Journal of Neuro-Ophthalmology, December 2006, Volume 26, Issue 4

Ocular Neuromyotonia With Spastic Lid Closure

Ocular neuromyotonia is characterized by tonic spasms of extraocular muscles evoked by eccentric gaze that induces transient strabismus and diplopia. We report the case of a 70-year-old woman who initially presented with unilateral deficits in fifth and sixth cranial nerve functions attributed to a fifth cranial nerve schwannoma. After radiation treatment, she developed neuromyotonia and synkinesis of the ipsilateral third cranial nerve. During the attacks of neuromyotonia, the left eyelids were often spastically closed, a phenomenon not previously reported. The ocular neuromyotonia regressed spontaneously within 3 years, but components of the synkinesis persisted. Ephaptic transmission in a damaged third cranial nerve may be responsible for the neuromyotonia and synkinesis. Synkinesis is a more enduring manifestation.

ORIGINAL CONTRIBUTION Ocular Neuromyotonia With Spastic Lid Closure Akihiko Oohira, MD and Tatsuyuki Furuya, MD Abstract: Ocular neuromyotonia is characterized by tonic spasms of extraocular muscles evoked by eccentric gaze that induces transient strabismus and diplopia. We report the case of a 70- year- old woman who initially presented with unilateral deficits in fifth and sixth cranial nerve functions attributed to a fifth cranial nerve schwannoma. After radiation treatment, she developed neuromyotonia and synkinesis of the ipsilateral third cranial nerve. During the attacks of neuromyotonia, the left eyelids were often spas-tically closed, a phenomenon not previously reported. The ocular neuromyotonia regressed spontaneously within 3 years, but components of the synkinesis persisted. Ephaptic transmission in a damaged third cranial nerve may be responsible for the neuromyo­tonia and synkinesis. Synkinesis is a more enduring manifestation. (/ Neuro- Ophthalmol 2006; 26: 244- 247) Ocular neuromyotonia is characterized by episodes of diplopia that are usually induced by holding the eyes in eccentric gaze. Most reported patients had earlier undergone radiation therapy to the parasellar region ( 1- 8). The myotonia often improves with membrane- stabilizing medication ( 1,3,4,8,9). Our patient suffered from third cranial nerve synkinesis and ocular neuromyotonia, in­cluding monocular spastic lid closure, a combination not previously described. CASE REPORT A 70- year- old woman developed diplopia and reduced sensation of the left face and unstable jaw move­ment. The diagnosis was a left sixth cranial nerve palsy and a left fifth cranial neuropathy. Imaging disclosed a mass in the posterior part of the left cavernous sinus ( Fig. 1). Its location and signal characteristics were most consistent with trigeminal schwannoma, which was presumptively Department of Ophthalmology, Tokyo Women's Medical University, Tokyo, Japan ( AO, TF); and Wakaba Eye Hospital, Tokyo, Japan ( AO). Address correspondence to Akihiko Oohira, Wakaba Eye Hospital, Kamata 4- 22- 11, Ohta- ku, Tokyo 144- 0052, Japan; E- mail: ohira@ wakaba- hp. or. jp diagnosed without biopsy. Radiation therapy produced central necrosis in the tumor ( Fig. 2) and slightly improved facial sensation. Four months after the radiation therapy, she began to notice that her left eye moved inward episodically. Subtle limitation of supraduction of the left eye and transiently increased esotropia were noted by an ophthalmologist. Examination at our clinic 18 months after radiation therapy revealed a left sixth cranial palsy and a left third cranial nerve palsy with aberrant regeneration ( Fig. 3). The left side of the face was hypesthetic, especially in the region of the first division of the fifth cranial nerve. The left pupil was mydriatic and unreactive to light and showed no size changes related to eye movements. The eyes were aligned in primary gaze ( 1 in Fig. 3) with slight ptosis of the left upper lid. In right gaze, the left palpebral fissure widened vertically, and there was full range of adduction of the left eye ( 2 in Fig. 3). After holding her eyes in right gaze for more than a few seconds, she noticed a pulling sensation in the left eye for about 30 seconds, and she could not refrain from closing the left eyelids ( 3 in Fig. 3). She felt no pain during the attack. Upon opening her eyes, she noticed diplopia in the primary gaze position due to esotropia ( 4 in Fig. 3). The esotropia continued for less than 30 seconds. On downgaze, incomplete downward movement of the left upper lid ( not shown) and a deficit of infraduction ( 5 in Fig. 3) were present. Sustained downgaze for several seconds induced the pulling sensation, which was some­times accompanied by the closing of both eyes and sus­tained left eyelid closure afterwards. When her left eye opened, it was transiently esotropic and hypotropic in the primary position ( 6 in Fig. 3). On upgaze, supraduction of the left eye was severely reduced, and the eye deviated inward ( 7 in Fig. 3). When the eyes returned to the primary position after several sec­onds of sustained upgaze, she transiently became esotropic and the ptosis disappeared ( 8 in Fig. 3). On left gaze ( 9 in Fig. 3), a mild deficit of abduc­tion was evident. The severe pulling sensation induced by sustained right gaze was relieved when she succeeded in moving her eyes to the left ( 10). She reported that these phenomena decreased after eat­ing meals or drinking water and that 200 mg carbamazepine 244 J Neuro- Ophthalmol, Vol. 26, No. 4, 2006 Ocular Neuromyotonia J Neuro- Ophthalmol, Vol. 26, No. 4, 2006 FIG. 1. Postcontrast T1 coronal ( A) and axial ( B) MRI at presentation shows an enhancing mass ( arrows) in the left posterior cavernous sinus later confirmed at surgery to be a fifth cranial nerve schwannoma. daily completely suppressed the uncomfortable attacks. However, she elected to discontinue the medication be­cause of sedative effects. She underwent recession of the left medial rectus muscle elsewhere 6 months later be­cause the esotropia had increased. Examination at our clinic 3 years after radiation therapy disclosed 40 prism- diopters of left esotropia in the primary gaze position and a complete abduction deficit. There was no deficit of adduction of the left eye. The patient reported that the neuromyotonia episodes with spastic lid closure had lessened to a few times per month. The sensation of discomfort during right gaze was much less FIG. 2. Postcontrast T1 axial MRI 18 months after com­pletion of radiation therapy shows low signal within the enhancing mass, indicative of tumor necrosis. severe than before. We could not elicit an increase in esotropia after right gaze. Right gaze no longer elicited vertical widening of the palpebral fissure, but the left upper lid became more ptotic on left gaze. Left upper lid retraction on downgaze was more prominent than before. Supraduction of the left eye was severely reduced, and the eye adducted during upgaze as before. One week later the tumor was resected and path­ologically confirmed as a trigeminal schwannoma; it did not involve the third or sixth cranial nerves. After the surgery, she received 200 mg phenytoin daily for 3 weeks. One month after surgery, our examination failed to dis­close evidence of neuromyotonia. Otherwise the examina­tion was unchanged except that left upper lid ptosis was slightly worse, and downward lid movement on down-gaze was much better. Five months after surgery, the left abducens nerve palsy had improved slightly, primary position esotropia had decreased to 20 prism- diopters, and adduction of the left eye had become mildly reduced ( Fig. 4). On follow- up examination one year after surgery, these neuro- ophthalmologic findings were stable. DISCUSSION The clinical phenomenology of our patient is in­teresting in that she initially presented with a deficit in sixth cranial nerve function and later developed neuromyotonia and synkinesis of the ipsilateral third ( not sixth) cranial 245 J Neuro- Ophthalmol, Vol. 26, No. 4, 2006 Oohira and Furuya FIG. 3. Ocular motility findings 18 months after radiation therapy. In primary gaze ( 1), the patient has left upper lid ptosis and normal alignment. In right gaze ( 2), full versions are present with vertical widening of the palpebral fissure and normal alignment. Sustained right gaze elicits spastic left eyelid closure ( 3), after which esotropia is present in primary gaze ( 4). Downgaze ( 5) discloses a deficit in infraduction of the left eye and induces a temporary esotropia and left hypotropia in primary gaze ( 6). Upgaze ( 7) discloses inward deviation and a deficit in supraduction of the left eye and briefly induces a temporary esotropia in primary gaze and resolves the left upper lid ptosis ( 8). A mild deficit in abduction of the left eye is obvious on left gaze ( 9). nerve months after radiation treatment of a fifth cranial nerve schwannoma. The neuromyotonia was manifested by esotropia after sustained right gaze, esotropia and dis­appearance of left upper ptosis after sustained upgaze, esotropia and hypotropia after sustained downgaze, and spastic left eyelid closure induced by eccentric gaze ( 1,2,5,7,10). The spastic eyelid closure has not been re­ported previously. Surviving branches of the fifth cranial nerve innervating the meninges near the orbital apex may have mediated the spasms of the orbicularis oculi muscle through the trigeminal blink reflex. An intimate relationship between ocular neuromyotonia and the fifth cranial nerve 246 © 2006 Lippincott Williams & Wilkins Ocular Neuromyotonia J Neuro- Ophthalmol, Vol. 26, No. 4, 2006 FIG. 4. Ocular motility 5 months after tumor resection. In primary gaze, left upper lid ptosis and esotropia are present. In right gaze, adduction of the left eye is mildly reduced, but vertical widening of the palpebral fissure no longer occurs. In upgaze, there is a left hypotropia and large esotropia. In downgaze, there is a trace of left upper lid retraction; when the eyelids are lifted, a left hypertropia is evident. In left gaze, the left upper lid ptosis and the mild deficit in abduction are still present. Eccentric gaze no longer evokes spastic left eyelid closure. was suggested by AbduUa et al ( 11). The neuromyotonia of their patient was believed to be triggered by excitation of the infraorbital branch of the fifth cranial nerve. In our patient, the ocular neuromyotonia had largely disappeared within 3 years. This is a somewhat unusual occurrence, although 2 other cases of spontaneous remis­sion of ocular neuromyotonia have been reported ( 6,8). Our patient was notable in displaying a combination of third cranial nerve synkinesis and ocular neuromyotonia. Such a combination has been reported rarely ( 1,8). Ephaptic transmission has been proposed as a cause of both third cranial nerve synkinesis ( 12) and ocular neuromyotonia ( 1,4,8,9,11). Carbamazepine has been reported to improve both phenomena ( Case # 4 of Shults et al [ 8]) and even the vertical eye movement deficits ( Case # 2 of Ezra et al [ 1]). In our patient, the ocular neuromyotonia and some of the lid synkinesis regressed spontaneously, leaving behind two synkinetic movements: ptosis on left gaze and adduc­tion on upgaze. The triggering signal of neuromyotonia might have been transmitted ephaptically where the myelin was damaged. Hyperexcitability of the axon membrane induced by radiation probably constitutes the perpetuating neural circuit for neuromyotonia. Presumably, as the myelin gradually regenerated in our patient, lid synkinesis and ocular neuromyotonia spontaneously ceased. The other components of the third cranial nerve were apparently more severely damaged, and their synkinetic features endured. l. 7 10 11 REFERENCES Ezra E, Spalton D, Sanders MD, et al. Ocular neuromyotonia. Br J Ophthalmol 1996; 80: 350- 5. 2. Newman SA. Gaze- induced strabismus. Surv Ophthalmol 1993; 38: 303- 9. 3. Bacskulin A, Guthoff R. Neuromyotonia of the abducens nerve after hypophysectomy and radiation. Strabismus 1999; 7: 37- 40. 4. 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