Oculomotor palsy refers to the paralysis (paresis) of the so-called oculomotor nerve (III cranial nerve). Oculomotor palsy is one of the cranial nerve disorders and is an extremely rare condition. It occurs with approximately equal frequency in both sexes.
What is oculomotor nerve palsy?
The oculomotor nerve innervates a large proportion of the external eye muscles via motor fibers and, in addition, two-thirds of the internal eye muscles. For this reason, oculomotor nerve dysfunction can cause very complex impairments in ocular motility as well as perceptual ability, depending on its location and extent. Depending on which muscles the paresis affects, a distinction is made between internal and external oculomotor nerve paresis. The latter may appear in the form of unilateral or bilateral paralysis. Also, it may be centrally located in the nucleus or peripherally located. In addition, oculomotor palsy may be partial or complete and may occur in combination with other paralyses of the eye muscles.
Causes
The causes of oculomotor nerve damage can vary widely. In many cases, supranuclear disorders must be considered for impairments in the area of the nucleus (nucleus nervi oculomotorii in medical terms). These include, for example, tumors in the brain stem, circulatory disorders or aneurysms. Damage in the peripheral course can also be caused by compression mechanisms, space-occupying processes or trauma. This can be the case, for example, in the so-called clivus edge syndrome. Oculomotor nerve palsy is often a concomitant symptom of a more pronounced disease complex, such as Nothnagel syndrome, Weber syndrome or Benedikt syndrome. In addition, in many cases there are combination disorders with simultaneous involvement of other cranial nerves, which also participate in the innervation of the external eye muscles. This can be the case in the so-called sinus cavernosus syndrome. In this case, combined paralysis of the oculomotor nerve and the abducens nerve can be diagnosed with some degree of certainty. On the other hand, a simultaneous disturbance of the trochlear nerve, for example, is less easy to detect and is therefore more easily overlooked. Oculomotor nerve palsy also occurs with increased frequency in association with diabetes mellitus.
Symptoms, complaints, and signs
The most important symptoms of oculomotor palsy include a wide, light-rigid pupil or so-called absolute pupillary rigidity. The ability to optically adjust the near (accommodation of the eye) is also limited. In the presence of an isolated, internal oculomotor palsy, in which the external eye muscles are not involved, the disease is called ophthalmoplegia interna. In addition, two forms of oculomotor palsy are differentiated, each with respect to its symptoms. The symptoms of complete oculomotor palsy are characterized by the total loss of the corresponding eye muscles. They manifest themselves in a disturbance of accommodation as well as pupillary reaction and mydriasis (dilatation of the pupil) as well as ptosis (drooping of the eyelid). In addition, the affected eye is directed outward and downward. The second form of oculomotor palsy is partial paresis of the oculomotor nerve. This is further differentiated into an internal and an external paresis. In the external paresis, the oculomotor nerve is paralyzed, which results in a disturbance of the mobility of the external eye muscles. Again, the eye is directed downward as well as outward. The internal paresis of the oculomotor nerve is manifested by a disturbance of accommodation as well as the appearance of mydriasis. However, no ocular malposition appears in this case.
Diagnosis and course of the disease
Many different diagnostic tools can be used in the diagnosis of ocular muscle paralysis. As part of the diagnosis of oculomotor palsy, checking the direction of gaze is of great importance. In this procedure, simple measures are used to check the patient’s ability to follow the eight directions of gaze. The patient is usually asked to follow the doctor’s moving finger with his eyes and at the same time to keep his head motionless.Instead of the finger, the test can also be performed using a pen or rod. If one of the directions of gaze is not possible, the affected impaired eye muscle and the respective impaired nerve can be inferred.
Complications
Oculomotor palsy affects the paired oculomotor nerve, also known as the third cranial nerve or eye movement nerve. Because the nerve provides motor control to several external and two internal eye muscles as well as the eyelid elevator, failure or partial failure of the motor fibers results in complex loss of eye and eyelid movement. Expected complications with or without treatment depend largely on the causative factors and whether oculomotor palsy occurs in isolation or together with other conditions. Most commonly, oculomotor palsy occurs due to compression of the oculomotor nerve. Such compression can be caused by space-occupying processes such as growing tumors or aneurysms that press on the nerve. Another causative factor may be a deficient supply to the nerve because the supplying vessels are arteriosclerotically narrowed or blood flow is disturbed for other reasons. An exact diagnosis of the factors that have caused the paresis or partial paresis of the nerve is of elementary importance in order to provide targeted treatment as early as possible. If left untreated, the prognosis can lead to immediately life-threatening complications in the case of a malignant tumor or an aneurysm in one of the supplying vessels. Even after a treatment that could eliminate the causative factor, a prognosis about healing chances or about further occurring complications is hardly possible. The extent to which the eye movement nerve has already been irreversibly damaged cannot be predicted with certainty beforehand.
When should one go to the doctor?
Abnormalities of the eye as well as vision should be examined by a physician. If the affected person cannot see objects or people in the immediate vicinity sharply, action is required. A doctor must be consulted so that a causal investigation can be initiated by means of various tests. Rigidity of the pupil is characteristic of oculomotor palsy and must be examined. If the eye muscles cannot be moved and coordinated sufficiently and according to one’s own will, a visit to the doctor is necessary. In case of an optical change of the eye, a drooping eyelid or a malposition of the eye, a doctor must be consulted. If there is an increased risk of accidents or falls due to the complaints, a restructuring of everyday life must take place. There is a risk of complications, which should be avoided by increased safety. A medical professional should be consulted to ensure that the person affected is sufficiently informed about his or her state of health and the corresponding consequences. If psychological problems arise in addition to the physical limitations, a doctor is also needed. If there is persistent stress, feelings of anxiety, an inner restlessness or insecurities, a doctor should be consulted. If there are behavioral changes or a depressive mood, the affected person needs help. If existing complaints increase in intensity or if further irregularities occur, medical support should be sought to improve the quality of life.
Treatment and therapy
Because it is a neurologic disorder, therapy must be provided by a neurologist after the cause has been determined. In oculomotor nerve palsies in which the trigger is tumor, trauma, or aneurysm, the prognosis is unfavorable in many cases. During the regeneration process, malinnervation often occurs. On the other hand, the chances of recovery are more positive when circulatory disorders are the cause. If the situation has not improved noticeably after approximately one year, strabismus surgery may be necessary. The aim of this surgical intervention is to shift the field of single vision to its original position without the use of head restraints and possibly to enlarge it. Depending on the findings, priority is given to operating on the affected muscles. In the case of only mild paresis, the fitting of prismatic lenses may improve the situation of the affected patient.
Outlook and prognosis
In internal or external oculomotor palsy, the prognosis depends largely on what the underlying condition is.Oculomotor nerve palsy can lead to complex disorders in the ability to see. The damage is unilateral or bilateral to the eye muscles. Such damage is triggered by compression pressure from space-occupying brain tumors. In addition, diabetes mellitus, trauma, aneurysms or other diseases affecting the brain and eye muscles can be triggers. The degree and extent of oculomotor nerve palsy is critical to the prognosis. If the effect is unilateral, the outlook is better than if it is bilateral. However, the decisive factor is whether and how successfully the causative disease can be treated. The prognosis is poor if the trigger is trauma, tumor, or aneurysm. This can lead to nerve damage with far-reaching consequences for the ability to see. The outlook is better if the trigger is a treatable circulatory disorder. If the strabismus associated with oculomotor palsy has not improved sufficiently after one year, it can be corrected surgically. In this case, single vision is improved so that there is no forced head posture. The field of vision should be widened again. In the case of mildly pronounced paresis, the prognosis can be improved by fitting prism glasses.
Prevention
There are no direct measures to prevent oculomotor nerve palsy. It is of all the more importance to consult a physician immediately if symptoms and disturbances of the visual apparatus occur. This is especially essential because oculomotor palsy can also indicate serious diseases such as brain tumors.
Follow-up
In most cases of oculomotor palsy, the patient has only a few and limited measures of follow-up care available. In this regard, the affected person should primarily see a physician early on to avoid complications or other complaints in the further course that could reduce the patient’s quality of life. Therefore, a doctor should be contacted at the first symptoms and signs of the disease in order to prevent the occurrence of further complaints. Most of the affected persons are dependent on a surgical intervention, by which the complaints can be permanently alleviated. After such an operation, patients should refrain from exertion and from stressful or physical activities. In many cases, the support and help of the patient’s own family is necessary to prevent the development of depression or psychological upsets. The further course of the oculomotor palsy depends strongly on the time of the diagnosis, so that a general course cannot be given thereby as a rule. Under certain circumstances, the life expectancy of the affected person is also reduced by this disease.
What you can do yourself
Oculomotor palsy can impair the ability to react in certain everyday situations, which is why patients should see a doctor in good time. If the eye can no longer see in all directions of gaze, it may be due to a deficiency in the supply to the affected nerve. A healthy lifestyle helps against arteriosclerotic constriction or other circulatory disorders. However, it takes a while to see improvement. If those affected have problems correctly recognizing their immediate surroundings, the risk of accidents increases significantly. Patients should therefore learn to assess their visual performance correctly themselves and prefer to be a little more cautious. By making certain adjustments in everyday life, falls and other accidents can be avoided. In addition, the doctor helps to clarify sensible safety measures. In this way, the physical impairments do not automatically lead to mental problems. If stress increases due to oculomotor palsy, depressive moods or inner restlessness may result. If circulatory disorders are the cause of the disease, the chances of recovery look quite good. It is more difficult if the oculomotor paresis is caused by a tumor, an aneurysm or a trauma. It is therefore all the more important that patients follow all the recommendations of the medical profession.
