Hereditary motor and sensory neuropathies are relatively common and are often inherited with other neuromuscular conditions, and these co morbidities cause an accelerated progression of the disease.

Most forms HMSN affects 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 prediliections, but other recessively inherited forms tend to impact specific ethnic groups. Onset of HMSN in 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.

Nerve injury is injury to nervous tissue. There is no single classification system that can describe all the many variations of nerve injury. In 1941, Seddon introduced a classification of nerve injuries based on three main types of nerve fiber injury and whether there is continuity of the nerve. Usually, however, (peripheral) nerve injury is classified in five stages, based on the extent of damage to both the nerve and the surrounding connective tissue, since supporting glial cells may be involved. Unlike in the central nervous system, neuroregeneration in the peripheral nervous system is possible. The processes that occur in peripheral regeneration can be divided into the following major events: Wallerian degeneration, axon regeneration/growth, and nerve reinnervation. The events that occur in peripheral regeneration occur with respect to the axis of the nerve injury. The proximal stump refers to the end of the injured neuron that is still attached to the neuron cell body; it is the part that regenerates. The distal stump refers to the end of the injured neuron that is still attached to the end of the axon; it is the part of the neuron that will degenerate but that remains in the area toward which the regenerating axon grows. The study of peripheral nerve injury began during the American Civil War and has greatly expanded to the point of using growth-promoting molecules.

The severe pain of HNA can be controlled with an anti-inflammatory drug such as prednisone, although it is unknown whether these anti-inflammatory drugs actually slow or stop the nerve degeneration process.

Nerve regeneration after an episode is normal, and in less severe cases a full recovery of the nerves and muscles can be expected. However, in a severe case permanent nerve damage may occur.

Electrical stimulation can promote nerve regeneration. The frequency of stimulation is an important factor in the success of both quality and quantity of axon regeneration as well as growth of the surrounding myelin and blood vessels that support the axon. Histological analysis and measurement of regeneration showed that low frequency stimulation had a more successful outcome than high frequency stimulation on regeneration of damaged sciatic nerves.

Surgery can be done in case a nerve has become cut or otherwise divided. Recovery of a nerve after surgical repair depends mainly on the age of the patient. Young children can recover close-to-normal nerve function. In contrast, a patient over 60 years old with a cut nerve in the hand would expect to recover only protective sensation, that is, the ability to distinguish hot/cold or sharp/dull. Many other factors also affect nerve recovery. The use of autologous nerve grafting procedures that involve redirection of regenerative donor nerve fibers into the graft conduit has been successful in restoring target muscle function. Localized delivery of soluble neurotrophic factors may help promote the rate of axon regeneration observed within these graft conduits.

An expanding area of nerve regeneration research deals with the development of scaffolding and bio-conduits. Scaffolding developed from biomaterial would be useful in nerve regeneration if they successfully exhibit essentially the same role as the endoneurial tubes and Schwann cell do in guiding regrowing axons.

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

While the exact incidence is unknown, estimates range from 33 - 57 percent of patients staying in the ICU for longer than 7 days. More exact data is difficult to obtain, since variation exists in defining the condition.

The three main risk factors for CIP and CIM are sepsis and systemic inflammatory response syndrome (SIRS), and multi-organ failure. Reported rates of CIP/CIM in people with sepsis and SIRS range from 68 to 100 percent. Additional risk factors for developing CIP/CIM include: female gender, high blood sugar (hyperglycemia), low serum albumin, and immobility. A greater severity of illness increases the risk of CIP/CIM. Such risk factors include: multi-organ dysfunction, renal failure, renal replacement therapy, duration of organ dysfunction, duration of ICU stay, low albumin, and central neurologic failure.

Certain medications are associated with CIP/CIM, such as corticosteroids, neuromuscular blocking agents, vasopressors, catecholamines, and intravenous nutrition (parenteral nutrition). Research has produced inconsistent results for the impact of hypoxia, hypotension, hyperpyrexia, and increased age on the risk of CIP/CIM. The use of aminoglycosides is "not" an independent risk for the development of CIP/CIM.

People who suffer from neurotmesis often face a poor prognosis. They will more than likely never regain full functionality of the affected nerve, but surgical techniques do give people a better chance at regaining some function. Current research is focused on new ways to regenerate nerves and advance surgical techniques.

Hereditary neuralgic amyotrophy (HNA) is a neuralgic disorder that is characterized by nerve damage and muscle atrophy, preceded by severe pain. In about half of the cases it is associated with a mutation of the "SEPT9" gene (17q25). While not much is known about this disorder, it has been characterized to be similar to Parsonage-Turner syndrome in prognosis. For a comprehensive overview of hereditary and idiopathic neuralgic amyotrophy and its consequences for patients: please see the pdf file link at the bottom of this page.

Cervical radiculopathy is less prevalent in the United States than lumbar radiculopathy with an occurrence rate of 83 cases per 100,000. According to the AHRQ’s 2010 National Statistics for cervical radiculopathy the most affected age group is between 45 and 64 years with 51.03% of incidents. Females are affected more frequently than males and account for 53.69% of cases. Private insurance was the payer in 41.69% of the incidents followed by Medicare with 38.81%. In 71.61% of cases the patients’ income was considered not low for their zipcode. Additionally over 50% of patients lived in large metropolitans (inner city or suburb). The South is the most severely affected region in the US with 39.27% of cases. According to a study performed in Minnesota, the most common manifestation of this set of conditions is the C7 monoradiculopathy, followed by C6.

The prognosis is usually good in terms of recovery. Rate of recovery depends on the distance from the site of injury, and axonal regeneration can go up to 1 inch per month. Complete recovery can take anywhere from 6 months to a year

Trauma is the most frequent cause of peripheral nerve lesions. There are two classifications of trauma which include civilian trauma and military trauma. Civilian trauma is most commonly caused by motor vehicle accidents but also by lacerations caused by glass, knives, fans, saw blades or fractures and occasionally sports injuries. Of the civilian injuries, stretch injuries are the most common types and are considered to be a closed injury, where the tissue is unexposed. Stretch injures are commonly the result of dislocation, such as a shoulder dislocation that stretches nerves. Opposite of civilian trauma, there is military trauma which most commonly results in open injuries from blasts often by bombs or improvised explosive devices. Other mechanisms of injury are less common but include ischemia, thermal, electric shock, radiation, adverse reactions to certain chemotherapy medications, percussion and vibration.

The cause of PBP is unknown. One form of PBP is found to occur within patients that have a CuZn-superoxide dismutase (SOD1) mutation. Progressive bulbar palsy patients that have this mutation are classified with FALS patients, Familial ALS (FALS) accounts for about 5%-10% of all ALS cases and is caused by genetic factors. Within these, about 20-25% are linked to the SOD1 mutation. It is not currently known if and how the decreased SOD1 activity contributes to Progressive Bulbar Palsy or FALS, and studies are being done in patients and transgenic mice to help further understand the impact of this gene on the disease.

A case study was done on a 42-year-old woman who complained of muscle weakness 10 months prior to admission in the hospital. Upon neurological examination, the patient showed muscle atrophy, fasciculation in all limbs and decreased deep tendon reflexes. The patient’s older brother, father, and paternal uncle had previously all died of ALS or an ALS type syndrome. The patient developed Progressive Bulbar Palsy, became dependent on a respirator, and had two episodes of cardiac arrest. The patient died from pneumonia two years after the onset of the disease. After studying the patient, it was found that the patient had a two base pair deletion in the 126th codon in exon 5 of the SOD1 gene. This mutation produced a frameshift mutation, which led to a stop codon at position 131. SOD1 activity was decreased by about 30%. The patient’s histological examination showed severe reduction in lower motor neurons. Upon further study, this case proved to be important because it demonstrated that SOD1 mutations might not effect steady neuropathological changes, and that environmental and genetic factors might affect the phenotype of the SOD1 mutations.

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

The site and type of brachial plexus injury determine the prognosis. Avulsion and rupture injuries require timely surgical intervention for any chance of recovery. For milder injuries involving buildup of scar tissue and for neurapraxia, the potential for improvement varies, but there is a fair prognosis for spontaneous recovery, with a 90–100% return of function.

Most often the radiculopathy found in the patients are located in the cervical spine, most commonly affecting C6-C8 spinal nerves.

Certain injuries can also lead to radiculopathy. These injuries include lifting heavy objects improperly or suffering from a minor trauma such as a car accident. Less common causes of radiculopathy include injury caused by tumor (which can compress nerve roots locally) and diabetes (which can effectively cause ischemia or lack of blood flow to nerves).

Transneuronal degeneration is the death of neurons resulting from the disruption of input from or output to other nearby neurons. It is an active excitotoxic process when a neuron is overstimulated by a neurotransmitter (most commonly glutamate) causing the dysfunction of that neuron (either damaging it or killing it) which drives neighboring neurons into metabolic deficit, resulting in rapid, widespread loss of neurons. This can be either anterograde or retrograde, indicating the direction of the degeneration relative to the original site of damage (see types). There are varying causes for transneuronal degeneration such as brain lesions, disconnection syndromes, respiratory chain deficient neuron interaction, and lobectomies. Although there are different causes, transneuronal degeneration generally results in the same effects (whether they be cellular, dendritic, or axonal) to varying degrees. Transneuronal degeneration is thought to be linked to a number of diseases, most notably Huntington's disease and Alzheimer's disease, and researchers recently have been performing experiments with monkeys and rats, monitoring lesions in different parts of the body to study more closely how exactly the process works.

In terms of prognosis radial neuropathy is not necessarily permanent, though sometimes there could be partial loss of movement/sensation.Complications may be possible deformity of the hand in some individuals.

If the injury is axonal (the underlying nerve fiber itself is damaged) then full recovery may take months or years ( or could be permanent). EMG and nerve conduction studies are typically performed to diagnose the extent and distribution of the damage, and to help with prognosis for recovery.

Five different clinical entities have been described under hereditary sensory and autonomic neuropathies – all characterized by progressive loss of function that predominantly affects the peripheral sensory nerves. Their incidence has been estimated to be about 1 in 25,000.

Axonotmesis is an injury to the peripheral nerve of one of the extremities of the body. The axons and their myelin sheath are damaged in this kind of injury, but the endoneurium, perineurium and epineurium remain intact. Motor and sensory functions distal to the point of injury are completely lost over time leading to Wallerian Degeneration due to ischemia, or loss of blood supply. Axonotmesis is usually the result of a more severe crush or contusion than neurapraxia.

Axonotmesis mainly follows a stretch injury. These stretch injuries can either dislocate joins or fracture a limb, due to which peripheral nerves are severed. If the sharp pain from the exposed axon of the nerve is not observed, one can identify a nerve injury from abnormal sensations in their limb. A doctor may ask for a Nerve Conduction Velocity (NCV) test to completely diagnose the issue. If diagnosed as nerve injury, Electromyography performed after 3 to 4 weeks shows signs of denervations and fibrillations, or irregular connections and contractions of muscles.

Left untreated, tabes dorsalis can lead to paralysis, dementia, and blindness. Existing nerve damage cannot be reversed.

Hereditary sensory neuropathy type 1 is a condition characterized by nerve abnormalities in the legs and feet (peripheral neuropathy). Many people with this condition have tingling, weakness, and a reduced ability to feel pain and sense hot and cold. Some affected individuals do not lose sensation, but instead feel shooting pains in their legs and feet. As the disorder progresses, the sensory abnormalities can affect the hands, arms, shoulders, and abdomen. Affected individuals may also experience muscle wasting and weakness as they get older, but this varies widely within families.

Affected individuals typically get open sores (ulcers) on their feet or hands or infections of the soft tissue of the fingertips (whitlows) that are slow to heal. Because affected individuals cannot feel the pain of these sores, they may not seek treatment right away. Without treatment, the ulcers can become infected and may require amputation of the surrounding area.

Albeit rarely, people with hereditary sensory neuropathy type 1 may develop hearing loss caused by abnormalities of the inner ear (sensorineural hearing loss).

The signs and symptoms of hereditary sensory neuropathy type 1 typically appear during a person's teens or twenties. While the features of this disorder tend to worsen over time, affected individuals have a normal life expectancy if signs and symptoms are properly treated.

Type 1 is the most common form among the 5 types of HSAN. Its historical names include "mal perforant du pied", ulcero-mutilating neuropathy, hereditary perforating ulcers, familial trophoneurosis, familial syringomyelia, hereditary sensory radicular neuropathy, among others. This type includes a popular disease Charcot-Marie-Tooth type 2B syndrome (HMSN 2B). that is also named as HSAN sub-type 1C.

Type 1 is inherited as an autosomal dominant trait. The disease usually starts during early adolescence or adulthood. The disease is characterized by the loss of pain sensation mainly in the distal parts of the lower limbs; that is, in the parts of the legs farther away from the center of the body. Since the affected individuals cannot feel pain, minor injuries in this area may not be immediately recognized and may develop into extensive ulcerations. Once infection occurs, further complications such as progressive destruction of underlying bones may follow and may necessitate amputation. In rare cases, the disease is accompanied with nerve deafness and muscle wasting. Autonomic disturbance, if present, appears as anhidrosis, a sweating abnormality. Examinations of the nerve structure and function showed signs of neuronal degeneration such as a marked reduction in the number of myelinated fibers and axonal loss. Sensory neurons lose the ability to transmit signals, while motor neurons has reduced ability to transmit signals.

Genes related to Hereditary sensory and autonomic neuropathy Type 1:

Mutations in the SPTLC1 gene cause hereditary sensory neuropathy type 1. The SPTLC1 gene provides instructions for making one part (subunit) of an enzyme called serine palmitoyltransferase (SPT). The SPT enzyme is involved in making certain fats called sphingolipids. Sphingolipids are important components of cell membranes and play a role in many cell functions.

SPTLC1 gene mutations reduce the amount of SPTLC1 subunit that is produced and result in an SPT enzyme with decreased function. A lack of functional SPT enzyme leads to a decrease in sphingolipid production and a harmful buildup of certain byproducts. Sphingolipids are found in myelin, which is the covering that protects nerves and promotes the efficient transmission of nerve impulses. A decrease in sphingolipids disrupts the formation of myelin, causing nerve cells to become less efficient and eventually die. When sphingolipids are not made, an accumulation of toxic byproducts can also lead to nerve cell death. This gradual destruction of nerve cells results in loss of sensation and muscle weakness in people with hereditary sensory neuropathy type 1.

Fazio–Londe disease is linked to a genetic mutation in the "SLC52A3" gene on chromosome 20 (locus: 20p13). It is allelic and phenotypically similar to Brown–Vialetto–Van Laere syndrome.

The condition is inherited in an autosomal recessive manner.

The gene encodes the intestinal riboflavin transporter (hRFT2).

Transneuronal degeneration can be grouped into two general categories: anterograde and retrograde.

The disease is more frequent in males than in females. Onset is commonly during mid-life. The incidence of tabes dorsalis is rising, in part due to co-associated HIV infection .

Since December 2016, autosomal recessive proximal spinal muscular atrophy can be treated with nusinersen. No cure is known to any of the remaining disorders of the spinal muscular atrophies group. The main objective there is to improve quality of life which can be measured using specific questionnaires. Supportive therapies are widely employed for patients who often also require comprehensive medical care involving multiple disciplines, including pulmonology, neurology, orthopedic surgery, critical care, and clinical nutrition. Various forms of physiotherapy and occupational therapy are frequently able to slow down the pace of nerve degeneration and muscle wasting. Patients also benefit greatly from the use of assistive technology.