Oesophageal Motility Disorders
Oesophageal motility disorders are a group of conditions characterised by abnormalities in oesophageal peristalsis.
They are less common than mechanical and inflammatory diseases of the oesophagus (such as oesophagitis), and typically manifest with difficulty swallowing solids and liquids.
In this article, we shall look at the two major causes of oesophageal dysmotility – achalasia and diffuse oesophageal spasm.
Oesophageal Anatomy and Physiology
The oesophagus is a 25cm long tube. Its structure can be divided into thirds:
- Upper third is composed of skeletal muscle.
- Middle third is a transition zone comprised of both skeletal and smooth muscle.
- Lower third is smooth muscle alone.
The upper oesophageal sphincter is comprised of skeletal muscle, and prevents air from entering the GI tract. The lower oesophageal sphincter is composed of smooth muscle, and prevents reflux from the stomach.
Peristaltic waves, controlled by the oesophageal myenteric neurones, propel ingested food down the oesophagus. The primary wave is under control of the swallowing centre and the secondary wave is activated in response to distention. As food descends the oesophagus, the lower oesophageal sphincter relaxes and remains so until food has passed.
Achalasia is a primary motility disorder of the oesophagus, characterised by a failure of smooth muscle relaxation.
It is relatively rare (incidence of 1 per 100,000), and has mean age of diagnosis at ~50 years. The pathophysiology of achalasia is poorly understood, but a common histological feature is progressive destruction of the ganglion cells in the myenteric plexus.
The inability of the oesophagus to relax causes difficulty in passing food boluses down the oesophagus. Likewise, the high resting tone and failure of relaxation of the lower oesophageal sphincter means that the food bolus may get stuck and fail to pass into the stomach – causing vomiting, discomfort and poor nutrition.
It is a progressive disease; as the ganglionitis results in the destruction of more and more neurones, the condition worsens in its severity.
Patients with achalasia will classically present with progressive dysphagia when ingesting both solids and liquids.
Other clinical features of achalasia include regurgitation of food, coughing (due to overspill and aspiration, especially at night), chest pain, and weight loss. The symptom severity frequently varies day-to-day.
On examination, there are rarely any obvious signs of note, except for visible weight loss in longstanding or severe cases.
Note: Most other causes of dysphagia are typically associated with difficulty swallowing solids or liquids, so difficulty with both is a characteristic feature of an oesophageal motility disorder.
The main differential diagnoses for achalasia include:
- Other oesophageal motility disorders (e.g diffuse oesophageal spasm, scleroderma).
- Gastro-oesophageal reflux disease (GORD).
- Oesophageal malignancy.
In any patient presenting with dysphagia, the diagnosis of oesophageal cancer needs to be excluded. Hence, nearly all such patients will require an urgent endoscopy. This is often normal in achalasia, but rarely a tight lower oesophageal sphincter can be observed (which may suddenly give way).
The gold standard in the diagnosis of motility disorders is oesophageal manometry (Fig 3). This is where a pressure sensitive probe is inserted into the oesophagus (tip placed 5cm above the lower oesophageal sphincter). It measures the pressure of the sphincter, and the surrounding muscle. In achalasia, the three key features of manometry are:
- Absence of oesophageal peristalsis.
- Failure of relaxation of the lower oesophageal sphincter.
- High resting lower oesophageal sphincter tone.
Barium swallows are now rarely performed, but they may show proximal dilation of the oesophagus with a characteristic ‘bird’s beak’ appearance distally (due to the failed dilation of the lower oesophageal sphincter).
The management of achalasia can be divided into conservative measures and surgical management:
Conservative measures include sleeping with many pillows to minimise regurgitation, eating slowly and chewing food thoroughly, and taking plenty of fluids with meals.
Calcium channel blockers or nitrates can be partly effective for temporary relief, but their action is typically short lived. Likewise, Botox injections into the lower oesophageal sphincter by endoscopy are effective for a few months at most.
The main surgical treatments for achalasia are: (i) division of the lower oesophageal sphincter (called a Heller’s cardiomyotomy), or (ii) endoscopic balloon dilatation. Both are effective techniques with similar results.
- Endoscopic balloon dilatation – insertion of a balloon into the lower oesophageal sphincter, which is dilated to stretch the muscle fibres.
- It provides a good response in ~75% of patients but carries the risks of perforation (~5%) and the need for further intervention.
- Laparoscopic Heller myotomy – the division of the specific fibres of the lower oesophageal sphincter which fail to relax (Fig. 4).
- A long-term improvement in swallowing is seen in ~85% of patients, with lower side-effect profile compared to endoscopic treatment (although both techniques appear to be approximately equivalent in terms of quality of life benefit).
Patients with long standing achalasia have an x8-16 increased risk of oesophageal cancer, although the absolute risk remains small.
Diffuse Oesophageal Spasm
Diffuse oesophageal spasm (DOS) is a disease characterised by multi-focal, high amplitude contractions of the oesophagus.
It is thought to be caused by the dysfunction of oesophageal inhibitory nerves. In some individuals, DOS can progress into achalasia.
Patients with diffuse oesophageal spasm will typically present with severe dysphagia to both solids and liquids. Central chest pain is a common finding, usually exacerbated by food.
Interestingly, the pain from DOS may respond well to nitrates, making it difficult to distinguish from angina (yet this pain is rarely exertional). Examination is often normal.
Diffuse oesophageal spasm is investigated in the same manner as achalasia – with an endoscopy to exclude malignancy, and the definitive diagnosis made via manometry.
Endoscopy is usually normal, whilst manometry characteristically shows a pattern of repetitive, simultaneous and ineffective contractions of the oesophagus. There may also be dysfunction of the lower oesophageal sphincter.
A barium swallow is rarely performed, but can show a ‘corkscrew’ appearance (Fig. 5).
The initial management is through agents which act to relax the oesophageal smooth muscle, typically nitrates or calcium channel blockers (CCBs) as first line. These limit the strongest of the contractions, and so provide a symptomatic improvement – although their long-term efficacy is uncertain.
Patients with diffuse oesophageal spasm and documented hypertension of the lower oesophageal sphincter may benefit from pneumatic dilatation.
Myotomy is reserved for the most severe cases and must be used with caution due to the invasive nature. The incision is extensive, involving the entire spasmic segment and the lower oesophageal sphincter.
Other Causes of Oesophageal Dysmotility
A number of autoimmune and connective tissue disorders are associated with oesophageal dysmotility. These include systemic sclerosis (most common), polymyositis, and dermatomyositis.
In these cases treatment is directed at the underlying cause (e.g immunosupression in autoimmune-mediated disease), with nutritional modification and PPIs as required.