November 13, 2012

Neurology of Vitamin B12 Deficiency

In this Blog update we will take a closer look at the neurological features of Vitamin B12 deficiency.

Broadly speaking, the neurology has central (cerebral) and/or peripheral manifestations.

"Gloves and Stockings":

Neurological features of vitamin B12 deficiency are usually chronic and progressive.  Typically the first symptoms are of altered sensation including a numbness or tingling of hands and feet and an unsteady gait.  Some patients also develop reduced manual dexterity, poor vision, memory impairment, personality change, dizziness on standing and rarely a loss of taste or smell.

They may have a reduced sensation to light touch in a "glove and stocking" distribution of hands and feet.

Other clinical signs include reduced vibration sense and impaired "proprioception" (awareness of joint positions and movements).

"Rombergs sign" (a loss of balance when standing with feet together and eyes closed) is frequently positive.

The "Field of Holes":

Classically the neuropathology comprises a reduction of myelin (which can be thought of as an "electrical insulator") around nerves in the spinal cord and brain.

There may also be some mild brain atrophy or shrinkage.

In the spinal cord, the loss of myelin gives the colour of "white matter" (long nerve fibres) a more greyish tone.  It can also make the spinal cord appear sponge-like.  This appearance was called a ‘lachen felden’ (field of holes) by the German physicians who first described the condition in the mid-nineteenth century.

In our next update we will look at some of the common causes of Vitamin B12 Deficiency.

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