[Alien hand sign observed at the initial stage of a case of Creutzfeldt-Jakob disease].

A 68-year-old man was admitted to our hospital in the mid-October of 2006 because of a one-month history of peculiar movements of the left hand, which had been preceded by one month by awkward motions in the left leg. Upon neurological examination, spontaneous involuntary movement of the left hand was found. His left hand with his index finger stretched moved toward his right side spontaneously. He could not control his left leg freely. Although he showed mild ataxia in his left hand, there was no weakness, no dystonia, and no apraxia. No sensory abnormality was detected except for mild deep-sensation impairment in his left foot. The results of magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI) were normal; however, single-photon emission computed tomography (SPECT) showed hypoperfusion in the right hemisphere. At the time of admission, although a clinical diagnosis could not be made, we considered that the involuntary movements of his left hand were consistent with alien hand sign (AHS). Two and a half months after its onset, with the development of rapidly progressive dementia and generalized myoclonus, AHS gradually disappeared. Three months after the AHS onset, MRI with DWI showed restricted diffusion within the cortex involving the cingulated gyrus and bilateral temporal lobes, which was more prominent on the right than on the left side. Four months after the AHS onset, 14-3-3 protein level of the cerebrospinal fluid was elevated, and EEG recordings showed diffuse slowing of basic activity with periodic complexes. The patient was clinically diagnosed as having CJD. The patient died of pneumonia four and a half months after the AHS onset. AHS has rarely been reported in patients with CJD. Our case illustrates the importance of considering CJD in the differential diagnosis, if the patient showed AHS, even with normal MRI findings.