Muscle extraocular

Thyroid-associated ophthalmopathy (TAO) is present in 90% of patients with the classical triad of Graves disease (goiter, ophthalmopathy, dermopathy) but these features may follow independent courses and successful control of the hyperthyroidism improves TAO in less than 5% cases. Immunosuppression has been used since theories of the etiology of TAO include the presence of circulating antibodies to both thyroid and ocular muscle fibers, and of thyroglobulin-antithy-roglobulin complexes with high affinity for extraocular muscles. 

The childhood- and adult-onset forms of AMD cause signs and symptoms that are limited to the musculature, with progressive weakness of truncal muscles and of proximal, more than distal, limb muscles, usually sparing facial and extraocular muscles. In the childhood form, onset is in infancy or childhood and progression tends to be rapid. In the adult form, onset is usually in the third or fourth decade but occasionally even later and the course is slower [7]. 

Muscle makes up 40-50% of body mass. It is the tissue which allows one to move the limbs, which is utilized in articulating the joints of the skeleton. On closer examination all the muscles in the human body show biochemical specialization allowing them to perform their particular physiological functions the muscles in the back and buttocks evolved for continuous heavy lifting where fuel economy is important. The eyeballs are steered by extraocular muscles when reading they must contract quickly and precisely. The hollow viscera often require a slow steady squeeze to function properly. The heart muscle must provide continuous circulation of blood for transport of oxygen and nutritive substances. The different muscles in the body can be divided in three main types, which are described in the following. 

Only in a few muscle types (e.g., extraocular muscle) are muscle fibers supplied with multiple endplates. Here succinylcholine causes depolarization distributed over the entire fiber, which responds with a contracture. Intraocular pressure rises, which must be taken into account during eye surgery. 

Primary axillary hyperhidrosis Adverse events (in at least 3% of patients) included injection site pain and hemorrhage, nonaxillary sweating, infection, pharyngitis, flu syndrome, headache, fever, neck or back pain, pruritus, and anxiety. Blepharospasm The most frequently reported treatment-related adverse reactions were ptosis (20.8%), superficial punctate keratitis (6.3%), and eye dryness (6.3%). Strabismus Extraocular muscles adjacent to the injection site can be affected, causing ptosis, vertical deviation, spatial disorientation, double vision, or past-pointing, especially with higher doses of botulinum toxin type A. 

Succinylcholine produces muscle fasciculation, which may result in myoglobinuria and postoperative muscle pain. The amount produced depends on the level of physical fitness. Succinylcholine causes contractions of extraocular muscles, posing the danger of transient elevated intraocular pressure. Succinylcholine may produce hyperkalemia in patients with large masses of traumatized or denervated muscle (e.g., spinal cord injury). Denervated muscle is especially sensitive to depolarizing drugs because of the increased number of AChRs on the sarcolemma (denervation supersensitivity). Succinylcholine also causes prolonged contraction of the diseased muscles of patients with myotonia or amyotrophic lateral sclerosis. 

The most common forms of EPS that occur early in the course of treatment include acute dystonic reactions (ADRs), drug-induced Parkinsonism, and akathisia. The ADRs are involuntary muscle spasms or contractions. An ADR typically involves muscles in the neck and/or the extraocular muscles, and can be painful and... 

The sclera is the outer white tough part of the eye, which is an important structural element, with the site of insertion of extraocular muscles. It covers 80% of the exterior surface and is white and nontransparent. It borders the transparent cornea at the pars planar. The sclera is divided into three layers episclera, stroma, and lamina fusca. Only a limited number of blood vessels, originating from arteriolar branches of the anterior ciliary vessels, are found and superficial vessels are mainly confined to the loose outer episclera. Scleral permeability approximates that of the corneal stroma and has been shown to be permeable to solutes up to 70 kDa in molecular weight [14]. 

Reverse transcriptase Saccade Enzyme that forms complementary DNA (cDNA). Abrupt, high velocity eye movement produced by a precisely timed pattern of activity in the motor neurons innervating the extraocular muscles. 

Physical exam reveals exophthalmos (abnormal protrusion of the eyeball) with weakened extraocular muscles (Figure A.6). Her skin was warm and moist... 

The most common feature of this syndrome includes uncontrollable tightening of the face and neck, and spasm and distortions of the patient s head and/or back (i.e., opisthotonos). If the extraocular muscles are involved, an oculogyric crisis may occur, wherein the eyes are elevated and locked in this position. Laryngeal involvement [spasm] may lead to respiratory and ventilatory difficulties. These reactions are often terrifying to the patient who has no prior experience with these problems or knowledge of this side effect. When a patient with psychosis experiences a dystonic reaction, the fragile trust developed between psychiatrist and patient may be irrevocably damaged, (pp. 909-910)... 

In a study in Rhesus monkeys, retrobulbar administration of local anesthetics resulted in a low incidence of muscle fiber lesions in the extraocular muscles closest to the site of injection. Most lesions resulted in the degeneration and regeneration of muscle fibers on the surface of the muscles, but occasionally a massive internal lesion was seen. 

Carabot EL, Amaro IP, Villalobos RR et al. (1988) Effects of mepivacaine on the microcirculation of the rat skeletal muscle. Acta Toxicol Ther 9 309-319 Carlson BM, Rainin EA (1985) Rat extraocular muscle regeneration. Repair of local anesthetic-induced damage. Arch Ophthalmol 103 1373-1377... 

Komorowski TE, Shepard B, Okland S, Carlson BM (1990) An electron microscopic study of local anesthetic-induced skeletal muscle fiber degeneration and regeneration in the monkey. J Orthop Res 8 495-503 Luduena FP, Hoppe JO, Coulston F, Drobeck HP (1960) The pharmacology and toxicology of mepivacaine, a new local anesthetic. Toxicol Appl Pharmacol 2 295-315 Okland S, Komorowski TE, Carlson BM (1989) Ultrastructure of mepivacaine-induced damage and regeneration of rat extraocular muscle. Invest Ophthalmol Vis Sci 30 1643-1651... 

Other effects on the visual system attributed to lithium include reduced accommodation, exophthalmos, extraocular muscle abnormalities, nystagmus (most characteristically downbeat), oscillopsia, photophobia, and papilledema with visual impairment (pseudotumor cerebri) (201). 

A man in his late twenties, with a several-year history of intravenous heroin use, developed diplopia after he had received single doses of chlorpromazine 100 mg and ibuprofen 400 mg for anxiety (202). There was no extraocular muscle paresis and neurological examination was unremarkable. The diplopia resolved after 6-8 hours. 

Transient reduction in visual acuity Extraocular muscle palsies Ptosis... 

If, however, the patient exhibits only a unilateral fixed and dilated pupil without evidence of ptosis or extraocular muscle involvement, the clinician should perform the pilocarpine test, first using a 0.125% solution to reveal any cholinergic hypersensitivity as evidence for Adie s pupil. If there is no local iris damage by slit-lamp examination, no sector palsy of the iris sphincter, and no cholinergic hypersensitivity demonstrated by the 0.125% pilocarpine test, then the condition might be associated with interruption of the preganglionic innervation to the iris sphincter (i.e., third-nerve palsy). If the patient has third-nerve palsy, topically instilled pilocarpine in moderate concentrations activates the muscarinic receptor sites on the iris sphincter. Therefore if 0.125% pilocarpine reveals no cholinergic hypersensitivity, the practitioner... 

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