Nerve Block: From 3 Different Sources
The injection of a local anaesthetic around a nerve to produce loss of sensation in a part of the body supplied by that nerve. For example, the palm of the hand may be anaesthetized by giving injections at sites up the arm, blocking the ulnar and median nerves.
A nerve may be blocked as it leaves the spinal cord. This occurs in epidural anaesthesia, used mainly in childbirth, and in spinal anaesthesia, used mainly for surgery of the lower abdomen and limbs. In a caudal block an anaesthetic is injected around nerves leaving the lowest part of the spinal cord. It produces anaesthesia in the buttock and genital areas, and is occasionally used in childbirth. A pudendal nerve block involves the injection of an anaesthetic into nerves passing under the pelvis into the floor of the vagina. This type of nerve block is sometimes used in a forceps delivery. (See also anaesthesia, local.)
See ANAESTHESIA – Local anaesthetics.
a method of producing *anaesthesia in part of the body by blocking the passage of pain impulses in the sensory nerves supplying it. A local anaesthetic, such as lidocaine, is injected into the tissues in the region of a nerve. In this way anaesthesia can be localized, so that minor operations can be performed without the necessity of giving a general anaesthetic. A *ring block is a common technique used for anaesthetizing a digit.
See VESTIBULOCOCHLEAR NERVE.... auditory nerve
Drugs used to slow the response to epinephrine (released by the adrenal medulla), usually to attempt controlling high blood pressure... beta blockers
An abnormality of the conduction of electrical impulses through the ventricles of the HEART, resulting in delayed depolarisation of the ventricular muscle. The electrocardiograph (see ELECTROCARDIOGRAM (ECG)) shows characteristic widening of the QRS complexes. Abnormalities of the right and left bundle branches cause delayed contraction of the right and left ventricles respectively.... bundle branch block
The seventh cranial nerve (arising from the BRAIN), supplying the muscles of expression in the face, being purely a motor nerve. It enters the face immediately below the ear after splitting up into several branches. (See BELL’S PALSY.)... facial nerve
The 12th cranial nerve, which supplies the muscles of the tongue, together with some others lying near it. This nerve is responsible for movements required for swallowing and talking. (See also NERVOUS SYSTEM.)... hypoglossal nerve
This NERVE arises from the BRACHIAL plexus in the axilla. At ?rst descending posteriorly and then anteriorly, it ends just above the elbow by dividing into the super?cial radial and interosseous nerves. It supplies motor function to the muscles which extend the arm, wrist, and some ?ngers, and supplies sensation to parts of the posterior and lateral aspects of the arm, forearm and hand.... radial nerve
The ?fth cranial nerve (arising from the BRAIN). It consists of three divisions: (1) the ophthalmic nerve, which is purely sensory in function, being distributed mainly over the forehead and front part of the scalp; (2) the maxillary nerve, which is also sensory and distributed to the skin of the cheek, the mucous membrane of the mouth and throat, and the upper teeth; and (3) the mandibular nerve, which is the nerve of sensation to the lower part of the face, the tongue and the lower teeth, as well as being the motor nerve to the muscles concerned in chewing. The trigeminal nerve is of special interest, owing to its liability to NEURALGIA – TRIGEMINAL NEURALGIA, or tic douloureux as it is also known, being the most painful form known.... trigeminal nerve
The fourth cranial nerve (arising from the BRAIN), which acts upon the superior oblique muscle of the EYE.... trochlear nerve
A major NERVE in the arm, it runs from the brachial plexus to the hand. The nerve controls the muscles that move the ?ngers and thumb and conveys sensation from the ?fth and part of the fourth and from the adjacent palm. Muscle weakness and numbness in the areas supplied by the nerve is usually caused by pressure from an abnormal outgrowth from the epicondyle at the bottom of the humerus (upper-arm bone).... ulnar nerve
Also called the pneumogastric nerve, this is the tenth cranial nerve, with many fibers leading to parasympathetic ganglia in internal organs, and can be considered the presynapse starter for the upper parts of the parasympathetic functions.... vagus nerve
The eighth cranial nerve. It consists of two sets of ?bres, which constitute two separate nerves. One is known as the vestibular nerve, which connects the semicircular canals and inner ear to the BRAIN and conveys information on posture and movement of the body; it is the nerve of equilibration or balance. The other is known as the cochlear nerve, which links the COCHLEA (organ that responds to sounds) with the brain and is the nerve of hearing. Disturbance of the former causes giddiness (VERTIGO), whilst disturbance of the latter causes DEAFNESS.... vestibulocochlear nerve
This is the sixth nerve rising from the brain and controls the external rectus muscle of the EYE, which turns the eye outwards. It is particularly liable to be paralysed in diseases of the nervous system, thus leading to an inward squint.... abducent nerve
A branch of the ophthalmic nerve supplying the lacrimal gland and conjunctiva of the EYE.... lacrimal nerve
See NEURON(E).... nerve cell
The NERVE which chie?y supplies the DIAPHRAGM. A phrenic nerve arises on each side of the SPINAL CORD from the third, fourth and ?fth cervical spinal nerves; both follow a long course down the neck, and through the chest to the diaphragm. They play a key part in RESPIRATION through control of the diaphragm. Injury to one nerve paralyses one half of the diaphragm. Occasionally the phrenic nerve may be surgically crushed as part of the treatment to repair a HIATUS HERNIA or, rarely, to stop intractable hiccups.... phrenic nerve
The nerve that operates the lowest muscles of the ?oor of the PELVIS and also the anal SPHINCTER muscle. It may be damaged in childbirth, resulting in INCONTINENCE.... pudendal nerve
A local anaesthetic agent (see ANAESTHESIA) injected into the circumference of the base of a digit. It numbs the nerves of the ?nger or toe and so permits minor surgery to be performed. Care must be taken to avoid damage to local blood vessels which can lead to GANGRENE.... ring block
The 11th cranial nerve. Unlike the other cranial nerves, most of the accessory nerve originates from the spinal cord. The small part of the nerve that originates from the brain supplies many muscles of the palate, pharynx (throat), and larynx (voice box). Damage to this part of the nerve may cause difficulty in speaking and swallowing. The spinal part of the nerve supplies large muscles of the neck and back, notably the sternomastoid and trapezius. Damage to the spinal fibres of the nerve paralyses these muscles.... accessory nerve
The part of the vestibulocochlear nerve (the 8th cranial nerve) that is concerned with hearing. It is also known as the auditory nerve.... acoustic nerve
The 3rd cranial nerve, controlling most of the muscles that move the eye. The oculomotor nerve also supplies the muscle that constricts the pupil, that which raises the upper eyelid, and the ciliary muscle, which focuses the eye. The nerve may be damaged due to a fracture to the base of the skull or a tumour. Symptoms include ptosis, squint, dilation of the pupil, inability to focus the eye, double vision, and slight protrusion of the eyeball. (See also trochlear nerve; abducent nerve.)... oculomotor nerve
The first cranial nerve, which conveys sensations of smell as nerve impulses from the nose to the brain. Each of the 2 olfactory nerves has receptors in the mucous membrane lining the nasal cavity. These receptors detect smells and send signals along nerve fibres, which pass through tiny holes in the roof of the nasal cavity and combine to form the olfactory bulbs. From here, nerve fibres come together to form the olfactory nerve, leading to the olfactory centre in the brain. Sense of smell may be lost or impaired due to damage to the olfactory nerves, usually as a result of head injury.... olfactory nerve
The main nerve in each leg and the largest nerve in the body.The sciatic nerves are formed from nerve roots in the spinal cord.... sciatic nerve
See TENS.... transcutaneous electrical nerve stimulation
Also called adrenoceptor-blocking agents or alpha blockers, these drugs stop the stimulation of alpha-adrenergic receptors at the nerve endings of the SYMPATHETIC NERVOUS SYSTEM by HORMONES with ADRENALINE-like characteristics. The drugs dilate the arteries, causing a fall in blood pressure, so they are used to treat HYPERTENSION and also benign enlargement of the PROSTATE GLAND. Examples of this group of drugs are doxazosin, indoramin, phentolamine and prazosin. The drugs should be used with caution as some may cause a severe drop in blood pressure when ?rst taken.... alpha adrenergic blockers
See BELL’S PALSY.... idiopathic facial nerve palsy
A method of electrical stimulation that is being used for the relief of PAIN, including that of MIGRAINE, NEURALGIA and phantom limbs (see AMPUTATION). Known as TENS, its mode of action appears to have some resemblance to that of ACUPUNCTURE. Several controlled trials suggest that it provides at least a modicum of relief of pain after operations, thereby reducing the amount of ANALGESICS that may be called for.... transcutaneous electrical nerve stimulation (tens)
See: SEDATIVE. ... nerve relaxant
A group of drugs used to treat hypertension (high blood pressure) and urinary symptoms due to enlargement of the prostate gland. Alpha-blockers are also used to treat urinary retention caused by an enlarged prostate gland (see prostate, enlarged). Side effects of the drugs may include dizziness and fatigue due to a sudden drop in blood pressure, nausea, dry mouth, and drowsiness.... alpha-blocker drugs
See nasal congestion; nasal obstruction.... blocked nose
One of a pair of nerves that carry instructions from the brain to the larynx and send sensations from the larynx to the brain.... laryngeal nerve
See nerve, trapped.... trapped nerve
the sixth *cranial nerve (VI), which supplies the lateral rectus muscle of each eyeball, responsible for turning the eye outwards.... abducens nerve
(alpha-adrenergic blocker) a drug that prevents the stimulation of alpha *adrenoceptors at the nerve endings of the sympathetic nervous system by noradrenaline and adrenaline: it therefore causes relaxation of smooth muscle, including widening of arteries (vasodilatation) and a drop in blood pressure. Alpha blockers include *doxazosin, *phentolamine, *phenoxybenzamine, *indoramin, *prazosin, *alfuzosin, and *tamsulosin.... alpha blocker
(beta-adrenergic receptor blocker) a drug that prevents stimulation of the beta *adrenoceptors at the nerve endings of the sympathetic nervous system. Blockade of ?1 receptors causes a decrease in heart rate and force; blockade of ?2 receptors causes constriction of the airways and the arteries. Beta blockers include *acebutolol, *atenolol, *bisoprolol, *oxprenolol, *propranolol, and *sotalol; they are used to control abnormal heart rhythms, to treat angina, and to reduce high blood pressure (although they are no longer regarded by some experts as the first choice of drug for treating hypertension in the absence of heart disease, being less effective than newer antihypertensive drugs). Beta blockers that block both ?1 and ?2 receptor sites cause constriction of air passages in the lungs, and these drugs should not be used in patients with asthma and bronchospasm. Other beta blockers are relatively selective for the heart (cardioselective) and are less likely to constrict the airways. Some beta blockers (e.g. *carteolol, *levobunolol, and *timolol) reduce the production of aqueous humour and therefore the pressure inside the eye; they are taken as eye drops in the treatment of *glaucoma.... beta blocker
n. any interruption of physiological or mental function, brought about intentionally (as part of a therapeutic procedure) or by disease. See also heart block; nerve block.... block
(calcium antagonist) a drug that inhibits the influx of calcium ions into cardiac and smooth-muscle cells; it therefore reduces the strength of heart-muscle contraction, reduces conduction of impulses in the heart, and causes *vasodilatation. Calcium-channel blockers, which include *amlodipine, *diltiazem, *nicardipine, *nifedipine, and *verapamil, are used to treat angina and high blood pressure.... calcium-channel blocker
a mixed sensory and motor nerve of the upper arm. It arises from the fifth and sixth cervical segments of the spinal cord and is distributed to the deltoid muscle of the shoulder and the overlying skin.... circumflex nerve
(acoustic nerve, auditory nerve) the nerve connecting the cochlea to the brain and therefore responsible for transmitting the nerve impulses relating to hearing. It forms part of the *vestibulocochlear nerve (cranial nerve VIII).... cochlear nerve
either of two nerves that supply the teeth; they are branches of the trigeminal nerve. The inferior dental nerve supplies the lower teeth and for most of its length exists as a single large bundle; thus anaesthesia of it has a widespread effect (see inferior dental block). The superior dental nerve, which supplies the upper teeth, breaks into separate branches at some distance from the teeth and it is possible to anaesthetize these individually with less widespread effect for the patient.... dental nerve
(House–Brackmann score, House–Brackmann scale, House–Brackmann facial weakness scale) a six-point grading system for patients with *Bell’s palsy or other forms of facial nerve palsy. Grade I is normal function; grade VI is a total palsy. [J. W. House and D. E. Brackmann (21st century), US otorhinolarygologists]... house–brackmann facial nerve grading system
(inferior alveolar nerve block) a type of injection to anaesthetize the inferior *dental nerve. Inferior dental block is routinely performed to allow dental procedures to be carried out on the lower teeth on one side of the mouth.... inferior dental block
(myelinated nerve fibre) see myelin.... medullated nerve fibre
one of the nerves that carry impulses outwards from the central nervous system to bring about activity in a muscle or gland. Compare sensory nerve.... motor nerve
a nerve of the *brachial plexus that supplies some muscles of the arm and the skin of the lateral part of the forearm.... musculocutaneous nerve
a test done to assess the peripheral nervous system. It involves activating the nerves electronically with electrical pulses and measuring the responses obtained.... nerve conduction study
the final part (terminal) of one of the branches of a nerve fibre, where a *neuron makes contact either with another neuron at a synapse or with a muscle or gland cell at a neuromuscular or neuroglandular junction.... nerve ending
any syndrome resulting from pressure on a nerve from surrounding structures. Examples include the *carpal tunnel syndrome and *meralgia paraesthetica.... nerve entrapment syndrome
the long fine process that extends from the cell body of a *neuron and carries nerve impulses. Bundles of nerve fibres running together form a *nerve. Each fibre has a sheath, which in medullated nerve fibres is a relatively thick layer containing the fatty insulating material *myelin.... nerve fibre
any gas that disrupts the normal functioning of nerves and thus of the muscles they supply. There are two groups, the G agents and the V agents. The latter are more than 300 times as deadly as mustard gas: one inhalation can kill by paralysing the respiratory muscles. V agents also act through the skin, therefore gas masks are ineffective protection against them.... nerve gas
(NGF) a protein (see growth factor), consisting of two polypeptide chains, that is required for the development and longevity of some neurons, including those in the sympathetic nervous system and some central nervous system and sensory neurons. Nerve growth factor is necessary for axon growth and also for initiating new neuronal connections with other cells. The role of NGFs in preventing the degeneration of brain cells is being explored in research into Alzheimer’s disease.... nerve growth factor
the electrical activity in the membrane of a *neuron that – by its rapid spread from one region to the next – is the means by which information is transmitted within the nervous system along the axons of the neurons. The membrane of a resting nerve is charged (polarized) because of the different concentrations of ions inside and outside the cell. When a nerve impulse is triggered, a wave of *depolarization spreads, and ions flow across the membrane (see action potential). Until the nerve has undergone *repolarization no further nerve impulses can pass.... nerve impulse
the growth of new nerve tissue, which occurs at a very slow rate (1–2 mm per day) after a nerve has been severed and is often partially or totally incomplete. *Microsurgery has improved the results by facilitating primary repair in the immediate aftermath of injury. See also axonotmesis; neurotmesis.... nerve regeneration
a type of squint (convergent *strabismus) that results from the use of the convergence mechanism to block or dampen down *nystagmus in an attempt to improve visual acuity.... nystagmus block syndrome
the smallest of the three branches of the *trigeminal nerve. It supplies sensory fibres to the eyeball, conjunctiva, and lacrimal gland, to a small region of the nasal mucous membrane, and to the skin of the nose, brows, and scalp.... ophthalmic nerve
a large branch of the *femoral nerve that arises in the upper thigh, travels down on the inside of the leg, and supplies the skin from the knee to below the ankle with sensory nerves.... saphenous nerve
a nerve that carries information inwards, from an outlying part of the body towards the central nervous system. Different sensory nerves convey information about temperature, pain, touch, taste, etc., to the brain. Compare motor nerve.... sensory nerve
a small subdivision of the *vestibular nerve that carries information from the posterior *semicircular canal to the brain. Singular neurectomy is a surgical procedure to divide the singular nerve, occasionally used in the treatment of *benign paroxysmal positional vertigo.... singular nerve
see accessory nerve.... spinal accessory nerve
a sudden halting of the flow of thought, usually manifested as an interruption to speech lasting for a few seconds or more; when speech resumes, it is often on an unrelated subject. Thought block is a common symptom in severe mental illness but may also arise in the context of *psychosis, severe anxiety, or depression.... thought block
any nerve, usually belonging to the autonomic nervous system, that controls the circulation of blood through blood vessels by its action on the muscle fibres within their walls or its action on the heartbeat. The *vagus nerve slows the heart and reduces its output, but sympathetic nerves increase the rate and output of the heart and increase blood pressure by causing the constriction of small blood vessels at the same time.... vasomotor nerve
the division of the *vestibulocochlear nerve that carries impulses from the semicircular canals, utricle, and saccule of the inner ear to the brain, conveying information about the body’s posture and movements in space and allowing coordination and balance.... vestibular nerve
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