Management of head tilt in infantile nystagmus syndrome: A case report.

Management of head tilt in infantile nystagmus syndrome (INS) is a challenge. In this case report, we have described successful management of right-sided head tilt in a child with INS by operating on three oblique muscles (superior oblique anterior tenectomy in the right eye, Harada-Ito procedure in the left eye, and inferior oblique recession in the left eye). The child had complete correction of head tilt without causing any cyclovertical strabismus or torsional diplopia postoperatively.

Infantile nystagmus syndrome (INS) is the most common type of infantile nystagmus having onset between birth and 12 weeks of age with no underlying ophthalmic or neurological problems.[1] It is bilateral, conjugate, mostly horizontal, either pendular or jerky, and usually associated with a “null zone” where the nystagmus has least intensity. If the null point does not coincide with the primary gaze position, a patient adopts a head posture to bring this null zone from eccentric position in primary gaze to reduce the nystagmus.[1] The most common head posture is horizontal face turn to right or left, followed by vertical chin up or chin down and the least common one being head tilt to right or left.[2] Management of horizontal face turns by extraocular muscle surgery like Kestenbaum Anderson's procedure bringing the null point in primary position is fairly well established.[1] But there are few case reports in literature about management of the head tilt in INS. In this case report, we present management of head tilt in a child with INS.[345]

Case Report

A 10-year-old child presented with head tilt to the right and shaking movement of eyes since birth. On examination, his best-corrected visual acuity was 20/80 and N6 at 10 cm in each eye. Cycloplegic refraction with 1.0% cyclopentolate and 0.5% tropicamide was + 1.5 diopter sphere/−2.5 diopter cylinder at 180° in both eyes. He had right head tilt of 25° as measured with goniometer [Fig. 1a]. There was horizontal, low-amplitude, and low-frequency right beating jerk nystagmus, decreasing on right head tilt and increasing on left head tilt and dampening on convergence. With glasses, the child was orthotropic. There was no torsion of fundus in either eye. The stereoacuity was 400 seconds of arc of arc by Titmus fly test. For correcting the head tilt, superior oblique (SO) anterior tenectomy was performed in the right eye [weakening right SO (RSO)], Harada–Ito procedure for SO in the left eye (strengthening left SO), and inferior oblique (IO) recession in the left eye (weakening left IO) under general anesthesia.

Figure 1

(a) Preoperative photograph showing large head tilt to right side. (b) Postoperative 5 months' photograph showing normal head posture

For Harada–Ito procedure in the left eye, we approached left SO through a superotemporal conjunctival incision, hooked the superior rectus muscle, and exposed its lateral border. We carefully identified SO tendon, explored its entire width using iris repositor and then hooked it with a small hook. We secured the anterior one-third fibers of SO with 6-0 vicryl suture, disinserted them, and reattached to sclera at a point just superior to the upper end of lateral rectus insertion.

For IO recession in the left eye, we used surgical technique described by Lueder and Galli.[4] We used inferotemporal fornix incision, hooked the inferior rectus and lateral rectus muscle, isolated IO muscle with a small hook, and brought it forward. After dissecting the connective tissues carefully and ensuring that no fibers of IO are left behind, we placed vicryl 6-0 absorbable suture as close to its insertion as possible and disinserted the muscle. Then we reattached anterior suture to the globe 7 mm posterior to the lateral border of the inferior rectus muscle and placed the posterior suture at 45° angle, 3 mm posterior and lateral to this point. We approached RSO through a superotemporal conjunctival incision as explained above for Harada–Ito procedure. After hooking RSO with a small hook, we disinserted the anterior 50% of the tendon and excised the anterior one half of the tendon between the insertion and the lateral border of the superior rectus muscle.[4]

On the first postoperative day and also after 5 months, the child did not have any head tilt while reading 20/80 line binocularly with glasses [Fig. 1b], and all extraocular movements were normal [Fig. 2]. There was no torsion of fundus as seen in the fundus photographs taken at 5 months' postoperative visit [Fig. 3: a – right eye, b – left eye].

Figure 2

Postoperative 5 months' photograph showing normal extraocular movements

Figure 3

Postoperative 5 months' fundus photograph showing no torsion of the fundus (a – right eye, b – left eye)

Discussion

The principle involved in the management of abnormal head posture in INS is to move the eyes in the direction of head posture which brings null zone in primary position.[1] Going by this principle, to correct right head tilt, we need to induce excyclotorsion in the right eye and incyclotorsion in the left eye. This can be achieved by strengthening/weakening the oblique muscles, vertical displacement of horizontal muscles, or by slanting the horizontal muscle insertions. Conrad and de Decker operated on all oblique muscles slanting the insertions to alter cyclotorsional effect.[6] Spielmann described slanting of insertion of horizontal muscles for the same purpose.[7] Kraft reported a 7-year-old boy with congenital nystagmus with right head tilt who underwent a left IO recession to incycloduct the left eye and a tenotomy of the RSO on the nasal side with insertion of a retinal band to excycloduct the right eye.[8]

In our case, we combined surgical principles as described by Lueder and Galli[4] and Prakash et al.[5] Since there was right head tilt, we induced excyclotorsion in the right eye by weakening SO by anterior 50% tenectomy.[4] In the left eye, we induced intorsion by strengthening intorsion effect of SO by Harada–Ito procedure and weakening extorsion by recessing IO.[5]

Prakash et al. have described IO strengthening by advancement procedure in the eye with Harada–Ito procedure.[5] We deferred it due to its technical difficulty and reserved it as a future modality of treatment in case of undercorrection postoperatively. But even without that, our patient had complete correction of head tilt. This may suggest that a step-wise approach may be adopted in selecting the number of muscles to be operated while correcting head tilt in INS.

Despite operating on three oblique muscles, there was no cyclovertical strabismus, no torsion of fundus, and the child did not experience any torsional diplopia postoperatively. This suggests that this approach is safe.

Head tilt in INS was successfully managed in this case by SO anterior tenectomy in the eye on the side of the head tilt and Harada–Ito procedure with IO recession in the other eye without causing any cyclovertical strabismus postoperatively.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

We acknowledge support from Hyderabad Eye Research Foundation.

Conflicts of interest

There are no conflicts of interest.