Trochlear Palsy

By | June 10, 2022

In the context of a trochlear paresis, a lesion of the fourth cranial nerve occurs, resulting in paralysis of the upper eye muscle. Trochlear paresis can be unilateral or bilateral, complete or partial.

What is trochlear paresis?

The fourth cranial nerve originates in the midbrain and then, as the only cranial nerve, crosses completely to the opposite side below the so-called quadruple ridge plate. It is a purely somatomotor nerve and supplies the oblique upper eye muscle, which is also known as the superior oblique muscle. A contraction of this muscle triggers a downward eye movement. The trochlear nerve is the smallest oculomotor cranial nerve whose palsy leads to trochlear palsy. If the fourth cranial nerve fails, eye movements are restricted or a typical squint pattern occurs. Of all the cranial nerves is the trochlear nerveleast affected by symptoms of paralysis, the most common cause being craniocerebral injuries. For metachromatic leukodystrophy definition and meaning, please visit


Trochlear paresis occurs as a result of strokes, microangiopathies, aneurysms or craniocerebral injuries. The trochlear nerves are particularly often affected by head trauma. Mucormycosis or cysticercosis are possible inflammatory causes, but trochlear paralysis can also be caused by tumors in the region of the upper brainstem (chardoma, metastases, lymphomas, gliomas).

These are usually accompanied by other symptoms. Trochlear pareses can also occur with hypertension or diabetes mellitus, in which case they have a very favorable prognosis. Other possible causes of trochlear paresis can be:

  • Tolosa Hunt Syndrome
  • Complications in neurosurgical operations
  • multiple sclerosis
  • meningitis

There are also congenital trochlear pareses or those that are acquired in early childhood. However, these show different symptoms. The cause of congenital or early acquired trochlear paresis is not known to date. Birth trauma could play an important role here. A congenital trochlear paresis should always be differentiated from a so-called sursoadductarius strabismus (congenital crossed position of the oblique eye muscles).

It is also necessary to consider possible injury to the trochlea in post-traumatic disorders of the upper eye muscle. In addition, spasmodic torticollis ( wry neck ) or dissociated squinting should be ruled out.

Symptoms, Ailments & Signs

If trochlear paresis occurs, the affected muscle loses its function. The oblique muscle of the superior eye normally performs three different tasks: outward turning, inward rolling, and lowering. In the case of a trochlear paresis, however, the gaze deviates, i.e. there is a squint or a rolling towards the temple.

In addition, those affected see double images that are perceived either tilted, vertically or horizontally. As a result, the patients adopt a forced head position in order to be able to eliminate the double images. In most cases, the head is tilted to the healthy side, but if it is tilted to the diseased side, the eye will be higher. This phenomenon is known as the so-called “Bielschowsky phenomenon”.

Trochlear paresis is extremely annoying, especially with everyday things such as eating, reading or desk work, where the gaze is directed downwards. Accidents can also occur when climbing stairs or when running, since the squinting angle cannot be compensated for in this case with the help of a forced head position. Another symptom is the difference between the primary and secondary squint angles.

The primary angle is the squinting deviation that can be measured with fixation with the non-diseased eye. The secondary angle describes the deviation when fixating with the affected eye. If paralytic squinting occurs, the primary angle is always smaller than the secondary angle. In the case of trochlear paresis, which occurs on both sides, it is quite possible that there is no squinting when looking up.

Diagnosis & course of disease

Trochlear palsies are diagnosed by a neurologist. This measures the squint angles in different viewing directions and with different fixations. In addition, the monocular excursion skills as well as the field of binocular single vision are assessed. The synoptometer or the tangent chart according to Harms is used for the investigation.

The Bielschowsky head tilt test also provides further information about the presence of trochlear paresis. If the head is tilted towards the diseased side, a higher position of the affected eye can be seen, but there is no squinting deviation on the healthy side or it is significantly reduced. In the case of spontaneous trochlear paresis, a Tensilon or glucose tolerance test and an orbital MRI are also carried out to rule out myasthenia. Trochlear paralysis is often recognized relatively late, since it is often quite inconspicuous or the symptoms are misinterpreted.


A trochlear paresis leads to various eye problems in those affected. Those affected suffer from double vision or blurred vision, which leads to significant limitations in the everyday life of the affected person. In many cases, the patients have to adopt a forced position of the head, so that it is tilted to the side.

This attitude can lead to severe discomfort and limitations in everyday life. Accidents can happen, especially when running. Furthermore, the disease can promote squinting. The affected person can often no longer look up. Especially in children, trochlear paresis can lead to bullying or teasing due to poor posture.

As a result, many children also suffer from mental health problems or depression. However, the disease leads to restrictions in child development, so that complications and symptoms can also occur in adulthood. The treatment of trochlear paresis is usually carried out at a very early age and is successful in most cases. There are no complications. As a rule, the complaints are completely resolved in the process.

When should you go to the doctor?

Immediate visit to a neurologist is advisable in the event of sudden visual disturbances with squinting and double vision. It may be a trochlear palsy that needs treatment. Above all, the cause must be determined. An ophthalmologist is often called in to diagnose this disorder.

Many patients first try to compensate for the typical symptoms of trochlear paresis by changing their head positions. Instead, they should go straight to the neurologist or ophthalmologist because of the drama of possible triggers. Trochlear paralysis can occur as a result of traumatic brain injury, microangiopathy, an aneurysm, a stroke or inflammatory processes. In all cases, a timely start of treatment is urgently recommended.

Careful differential diagnosis and anamnesis ensure that the cause of the phenomenon is determined and, if possible, treated successfully. At the same time, attempts are being made to improve the symptoms of trochlear paresis. This can be done through prism glasses or an operation. Whether or not the paralysis of the upper eye muscle completely resolves after this treatment varies.

Trochlear paresis is often an idiopathic symptom with no identifiable cause. So far, only a few triggers have been identified. Other triggers that can lead to trochlear paresis are still undiscovered. There are congenital trochlear pareses or those that occur in small children. However, they have different symptoms.

Treatment & Therapy

The squint can be improved with the help of prism glasses. If the paralysis does not recede after six to nine months, an operation is necessary in order to be able to reduce the constrained head position or the cyclotropia. Muscle-strengthening procedures in which the affected eye muscle is folded or protruded are also effective.

However, a restoration of the function can usually only be assessed after six to twelve months. Therefore, an operation is usually only considered after a year has passed. During this time, the lower part of the lens is often also covered in order to avoid annoying double images. A treatment with botulinum toxin is also possible in order to weaken the antagonistic muscle.


Because trochlear palsy can occur as a result of stroke or head trauma, it is not possible to prevent the lesion.


After treatment of the trochlear paresis, those affected should undergo special vision training. In addition, regular examinations should be carried out by the doctor in charge. In order to avoid recurrence, the ophthalmologist must monitor the vision of those affected and, if necessary, prescribe further medication.

Those affected should list all the symptoms that occur in a diary and present this to the doctor treating them so that the doctor can take action at an early stage. Physiotherapy should also be started because of the forced posture. Affected people should take great care of their social environment so that the help of relatives, for example, can be taken up at any time. Patients can also use naturopathic painkillers after the final treatment in consultation with the doctor treating them.

Since the disease can be a serious burden for many sufferers and their families, it is recommended to undergo ongoing psychological counseling. In this way, those affected and their families can learn how to deal with the disease. In order to improve their quality of life, those affected should pursue activities that they enjoyed before the illness. The social environment also plays a major role. A support group can also be beneficial. In this way, those affected can exchange ideas with other sufferers and compare their lifestyles.

You can do that yourself

Trochlear paresis can sometimes be corrected with special prism lenses. If necessary, an additional operation must be performed. Those affected can take various measures to support treatment.

Targeted vision training and regular visits to the doctor are recommended first. The ophthalmologist must monitor vision and, if necessary, prescribe other medications to prevent the condition from getting worse. In the case of congenital trochlear paresis, it is also necessary to differentiate it from other diseases with similar symptoms. Those affected should therefore keep a complaint diary and write down the various symptoms in detail. The information can then be used for diagnosis. The forced head position can be corrected by targeted physiotherapy. Accompanying this, pain medication must be used.

In consultation with the doctor, gentle painkillers from naturopathy can be used, especially after the end of the therapy. There are, for example, preparations with valerian or St. John’s wort, since these can also be taken together with normal medication due to the fewer side effects. If these measures are followed, the trochlear paresis can be treated well. In any case, however, close medical monitoring of the person concerned is also necessary.

Trochlear Palsy