The dysfunction of motor neurons resulting in muscle weakness or paralysis. The dysfunction of sensory neurons leads to abnormal or absent sensation. Some disorders are progressive and fatal.

The peripheral nervous system refers to parts of the nervous system outside the brain and spinal cord. This includes the brain and spinal nerves from their origin to their end point. The anterior horn cells, although they are formally a part of the CNS, sometimes treated together with the peripheral nervous system, since they belong to the motor unit. The dysfunction of motor neurons resulting in muscle weakness or paralysis. The dysfunction of sensory neurons leads to abnormal or absent sensation. Some disorders are progressive and fatal. Anatomy A motor unit consists of an anterior horn cell His motor axon The muscle fibers that it stimulates the connection therebetween (neuromuscular junction), the anterior horn cells are localized in the gray matter of the spinal cord and thus formally a part of the CNS. In contrast to the motor system, the cell bodies of the sensory afferent fibers lie outside the spinal cord in the spinal ganglia. The nerve fibers outside the spinal cord unite and form anterior (ventral) and posterior motor (dorsal) sensory nerve roots. The front and rear roots form a spinal nerves together. 30 of the 31 pairs of spinal nerves have dorsal and ventral roots; C1 has no sensory root (spinal nerve). The spinal nerve spinal nerves leave the spinal column via an intervertebral foramen. Since the spinal cord is shorter than the spine, are the caudal foramen of progressively further away from the original segment. Thus, in the lumbosacral nerve roots of the lower segments to rise within the spinal canal in a nearly vertical bundle and form the cauda equina. Just behind the intervertebral foramen, the spinal nerves branch out into several parts. Branches of the cervical and lumbosacral spinal nerves anastomose peripherally in the nerve plexus and then branch into nerves that terminate in up to 1 m in peripheral structures (plexus). The intercostal nerves are segmentally divided. Plexus as peripheral nerve of the part of the spinal nerves distally referred to by root and plexus. Peripheral nerves are bundles of nerve fibers. Its diameter is 0.3 to 22 microns. Schwann cells form a thin cytoplasmic tube around each fiber, and also wrap thicker fibers having a multilayer barrier membrane (myelin sheath). Physiology The myelin sheath improves impulse conduction. The largest and most myelinated fibers conduct fast; transfer them motorized, touch and proprioceptive impulses. The less myelinated and unmyelinated fibers conduct more slowly; they conduct pain, temperature and autonomous impulses. Since nerves are metabolically active tissue, they need nutrients through small blood vessels, called vasa nervorum provided. Etiology Peripheral nerve disorders can result from damage or malfunction of one of: cell body myelin sheath axons Neuromuscular end plate The disorders may be genetic or acquired (due to toxic, metabolic, traumatic, infectious or inflammatory causes-see table: Some causes of disturbances peripheral nervous system). Peripheral neuropathies can affect a nerve (mononeuropathy) Several different nerves (multiple mononeuropathy or mononeuritis multiplex) Multiple Nervendiffusivität (polyneuropathy) A plexus (plexopathy) A nerve root (radiculopathy) There may be more than one location affected; in the most common variant of Guillain-Barre syndrome z can. As multiple cranial nerve segments, usually the two Fazialisnerven be affected. Some causes of disorders of the peripheral nervous system localization type Examples motor neuron * Hereditary Spinal Muscular Atrophy Type I-IV acquired, acute polio infection by Coxsackie virus and other enteroviruses (rare), West Nile virus infection acquired, chronic amyotrophic lateral sclerosis, paraneoplastic syndromes, Post polio syndrome, progressive bulbar paralysis. (Editor’s note: The progressive bulbar paralysis actually applies as a variant of ALS.) Nerve root Hereditary neurofibroma Acquired lumbar disc herniation, infection, tumor metastasis, trauma plexus Acquired Acute Armplexusneuritis, diabetes mellitus, hematoma, local tumors (eg schwannoma.) Turmometastasen, neurofibromatosis (rare), traction during childbirth, major trauma Peripheral nerve compression Carpal tunnel syndrome, cubital tunnel syndrome, radial nerve palsy; Peroneal nerve palsy, tarsal tunnel syndrome Congenital Hereditary neuropathy with adult onset, hereditary sensory and motor neuropathies, hereditary sensory and autonomic neuropathies Infectious hepatitis C, herpes zoster, HIV infection, Lyme disease, syphilis in developing countries: diphtheria, Leprosy, parasitic infections flammable Chronic inflammatory demyelinating polyneuropathy, Guillain-Barre syndrome and Ischemic variants N. fem oralis infarction (diabetic amyotrophy), vasculitis, the multiple mononeuropathy (Mononeuritis Multiplex) causes toxic-metabolic amyloidosis, diabetes mellitus, dysproteinämische neuropathy, chronic excessive alcohol consumption with malnutrition (in particular lack of B-complex vitamins), critical illness neuropathy, leukodystrophies ( rare), kidney failure, toxins (eg. As arsenic, thallium, mercury, chemotherapy drugs, lead, pyridoxine toxicity) Neuromuscular end plate – botulism in infants, congenital myasthenia (very rare), Eaton-Lambert syndrome, myasthenia gravis, toxic or substance-induced neuromuscular dysfunction (eg. due to exposure to insecticides or nerve gas, abnormally high Mg-level or the use of neuromuscular inhibitors) muscle dystrophies distal muscular dystrophy (late distal hereditary myopathies; rare), Duchenne muscular dystrophy and related dystrophies, faszioskapulohumerale muscular dystrophy, muscular dystrophy limb girdle type okul opharyngeale dystrophy (rare) Channelopathies (myoton) Familial periodic paralysis, myotonia congenita (Thomsen’s disease), myotonic dystrophy (Steinert’s disease). (Editor’s note: instead of myotonia congenita [Thomsen’s disease], “myotonia congenita type Thomsen / Model Becker” instead myotonic dystrophy [Steinert’s disease]: myotonic dystrophy type I [Curschmann Steinert], myotonic dystrophy type II [proximal myotonic muscular dystrophy; PROMM]) Congenital Central core disease (central core myopathy) disease centronuclear myopathy, nemaline myopathy (very rare) Endocrine acromegaly, Cushing’s syndrome, diabetes mellitus, hypothyroidism, thyrotoxic myopathy (flammable infection more viral than bacterial) , polymyositis and Dermatomyosi tis (Note / complement the editorial: inclusion body) Metabolically lack of acid maltase, alcoholism, carnitine deficiency, Glykogenspeicher- and lipid storage diseases (rare), hypokalemia (Editor’s note: The acid-maltase deficiency (glycogen storage disease type II, Pompe disease) also one of the glycogen storage diseases) * diseases of the lower motor neurons (eg. B. spinal muscular atrophies) are formally to the CNS, because the cell bodies of the motor neurons (ventral horn cells) are in the spinal cord. Adapted from Tandan R, Bradley WA: Amyotrophic lateral sclerosis. Part I: Clinical features, pathology and ethical issues in management. Annals of Neurology 18: 271-280, 1985; Used with permission of Little, Brown and Company. Since pathophysiology sensory and motor cell bodies are located in various places, a disorder of nerve cell bodies typically affects either the sensory or motor component, but seldom both. Damage Damage to the myelin sheath (demyelination) slowed nerve conduction. Demyelination mainly concerns strong myelinated fibers, causing loss of sensory large fibers (tingling and electrifying), motor weakness and decreased muscle reflexes. Hallmark of acquired demyelinating polyneuropathy is a severe motor weakness with minimal atrophy. Because the vasa nervorum not reach the center of a nerve, the centrally located fascicles are most sensitive to vascular disorders (eg. B. vasculitis, ischemia). These disturbances lead to sensory dysfunction thin fibers (sharp pain and burning sensations) to motor weakness, which is proportional to atrophy, and less intense reflex abnormalities than other nervous disorders. The two distal third of a limb are most often affected. At the beginning of the deficits due to the random distribution of vasculitis or ischemic process are more asymmetric. Later, the multiple infarcts can merge and create symmetrical deficits (multiple mononeuropathy). Toxic-metabolic or genetic disorders usually begin symmetrical. Immune-mediated processes can be symmetrical or, at the beginning of rapidly evolving processes, even asymmetrical. Damage to the axonal transport system for cellular components, v. a. of microtubules and microfilaments causes substantial axonal dysfunction. First, the thinner fibers are affected in the most distal parts of the nerve (because they have a higher metabolic demand). After that, the axonal degeneration aszendiert slowly and calls it the characteristic of distal to proximal reaching symptom patterns produced (a stocking and glove-shaped sensory disturbances, followed by weakness) .Regeneration Damage to the myelin sheath (z. B. by an injury or Guillain-Barre syndrome ) can be repaired by surviving Schwann cells often within 6-12 weeks. After axonal damage the fiber grows within the group formed by the Schwann cell tube at a speed of 1 mm / day, as soon as the pathologic process is finished. However, the sprout can be misguided and lead to aberrant innervation (z. B. fibers in the wrong muscle, a touch receptor at the wrong place or a temperature, instead of a touch receptor). Regeneration is impossible if the cell body dies, and unlikely if the axon is lost completely. Clarification determining the deficits on the basis of history and examination to observe the clinical evidence of disorders of the peripheral nervous system usually studies of nerve conduction and electromyography Sometimes punch biopsy of nerve or skin genetic testing Clinical (in hereditary neuropathies) assessing the medical history should focus on the nature of the symptoms, the onset , progression and localization, as well as information about possible causes (eg. as family history, exposure to toxins, past illnesses). Physical and neurological examination should further clarify the nature of the deficit (z. B. motor deficit, type of sensory loss, combination of both). Sensor (using a needle and temperature for thin fibers, by means of vibration, and proprioception tests with thick fibers), force and tendon reflexes are assessed. The function of the cranial nerves and the central and peripheral nervous is evaluated. It is noted that the motor weakness is proportional to the degree of atrophy, as well as the type and distribution of reflex abnormalities. The autonomous function is clarified. Physicians should proceed based on the pattern and type of neurological deficits of a disorder of the peripheral nervous system, v. a. wherein localization of the deficiencies in individual nerve roots, spinal nerve, plexus, certain peripheral nerves or a combination thereof. Suspicion of these disorders is also in patients with mixed sensory and motor failures, with a plurality of foci or with a focus, which does not fit into a single anatomical site in the CNS. In patients with generalized or diffuse weakness, but without sensory loss, doctors should also accept disorders of the peripheral nervous system; In these cases, disorders of the peripheral nervous system can be overlooked because they are not the most likely cause of such symptoms. Evidence of a disorder of the peripheral nervous system as a possible cause general weakness are: Patterns general weakness in favor of a specific cause (eg prevailing ptosis and diplopia, suggesting an early myasthenia gravis points.) Other signs and symptoms as weakness, to a specific disease or group of disorders (eg. B. cholinergic effects, suggesting an organophosphate) indicate hosiery / glove-shaped distribution patterns of failures that speaks for diffuse axonal disorders or a polyneuropathy fasciculations hypotension muscle wasting without hyperreflexia progressive, chronic and unexplained weakness Among the indications that the cause can not be a disorder of the peripheral nervous system include hyperreflexia hypertension This Def izite suggest a disturbance of the upper motor neurons as a cause of weakness. Hyporeflexia is consistent with deficits of the peripheral nervous system, but is non-specific. For example, cervical cord compression Guillain-Barre syndrome can mimic, especially in patients with pre-existing neuropathy. Despite many possible exceptions certain clinical evidence can also point to possible causes of deficits of the peripheral nervous system (see table: Clinical notes on causes of disorders of the peripheral nervous system *). Clinical notes on causes of disorders of the peripheral nervous system * findings to be considered cause Symmetrical, diffuse deficits Diffuse disorders (eg. As toxic-metabolic, genetic, infectious or inflammatory diseases, most immune-mediated diseases) Unilateral deficits Focal disorders (eg. B. mononeuropathies, plexopathies) deficits in localization of one or more structures of the peripheral nervous system (eg. B. nerve roots, the spinal nerve, nerve plexus, single peripheral nerve, ? 2 discrete nerves in separate areas [multiple mononeuropathy]) lesion in a structure of the peripheral nervous system stocking-glove distribution pattern of deficits Diffuse peripheral polyneuropathies, possibly axonal Disproportionate weakness of proximal muscles (eg. As difficulty climbing stairs or combing hair) without sensory deficits Diffuse muscular dysfunction, as with diffuse disease myopathies Maybe the neuromuscular junction, where the eye movements are affected chronic, progressive weakness, v. a. distal muscles without sensory deficits affects motor neuron disease Electrifying / tingling discomfort with motor weakness and decreased reflexes proximal demyelination Profound and distal motor weakness with minimal atrophy Acquired demyelinating polyneuropathy Impaired pain and temperature sensation; painful, often burning sensations weakness proportional to atrophy; disproportionately mild reflex abnormalities, usually more distally than proximally vascular disease (eg. as vasculitis, ischemia, Hyperkoagulationszustände) * disorders of the lower motor neurons (z. B. spinal muscular atrophy) belong formally to the CNS, as the cell body of the motor neuron (anterior horn cells) in spinal cord are. The clinical assessment narrows the diagnostic possibilities and thus leads the other Untersuchungen.Tests Usually studies of nerve conduction and electromyography (here electrodiagnostic testing referred to collectively as) performed. These tests help (nerve plexus, root) and in distinguishing demyelinating diseases (very slow nerve conduction) of axonal dysfunction in the identification of the level in question. Other tests, such as imaging, is based on whether a CNS lesion is excluded (eg. As MRI when all limbs are affected in order to exclude a cervical spinal cord compression). A nerve biopsy is sometimes carried out to support the differentiation of demyelinating and vasculitic neuropathies thicker fibers. When vasculitis is a consideration, the biopsy should include skin and muscle to increase the chance for a definitive diagnosis. When a neuropathy of small-caliber nerve fibers (small fiber neuropathy) is suspected, a biopsy of the skin can be carried out; the loss of nerve endings supports this diagnosis. Tips and risks Are the clinical and electrodiagnostic test results inconclusive, perform a biopsy (nerve biopsy in suspected. Neuropathy thicker fibers or punch biopsy of the skin in V. a. Small fiber neuropathy) If all limbs are affected, an MRI should be considered to rule out cervical spinal cord compression. Genetic testing is displayed when a hereditary neuropathy is suspected. Patients with weakness, but without sensory deficits of weakness are concerning. Clarified. The electro-diagnostic testing contributes to distinction of disorders of the peripheral nervous system and other causes of weakness and helps to identify individual disorders of the peripheral nervous system (eg. B. root, plexus, peripheral nerve, neuromuscular junction, muscle fiber). It helps to differentiate between axonal and demyelinating peripheral neuropathies. Treatment The underlying disease is treated. Supportive treatment, often by a multidisciplinary team possible, the treatment is directed to the underlying disease. Otherwise, treatment is supportive. A multidisciplinary treatment approach in a team helps patients deal with the progressive neurological disabilities: physical therapist can help to preserve muscle function, patients dabie. Occupational therapists can customize adaptive rails and walking aids, to make the activities of daily living easier. Specialized speech therapists can provide alternative communication aids. If pharyngeal weakness developed to a speech therapist or a multidisciplinary team that specializes in swallowing, help the risk of aspiration to assess preventive measures and recommend (z. B. Precautions for oral ingestion and / or need for tube feeding). A gastroenterologist may recommend a percutaneous endoscopic gastrostomy. If a respiratory depression develops, forced vital capacity is measured and lung specialists or intensivists help determine whether intensive care, non-invasive respiratory support (z. B. bilevel positive airway pressure, BiPAP) or a tracheotomy with complete ventilation required. Early in the course of deadly diseases the doctors who care need to speak openly with the patient, family members and caregivers about the acceptable for them degree of intervention. Patients are asked to record their decisions in writing (orders ahead) before being incapacitated. These decisions should be reconsidered in the various stages of the disease again and again and possibly confirmed. Conclusion are disorders of the peripheral nervous system often assumed based on clinical findings (z. B. hosiery / glove-shaped distribution pattern hyporeflexia distal muscle weakness and wasting, localization to a peripheral innervation area). Patients have a massive motor weakness with minimal atrophy and areflexia, consider a demyelinating polyneuropathy. Refer patients abnormal pain and abnormal sensations of temperature and atrophy in proportion to the weakness (sometimes used excessive preservation of reflexes) that you should consider vasculitis or ischemic neuropathy into consideration. Consider a motor neuron disease in patients with chronic progressive muscle weakness, fasciculations, muscle atrophy and without sensory deficits. Studies of nerve conduction and electromyography are helpful to identify the beiteiligte level (root, plexus, peripheral nerve, neuromuscular junction, muscle fiber), and contribute to the differentiation of demyelinating and axonal disorders.

Health Life Media Team

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