ocular torticollis

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[Torticollis]

OCULAR TORTICOLLIS

The term torticollis refers to an abnormal head posture, regardless of the cause. Torticollis has several different possible causes including, but not limited to, skeletal, muscular, and nerve problems. Torticollis can also be caused by visual conditions like strabismus (misalignment of the eyes), visual field defects, or nystagmus (rapid jerking movement of the eye). When head tilt is caused by vision problems it is called ocular torticollis.

There are two ocular reasons for abnormal head posture. A person with ocular torticollis is either trying to improve their vision (as in nystagmus), or they are attempting to maintain binocular vision and central fusion and prevent double vision (as in strabismus).

Persistent head tilting is most often caused by vertical misalignment of the eyes. This can be caused by weakness of one of the eight muscles which control vertical movement of the two eyes. The most frequent cause of ocular torticollis seen at Spokane Eye Clinic is probably weakness found in the superior oblique muscle of one eye. Weaknesses of the superior oblique muscle are usually caused by a palsy of the fourth cranial nerve which has one function - to “supply” or “power” that muscle. Causes of fourth nerve palsy include congenital problems (present from birth), birth trauma, head injury, things inside the head pressing on the nerve (called mass lesions, these include aneurysm, benign or malignant tumor, and blood clots), diabetes, multiple sclerosis, and other diseases of the nerves. Other things that can cause weakness in these muscles include myasthenia gravis (a disease of the muscles) and Graves disease (a type of thyroid disorder). Ocular torticollis can also be sign of brain tumor or other problems of a serious nature. Because ocular torticollis can occasionally have such serious causes, it is very important for anyone who exhibits the symptoms of ocular torticollis to see a doctor.

At Spokane Eye Clinic the doctors see an average of 10 cases of ocular torticollis per year in which fourth nerve palsy is the main cause. Fourth nerve palsy effects the superior oblique muscle and causes vertical misalignment of the eyes in certain positions. In order to determine whether an eye muscle weakness is indeed the cause of the torticollis the doctor will perform a series of tests that isolate the effect of each of the vertical muscles by measuring the amount of misalignment in certain, specific head and gaze positions. If the basic cause of the torticollis is determined to be ocular and due to an eye muscle palsy, the doctor will search for the underlying cause of the nerve palsy. Fortunately most ocular torticollis is either of sudden onset and due to a known and easily recognizable thing like head trauma, or it is congenital or long standing but only recently recognized. Despite this, the doctor must rule out the possibilities of serious underlying disease such as mass lesion, multiple sclerosis, and diabetic palsy.

If the head tilt or associated vision symptoms such as double vision are not a major problem and its causes are non-threatening, the doctor may simply allow the patient to continue without further treatment. If the ocular torticollis is a problem, however, treatment may be needed to prevent neck problems, facial asymmetry, allow single vision and binocular vision, and prevent amblyopia and anomalies of binocular vision or loss of binocular vision. These conditions are more prone to effect young, growing and developing patients than those who are grown. In mild cases glasses with prism correction may be sufficient. Often though, the doctor will realign the eyes by balancing the muscles in surgery, thus allowing the head posture and vision to return to normal.

Before surgery the doctor must determine which muscle is causing the misalignment by measuring vertical deviation in left and right gaze and with the head tilted both right and left. This is called the Bilchowsky 3 step head tilt test. Once the muscle imbalance is diagnosed, it is possible to for the doctor to move the attachments of muscles on the eye in surgery to improve or reestablish the balance of the muscles and allow the eyes to align and work together more normally. This surgery can be done on an outpatient basis and most normal activities can be resumed a few days after surgery.

In some cases prism glasses can re-establish alignment in straight ahead gaze. The problem with this, however, is that characteristically in ocular torticollis, the deviation in left and right gaze is different from that in straight ahead gaze and requires a different prism correction, but in prism glasses the correction is the same in all parts of the lenses. The difference between side (to right or left) gaze deviation and front gaze deviation exists because the 4 vertical oblique muscles — the superior oblique and inferior oblique in each eye — have more effect on vertical vision when eye is turned toward nose, while their opposites, the 4 vertical rectus muscles — the superior and inferior rectus muscles in each eye — have more effect in straight ahead gaze and temporal (towards the ear) gaze. The rectus and oblique muscles in the opposite eyes are paired and work together, so that when one eye moves temporally, the other will move towards the nose and the eyes will stay aligned.

Hering’s law helps explain why eyes will become misaligned in some situations and not in others. Hering’s law states that when paired muscles are working together, each of them receives the same amount of impulse or power from the brain. When one of the muscles in a pair is weak and cannot contract as well or as strongly as its partner, the brain sends a stronger signal to both, trying to make the weak muscle work as well as the normal. So both the normal and the weakened muscles in the pair receive the same amount of impulse, but the weakened muscle cannot contract as much as the normal muscle, so the normal muscle overshoots its goal while the weakened muscle undershoots it. For example, if the superior oblique muscle in the right eye (which is paired with the inferior rectus muscle in the left eye) is weak while the inferior rectus in the left eye is uninjured, the eyes will become misaligned primarily when the patient looks down and to the left, but remain better aligned in gazes away from that position.

Torticollis, if left uncorrected, can result in neck muscle and spinal problems, especially in the young, growing bones of a child. Torticollis has also been found to contribute to facial asymmetry , especially when the torticollis is present from an early age. Ocular torticollis can sometimes act as a warning beacon pointing to a larger, underlying problem like a tumor or a disease of the nerves. Ocular torticollis can be a relatively easy problem for your ophthalmologist to treat, but they must first be alerted to the existence of the condition.

1., M.E. and J. Hoxie, Facial asymmetry in superior oblique muscle palsy. J Pediatr Ophthalmol Strabismus, 1993. 30: p. 325-318.

2.Rao, R., G.V. Morton, and B.J. Kushner, Ocular Torticollis and facial asymmetry. Binocular Vision and Strabismus Quarterly, 1999. 14(1): p. 27-32.

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