Olfactory bulb

Looks like

A small swelling of brain tissue on each side, lying on the thin sieve-like plate of bone (cribriform plate) above the nose. Smell nerve fibres pass up through the holes in the plate into it.

What it does

Receives the smell signals from the nose, sorts them and sends them on to the brain's smell areas, which link directly to memory and emotion.

Keeping it well

A blow to the back of the head can tear the fibres at the plate and cause lasting loss of smell. Loss of smell can come years before Parkinson's disease. It is missing or small in Kallmann syndrome (no smell, no puberty). Tumours of the skull floor here (olfactory groove meningiomas) slowly take away smell.

Related conditions

• Amyloidosis (AL and ATTR)
• Botulism
• Chickenpox (varicella)
• Chronic neuropathic pain
• Chronic pain syndrome
• Fibromyalgia
• Guillain-Barré syndrome
• Loss of smell (anosmia)
• Lyme disease
• Myasthenia gravis
• Peripheral neuropathy
• Rabies
• Restless legs syndrome
• Shingles (herpes zoster)
• Tetanus
• Vitamin B1, C and other deficiencies