Presented in section “Others” are unique three neuroimaging studies as the following: The Wada test, named after Dr. Juan Wada, is a SPECT brain perfusion study, also referred to as intracarotid sodium amobarbital procedure (ISAP), during which images typically demonstrate global hypoperfusion of the tested brain hemisphere and while normal/preserved perfusion is present in the contralateral brain. These help determine brain hemispheric memory and language dominance as part of pre-surgical evaluation mainly for epileptic patients (Wada Igaku to Seibutsugaki 14:221–222, 1949). The second case shows a patient with known chronic left middle cerebral artery (MCA) occlusion who had an essentially normal baseline brain perfusion study. After Diamox challenge, however, profound hypoperfusion is demonstrated in the left MCA territory, a finding often referred to as “intracerebral steal phenomenon (ISP),” indicating a poor cerebrovascular reserve (CVR) (Vagal et al. AJNR 30:876–884, 2009). The third case is a brain FDG PET showing diffuse hypermetabolism mainly in the frontal and insular lobes in a 14-year-old male presenting with fever, atypical measles syndrome, altered mental status, and positive Mycoplasma titers, suspicious for Mycoplasma encephalitis.
KeywordsBrain death Lyme encephalopathy Wada test Cerebrovascular reserve Mycoplasma encephalitis
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