Trochlear palsy

Classification according to ICD-10
H49.1	Paralysis of the trochlear nerve [IV. Cranial nerve]
ICD-10 online (WHO version 2019)

The fourth nerve palsy is a lesion of the trochlear nerve , the IV. Cranial nerves . The result is paralysis of the superior oblique muscle , the oblique, upper eye muscle . It is innervated exclusively with motor fibers by the trochlear nerve. Trochlear palsy can occur partially or completely, unilaterally or bilaterally.

Symptoms

Primarily there is a loss of function of the affected muscle with a corresponding squint and an increase in the deviation when looking in the direction of the muscle pull ( incomitance ). The superior oblique muscle fulfills three different functions, depending on the direction in which the eye is looking and due to its anatomical course: a lowering ( infraduction ), an inward rolling ( incyclic production ) and an outward turning ( abduction ). A loss of function therefore means that depending on the direction of gaze, there is a higher stance, a roll towards the temple (outside) and a squint deviation towards the nose (inside), possibly with additional V-symptoms when looking up and down. Correspondingly, double images appear, which are perceived horizontally, vertically and tilted analogously to the deviation .

In this situation, the patient usually tries to eliminate the annoying double vision by adopting a compensatory head posture and to achieve binocular single vision . A corresponding compensation is often the inclination of the head to the healthy side. On the other hand, if you tilt your head to the diseased side, a noticeably higher position of the affected eye becomes visible. This phenomenon is also known as the Bielschowsky phenomenon .

Another classic symptom of paresis can be found in the distinction between primary and secondary squint angles. The primary angle is the measured squint deviation during fixation with the healthy eye, while the secondary angle is that which is measured during fixation with the affected eye. In the case of paralysis strabismus, according to Hering's law of the same side innervation, the secondary angle is always greater than the primary angle.

In the case of bilateral trochlear palsy, it is quite possible that when looking straight ahead into the distance ( primary position ) and when looking up, a noticeable squint deviation is missing, and this only becomes apparent when looking to the right or left. Nonetheless, patients complain of visual disturbances in all directions of vision, since failure of the inward rolling effect leads to a cumulative curl squint outward ( excyclotropia ).

causes

Common causes of trochlear palsy are traumatic brain injuries , aneurysms , tumors , microangiopathies or strokes , but also inflammatory processes. Since the trochlear nerve is the only cranial nerve that crosses completely, the two trochlear nerves at the point of intersection on the back of the brain stem below the four-knuckle plate are particularly often affected in cranial trauma. There are also congenital and trochlear palsy acquired in early childhood, which, however, have different symptoms.

Diagnosis

As with all neurological disorders, once the cause has been clarified, treatment is primarily in the hands of a neurologist.

The strabologische diagnostics performed by a Orthoptistin or ophthalmologist , is the accurate measurement of the squint angle in different directions and at different fixation, in the judgment of the monocular excursion capability (s) of the field binocular single vision, and the area occupied head posture. The synoptometer is suitable as an apparatus-based examination environment , and for free-space examinations the so-called Tangent table according to Harms in combination with a dark red glass filter.

The so-called Bielschowsky head tilt test provides further diagnostic clarification . Here, when the head is tilted towards the affected side, the hemiplegic eye is clearly elevated, but when the head is tilted towards the healthy side, a squint deviation does not occur or is greatly reduced. This phenomenon is explained by compensatory innervations of the straight vertical motors due to the physiological counter-roll and the lack of inward rolling effect of the superior oblique muscle.

therapy

Depending on the extent of the squint deviation, a relative improvement of the situation can be achieved with prism lenses. If the paralysis has not resolved satisfactorily after about 6–9 months, an additional squint operation may be indicated to reduce the cyclotropy and forced head posture. The type and scope depend on the respective findings. Effective to muscle-strengthening interventions using have preliminary storage or folding of the affected superior oblique proved, as is the equilateral inferior oblique debilitating back storage or tenotomy . A botulinum toxin treatment to weaken the antagonistic muscle is possible.

Intervention on the straight vertical motors is less advisable, since here it appears that almost exclusively the vertical deviations are improved and the rotational components are not given enough consideration.

Differential diagnosis

Trochlear palsy - especially congenital - must always be differentiated from non-paretic, concomitant or decompensated strabismus sursoadductorius .
Furthermore, an injury to the trochlea should also be considered in post-traumatic disorders of the superior oblique muscle .
When assessing the assumed forced head posture, a torticollis spasticus should be excluded.
A dissociated vertical squint can also be ruled out by means of a suitable examination.

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literature

Herbert Kaufmann (Ed.): Strabismus. With the collaboration of Wilfried de Decker et al. Enke, Stuttgart 1986, ISBN 3-432-95391-7 .

Individual evidence

↑ ^a ^b D. Wieser: [Illustration of the incomitance pattern in congenital unilateral obliquus superior paresis with the synoptometer (author's transl)]. In: Clinical monthly sheets for ophthalmology. Volume 178, Number 2, February 1981, ISSN 0023-2165 , pp. 95-101, doi : 10.1055 / s-2008-1055306 . PMID 7230707 .
↑ Commission "Guidelines of the German Society for Neurology" (Ed.): Guidelines for Diagnostics and Therapy in Neurology. 3rd, revised edition. Georg Thieme, Stuttgart et al. 2005, ISBN 3-13-132413-9 , keyword: Peripheral eye muscle and nerve paresis; AWMF guidelines register: No. 030/033.

[syn-1] D. Wieser: [Illustration of the incomitance pattern in congenital unilateral obliquus superior paresis with the synoptometer (author's transl)]. In: Clinical monthly sheets for ophthalmology. Volume 178, Number 2, February 1981, ISSN 0023-2165 , pp. 95-101, doi : 10.1055 / s-2008-1055306 . PMID 7230707 .

[2] Commission "Guidelines of the German Society for Neurology" (Ed.): Guidelines for Diagnostics and Therapy in Neurology. 3rd, revised edition. Georg Thieme, Stuttgart et al. 2005, ISBN 3-13-132413-9 , keyword: Peripheral eye muscle and nerve paresis; AWMF guidelines register: No. 030/033.