Demencia por déficit de vitamina B12. Caso clínico / Dementia caused by vitamin B12 deficiency. Clinical case

Cyanocobalamin (vitamin B12) deficiency can cause polyneuropathy, myelopathy, blindness, confusion, psychosis and dementia. Nonetheless, its deficiency as the sole cause of dementia is infrequent. We report a 59 years old man with a 6 months history of progressive loss of memory, disorientation, apathy, paranoid delusions, gait difficulties with falls, and urinary incontinence. He had suffered a similar episode 3 years before, with a complete remission. On examination there was frontal type dementia with Korsakoff syndrome, a decrease in propioception and ataxic gait. Cerebrospinal fluid examination showed a protein of 0.42 g/L. Brain computed tomography showed sequelae of a frontal left trauma. Brain single photon computed tomography (SPECT) was normal. Complete blood count showed a macrocytic anemia with a hematocrit 29 per cent and a mean corpuscular volume of 117 micron3. Plasma vitamin B12 levels were undetectable, erythrocyte folate levels were 3.9 ng/ml and plasma folate was normal. The myelogram showed megaloblastosis and the gastric biopsy showed atrophic gastritis. Treatment with parenteral B12 vitamin and folic acid reverted the symptoms, with normalization of the neuropsychological tests and reintegration to work.

Calcium-activated potassium channels of large unitary conductance

The large unitary conductance Ca2+ -activated K+ channel is a widely distributed channel in cellular membranes of diverse tissues. This type of channel may serve as a link between membrane excitability and cell metabolism. In this review we discuss some aspects of the gating mechanism, calcium activation and function and modulation of BK channels