Given the wide range of manifestations of parkinsonism and its mimics, the diagnosis may remain elusive or be misattributed in some patients. Dopamine transporter (DAT) single photon emission computed tomography (SPECT) (DaTscan), an imaging technique that probes the integrity of the presynaptic nigrostriatal system, can be useful in the evaluation of clinically complex parkinsonian disorders in the appropriate context and when adequately interpreted. Pearls and pitfalls in the use of DaTscan for the differential diagnosis of parkinsonisms are reviewed using a case-based format. While the DaTscan is no replacement for a careful neurological examination in ascertaining the likelihood of Parkinson disease or other parkinsonisms in most clinical scenarios, it can be useful in the assessment of disorders where an abducting resting tremor, a prominent postural tremor, or incongruent features are not sufficiently clear on exam to distinguish neurodegenerative parkinsonism from dystonia, drug-induced parkinsonism and functional (psychogenic) parkinsonism, respectively.

Anti-NMDA receptor encephalitis can coexist with an overlapping demyelinating syndrome. c An atypical presentation of a single autoimmune disorder should prompt investigation for coexistent autoimmune disorders. c Discovery of overlap syndromes is important because the management and prognosis may be different. Oysters c In autoimmune encephalitis, shorter time from symptom onset to treatment initiation has been associated with better outcome. 1 c Treatment should not be delayed until the result of autoantibody testing is available. Case report A 31-year-old man developed a subacute onset of headache, left-sided numbness, and anterograde amnesia. In the following 2 weeks, he experienced personality changes, anxiety, paranoid thoughts, 7 kg weight loss, and worsening cognitive changes. He said that he felt as though he was trapped in a time loop, meaning that events seemed to be constantly recurring to him. He denied fever, night sweats, viral prodromal symptoms, or recent vaccinations. He was diagnosed with acute disseminated encephalomyelitis (ADEM) in 2007 from which he made a full recovery. On neurologic examination, he was inattentive and agitated. His word registration and short-term recall at 5 minutes were 0 of 5. He had verbal and motor perseveration with echolalia. He had decreased sensation to pinprick on his entire left side. He also had left pronator drift and bilateral athetosis of the upper limbs. The remainder of his examination was normal. His overall clinical examination finding was consistent with a multifocal process involving subcortical and cortical regions. On day 1, routine blood testing including complete blood cell count with differential, metabolic panel, liver function test, RPR, ESR, ANA, thyroid function tests, thiamine, B12, urinalysis, urine toxicology screen, heavy metal screening, and HIV were normal or negative. Brain MRI revealed multiple T2 hyperintensities within the right internal capsule, periventricular white matter, and bilateral mesial temporal lobes. There were contrast-enhancing lesions involving the right dorsal pons and right internal capsule and thalamus (figure, A-F). CSF analysis demonstrated 9 nucleated cells/μL with lymphocytic predominance. On day 2, CT of the chest, abdomen, and pelvis and testicular ultrasound were negative for malignancy. Cervical and thoracic spine MRI was performed to look for any past or active demyelinating lesions, especially in the setting of previous history of ADEM, and the result was normal. Video EEG did not demonstrate abnormal ictal or interictal epileptiform discharges. By this time, CSF Gram stain, cultures, and viral PCRs returned negative, and 8 CSF-specific oligoclonal bands were present. Serum and CSF NMDA-R IgG and serum MOG-IgG1 antibodies were sent to the laboratory. On hospital day 3, IV methylprednisolone