As swallowing is a complex process, there are many reasons why dysphagia can develop.

There are 2 main types of dysphagia, caused by problems with the:

• mouth or throat – known as oropharyngeal dysphagia
• oesophagus (the tube that carries food from your mouth to your stomach) – known as oesophageal dysphagia

Some causes of dysphagia are explained here.

Neurological causes

Damage to the nervous system (in the brain and spinal cord) can interfere with the nerves responsible for starting and controlling swallowing.

Some neurological causes of dysphagia include:

• a stroke 
• neurological conditions that cause damage to the brain and nervous system over time, including Parkinson's disease, multiple sclerosis, dementia, and motor neurone disease
• brain tumours 
• myasthenia gravis – a rare condition that causes your muscles to become weak

Congenital and developmental conditions

The term "congenital" refers to something you're born with. Developmental conditions affect the way you develop.

Congenital or developmental conditions that may cause dysphagia include: 

• learning disabilities – where learning, understanding, and communicating are difficult
• cerebral palsy – a group of neurological conditions that affect movement and co-ordination
• a cleft lip and palate – a common birth defect that results in a gap or split in the upper lip or roof of the mouth

Obstruction

Conditions that cause an obstruction in the throat or a narrowing of the oesophagus (the tube that carries food from your mouth to the stomach) can make swallowing difficult.

Some causes of obstruction and narrowing include:

• mouth cancer or throat cancer, such as laryngeal cancer or oesophageal cancer – once these cancers are treated, the obstruction may no longer be an issue
• pharyngeal (throat) pouches – a large sack develops in the upper part of the oesophagus, which reduces the ability to swallow both liquids and solids; it's a rare condition that mainly affects older people
• eosinophilic oesophagitis – a type of white blood cell (eosinophil) builds up in the lining of the oesophagus due to a reaction to foods, allergens or acid reflux; the build-up damages the lining of the oesophagus and causes swallowing difficulties
• radiotherapy treatment – can cause scar tissue, which narrows the passageway in your throat and oesophagus
• gastro-oesophageal reflux disease (GORD) – stomach acid can cause scar tissue to develop, narrowing your oesophagus 
• infections, such as tuberculosis or thrush – can lead to inflammation of the oesophagus (oesophagitis)

Muscular conditions

Any condition that affects the muscles used to push food down the oesophagus and into the stomach can cause dysphagia, although such conditions are rare.

Two muscular conditions associated with dysphagia are:

• scleroderma – where the immune system (the body's natural defence system) attacks healthy tissue, leading to a stiffening of the throat and oesophagus muscles
• achalasia – where muscles in the oesophagus lose their ability to relax and open to allow food or liquid to enter the stomach

Other causes

The muscles used for swallowing can become weaker with age. This may explain why dysphagia is relatively common in elderly people.

Chronic obstructive pulmonary disease (COPD) is a collection of lung conditions that make it difficult to breathe properly. Breathing difficulties can sometimes affect your ability to swallow.

Dysphagia can also sometimes develop as a complication of head or neck surgery.