Parkinsonian syndromes are considered clinicopathological conditions that are challenging to diagnose. Molecular imaging with [18F]-FDOPA and [18F]-FDG contributes to a more accurate clinical diagnosis by evaluating presynaptic dopaminergic pathways and glucose metabolism, respectively. The aim of this study was to correlate diagnoses made from dual PET/CT with the initial clinical diagnoses, as well as during follow-ups in patients with Parkinsonian syndromes. A secondary objective was to describe the imaging findings. Methods: A total of 150 patients with a clinical diagnosis of neurodegenerative Parkinsonism were evaluated using dual PET/CT. Clinically, 82% were diagnosed with PD, while the remaining 18% had an atypical Parkinsonism. Results: Using dual PET/CT, the most frequent diagnosis was PD in 67% of the patients, with the rest being diagnosed with an atypical Parkinsonism. In an agreement analysis between the initial clinical diagnosis and the imaging diagnosis by dual PET/CT, a concordance of 94.1% (n = 95) was observed for PD. In the remaining patients, the clinical diagnosis differed from that suggested by dual PET/CT, with atypical Parkinsonian syndromes being diagnosed as DLB in 40% (n = 4), PSP in 46.7% (n = 7), MSA-C in 75% (n = 6), MSA-P in 70% (n = 7), and CBD in 66.7% (n = 4). A total of 38.66% (n = 58) of patients were followed up (median follow-up of 27 months), with a Kappa coefficient of 0.591 (p < 0.001), suggesting substantial agreement. Conclusions: Dual FDOPA–FDG PET/CT demonstrated moderate agreement with the initial clinical diagnosis of Parkinsonism and moderate to substantial agreement during follow-up. This dual technique, therefore, stands out in differentiating between types of Parkinsonisms.

Introduction: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative, multisystem disorder. Its clinical presentation typically consists of progressive focal muscle atrophy and weakness. In addition to motor disorders, the association between ALS and cancer has been researched, such as frontotemporal dementia and progressive supranuclear palsy. The diagnosis is based primarily on the clinical history, physical examination, electrodiagnostic tests (with an EMG needle), and neuroimaging, such as MRI and ¹⁸F-FDG PET/CT.Presentation of the case: A 67-year-old male patient was diagnosed with prostate adenocarcinoma with a clinical picture of muscle weakness in the lower limbs that caused falls and was associated with fasciculations in the thighs and arms, alterations in the tone of voice, poor memory, and difficulty articulating words. In the neurological assessment, he described walking supported by a walker with decreased strength in both lower limbs and sensitivity without alterations. The diagnoses of upper and lower motor neuron disease and probable ALS were integrated. Furthermore, the probable coexistence of frontotemporal dementia/disorder (FDD) with ALS was considered. The main findings in the ¹⁸F-FDG PET/CT study was hypometabolism in the cortex of the bilateral motor and premotor areas, the anterior cingulate, both caudate and putamen, a metabolic pattern compatible with ALS, and progressive supranuclear palsy.Conclusion: Through the PET/CT studies, we demonstrated a case in which ALS, prostate cancer and progressive supranuclear palsy coexisted molecularly; it was clinically difficult to diagnose. Molecular imaging has potential in the diagnostic and prognostic evaluation of ALS. It is crucial to identify the disease early and reliably through metabolic patterns that allow us to confirm the disease or differentiate it from other pathologies.

Background: Brain 18 FDG PET is very useful in the diagnosis of autoimmune encephalitides against post-synaptic receptors. However, little is known about the metabolic changes in other autoimmune encephalitides, such as Bickerstaff stem encephalitis (BBE). Objective: to report the case of a patient with BBE with an 18 FDG PET study and to review the literature. Results: A 20-year-old man with no relevant history presented to the emergency department due to a clinical picture of 7 days of evolution, characterized by non-painful distal paresthesias in the 4 extremities, diplopia, instability on gait and dysphagia. On the day of his hospital stay, he presented alterations in his awake state. The clinical diagnosis of Bikerstaff's stem encephalitis was made. In his paraclinical tests, the cerebrospinal fluid was normal. He received treatment with human immunoglobulin (2 grams/kg) for 5 days. An 18 FDG PET study reported hypermetabolism in the putamen and bilateral caudate nucleus and bilateral occipital hypometabolism. Conclusion: brain 18-FDG PET may be a subrogate marker for understanding CNS compromise in BBE.

Word count: 248 Introduction: Bickerstaff's Encephalitis (BE) is considered a rare immune-mediated disorder, characterized by the clinical triad of ophthalmoplegia, ataxia and impaired consciousness. It falls within the spectrum of anti-GQ1b diseases. Diagnosis uses clinical and laboratory criteria, and imaging techniques allows other diseases to be ruled out. The use of 18F-fluorodeoxyglucose positron emission tomography (PET) in BE has not been extended, so a case with PET follow-up is presented. Presentation of the case: This is a 29-year-old patient, with a history of chronic headache, hypertension and grade III obesity presented 72 hours prior to admission drowsiness, ophthalmoplegia, right peripheral facial palsy, dysarthria, and gait disturbance, flaccid tetra paresis and generalized hyperreflexia. An autoimmune inflammatory disease was suspected. The determination for antiganglioside antibodies (anti GT1a IgG and anti GQ1b IgG) were positive. The diagnosis of Bickerstaff encephalitis was integrated. The main findings in the PET/CT with 18F-FDG study were cortical hypometabolism in occipital region, and cerebellum, and hypermetabolism in the striatum bilaterally, with normalization of the brain metabolism after treatment on the second PET-FDG scan performed after 4 months of onset of the clinical picture. Conclusion: We demonstrate a case of BE by molecular imaging with PET-FDG before and after treatment with normalization of brain metabolism with cognitive improvement. Molecular Imaging has a potential in the diagnostic, and monitoring evaluations of BE. PET (Positron Emission Tomography) could be an earlier marker for neurological conditions as BE and an excellent tool to aid diagnosis, to provide timely treatment and follow-up BE patients.