|Year : 1996 | Volume
| Issue : 3 | Page : 170-172
Periodic alternating nystagmus treated with retrobulbar botulinum toxin and large horizontal muscle recession
Ravi Thomas1, Annie Mathai1, Andrew Braganza1, Frank Billson2
1 Department of Ophthalmology, Christian Medical College, Vellore, India
2 From The Save Sight & Eye Health Institute, Sydney, Australia
Schell Eye Hospital, Arni Road, Vellore 632 001
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Thomas R, Mathai A, Braganza A, Billson F. Periodic alternating nystagmus treated with retrobulbar botulinum toxin and large horizontal muscle recession. Indian J Ophthalmol 1996;44:170-2
|How to cite this URL:|
Thomas R, Mathai A, Braganza A, Billson F. Periodic alternating nystagmus treated with retrobulbar botulinum toxin and large horizontal muscle recession. Indian J Ophthalmol [serial online] 1996 [cited 2020 Sep 18];44:170-2. Available from: http://www.ijo.in/text.asp?1996/44/3/170/24581
Periodic Alternating Nystagmus (PAN) has been described with hindbrain abnormalities and other pathological conditions; a congenital form is also recognized., The treatment of PAN includes Baclofen., More recently, symptomatic nystagmus has been successfully treated with botulinum toxin injections, or large recessions of the horizontal rectus muscles. We report a case of PAN with symptoms of oscillopsia who was treated with retrobulbar injections of botulinum toxin, and subsequently with large recessions of all horizontal muscles.
| Case report|| |
A 17 year old male complained of intermittent oscillopsia not interfering with normal activity, first noticed at the age of thirteen years; his parents had noticed "shaky eyes" at the age of two years. On examination vision (uniocular and binocular) in both eyes was 6\6 Jl. He had a jerk nystagmus beating to the right which decreased in amplitude, stopped completely, and then restarted as a left beating nystagmus. The duration of the nystagmus was about two and a half minutes; the "null phase" lasted about two minutes. This cycle repeated itself continuously. The complaints of oscillopsia could be correlated with the presence of manifest nystagmus. Despite complaints, the vision remained 6\6, Jl throughout the cycle and did not degrade with simultaneous head movements; the patient could not appreciate a change in the oscillopsia, or a change in the direction of the perceived movement of objects. There was no head turn at any stage and ocular movements were full. The anterior segment as well as the fundus were within normal limits. A cycloplegic refraction did not reveal any refractive error; the visual fields were unremarkable.
Two years later he returned with complaints of increasing oscillopsia interfering with his studies. On examination the uniocular and binocular vision was still 6\6, Jl with the same pattern of PAN. The anterior and posterior segments were within normal limits. Cycloplegic refraction revealed a mild hypermetropia (+0.50D sphere); correction did not alleviate his symptoms. A complete neurological evaluation including a CT scan was reported as normal and no treatment was advised. Three months later, in consultation with a neurologist he was prescribed Baclofen 2.5 mg three times a day; within two weeks the dose was increased to 10 mg three times a day. This was continued for six weeks. As there was neither relief of symptoms nor clinically evident decrease in the nystagmus, the drug was discontinued.
On 5-3-92, 25 units of botulinum toxin (Oculinum) were injected retrobulbar in each eye. One week later the patient reported that the oscillopsia had disappeared. On examination, uniocular vision was 6\6, Jl. The patient had a right partial ptosis that covered the pupil and a right exotropia of about 20 prisms. On manual elevation of the lid he could appreciate crossed diplopia. Even on prolonged observation there was no nystagmus. The right pupil measured 4 mm, the left 2.5 mm and pupillary reactions were normal in both eyes. The ptosis and exotropia resolved over three weeks. The patient was asymptomatic for approximately two more months following which the nystagmus and the oscillopsia gradually returned. Despite the cosmetic deformity caused by the ptosis the patient requested a repeat dose. Due to short supply of the toxin, economic considerations and a reluctance to commit him to repeated retrobulbar injections, we decided against this. The patient continued to complain and demand treatment. On 20-1-94, following informed consent he underwent retroequatorial recessions of all four horizontal rectus muscles. As we were concerned about inducing a tropia, a hang-back adjustable suture technique was used on all muscles. The lateral recti were recessed by 13 mm, and the medial recti by 10 mm from their respective insertions; 6-0 Vicryl was used. At completion of surgery the sutures were slack against the globe. On the first postoperative day the eyes were orthotropic and the sutures were tied down. There was minimal limitation of adduction and abduction; no prominence of the eyes was noticed. The nystagmus was still present, followed the same pattern, and clinically was of the same amplitude. The patient however claimed he had no oscillopsia. On follow up at one week, one month and three months postoperatively, the nystagmus was present as before; the patient agreed that his eyes were still "shaky", but denied any oscillopsia and claimed he now had no problems with reading or other daily activities. Four months post operatively with the same clinical findings he was beginning to experience a little oscillopsia; at one year while the clinical findings appeared to be the same, the patient said his symptoms were as bad as before the operation.
Video recordings were used to document the nystagmus at the original visit; the effect of each treatment modality was similarly recorded. Clinical change in the amplitude of nystagmus was determined by reviewing these videotapes.
| Discussion|| |
Symptomatic patients with nystagmus are difficult to treat. The gamma-aminobutyric acid against Baclofen has been reported to be useful in the treatment of PAN,, but this drug did not help our patient.
The successful use of Botulinum toxin in patients with nystagmus and oscillopsia has been reported. Retrobulbar injection of botulinum abolished the clinically observable nystagmus and provided dramatic objective as well as symptomatic relief for our patient. The side effect of ptosis in one eye fortuitously eliminated the diplopia that would otherwise have been induced by the iatrogenic exotropia. Patient satisfaction was emphasized by the fact that despite the cosmetically significant complications, once the symptoms recurred he requested a repeat injection. The lack of control over ocular alignment as well as the occurrence of ptosis are significant disadvantages in the use of retrobulbar Botulinum for nystagmus., These complications can occur even if the injection is made under electromyographic control into the individual muscles., This unpredictability along with economic factors and concern about the safety of repeated retrobulbar injections dissuaded us from repeating the treatment. Nevertheless, retrobulbar botulinum toxin alleviated our patient's symptoms entirely, and seems a valuable form of treatment for individual patients with symptomatic nystagmus, especially where other modes of therapy have been unsuccessful.
Large recessions of the horizontal muscles placing their insertions well behind the equator have been described to dampen nystagmus and increase the visual acuity., The use of this treatment for nystagmus, its mechanism of action, as well as the results are controversial., One case of PAN was included amongst the three patients with nystagmus for whom this surgery was reported as successful. In the patient reported, nystagmus improved in the primary position, preoperative alternating head turn was eliminated, and subjective improvement in reading speed was reported. In our patient, the large muscle recessions had no clinically detectable effect on the intensity of the nystagmus. The published reports of this technique do not specifically mention whether standard or hang-back techniques were used for the recessions. As we were concerned about the possibility of an induced tropia following the recessions, we used an adjustable hang-back technique. This provided us with the option of adjusting any unwanted tropia, and indeed of reversing the operation if that were deemed necessary in the immediate postoperative period. It could be argued that we may have achieved more "consistent slack" in the muscles and hence a better result had the muscles been tied down behind the equator, instead of being "hung back". Experimental studies have shown that the site of muscle insertion postoperatively is almost the same with standard or the hangback technique. [13,14] In one report, there was approximately a I mm forward movement of muscle insertion with large recessions, and a pseudotendon was seen in some eyes. Such a small forward movement should not have a major functional effect with the large recessions that we performed, and the clinical significance of the pseudotendon in this situation is unknown. Also, both these factors should be minimal in the immediate postoperative period.
Our patient was only evaluated on a clinical basis. Sophisticated methods of nystagmus recording may have revealed the foveation strategy that was utilized to maintain good visual acuity in the presence of manifest nystagmus. Also, following surgery it may have been possible to document a decrease in the amplitude of the nystagmus that was clinically inappreciable. This may be especially applicable to our patient who despite having the nystagmus from at least two years of age, started experiencing progressively worsening oscillopsia only at the age thirteen years. It is known that the brain compensates for excessive retinal image movement, and the magnitude of oscillopsia is usually less than the magnitude of the nystagmus. It is possible that our patient was "adapted" from childhood to a particular amplitude of nystagmus, and with increasing amplitude, adaption was no longer effective and resulted in appreciation of oscillopsia. A dampening of the nystagmus caused by surgery may have been enough to allow the patient to again compensate and eliminate the symptoms of oscillopsia, without a clinically detectable decrease in nystagmus amplitude. The reason why our patient was asymptomatic till the age of 13 years is speculative. The patient as well as the parents were sure about the history. It is possible that hormonal changes, as well as the increasingly competitive nature of studies and other activities around that age were factors that contributed towards manifestation of symptoms.
It is acknowledged that improvement of nystagmus as well as vision following large muscle recessions is not dramatic., The recurrence of symptoms at four months postoperatively suggests that the benefit of surgery, if any, may be transient. Obviously the occurrence and duration of benefit are difficult to predict in the individual case.
It is also well known that any treatment can have a placebo effect, which may be especially powerful in a motivated patient., The alleviation of oscillopsia despite the persistence of nystagmus clinically the same as that present preoperatively, raised the possibility that improvement noticed by the patient could probably be a placebo effect. In effect, it is possible that we could have obtained a similar improvement had we only anaesthetized the patient, or at the most made a conjunctival incision.
Whatever the explanation for the transient improvement in our patient, it would seem that the use of large muscle recessions for the treatment of nystagmus remains experimental, and at present should be used for specific indications. Its routine use awaits further study.
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