In a candid and heartfelt interview on the Today show with Jenna Bush Hager, country music legend Alan Jackson shared a deeply personal aspect of his life: his diagnosis with Charcot-Marie-Tooth (CMT) disease. This announcement brought awareness to a condition that the 62-year-old icon has been managing for over a decade. Jackson revealed that while he was diagnosed ten years prior, the neurological disorder’s effects have become increasingly noticeable in recent times.
“I have this neuropathy and neurological disease. It’s Charcot-Marie-Tooth disease — it’s genetic that I inherited from my daddy,” Jackson explained, shedding light on the hereditary nature of CMT. He openly discussed the challenges he faces, stating, “There’s no cure for it, but it’s been affecting me for years. And it’s getting more and more obvious. And I know I’m stumbling around on stage. And now I’m having a little trouble balancing, even in front of the microphone, and so I just feel very uncomfortable.”
Despite the discomfort and challenges posed by CMT, Jackson reassured his fans about his future. “It’s not going to kill me. It’s not deadly,” he affirmed, dispelling immediate concerns about his health. Moreover, fans will be relieved to know that retirement is not on the horizon for this beloved artist. “I’m not saying I won’t be able to tour. I’ll try to do as much as I can,” Jackson stated, expressing his commitment to continue performing and connecting with his audience.
Understanding Charcot-Marie-Tooth Disease (CMT)
Charcot-Marie-Tooth disease, often abbreviated as CMT, is named after the three physicians—Jean-Martin Charcot, Pierre Marie, and Howard Henry Tooth—who first described it in 1886. It is not a single disease, but rather a group of inherited disorders that damage the peripheral nerves. These nerves, located outside the brain and spinal cord, are crucial for transmitting signals between the central nervous system and the rest of the body. CMT affects both motor nerves, which control muscle movement, and sensory nerves, which relay sensory information like touch, pain, and temperature.
CMT is recognized as one of the most prevalent inherited neurological disorders globally. The National Institute of Neurological Disorders and Stroke estimates that CMT affects approximately 150,000 individuals in the United States and a staggering 2.6 million people worldwide. This widespread impact underscores the importance of understanding this condition and its effects.
The complexity of CMT is further highlighted by the existence of over 40 different types. Adding to this complexity, it is possible for an individual to have multiple types of CMT, particularly if they inherit mutations in more than one gene associated with the disease. This genetic heterogeneity means that mutations in various genes can lead to similar clinical manifestations, making diagnosis and personalized treatment strategies crucial.
The Genetic Roots of CMT
At its core, CMT is a genetic disorder, stemming from mutations in genes that are essential for the healthy structure and function of peripheral nerves. These genes provide instructions for creating proteins involved in either the axon (the core of the nerve fiber) or the myelin sheath (the protective insulation around the axon). The specific protein affected varies depending on the type of CMT, but in all cases, the mutations disrupt the normal functioning of peripheral nerves.
Mutations affecting myelin primarily cause dysfunction of this protective coating. Myelin is crucial for efficient nerve signal transmission, and its damage can distort or completely block these signals. Conversely, other mutations target the axon itself, impairing its function and leading to axonal loss, which further disrupts nerve signaling and muscle control.
To date, scientists have identified over 40 genes implicated in CMT, with each gene potentially linked to multiple types of the disease. Interestingly, a single type of CMT can also be associated with mutations in several different genes. A significant portion of CMT cases, over half, are attributed to a duplication of the PMP22 gene located on chromosome 17. The inheritance patterns of these gene mutations in CMT are diverse, falling into three main categories: autosomal dominant, autosomal recessive, and X-linked inheritance.
Types of CMT: A Diverse Spectrum
While different types of CMT share overlapping symptoms, they are distinguished by their inheritance patterns, the age of onset, and whether the primary damage affects the axon or the myelin sheath. This classification is crucial for understanding the prognosis and managing the specific challenges associated with each type.
CMT Type 1: This type is characterized by abnormalities in the myelin sheath. CMT type 1 is typically inherited in an autosomal dominant pattern and encompasses several subtypes.
- CMT1A: The most common form of CMT1, resulting from a duplication of the PMP22 gene on chromosome 17. CMT1A is known for its slow progression. Symptoms usually manifest in childhood with weakness and muscle atrophy in the lower legs, followed by hand weakness, sensory loss, and foot and leg deformities later in life.
- CMT1B: Caused by mutations in the gene responsible for producing myelin protein zero (MPZ or P0), another vital component of the myelin sheath. CMT1B presents with symptoms similar to CMT1A.
- Other CMT1 Subtypes: Less common forms are linked to mutations in genes such as SIMPLE (or LITAF), EGR2, PMP22 (different mutations than CMT1A), and NEFL.
CMT Type 2: In contrast to CMT type 1, CMT type 2 involves abnormalities in the axon of the peripheral nerve cell. It is less prevalent than CMT1 and is also typically autosomal dominant. Symptoms are similar to CMT1 but often less severe, with individuals experiencing less disability and sensory loss. Onset is usually in childhood or adolescence. Some subtypes of CMT2 can affect the vocal cords or phrenic nerve, leading to speech or breathing difficulties.
CMT Type 3 (Dejerine-Sottas disease): This is a severe form of demyelinating neuropathy that begins in infancy. Infants with CMT3 exhibit significant muscle atrophy, weakness, delayed motor skill development, and sensory problems. The condition can progress to severe disability, loss of sensation, and spinal curvature. It is a rare disorder caused by mutations in genes like PMP22, MPZ, and EGR2, and can be inherited dominantly or recessively.
CMT Type 4: Rare in the U.S., CMT type 4 includes various subtypes of demyelinating and axonal neuropathies inherited in an autosomal recessive manner. These subtypes can be more prevalent in specific ethnic populations and have unique clinical features. Typically, individuals with CMT4 develop leg weakness in childhood and may lose the ability to walk by adolescence.
CMTX1: The second most common form of CMT, CMTX1 is an X-linked disease. It is caused by mutations in the gene for connexin-32, a protein found in Schwann cells, which form the myelin sheath. Males inheriting the mutated gene usually experience moderate to severe symptoms starting in late childhood or adolescence. Females with the same mutation may have milder symptoms or be asymptomatic due to having two X chromosomes.
Symptoms of CMT: Varied and Progressive
CMT affects both sensory and motor nerves, primarily in the arms, hands, legs, and feet. The hallmark of CMT is the slow degeneration of these nerves, impairing their ability to communicate with muscles and sensory organs. This nerve degeneration leads to a range of symptoms that typically progress over time.
Motor nerve damage results in muscle weakness and atrophy, or muscle wasting, in the affected limbs. Early signs often include weakness in the feet and lower legs, causing foot drop—difficulty lifting the front part of the foot—and a characteristic high-stepped gait with increased tripping and falls. Balance problems are also common. Foot deformities, such as high arches (pes cavus) and hammertoes (curled toes), are frequently observed in CMT. The lower legs may develop an “inverted champagne bottle” shape due to muscle loss.
As CMT progresses, weakness and atrophy can extend to the hands, impacting fine motor skills and making tasks requiring dexterity challenging. Sensory nerve degeneration diminishes the ability to feel temperature, pain, and touch, and often reduces the senses of vibration and body position (proprioception).
Beyond limb weakness and sensory issues, CMT can also lead to scoliosis (spinal curvature) and hip dysplasia. Contractures, the permanent shortening of muscles and tendons around joints, are common, limiting joint movement. Muscle cramps and nerve pain, ranging from mild to severe, are frequent complaints. Some individuals may require orthopedic aids like braces or splints to maintain mobility. In some cases, tremor, vision, and hearing can also be affected. Rarely, CMT can impact breathing if the nerves controlling the diaphragm muscles are involved.
Diagnosing CMT: A Multifaceted Approach
Diagnosing CMT involves a comprehensive evaluation that starts with a detailed medical and family history and a thorough neurological examination. Physicians look for clinical signs such as muscle weakness, reduced muscle bulk, decreased tendon reflexes, foot deformities, and sensory loss.
To confirm the diagnosis and assess the extent of nerve damage, nerve conduction studies and electromyography (EMG) are essential. Nerve conduction studies measure the speed at which electrical signals travel through nerves, while EMG assesses the electrical activity of muscles. Genetic testing is available to identify specific gene mutations associated with the most common types of CMT, providing a definitive diagnosis in many cases. In some instances, a nerve biopsy, typically from the calf, may be performed to examine nerve tissue under a microscope. A characteristic finding in CMT is the presence of “onion bulb” formations, which are layers of Schwann cells surrounding axons, indicative of repeated cycles of demyelination and remyelination.
Managing CMT: Treatment and Therapies
Currently, there is no cure for CMT. Treatment focuses on managing symptoms and improving quality of life. A multidisciplinary approach involving physical and occupational therapies, orthopedic devices, and in some cases, surgery, is employed to help individuals cope with the disabling aspects of CMT. Pain management is also a crucial component of care for those experiencing nerve pain.
Maintaining mobility, flexibility, and muscle strength is paramount. Early initiation of a treatment program can help slow down nerve degeneration and muscle weakness before significant disability sets in. Physical therapy programs typically include muscle strengthening exercises, stretching, and moderate aerobic activities. A customized exercise regimen, developed in consultation with a physician, can enhance stamina, endurance, and overall well-being.
Orthopedic devices play a significant role in managing CMT symptoms. Ankle braces and supports provide stability and prevent ankle sprains, particularly during activities like walking or climbing stairs. High-top shoes or boots can offer additional ankle support. Thumb splints can aid with hand weakness and fine motor skill difficulties. The proactive use of assistive devices is encouraged to prevent muscle strain and further weakening. For severe deformities or contractures, orthopedic surgery may be considered to improve function and reduce pain.
While Alan Jackson’s diagnosis brings CMT into the spotlight, it also highlights the resilience of individuals living with this condition. His openness about his health journey serves to educate and inspire, emphasizing that while CMT presents challenges, it does not define a person’s capabilities or limit their passion for life and work.
Medical information in this article is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional for diagnosis and treatment.
