[A case of Creutzfeldt-Jakob disease presenting with arm levitation as an initial symptom].

A 74-year-old, right handed man, developed insidiously with levitation and clumsiness of the right upper limb. His right arm tended to levitate spontaneously, when he was examined. He could put the elevated arm down on command, while the arm resumed to antigravity posture when his attention was diverted. His right arm also exhibited unwilled elevation when performing complex finger movements on the right side. He had a feeling of strangeness of the elevated limb, especially with the eyes closed. In addition to asymmetric limb-kinetic apraxia, combined sensations such as stereognosis were disturbed on the right side. Brain MRI showed high signal lesions predominantly in the left cerebral cortices and basal ganglia. SPECT with (123)I-IMP revealed asymmetric hypoperfusion, predominantly in the left medial frontal and parietal regions. Two months after the onset, levitation of the arm gradually disappeared, with the development of rapidly progressive dementia, frontal signs, dystonia and generalized myoclonus. The diagnosis of Creutzfeldt-Jakob disease (CJD) was made based on the clinical features and cerebrospinal fluid biomarkers. The early manifestation of the patient mimicked corticobasal degeneration which presents with arm levitation or alien hand syndrome. It is suggested that CJD can represent involuntary movements with higher brain dysfunction resembling corticobasal degeneration at the early stage of the illness. Although the underlying mechanism of arm levitation is still unknown, frontal disinhibition and parietal cortical sensory disturbance may contribute to the development of involuntary arm levitation in our patient.