Peripheral Neuropathies – Polyneuropathies and Mononeuritis Multiplex – part 1

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Peripheral neuropathies are classified on the basis of the structure that is primarily affected. The predominant pathologic feature may be axonal degeneration (axonal or neuronal neuropathies) or paranodal or segmental demyelination. The distinction may be possible on the basis of neurophysiologic findings. Motor and sensory conduction velocity can be measured in accessible segments of peripheral nerves. In axonal neuropathies, conduction velocity is normal or reduced only mildly and needle electromyography provides evidence of denervation in affected muscles. In demyelinating neuropathies, conduction may be slowed considerably in affected fibers, and in more severe cases, conduction is blocked completely, without accompanying electromyographic signs of denervation.

Peripheral neuropathies may also occur as a result of disorders affecting the connective tissues of the nerves or the blood vessels supplying the nerves, but these are much less common than the preceding varieties. Buy Celexa

Nerves may be injured or compressed by neighboring anatomic structures at any point along their course. Common mononeuropathies of this sort are considered below. They lead to a sensory, motor, or mixed deficit that is restricted to the territory of the affected nerve. A similar clinical disturbance is produced by peripheral nerve tumors, but these are rare except in patients with Recklinghausen’s disease. Multiple mononeuropathies suggest a patchy multifocal disease process such as vasculopathy (eg, diabetes, arteritis), an infiltrative process (eg, leprosy, sarcoidosis), radiation damage, or an immunologic disorder (eg, brachial plexopathy). Diffuse polyneuropathies lead to a symmetric sensory, motor, or mixed deficit, often most marked distally. They include the hereditary, metabolic, and toxic disorders; idiopathic inflammatory polyneuropathy (Guillain-Barre Guillain-Barré syndrome); and the peripheral neuropathies that may occur as a nonmetastatic complication of malignant diseases. Involvement of motor fibers leads to flaccid weakness that is most marked distally; dysfunction of sensory fibers causes impaired sensory perception. Tendon reflexes are depressed or absent. Paresthesias, pain, and muscle tenderness may also occur.

1. Polyneuropathies and Mononeuritis Multiplex

The cause of polyneuropathy or mononeuritis multiplex is suggested by the history, mode of onset, and predominant clinical manifestations. Laboratory workup includes a complete blood count and sedimentation rate, serum protein electrophoresis, determination of plasma urea and electrolytes, liver and thyroid function tests, tests for rheumatoid factor and antinuclear antibody, HBsAg determination, a serologic test for syphilis, fasting blood glucose level, urinary heavy metal levels, cerebrospinal fluid examination, and chest radiography. These tests should be ordered selectively, as guided by symptoms and signs. Measurement of nerve conduction velocity is important in confirming the peripheral nerve origin of symptoms and providing a means of following clinical changes, as well as indicating the likely disease process (ie, axonal or demyelinating neuropathy). Cutaneous nerve biopsy may help establish a precise diagnosis (eg, polyarteritis, amyloidosis). In about half of cases, no specific cause can be established; of these, slightly less than half are subsequently found to be heredofamilial. licensed drug store

Treatment is of the underlying cause, when feasible, and is discussed below under the individual disorders. Physical therapy helps prevent contractures, and splints can maintain a weak extremity in a position of useful function.

Anesthetic extremities must be protected from injury. To guard against burns, patients should check the temperature of water and hot surfaces with a portion of skin having normal sensation, measure water temperature with a thermometer, and use cold water for washing or lower the temperature setting of their hot-water heaters.

Shoes should be examined frequently during the day for grit or foreign objects in order to prevent pressure lesions.

Patients with polyneuropathies or mononeuritis multiplex are subject to additional nerve injury at pressure points and should therefore avoid such behavior as leaning on elbows or sitting with crossed legs for lengthy periods. online canadian drugs

Neuropathic pain is sometimes troublesome and may respond to simple analgesics such as aspirin. Narcotics or narcotic substitutes may be necessary for severe hyperpathia or pain induced by minimal stimuli, but their use should be avoided as far as possible. The use of a frame or cradle to reduce contact with bedclothes may be helpful.

Many patients experience episodic stabbing pains, which may respond to phenytoin, carbamazepine, or tricyclic antidepressants.

Symptoms of autonomic dysfunction are occasionally troublesome. Postural hypotension is often helped by wearing waist-high elastic stockings and sleeping in a semierect position at night. Fludrocortisone reduces postural hypotension, but doses as high as 1 mg/d are sometimes necessary in diabetics and may lead to recumbent hypertension. Indomethacin (25 or 50 mg three times daily) is sometimes helpful. Impotence and diarrhea are difficult to treat; a flaccid neuropathic bladder may respond to parasympathomimetic drugs such as bethanechol chloride, 10–50 mg three or four times daily.

Inherited Neuropathies

A. Charcot-Marie-Tooth Disease: Several distinct varieties of Charcot-Marie-Tooth disease can be recognized.

There is usually an autosomal dominant mode of inheritance, but occasional cases occur on a sporadic, recessive, or X-linked basis. The responsible gene is commonly located on the short arm of chromosome 17 and less often shows linkage to chromosome 1 or the X chromosome. Clinical presentation may be with foot deformities or gait disturbances in childhood or early adult life. Slow progression leads to the typical features of polyneuropathy, with distal weakness and wasting that begin in the legs, a variable amount of distal sensory loss, and depressed or absent tendon reflexes. Tremor is a conspicuous feature in some instances. Pathologic examination reveals segmental demyelination and remyelination of peripheral nerves, an increase in their transverse fascicular area, and hyperplasia of Schwann cells. Electrodiagnostic studies show a marked reduction in motor and sensory conduction velocity (hereditary motor and sensory neuropathy [HMSN] type I). Weight Loss Pills

In other instances (HMSN type II), motor conduction velocity is normal or only slightly reduced, sensory nerve action potentials may be absent, and signs of chronic partial denervation are found in affected muscles electromyographically. The predominant pathologic change is axonal loss rather than segmental demyelination.

A similar disorder may occur in patients with progressive distal spinal muscular atrophy, but there is no sensory loss; electrophysiologic investigation reveals that motor conduction velocity is normal or only slightly reduced, and nerve action potentials are normal.

B. Dejerine-Sottas Disease (HMSN Type III): Most cases are sporadic or autosomal recessive. The recessive form has its onset in infancy or childhood and leads to a progressive motor and sensory polyneuropathy with weakness, ataxia, sensory loss, and depressed or absent tendon reflexes. The peripheral nerves may be palpably enlarged and are characterized pathologically by segmental demyelination, Schwann cell hyperplasia, and thin myelin sheaths.

Electrophysiologically, there is slowing of conduction, and sensory action potentials may be unrecordable.

C. Friedreich’s Ataxia: Patients generally present in childhood or early adult life with this autosomal recessive disorder, which has been related to a genetic defect on the long arm of chromosome 9. The gait becomes atactic, the hands become clumsy, and other signs of cerebellar dysfunction develop accompanied by weakness of the legs and extensor plantar responses. Involvement of peripheral sensory fibers leads to sensory disturbances in the limbs and depressed tendon reflexes. There is bilateral pes cavus. Pathologically, there is a marked loss of cells in the posterior root ganglia and degeneration of peripheral sensory fibers. In the central nervous system, changes are conspicuous in the posterior and lateral columns of the cord. Electrophysiologically, conduction velocity in motor fibers is normal or only mildly reduced, but sensory action potentials are small or absent. Generic Propecia (FINASTERIDE) is the first and only FDA approved pill proven to treat male pattern hair loss on the vertex (top of head) and anterior mid-scalp area in men.

D. Refsum’s Disease (HMSN Type IV): This autosomal recessive disorder is due to a disturbance in phytanic acid metabolism. Clinically, pigmentary retinal degeneration is accompanied by progressive sensorimotor polyneuropathy and cerebellar signs. Auditory dysfunction, cardiomyopathy, and cutaneous manifestations may also occur. Motor and sensory conduction velocity is reduced, often markedly, and there may be electromyographic evidence of denervation in affected muscles. Dietary restriction of phytanic acid and its precursors may be helpful therapeutically.

E. Porphyria: Peripheral nerve involvement may occur during acute attacks in both variegate porphyria and acute intermittent porphyria. Motor symptoms usually occur first, and weakness is often most marked proximally and in the upper limbs rather than the lower. Sensory symptoms and signs may be proximal or distal in distribution.

Autonomic involvement is sometimes pronounced. The electrophysiologic findings are in keeping with the results of neuropathologic studies suggesting that the neuropathy is axonal in type. Hematin (4 mg/kg intravenously over 15 minutes once or twice daily) may lead to rapid improvement. A high-carbohydrate diet and, in severe cases, intravenous glucose or levulose may also be helpful. Propranolol (up to 100 mg every 4 hours) may control tachycardia and hypertension in acute attacks.