An oculomotor nerve palsy refers to the paralysis (paresis) of the so-called oculomotor nerve (III. cranial nerve). The oculomotor nerve palsy is one of the cranial nerve disorders and is an extremely rare disease. It occurs in both sexes with about the same frequency.
What is oculomotor nerve palsy?
The oculomotor nerve innervates a large proportion of the extraocular muscles via motor fibers and also two-thirds of the intraocular muscles. For this reason, a disorder of the oculomotor nerve can cause very complex impairments in eye mobility and perception, depending on the location and extent. See acronymmonster for Definition of CH in English.
Depending on which muscles the paresis affects, a distinction is made between an inner and an outer oculomotor nerve palsy. This can appear in the form of unilateral or bilateral paralysis. It can also be located centrally in the core area or peripherally. In addition, the oculomotor nerve palsy can occur only partially or completely and in combination with other paralysis of the eye muscles.
Causes
The causes of damage to the oculomotor nerve can be very different. In the case of impairments in the core area (medically, the nucleus nervi oculomotorii), supranuclear disorders must be considered in many cases. These include tumors in the brainstem, circulatory disorders and aneurysms. Damage that is in the peripheral course can also be caused by compression mechanisms, space-occupying processes or trauma.
This can be the case, for example, with the so-called clivus edge syndrome. Oculomotor nerve paresis is often an accompanying symptom of a more pronounced disease complex, such as Nothnagel syndrome, Weber syndrome or Benedict syndrome. In addition, in a number of cases there are combined disorders with simultaneous involvement of other cranial nerves, which also contribute to the innervation of the outer eye muscles. This can apply, for example, to the so-called cavernous sinus syndrome.
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 is less easy to identify and is therefore more easily overlooked. Oculomotor nerve palsy also occurs with increased frequency in connection with diabetes mellitus.
Symptoms, Ailments & Signs
One of the most important symptoms of oculomotor nerve palsy is a dilated, rigid pupil or the so-called absolute pupillary rigidity. The ability to focus close-up optically (accommodation of the eye) is also only possible to a limited extent. If there is an isolated, internal oculomotor nerve palsy in which the extraocular muscles are not involved, the disease is referred to as ophthalmoplegia interna.
In addition, a distinction is made between two forms of oculomotor nerve palsy, which differ from each other in terms of their symptoms. The symptoms in the presence of a complete oculomotor nerve palsy are characterized by the total loss of the corresponding eye muscles. They manifest themselves in disturbances of accommodation and pupillary reaction, mydriasis (dilation of the pupil) and ptosis (eyelid drooping). In addition, the affected eye is directed outwards and downwards.
The second form of oculomotor nerve palsy is partial paresis of the oculomotor nerve. This is again differentiated into an inner and an outer paresis. In the context of external paresis, the oculomotor nerve is paralyzed, resulting in a mobility disorder in the external eye muscles. Again, the eye is directed downwards as well as outwards. The internal paresis of the oculomotor nerve is manifested in a disturbance of accommodation, as well as the appearance of mydriasis. In this case, however, no eye deformity occurs.
Diagnosis & course of disease
When diagnosing paralysis of the eye muscles, numerous different diagnostic tools can be used. In the context of diagnosing an oculomotor nerve palsy, checking the direction of gaze is of great importance. In this procedure, simple measures are used to test the extent to which the patient is able to follow the eight directions of vision.
The patient is usually asked to follow the moving finger of the doctor with his eyes and at the same time to keep his head motionless. Instead of the finger, the test can also be carried out using a pen or rod. If one of the viewing directions is not possible, the affected affected eye muscle and the respective disturbed nerve can be inferred.
Complications
Oculomotor nerve palsy affects the paired oculomotor nerves, also known as the third cranial nerve or eye motor nerve. Because the nerve provides a motor supply to several outer and two inner eye muscles as well as the levator of the eyelid, a failure or a partial failure of the motor fibers leads to complex loss of movement of the eyes and eyelids.
The complications that can be expected, with or without treatment, depend largely on the causative factors and whether the oculomotor nerve palsy occurs in isolation or together with other diseases. Oculomotor nerve palsy usually occurs due to compression of the oculomotor nerve. Such compressions can be caused by space-occupying processes such as growing tumors or aneurysms pressing on the nerve.
Another causative factor can be a lack of supply to the nerve because the supplying vessels are narrowed by arteriosclerosis or the blood flow is disturbed for other reasons. A precise diagnosis of the factors that caused the paresis or partial paresis of the nerve is of elementary importance in order to initiate targeted treatment as early as possible.
If left untreated, the prognosis in the case of a malignant tumor or an aneurysm in one of the supplying vessels can lead to immediately life-threatening complications. Even after treatment that has been able to eliminate the causal factor, it is almost impossible to make a prognosis about the chances of recovery or further complications. The extent to which the eye movement nerve has already been irreversibly damaged cannot be predicted with certainty in advance.
When should you go to the doctor?
Any abnormalities in the eye or vision must be examined by a doctor. If the person concerned cannot clearly see objects or people in the immediate vicinity, there is a need for action. A doctor must be consulted so that various tests can be used to investigate the cause. Pupillary rigidity is characteristic of oculomotor nerve palsy and needs to be evaluated.
If the eye muscles cannot be moved and coordinated sufficiently and according to one’s own will, a doctor’s visit is necessary. A doctor must be consulted if there are optical changes in the eye, a drooping eyelid or an eye malposition.
If the symptoms lead to an increased risk of accidents or falls, everyday life must be restructured. There is a risk of complications that should be avoided by increased safety. A doctor should be consulted so that the person concerned is sufficiently informed about their state of health and the corresponding consequences.
If psychological problems arise in addition to the physical limitations, a doctor is also required. In the event of persistent stress, feelings of anxiety, inner restlessness or insecurities, a doctor should be consulted. If there are changes in behavior or a depressive mood, the person concerned needs help. If existing symptoms increase in intensity or if further irregularities appear, medical support should be sought to improve the quality of life.
Treatment & Therapy
Since it is a neurological disorder, the therapy must be carried out by a neurologist after the cause has been clarified. In the case of oculomotor nerve palsies, which are caused by tumors, trauma or aneurysms, the prognosis is often unfavorable. During the regeneration process, false innervations often occur. On the other hand, the chances of recovery are more positive if the cause is circulatory disorders.
If the situation has not improved noticeably after about a year, a squint operation may be necessary. The aim of this surgical intervention is to shift and possibly enlarge the field of single vision to its original position without adopting a forced head position. Depending on the findings, the affected muscles are primarily operated on. In the event that the paresis is only mildly pronounced, the fitting of prism glasses can improve the situation of the affected patient.
Outlook & Forecast
With internal or external oculomotor nerve palsy, the prognosis depends to a large extent on what the underlying condition is. Oculomotor nerve palsy can lead to complex visual impairments. The damage is on one or both sides of the eye muscles. Such damage is triggered by compression pressure from extensive brain tumors. In addition, diabetes mellitus, trauma, aneurysms or other diseases that affect the brain and eye muscles can be triggers.
The extent and scope of the oculomotor nerve palsy is decisive for the prognosis. If the impact is one-sided, the prospects are better than if it is bilateral. However, the decisive factor is whether and how successfully the triggering disease can be treated. The prognosis is poor if the trigger is to be found in a trauma, a tumor or an aneurysm. This can lead to nerve damage with far-reaching consequences for vision.
The prospects are better if the trigger is a treatable circulatory disorder. If the squinting associated with oculomotor nerve palsy has not improved enough after a year, it can be corrected surgically. This improves single vision so that the head is not constrained. The field of view should be expanded again. In the case of milder paresis, the prognosis can be improved by fitting prism glasses.
Prevention
There are no direct measures to prevent oculomotor nerve palsy. It is all the more important to consult a doctor immediately if symptoms or visual disorders occur. This is particularly essential because the oculomotor nerve palsy can also indicate serious diseases such as brain tumors.
Aftercare
In most cases, patients with oculomotor nerve palsy have only a few and limited follow-up measures available. The person concerned should first and foremost consult a doctor at an early stage so that complications or other complaints that could reduce the patient’s quality of life do not occur in the further course of the disease.
Therefore, a doctor should be contacted as soon as the first symptoms and signs of the disease appear in order to prevent the occurrence of further complaints. Most of those affected are dependent on a surgical procedure, through which the symptoms can be permanently relieved. After such an operation, exertion and stressful or physical activities should be avoided.
In many cases, the support and help of one’s own family is necessary to prevent the development of depression or mental disorders. The further course of the oculomotor nerve palsy depends heavily on the time of diagnosis, so that a general course cannot usually be given. This disease can also reduce the life expectancy of those affected.
You can do that yourself
The oculomotor nerve palsy can impair the ability to react in certain everyday situations, so patients should see a doctor in good time. If the eye can no longer see in all directions, this may be due to a lack of supply to the nerve in question.
A healthy lifestyle helps against arteriosclerotic narrowing or other circulatory disorders. However, it takes a while before an improvement can be seen. If those affected have problems recognizing their immediate surroundings correctly, the risk of an accident increases significantly. Patients should therefore learn to correctly assess their visual performance themselves and rather be a little cautious. Certain adjustments in everyday life can help prevent falls and other accidents. The doctor also helps clarify sensible safety measures. In this way, the physical impairments do not automatically lead to mental problems.
If the stress caused by the oculomotor nerve palsy increases, this may result in depressive moods or inner restlessness. If circulatory disorders are the cause of the disease, the chances of recovery are pretty good. It becomes more difficult if the oculomotor nerve palsy is caused by a tumor, an aneurysm or trauma. It is all the more important that the patients follow all the recommendations of the doctors.
