Vitamin B12 Deficiency

• Severity of anaemia appears inversely correlated with severity of neurological dysfunction

• 20% of patients with neurological dysfunction do not have anaemia

• Clinical syndrome is of demyelination

o Dorsal and lateral columns

o Optic neuropathy

o Peripheral neuropathy

- Secondary axonal loss means that it may present as a mixed neuropathy

• Investigation

o False positive B12 levels in up to 50%

o Transobalamin assay can be used

o Methlmalonic acid

- Elevated in B12 deficiency

- Quite specific and sensitive

o Homocysteine

- Elevate in B12 deficiency, folate deficiency, homocystinuria, renal failure