WHAT IS CMT?
A Brief Explanation of a Charcot-Marie-Tooth Disease; a Complex Disease, Symptoms and Diagnosis Methods
Charcot–Marie–Tooth disease (CMT), also known as Hereditary Motor and Sensory Neuropathy (HMSN), is a genetic condition of the peripheral nervous system (long nerves) characterized by progressive loss of muscle and sensation across various parts of the body, starting in the feet and potentially progressing up the legs and into the hands. Depending on the type of CMT, there are many other symptoms of the disease, including hearing loss, high-arched feet and constantly cold hands and feet.
Currently incurable, but not lethal, this disease is the most commonly inherited neurological disorder affecting about one in 2,500 people, which is just over 3 million people worldwide. CMT was previously classified as a subtype of muscular dystrophy and has commonly been misdiagnosed as Diabetes. To understand the complex mechanisms behind CMT, this can be found here.
SYMPTOMS OF CMT
CMT can cause a variety of symptoms, usually first noticed during adolescence.
LOSS OF FEELING IN FEET/HANDS
TIGHT PERIPHERAL MUSCLES
Permanent lack of sensation in peripheral limbs
High arched feet that turn inward with contracted toes
Tightness, reduced motion in muscle atrophy in limbs
One of the main symtpoms of CMT is a lack of sensation that begins in the toes and can extend through the foot, up the lower leg and also from the fingers and into the hands. This is a result of nerve damage caused by the disease and as of yet, is unfortunately irreversible.
Impacting around 80% of CMT patients, cavovarus feet can cause issues such as poor balance, tripping over due to one foot catching on the heel of the other, and sore feet due to pressure imbalance caused by weight distribution from the high arched feet. Walking bare footed can be painful, as well as walking on uneven surfaces.
Tight Achilles tendons, calf muscles, hamstrings and quadriceps, with or without signs of muscle wasting (atrophy) can be a sign of CMT. Toe-walking, either early morning or throughout the day, can also be a sign of CMT, as muscles tighten to compensate for the mechanical issues that are a result of CMT.
CHRONICALLY COLD FEET AND/OR HANDS
Muscle fasciculation in peripheral limbs
Persistently cold hands and feet, regardless of external factors
A constant high-pitched ringing with partial loss of hearing
Muscle twitching, technicaly labelled as muscle fasciculation, is the twitching of muscles. This can occur in people with CMT, commonly in the calf muscle and varying in scale, from barely noticable twitching, to extremely large movements, that can cause either cramp or discomfort.
Due to muscle development being hindered by CMT, as well as tight muscles, this can result in circulatory systems in the body to not work correctly. This results in cold hands and/or feet, regardless of whether it is hot or cold outside, or even layers of clothes.
While usually only occurring in patients with CMT type 2A, Tinnitus can occur as a result of all type of CMT, due to damage to one of the main auditory nerves in the ear. Hearing loss can range from mild to severe and currently there is no treatment for tinnitus.
DEFORMED HIP JOINT
Neuromuscular hip dysplasia
Issues with diaphragm strength
Although rare, CMT can increase the chance of suffering from hip dysplasia. This can result in impacting a person's gait, increase the chance of hip dislocation, and in extreme cases it can cause osteoarthritis of the hip.
Some CMT patients find that they suffer from erectile dysfunction (ED). Although this may seem embarrassing at first, it is always best to address any issue related to CMT head-on. For most people, ED can be quickly resolved by talking to your local doctor and receiving appropriate medication.
While not common, breathing issues can occur in people with CMT. Breathing can become difficult, with shortness of breath being the main symptom, the cause of which is the weakness of the diaphragm. The direct relation between this symptom and CMT is not yet known.
HOW DO I KNOW IF I HAVE CMT?
Symptoms of CMT are usually first notable during puberty. As the body develops, the severity of the CMT disorder can become more apparent. This includes pain when walking barefooted, extremely tight calf muscles and Achilles's tendons, loss of sensation in extremities e.g. numbness in the toes, and cold feet or hands. For a diagnosis of CMT to be made by a doctor, several tests may be carried out.
VISUAL INSPECTION AND BASIC TESTING
The quickest way to get an indication if someone may have CMT is with basic movement tests, visual inspection of the feet and hands (to see if the patient has high arches in their feet, if the feet turn inwards etc), and an Xray of the feet to confirm high arches and other deformities. While this will not confirm CMT, it is usually the first step before other tests are undertaken
NERVE VELOCITY TESTING
A nerve conduction velocity test is an electrical test that is used to determine the conduction of a nerve as current passes down it. As CMT impacts the peripheral limbs, it is likely that this testing will happen on the foot, the lower leg, the hand, and the forearm. The test uses surface patch electrodes placed at the top and bottom of the area being tested, with a relatively painless impulse being sent between the electrodes. For more accurate readings, the healthcare professional may gradually increase the electrical impulse. The pulses are usually reported as being uncomfortable to mildly painful, although a few people report severe pain. However, the test leaves no lasting issues once it is concluded.
The purpose of the test is to see if the nerves are conducting the impulse at the correct velocity. A reduced velocity may indicate a peripheral neuropathy but is usually not enough evidence on its own to make a diagnosis of CMT.
Genetic testing involves taking a blood sample from the patient which is then analysed for the genetic markers of CMT. This should confirm whether a person has CMT or not, as well as the type of CMT a person has. It can also be used throughout a family to determine whether the CMT has been hereditary or a spontaneous mutation. Though it is worth noting that a genetic test for CMT may only be for several types - unless all varients have been tested for, a doctor should not rule out a diagnosis of CMT.