Advices for Life

Latest

November 30, 2016 00:17

A study of the cranial nerves .III, IV, VI pairs : oculomotor , trochlear and abducens

oculomotor nerve contains motor fibers that innervate the medial upper and lower rectus muscles of the eyeball, the lower oblique muscle and the muscle that lifts the upper eyelid, and autonomic fibers that are interrupted in the ciliary ganglion innervate inner smooth muscles of the eye - sphincterpupil and ciliary muscle.Trochlear nerve innervates the upper oblique muscle, and abducens - external rectus muscle of the eyeball.

When collecting history trying to find out whether the patient has diplopia and, if present, as the items are located doublemindedness - horizontally (pathology pair VI), vertically (pathology pair III) or when looking down (defeat IV pairs).Monocular diplopia possible with intraocular pathology, leading to a dispersion of the light rays on the retina (for astigmatism, corneal diseases, starting with cataract, vitreous hemorrhage) as well as in hysteria;with paresis external (striated) muscles of the eye monocular diplopia does not happen.Feeling shake imaginary objects (oscill

opsia) is possible with vestibular disease and some forms of nystagmus.

movements of the eyeballs and their research

There are two forms of friendly movements of the eyeballs - conjugated (eyes), in which the eyeballs turn simultaneously in the same direction;and Vergence or diskonyugirovannye in which the eyeballs are both moving in opposite directions (convergence or divergence).

When neurological disorders observed four basic types of oculomotor disorders.

  • misalignment movements of the eyeballs due to weakness or paralysis of one or more eyes striated muscle;The result is a squint (strabismus) and ghosting due to the fact that the object is projected in the right and in the left eye than a similar, but on the disparity of retinal areas.
  • Friendly violation conjugated movements of the eyeballs, or friendly gaze palsy: both eyeballs in unison (together) are no longer freely move in either direction (left, right, up or down);in both eyes deficits reveal the same movements and at the same time doubling the squint does not arise.
  • combination of eye muscle paralysis and paralysis of the eye.
  • spontaneous abnormal eye movement occurring mainly in patients in a coma.

Other options oculomotor disorders (strabismus friendly, internuclear ophthalmoplegia) observed less frequently.These neurological disorders should be distinguished from congenital imbalance of eye muscle tone (non-paralytic strabismus congenital or non-paralytic strabismus, oftoforiya), in which the misalignment of the optical axes of the eyeballs were observed for both the eye movements in all directions and at rest.Often watch hidden non-paralytic strabismus, in which images can not get on identical retinal space, but this defect is compensated by corrective reflex movements hidden squinting eyes (fusional movement).When exhaustion, mental stress or other reasons fusional movement can be weakened, and the hidden becomes manifest strabismus;in this case, there is a doubling in the absence of paresis of the external eye muscles.

rank parallel to the optical axis, strabismus and diplopia analysis

doctor is in front of the patient and asks him to look straight away and fixing eyes on the remote object.Normally in this case the pupils of both eyes should be at the center of the optic fissure.Deviation of the axis of one of the eyeballs inwards (esotropia) or outward (exotropia) when viewed straight away and shows that the eyeballs are not parallel to the axis (strabismus), and that this is due to double vision (diplopia).To detect a slight strabismus can use the following method: holding the light source (eg a light bulb) at a distance of 1 m from the patient on his eye level, follow the symmetry of reflection light from the irises.In the eye, the axis of which is rejected, the reflection does not coincide with the center of the pupil.

patient then offer to fix on an object that is at the level of his eyes (pen, own thumb), and then close one by one, then the other eye.If the closing of the "normal" eyes squinting eye makes an additional motion to save the fixation on the subject ( "alignment movement"), then most likely, the patient congenital strabismus, rather than paralysis of the eye muscles.When congenital strabismus movement of each of the eyeballs, if tested separately, stored and executed in full.

Evaluate the performance of the smooth pursuit test.Ask the eyes of the patient (without turning his head) follow the subject, held at a distance of 1 meter from his face and slowly move it horizontally to the right, then to the left, then on each side up and down (the trajectory of the doctor motions in the air must comply with the letter "H").Keep an eye on the movements of the eyeballs in six directions: left, right, up and down with eyeballs leads in turn to both sides.Interest does not appear if the patient has double vision when looking in one direction or another.In the presence of diplopia find out when moving in which direction a doubling increases.If placed in front of one eye color (red) glass, the patient with diplopia easier to distinguish between the double image, and the doctor to find out which image belongs to any eye.

Light paresis of the outer muscles of the eye does not give a noticeable squint, but subjectively the patient has diplopia occurs.Sometimes the doctor is enough to report the patient about ghosting occurs when one or another movement to determine which eye muscle is affected.Almost all cases of the newly formed double vision caused by acquired paresis or paralysis of one or more striated (outer, extraocular) muscles of the eye.As a rule, any newly arising paresis of the extraocular muscles causes diplopia.Over time, the visual perception on the affected side is braked, and at the same time doubling passes.There are two basic rules that need to be taken into account by analyzing patient complaints of diplopia to determine which of the muscles of the eye suffers:

  • distance between the two images increases when viewed in the direction of the paretic muscles;
  • image created with an eye paralyzed muscle, the patient seems more peripherally located, that is more remote from the neutral position.

In particular, you can ask the patient, which intensifies diplopia when looking to the left, look at an object on the left and ask him which of the image disappears when the doctor closes the right hand of the patient eye.If the picture disappears, located closer to the neutral position, this means that for peripheral image "responsible" open left eye, and therefore muscle is defective.Because ghosting occurs when you look left paralyzed lateral rectus of the left eye.

Full trunk of the oculomotor nerve damage leading to diplopia in the vertical and horizontal plane as a result of the weakness of the upper, lower and medial rectus muscles of the eyeball.In addition, the complete paralysis of the nerve on the affected side there are ptosis (muscle weakness, lifting the upper eyelid), the deviation of the eyeball outwards and slightly downwards (due to the action of intact lateral rectus muscle innervated by the abducens, and superior oblique muscles innervated pathetic), mydriasis and loss of its reaction to light (paralysis of the sphincter of the pupil).

defeat abducens palsy causes lateral rectus muscle and consequently the medial deviation of the eyeball (esotropia).When viewed in the direction of destruction occurs ghosting across.Thus, diplopia horizontally without ptosis and a change accompanied pupillary reactions, often indicates lesion VI pair.If the lesion is located in the brain stem, in addition to the paralysis of the lateral rectus muscle, as occurs paralysis of horizontal gaze.

Defeat block nerve causes paralysis of the superior oblique and manifest restriction of movement of the eyeball down and complaining of a vertical double vision, which is the most pronounced when you look down and to the opposite side of the hearth.Diplopia adjusted inclination of the head-to-shoulder on the healthy side.

combination of paralysis of the eye muscles and paralysis of the eye indicates the defeat of the bridge structures of the brain or midbrain.Double vision, worse after physical exertion or the end of the day, typical for myasthenia gravis.

With a significant reduction of visual acuity in one or both eyes of the patient may not observe diplopia paralysis even if one or more of the extraocular muscles.

Evaluation coordinated movements of the eyeballs

gaze palsy results from supranuclear disorders, and not as a result of the defeat of III, IV or VI pairs CHN.Look (eye) in the norm is a friendly conjugated movements of the eyeballs, that is, their coordinated movements in the same direction.There are two types of conjugated movements - saccades and smooth pursuit.Saccades - very precise and fast (200 ms) phase-tonic movements of the eyeballs, which normally occur at random or look for (team "look to the right," "left, and look up", etc.), or reflexwhen a sudden visual or audible stimulus causes eye turn (usually the head) in the direction of the stimulus.Cortical control of saccades performed the frontal lobes of the contralateral hemisphere.

second type conjugated movements of the eyeballs - smooth tracking: When the subject movement, got into the field of view, eyes involuntarily fixed on him and follow him, trying to keep the image of the object in the zone of the most clear vision, that is, in the field of yellow spots.These movements of the eyeballs slower compared to saccades and compared them to a greater extent involuntary (reflex).Cortical their control is the parietal lobes of the ipsilateral hemisphere.

Violations sight (unless struck nucleus III, IV or VI pairs) are not accompanied by violation of the isolated movements of each of the eyeball individually and do not cause diplopia.In the study of sight is necessary to find out whether the patient nystagmus, which is detected by a smooth tracking test.Normally the eyeballs when following a moving object smoothly and friendly.The emergence of jerky twitching of the eyeballs (involuntary corrective saccade) constitutes a violation of the capacity for smooth tracking (subject immediately disappears from the best vision and sought again with corrective eye movements).Check the patient's ability to keep the eyes in the end position when viewed in different directions: left, right, up and down.Pay attention, does not arise whether a patient with abduction eyes from middle position induced gaze nystagmus, ie,nystagmus that changes direction depending on the direction of gaze.Fast phase induced nystagmus gaze directed toward the eye (when viewed from the left fast nystagmus component directed to the left, when viewed from the right - to the right, when looking up - straight up, looking down - vertically downwards).Violation of the ability to smooth the appearance of tracking and gaze nystagmus induced lesions are signs of cerebellar connections with the neurons of the brain stem or central vestibular connections, and can also be the result of side effects of anti-convulsant, tranquilizers and other drugs.When the lesion in the occipital-parietal region, regardless of the presence or absence of hemianopsia, reflex slow tracking eye movements in the direction of the lesion is limited or impossible, but the random motion and the motion are stored (ie, the patient can perform voluntary movements eyes in all directions,but can not follow the object moving in the direction of the lesion).Slow down, fragmented, dismetrichnye tracking movements observed at supranuclear palsy and other extrapyramidal disorders.

To check the voluntary movements of the eyeballs and saccades asking the patient to look left, right, up and down.Estimate the time required to start the movement, accuracy, speed and fluidity (often a sign of dysfunction detected light friendly movements of the eyeballs in the form of "tripping").Then the patient is asked to fix the eye alternately on the tips of the two index fingers, which are arranged at a distance of 60 cm from the patient's face, and approximately 30 cm apart.Evaluate the accuracy and speed of arbitrary movements of the eyeballs.

saccadic dysmetria in which an arbitrary gaze accompanied by a series of jerky jerky eye movements, typical for the defeat relations of the cerebellum, although it can also occur in the pathology of the occipital and parietal lobe of the brain - in other words, the inability to overtake the purpose eye (gipometriya) or "overshoot" gazethrough the target due to excessive amplitude movements of the eyeballs (hypermetric), modifiable using saccades, indicate a deficit koordinatornyh control.Marked slowness of saccades can be observed in diseases such as hepatolenticular dystrophy or Huntington's chorea.Acutely arisen frontal lobe damage (stroke, traumatic brain injury, infection) is accompanied by paralysis of horizontal gaze to the opposite side of the hearth.Both eyeballs and head turned down towards the lesion (patient 'looks at home "and turns away from the paralyzed limbs) due to the preserved functions opposite the center of rotation of the head and eyes to the side.This symptom is temporary and lasts only a few days, as soon compensated imbalance sight.The ability to reflex tracking with frontal gaze palsy may persist.Paralysis of the eye horizontally with the defeat of the frontal lobe (cortex and internal capsule) is usually accompanied by hemiparesis or hemiplegia.With the localization of the pathological focus in the area of ​​the midbrain roof (pretectal damage involving epithalamus part of the posterior commissure of the brain) develops vertical gaze palsy, combined with the violation of convergence (Parinaud syndrome);more usually suffers gaze upwards.If it affects the brain of the bridge and the medial longitudinal fasciculus, providing this level lateral friendly eye movement, there is a paralysis of the eye horizontally in the direction of the hearth (eye laid in the opposite hearth side of the patient "turned away" from the brainstem lesion and looks at the paralyzed limb).Such a gaze palsy usually persists for a long time.

rank diskonyugirovannyh movements of the eyeballs (convergence, divergence)

Convergence check by asking the patient to focus on an object that is moving in the direction of his eyes.For example, offer to fix the patient look at the tip of the hammer or the index finger, which the doctor brings gradually to the bridge of his nose.When an object approaches to the bridge axis is normal both eyeballs are rotated in the direction of the subject.At the same time narrowing the pupil, ciliary (ciliary) muscle relaxes, and the lens becomes convex.With this object image is focused on the retina.Such a reaction in the form of convergence, pupillary constriction and accommodation is sometimes called accommodative triad.Divergence - the reverse process: when you delete an object the pupil expands and causes the contraction of the ciliary muscle flattening lens.

If convergence or divergence is broken, there is a horizontal diplopia when looking at nearby objects or deleted accordingly.

Convergence Paralysis occurs in lesions pretectal area of ​​the midbrain at the level of the roof of the upper hills quadrigemina plate.It can be combined with paralysis of gaze up at Parinaud syndrome.Paralysis of divergence is usually caused by bilateral lesions VI pairs of cranial nerves.