[A case presenting with ataxic gait and dementia due to vitamin B₁₂ deficiency without megaloblastic anemia or subacute combined degeneration of the spinal cord].

: A 36-year-old man was admitted to our hospital because of subacute progressive ataxic gait and dementia. His blood test results vitamin B₁₂ deficiency due to presence of anti-intrinsic factor antibody and his endoscopic examination findings showed chronic gastritis. Treatment was administered on the bass of on a diagnosis of vitamin B₁₂ deficiency. Consequently, ataxic gait improved and dementia regressed. ¹²³I-IMP cerebral blood flow scintigraphy conducted at 8 months after treatment initiation showed increased blood flow the area around the parietal lobe to the corpus callosum, and flow both temporal lobes to the hippocampus compared. The diagnosis was difficult in this case because the patient did not show the typical symptoms and complications associated with vitamin B₁₂ deficiency, such as megaloblastic anemia, or subacute combined degeneration of the spinal cord. However, the disturbance in cerebral blood flow may be related to the dysfunction of higher brain function caused by vitamin B₁₂ deficiency.