News about Medicine - Part 186
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. Read the rest of this entry »
Parkinsonism is a movement disorder characterized by tremor, rigidity, bradykinesia, and postural instability.
Parkinsonism is a relatively common disorder that occurs in all ethnic groups, with an approximately equal sex distribution. The most common variety, idiopathic Parkinson’s disease (paralysis agitans), begins most often between 45 and 65 years of age.
Exposure to certain toxins (eg, manganese dust, carbon disulfide) and severe carbon monoxide poisoning may rarely lead to parkinsonism. Typical parkinsonism has occurred in individuals who have taken 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) for recreational purposes. This compound is converted in the body to a neurotoxin that selectively destroys dopaminergic neurons in the substantia nigra. Reversible parkinsonism may develop in patients receiving neuroleptic drugs and has also been caused by reserpine and metoclopramide. Only rarely is hemiparkinsonism the presenting feature of a brain tumor or some other progressive space-occupying lesion.
In idiopathic parkinsonism, dopamine depletion due to degeneration of the dopaminergic nigrostriatal system leads to an imbalance of dopamine and acetylcholine, which are neurotransmitters normally present in the corpus striatum. Treatment is directed at redressing this imbalance by blocking the effect of acetylcholine with anticholinergic drugs or by the administration of levodopa, the precursor of dopamine.
Tremor, rigidity, bradykinesia, and postural instability are the cardinal features of parkinsonism and may be present in any combination. There may also be a mild decline in intellectual function. The tremor of about four to six cycles per second is most conspicuous at rest, is enhanced by emotional stress, and is often less severe during voluntary activity. Although it may ultimately be present in all limbs, the tremor is commonly confined to one limb or to the limbs on one side for months or years before it becomes more generalized. In some patients, tremor is absent. Read the rest of this entry »
Tourette’s Syndrome is initially characterized by motor tics in 80% of cases, and these tics most commonly involve the face. In the remaining 20%, the initial symptoms are phonic tics; all patients ultimately develop a combination of different motor and phonic tics. These are noted first in childhood, generally between the ages of 2 and 15. Motor tics occur especially about the face, head, and shoulders (eg, sniffing, blinking, frowning, shoulder shrugging, head thrusting, etc).
Phonic tics commonly consist of grunts, barks, hisses, throat-clearing, coughs, etc, but sometimes also of verbal utterances including coprolalia (obscene speech). There may also be echolalia (repetition of the speech of others), echopraxia (imitation of others’ movements), and palilalia (repetition of words or phrases). Some tics may be self-mutilating in nature, such as nail-biting, hair-pulling, or biting of the lips or tongue. The disorder is chronic, but the course may be punctuated by relapses and remissions.
Obsessive-compulsive behaviors are commonly associated and may be more disabling than the tics themselves.
Examination usually reveals no abnormalities other than the tics. In addition to obsessive-compulsive behavior disorders, psychiatric disturbances may occur because of the associated cosmetic and social embarrassment. Electroencephalography may show minor nonspecific abnormalities of no diagnostic relevance. Read the rest of this entry »
Myasthenia gravis occurs at all ages, sometimes in association with a thymic tumor or thyrotoxicosis, as well as in rheumatoid arthritis and lupus erythematosus. It is commonest in young women with HLA-DR3; if thymoma is associated, older men are more commonly affected.
Onset is usually insidious, but the disorder is sometimes unmasked by a coincidental infection that leads to exacerbation of symptoms. Exacerbations may also occur before the menstrual period and during or shortly after pregnancy. Symptoms are due to a variable degree of block of neuromuscular transmission caused by autoantibodies binding to acetylcholine receptors; these are found in most patients with the disease and have a primary role in reducing the number of functioning acetylcholine receptors. Additionally, cellular immune activity against the receptor is found. Clinically, this leads to weakness; initially powerful movements fatigue readily. The external ocular muscles and certain other cranial muscles, including the masticatory, facial, and pharyngeal muscles, are especially likely to be affected, and the respiratory and limb muscles may also be involved.
A. Symptoms and Signs: Patients present with ptosis, diplopia, difficulty in chewing or swallowing, respiratory difficulties, limb weakness, or some combination of these problems. Read the rest of this entry »
Fibrositis (also called fibromyalgia) affects about 3–10% of the population, making it one of the most common rheumatic syndromes in general medicine. It shares many features with the chronic fatigue syndrome, namely, an increased frequency among women aged 20–50, absence of objective findings, and absence of diagnostic laboratory tests. While many of the clinical features of the two conditions overlap, musculoskeletal pain predominates in fibrositis whereas lassitude dominates the chronic fatigue syndrome.
The cause is unknown, but sleep disorders, depression, viral infections, and aberrant perception of normal stimuli have all been proposed. Fibrositis can be a complication of hypothyroidism, rheumatoid arthritis, or, in men, sleep apnea.
The patient complains of chronic aching pain and stiffness, frequently involving the entire body but with prominence of pain around the neck, shoulders, low back, and hips. Fatigue, sleep disorders, subjective numbness, chronic headaches, and irritable bowel symptoms are common. The patient feels incapable of performing normal activities, and even minor exertion aggravates pain and increases fatigue. Patients occasionally trace the onset of symptoms to an acute event or viral-like illness. Physical examination is normal except for “trigger points” of pain produced by palpation of various areas such as the trapezius, the medial fat pad of the knee, and the lateral epicondyle of the elbow. Read the rest of this entry »
Multiple sclerosis is initially characterized by weakness, numbness, tingling, or unsteadiness in a limb; spastic paraparesis may follow. This common neurologic disorder of unknown cause has its greatest incidence in young adults.
Epidemiologic studies indicate that multiple sclerosis is much more common in persons of western European lineage who live in temperate zones. No population with a high risk for multiple sclerosis exists between latitudes 40 °N and 40 °S.
Genetic, dietary, and climatic factors cannot account for these differences. There may be a familial incidence of the disease, since affected relatives are sometimes reported. The strong association between multiple sclerosis and specific HLA antigens (HLA-DR2) provides support for a theory of genetic predisposition. Many believe that the disease has an immunologic basis. Pathologically, Focal-often perivenular-areas of demyelination with reactive gliosis are found scattered in the white matter of brain and spinal cord and in the optic nerves.
A. Symptoms and Signs: The common initial presentation is weakness, numbness, tingling, or unsteadiness in a limb; spastic paraparesis; retrobulbar neuritis; diplopia; disequilibrium; or a sphincter disturbance such as urinary urgency or hesitancy. Symptoms may disappear after a few days or weeks, although examination often reveals a residual deficit.
In most patients, there is an interval of months or years after the initial episode before new symptoms develop or the original ones recur. Eventually, however, relapses and usually incomplete remissions lead to increasing disability, with weakness, spasticity, and ataxia of the limbs, impaired vision, and urinary incontinence. The findings on examination at this stage commonly include optic atrophy, nystagmus, dysarthria, and pyramidal, sensory, or cerebellar deficits in some or all of the limbs. Read the rest of this entry »
The cause of benign essential tremor is uncertain, but it is sometimes inherited in an autosomal dominant manner. Tremor may begin at any age and is enhanced by emotional stress. The tremor usually involves one or both hands, the head, or the hands and head, while the legs tend to be spared. Examination reveals no other abnormalities. Ingestion of a small quantity of alcohol commonly provides remarkable but short-lived relief by an unknown mechanism.
Although the tremor may become more conspicuous with time, it generally leads to little disability, and treatment is often unnecessary. Occasionally, it interferes with manual skills and leads to impairment of handwriting. Speech may also be affected if the laryngeal muscles are involved. In such circumstances, propranolol may be helpful but will need to be continued indefinitely in daily doses of 60–240 mg. However, intermittent therapy is sometimes useful in patients whose tremor becomes exacerbated in specific predictable situations. Primidone may be helpful when propranolol is ineffective, but patients with essential tremor are often very sensitive to it. They are therefore started on 50 mg daily, and the daily dose is increased by 50 mg every 2 weeks depending on the response; a maintenance dose of 125 mg three times daily is commonly effective. Occasional patients fail to respond to these measures but are helped by alprazolam (up to 3 mg daily in divided doses).