Vitamin B12 deficiency can affect every body system potentially. It is more common in vegetarians and vegans as it is mostly available from animal sources but also common in people taking certain medications which reduce its absorption from the stomach and anyone with malabsorption disorders such as coeliac disease or after gastric bypass surgery. I see patients presenting with all sorts of neurological symptoms like tingling, headaches, tremor, memory problems, dizziness, tinnitus, anxiety, depression and fatigue is very common.
English 
Spanish