Lambert-Eaton myasthenic syndrome (LEMS): symptoms, tests and treatment

Normally, a nerve signal travelling to a muscle makes the nerve ending release a chemical called acetylcholine, which helps activate the muscle. In LEMS, the NHS explains, the immune system attacks and damages the nerves, so the nerve endings produce less acetylcholine and signals do not reach the muscles properly. The result is muscle weakness and a range of other symptoms.

Patient.info, in its professional reference article written for UK clinicians, gives more detail. It says LEMS results from an autoimmune attack against a type of calcium channel (voltage-gated P/Q-type calcium channels) on the nerve terminal. These channels are also found in high numbers in small cell lung cancer cells, and the antibodies made against the tumour are thought to be responsible for the attack on normal nerve cells.

The condition is also called myasthenic syndrome or Eaton-Lambert syndrome, according to the NHS. It can look like myasthenia gravis in the early stages, but the course of the two diseases may be very different, Patient.info says.

The NHS says the main symptoms are weakness in the legs, arms, neck and face, together with problems with automatic body functions such as controlling blood pressure. They develop gradually over weeks or months and get worse with time. The weakness is typically in the muscles closest to the trunk, especially in the legs, so the first thing people notice is often difficulty with walking or stairs.

• Aching muscles and feeling very tired all the time.

• Difficulty walking and climbing stairs.

• Difficulty lifting objects or raising the arms.

• Drooping eyelids, dry eyes and blurred vision.

• Swallowing problems.

• Dizziness on standing.

• A dry mouth and constipation.

• Erectile dysfunction.

The NHS advises seeing a GP if you have a combination of these symptoms. Because LEMS is rare and its symptoms overlap with many other conditions, it is common for it to take time to be recognised. Patient.info says that many patients are undiagnosed for months or years.

Patient.info notes that breathing and swallowing muscles are usually spared in LEMS, although occasional difficulty with chewing, speech or swallowing can occur. As with any sudden change in breathing, swallowing or strength, get urgent help through NHS 111, or call 999 in an emergency.

The NHS says the GP will check your medical history, ask about symptoms, examine you and test your reflexes. If a nerve problem is suspected you will be referred to a neurologist for further tests to determine the cause.

Tests described by the NHS include blood tests to detect antibodies resulting from the immune system attacking the nerves, nerve studies in which a needle is inserted into the skin to check how well signals reach the muscles, and CT or PET scans to look for lung cancer.

Patient.info adds detail for clinicians. It says that reduced or absent tendon reflexes are typical, that strength can improve briefly with exercise before lessening as it continues, and that antibodies to voltage-gated calcium channels have been reported in more than 90% of patients. It reports that nerve conduction testing with repetitive stimulation is highly sensitive and specific, and that screening for an underlying cancer is recommended for two years after diagnosis.

The link with cancer is the most important thing to understand about LEMS. Patient.info says that cancer, typically small cell lung cancer, is present when weakness begins or is found later in about half of patients, and that in most cases the cancer is found within two years of the onset of LEMS and in virtually all cases within four years. It describes smoking and age at onset as major risk factors for cancer in LEMS.

This is why a person with LEMS is investigated for cancer soon after diagnosis and then followed up. For some people, the muscle symptoms are the first sign of a lung tumour, which can allow it to be found early. Patient.info notes that patients with LEMS and small cell lung cancer may therefore have a better prognosis because the cancer is detected early.

If no cancer is found after two years of symptoms, Patient.info says the LEMS is most likely to be of autoimmune origin without an underlying tumour. The NHS says LEMS does not affect life expectancy if it is not associated with cancer.

The NHS says there is no cure for LEMS, but treatments can reduce symptoms. Medicine is the main treatment. Plasmapheresis and immunoglobulin therapy may be recommended in the short term, or if muscle weakness is severe and other treatments have not helped.

The NHS says some people respond well to treatment and find their symptoms are kept under control, while others respond less well and find that the condition affects everyday activities and quality of life. Patient.info says that most people find therapy relieves symptoms partially and that symptoms usually progress over time, with maximum severity usually established within months of the first symptoms.

Patient.info lists several medicines that can make LEMS worse, including neuromuscular blocking agents used in anaesthesia, aminoglycoside antibiotics, magnesium, iodinated contrast and calcium-channel blockers. It is sensible to tell every doctor, dentist, pharmacist and anaesthetist that you have LEMS before any new medicine or procedure.

The NHS says your clinical team may pass information about you to the National Congenital Anomaly and Rare Disease Registration Service, which helps scientists look for better ways to prevent and treat the condition, and that you can opt out at any time.

Fatigue, difficulty with stairs and dizziness on standing can make daily routines harder. Pacing activity, sitting down for tasks and standing up slowly are common-sense measures to discuss with your neurology team, alongside any support from an occupational therapist or physiotherapist.

On the NHS, LEMS is usually diagnosed and managed by a neurologist, with chest imaging and oncology involved if a tumour is found. Because the condition is rare, it can be worth asking whether your team has experience of neuromuscular conditions.

Some people choose a private neurologist for a quicker appointment or a second opinion. Antibody tests, nerve studies and scans are the same whichever route is used, so the differences are mainly waiting times and choice of clinician. Whichever route you use, make sure someone is responsible for follow-up scans and for coordinating your treatment.