Hereditary motor and sensory neuropathy

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Hereditary motor and sensory neuropathy
Onion bulb formation HMSN.jpg
Onion bulb formations in a nerve biopsy in a case of HMSN type I
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Hereditary motor and sensory neuropathies (HMSN) is a name sometimes given to a group of different neuropathies which are all characterized by their impact upon both afferent and efferent neural communication. HMSN are characterised by atypical neural development and degradation of neural tissue. The two common forms of HMSN are either hypertrophic demyelinated nerves or complete atrophy of neural tissue. Hypertrophic condition causes neural stiffness and a demyelination of nerves in the peripheral nervous system, and atrophy causes the breakdown of axons and neural cell bodies. [1] In these disorders, a patient experiences progressive muscle atrophy and sensory neuropathy of the extremities. [2]

Contents

The term "hereditary motor and sensory neuropathy" was used mostly historically to denote the more common forms Charcot–Marie–Tooth disease (CMT). With the identification of a wide number of genetically and phenotypically distinct forms of CMT, the term HMSN is now used less frequently.

Symptoms and signs

Foot showing features of HMSN: pes cavus and clawing of the toes Charcot-marie-tooth foot.jpg
Foot showing features of HMSN: pes cavus and clawing of the toes

Neuropathy disorders usually have onset in childhood or young adulthood. Motor symptoms seem to be more predominant than sensory symptoms. [2] Symptoms of these disorders include: fatigue, pain, lack of balance, lack of feeling, lack of reflexes, and lack of sight and hearing, which result from muscle atrophy. Patients can also have high arched feet, hammer toes, foot drop, foot deformities, and scoliosis. These symptoms are a result of severe muscular weakness and atrophy. In patients with demyelinating neuropathy, symptoms are due to slow nerve conduction velocities; however people with axonal degradation have average-to-normal nerve conduction velocities.[ citation needed ]

Causes

All hereditary motor and sensory neuropathies are inherited. Chromosomes 17 and 1 seem to be the most common chromosomes with mutations. [1] The disease can be inherited in an autosomal dominant, autosomal recessive or X-linked manner.[ citation needed ]

Diagnosis

Patients with hereditary motor and sensory neuropathies are diagnosed through a physical evaluation that looks for muscle atrophy, weakness, and sensory responses. [3] In addition to this, electromyography and motor nerve conduction tests can help clinicians decide what type of motor and sensory neuropathy it is and how severe the disease is. Final confirmation can come through genetic testing.[ citation needed ]

Classification

Charcot–Marie–Tooth disease was first described in 1886 by Jean-Martin Charcot, Pierre Marie, and independently Howard Henry Tooth. [2] In the 1950s, further classification occurred and separated patients into two distinct groups. Group one was characterized by slow nerve conduction velocities and demyelinating neuropathy. Group two was characterized by mostly normal nerve conduction velocities and degeneration of axons. In 1968, HMSN were classified again into seven groups: [1] [4]

TypeOther names Diseases

Database

OMIM
HMSN1 Charcot–Marie–Tooth disease type 1A and 1B 5815 (multiple)Hypertrophic demyelinating type: affected individuals experience weakness and atrophy in the lower legs in adolescence, and later develop weakness in the hands. This is the most common type of CMT.
HMSN2 Charcot–Marie–Tooth disease type 2 2343 (multiple)Neuronal type: symptoms similar to type1, onset in adolescence.
HMSN3 Dejerine–Sottas disease (Charcot–Marie–Tooth type 3) 5821 145900 Onset in infancy and results in delayed motor skills, much more severe than types 1 & 2.
HMSN4 Refsum disease 11213 266500 Spinal type: Muscle weakness and atrophy as in other types of CMT, but set apart by being autosomal recessive inheritance.
HMSN5 Charcot–Marie–Tooth with pyramidal features 600361 Pyramidal type: onset between ages 5–12. Lower legs are affected first by muscle weakness and atrophy followed by the upper extremities. Type 5 is also associated with visual and hearing loss.
HMSN6 Charcot–Marie–Tooth type 6 32095 601152 Early onset muscular weakness and atrophy followed by optic atrophy resulting in vision loss and possibly blindness.
HMSN7HMSN+retinitis pigmentosa 32094 Later onset with muscular weakness and atrophy mostly in the lower extremities.

Treatment

There is currently no known pharmacological treatment to hereditary motor and sensory neuropathy. However, the majority of people with these diseases are able to walk and be self-sufficient. [3] Some methods of relief for the disease include physical therapy, stretching, braces, and sometimes orthopedic surgery. Since foot disorders are common with neuropathy, precautions must be taken to strengthen these muscles and use preventative care and physical therapy to prevent injury and deformities.[ citation needed ]

Prognosis

Hereditary motor and sensory neuropathy are relatively common and are often inherited with other neuromuscular conditions, and these comorbidities cause an accelerated progression of the disease.[ citation needed ]

Most forms of HMSN affect males earlier and more severely than females, but others show no predilection to either sex. HMSN affects all ethnic groups, with the most common forms having no racial predilection, but other recessively inherited forms tending to impact specific ethnic groups. Onset of HMSN is most common in early childhood, with clinical effects occurring before the age of 10, but some symptoms are lifelong and progress slowly. Therefore, these symptoms do not appear until later in life. [1]

See also

Related Research Articles

Motor neuron disease Group of neurological disorders affecting motor neurons

Motor neuron diseases or motor neurone diseases (MNDs) are a group of rare neurodegenerative disorders that selectively affect motor neurons, the cells which control voluntary muscles of the body. They include amyotrophic lateral sclerosis (ALS), progressive bulbar palsy (PBP), pseudobulbar palsy, progressive muscular atrophy (PMA), primary lateral sclerosis (PLS), spinal muscular atrophy (SMA) and monomelic amyotrophy (MMA), as well as some rarer variants resembling ALS.

Charcot–Marie–Tooth disease Neuromuscular disease

Charcot–Marie–Tooth disease (CMT) is a hereditary motor and sensory neuropathy of the peripheral nervous system characterized by progressive loss of muscle tissue and touch sensation across various parts of the body. This disease is the most commonly inherited neurological disorder affecting about one in 2,500 people. It is named after those who classically described it: the Frenchman Jean-Martin Charcot (1825–1893), his pupil Pierre Marie (1853–1940), and the Briton Howard Henry Tooth (1856–1925).

Spinal muscular atrophies Wikipedia list article

Spinal muscular atrophies (SMAs) are a genetically and clinically heterogeneous group of rare debilitating disorders characterised by the degeneration of lower motor neurons and subsequent atrophy (wasting) of various muscle groups in the body. While some SMAs lead to early infant death, other diseases of this group permit normal adult life with only mild weakness.

Polyneuropathy Medical condition

Polyneuropathy is damage or disease affecting peripheral nerves in roughly the same areas on both sides of the body, featuring weakness, numbness, and burning pain. It usually begins in the hands and feet and may progress to the arms and legs and sometimes to other parts of the body where it may affect the autonomic nervous system. It may be acute or chronic. A number of different disorders may cause polyneuropathy, including diabetes and some types of Guillain–Barré syndrome.

Nerve conduction study Diagnostic test for nerve function

A nerve conduction study (NCS) is a medical diagnostic test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body. These tests may be performed by medical specialists such as clinical neurophysiologists, physical therapists, chiropractors, physiatrists, and neurologists who subspecialize in electrodiagnostic medicine. In the United States, neurologists and physiatrists receive training in electrodiagnostic medicine as part of residency training and in some cases acquire additional expertise during a fellowship in clinical neurophysiology, electrodiagnostic medicine, or neuromuscular medicine. Outside the US, clinical neurophysiologists learn needle EMG and NCS testing.

Nerve conduction velocity Speed at which an electrochemical impulse propagates down a neural pathway

In neuroscience, nerve conduction velocity (CV) is an important aspect of nerve conduction studies. It is the speed at which an electrochemical impulse propagates down a neural pathway. Conduction velocities are affected by a wide array of factors, which include; age, sex, and various medical conditions. Studies allow for better diagnoses of various neuropathies, especially demyelinating diseases as these conditions result in reduced or non-existent conduction velocities.

Polyneuropathy in dogs and cats is a collection of peripheral nerve disorders that often are breed-related in these animals. Polyneuropathy indicates that multiple nerves are involved, unlike mononeuropathy. Polyneuropathy usually involves motor nerve dysfunction, also known as lower motor neuron disease. Symptoms include decreased or absent reflexes and muscle tone, weakness, or paralysis. It often occurs in the rear legs and is bilateral. Most are chronic problems with a slow onset of symptoms, but some occur suddenly.

Neuromuscular disease Medical condition

A neuromuscular disease is any disease affecting the peripheral nervous system (PNS), the neuromuscular junction, or skeletal muscle, all of which are components of the motor unit. Damage to any of these structures can cause muscle atrophy and weakness. Issues with sensation can also occur.

Chronic inflammatory demyelinating polyneuropathy Medical condition

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired autoimmune disease of the peripheral nervous system characterized by progressive weakness and impaired sensory function in the legs and arms. The disorder is sometimes called chronic relapsing polyneuropathy (CRP) or chronic inflammatory demyelinating polyradiculoneuropathy. CIDP is closely related to Guillain–Barré syndrome and it is considered the chronic counterpart of that acute disease. Its symptoms are also similar to progressive inflammatory neuropathy. It is one of several types of neuropathy.

Rheobase

Rheobase is a measure of membrane potential excitability. In neuroscience, rheobase is the minimal current amplitude of infinite duration that results in the depolarization threshold of the cell membranes being reached, such as an action potential or the contraction of a muscle. In Greek, the root rhe translates to "current or flow", and basi means "bottom or foundation": thus the rheobase is the minimum current that will produce an action potential or muscle contraction.

Dejerine–Sottas disease Medical condition

Dejerine–Sottas disease, also known as, Dejerine–Sottas neuropathy, progressive hypertrophic interstitial polyneuropathy of childhood and onion bulb neuropathy, is a hereditary neurological disorder characterised by damage to the peripheral nerves and resulting progressive muscle wasting. The condition is caused by mutations in a various genes and currently has no known cure.

Myelin protein zero

Myelin protein zero is a single membrane glycoprotein which in humans is encoded by the MPZ gene. P0 is a major structural component of the myelin sheath in the peripheral nervous system (PNS). Myelin protein zero is expressed by Schwann cells and accounts for over 50% of all proteins in the peripheral nervous system, making it the most common protein expressed in the PNS. Mutations in myelin protein zero can cause myelin deficiency and are associated with neuropathies like Charcot–Marie–Tooth disease and Dejerine–Sottas disease.

Hereditary neuropathy with liability to pressure palsy Medical condition

Hereditary neuropathy with liability to pressure palsy (HNPP) is a peripheral neuropathy, a condition that affects the nerves. Pressure on the nerves can cause tingling sensations, numbness, pain, weakness, muscle atrophy and even paralysis of the affected area. In normal individuals, these symptoms disappear quickly, but in sufferers of HNPP even a short period of pressure can cause the symptoms to occur. Palsies can last from minutes or days to weeks or even months.

Neuropathy may refer to:

Distal hereditary motor neuronopathies, sometimes also called distal hereditary motor neuropathies, are a genetically and clinically heterogeneous group of motor neuron diseases that result from genetic mutations in various genes and are characterized by degeneration and loss of motor neuron cells in the anterior horn of the spinal cord and subsequent muscle atrophy.

Roussy–Lévy syndrome, also known as Roussy–Lévy areflexic dystasia, is a rare disorder of humans that results in progressive muscle wasting. It is caused by mutation the s that code for proteins necessary for the functioning of the myelin sheath of the, affecting the conductance of nerve signals and resulting in loss of muscles' ability to move.

Distal hereditary motor neuropathy type V is a particular type of neuropathic disorder. In general, distal hereditary motor neuropathies affect the axons of distal motor neurons and are characterized by progressive weakness and atrophy of muscles of the extremities. It is common for them to be called "spinal forms of Charcot-Marie-Tooth disease (CMT)", because the diseases are closely related in symptoms and genetic cause. The diagnostic difference in these diseases is the presence of sensory loss in the extremities. There are seven classifications of dHMNs, each defined by patterns of inheritance, age of onset, severity, and muscle groups involved. Type V is a disorder characterized by autosomal dominance, weakness of the upper limbs that is progressive and symmetrical, and atrophy of the small muscles of the hands.

Mary M. Reilly FRCP is an Irish neurologist who works at National Hospital for Neurology and Neurosurgery. She studies peripheral neuropathy. She is the President of the Association of British Neurologists.

Charlotte Sumner American neurologist

Charlotte Jane Sumner is an American neurologist. She is a professor in the Departments of Neurology and Neuroscience at Johns Hopkins School of Medicine. Dr. Sumner cares for patients with genetically-mediated neuromuscular diseases and directs a laboratory focused on developing treatments for these diseases. She co-directs the Johns Hopkins Muscular Dystrophy Association Care Center, the Spinal Muscular Atrophy (SMA), and the Charcot-Marie-Tooth (CMT) clinics, which deliver multidisciplinary clinical care, engage in international natural history studies, and provide cutting edge therapeutics.

References

  1. 1 2 3 4 Charcot-Marie-Tooth and Other Hereditary Motor and Sensory Neuropathies at eMedicine
  2. 1 2 3 Vance, Jeffery M. (1991). "Hereditary motor and sensory neuropathies". Journal of Medical Genetics. 28 (1): 1–5. doi:10.1136/jmg.28.1.1. PMC   1016739 . PMID   1999826.
  3. 1 2 American Association of Neuromuscular & Electrodiagnostic Medicine. (2013). Hereditary Motor Sensory Neuropathy. http://www.aanem.org/Education/Patient-Resources/Disorders/Hereditary-Motor-Sensory-Neuropathy.aspx Accessed on 11/10/13.
  4. Dyck, Peter James; Lambert, Edward H. (1968). "Lower Motor and Primary Sensory Neuron Diseases With Peroneal Muscular Atrophy". Archives of Neurology. 18 (6): 603–18. doi:10.1001/archneur.1968.00470360025002. PMID   4297451.

Further reading