Skeletal muscle channelopathies are rare neuromuscular diseases that cause symptoms of episodic muscle weakness/paralysis or cause difficulty in relaxing muscles (the muscle can feel stuck or cramped) once they are contracted. They affect approximately 1 in 100 000 people in the UK. They are genetic conditions. Each one is caused by a mutation in a gene that codes for proteins in our muscles called ion channels.

Ion channels act like gates. They open and close on command when we want to contract or relax our muscles. Muscle contraction occurs when an electrical signal is conducted along the muscle membrane. The electrical signal is made when positively or negatively charged ions like potassium or sodium move in or out of the muscle cell via one of these specialised channels or “gates”.

So ion channels are very important in controlling muscle excitability and contraction. There are many ion channels in the muscle membrane and each one can malfunction. This means there is more than one type of muscle channelopathy. Broadly speaking however they are divided into two main groups called Non-dystrophic Myotonias and the Periodic Paralyses depending on the main symptoms that occur.

As these are very rare conditions most general physicians will only see 1 or 2 people with these disorders during their career. Our specialist clinic at the National Hospital for Neurology and Neurosurgery was created to provide a central service that has experience and expertise in diagnosing and managing these conditions.  It is directly funded by NHS England to promote equality in health care for rare diseases. Even if a diagnosis of a channel problem has already been made then you may still be referred to us for advice on management and treatment of your muscle symptoms.

We are also actively involved in research including clinical trials that may be of interest to you.

Other contact information

Our HSS Senior Medical Secretary can answer any queries regarding appointments on 020 3448 8155

Other referral information

Our HSS Senior Medical Secretary can answer any queries regarding appointments on 020 3448 8155

For all general queries, please email the team:

To make a referral please email:

The conditions that we see include:

  • Hypokalaemic periodic paralysis 
  • Hyperkalaemic periodic paralysis 
  • Andersen-Tawil syndrome (ATS)
  • Myotonia congenita 
  • Paramyotonia congenita
  • Sodium channel myotonia

The out-patient clinic takes place every other Tuesday at the National Hospital for Neurology and Neurosurgery. The first appointment is usually an all day visit and as well as talking to the doctor in clinic and being examined you may undergo neurophysiology tests (electrical recordings of the nerves and muscles), blood tests and an ECG (electrical recording of the heart).

In addition the Clinical Nurse Specialist (Natalie James) offers telephone clinics to support patients between clinic appointments. This often includes monitoring response to medications that are started in clinic. Natalie can also provide advice to your employer or school on your condition, and to other specialists e.g. if you are to need an operation and anaesthetic or if you are pregnant.

Physiotherapy assessments are available with the Clinical Specialist Physiotherapist (Sarah Holmes). These take place at your first clinic visit and then you may be offered follow up visits with Sarah in person or via phone or email. Sarah can also liaise with and offer advice about the management of your condition to a neurological physiotherapist nearer where you live.

The service also has direct links to a specialist orthotics clinic, vocational rehabilitation if you need advice on modifications at work and a psychologist.

We recognise not all patients can travel to London for review and we are also happy to offer an advisory service via letter or email to other specialists who may be looking after patients with a muscle channelopathy.

Make a referral – Word referral link

We offer a specialist diagnostic and advisory service for muscle channelopathies. This includes a combination of:

  • Detailed clinical assessment
  • Specialist neurophysiology (including short and long exercise testing)
  • Genetic testing
  • MRI scanning of the muscles

A muscle biopsy is not routinely needed to make a diagnosis of muscle channelopathy but may be performed if required in complex cases.

We have close links with specialist cardiologists at Bart’s Health Care and refer to them if any detailed cardiac investigation or advice is required. 


There are a number of treatments available through the clinic although these drugs are not always readily available from general practitioners or other hospital physicians. 

We can supply the following: 

Drug type 

Drug name


Sodium channel blockers

Mexiletine, Lamotrigine and Carbamazepine

Myotonic disorders - significantly improve symptoms of muscle stiffness 

Potassium wasting diuretics

Potassium sparing diuretics


Spironolactone, Amiloride

Hyperkalaemic Periodic paralyses

 - reduce the number and/or severity of paralytic attacks

Hypokalaemic periodic paralysis and ATS – reduce the number and/or severity of paralytic attacks

Carbonic anhydrase inhibitors


Periodic paralyses and ATS - Can reduce the number and/or severity of paralytic attacks