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Show ORIGINAL CONTRIBUTION Primary Aberrant Regeneration and Neuromyotonia of the Third Cranial Nerve Kwang- Dong Choi, MD, Jung- Min Hwang, MD, Seong- Ho Park, MD, and Ji Soo Kim, MD Abstract: A 52- year- old woman presented with episodic diplopia with a duration of 6 months. Between the episodes, infraduction of the right eye was mildly impaired with retraction of the right upper lid on downgaze. On resuming the primary position after prolonged left gaze, she developed a right esotropia and reduced abduction, supraduction, and infraduction of the right eye. There was no history of cranial radiation or previous diagnosis of a brain lesion. Brain imaging results were negative. The in-terictal infraduction deficit and lid retraction were interpreted as signs of a mild right third cranial nerve palsy with primary aberrant regeneration. The episodic esotropia and ductional deficits were considered to be signs of neuromyotonia. This combination of findings, rarely described before, suggests a link between primary aberrant regeneration and neuromyotonia. Abnormal and excessive conduction triggered by stimulation of a partially damaged nerve probably underlies ocular neuromyotonia. (/ Neuro- Ophthalmol 2006; 26: 248- 250) Ocular neuromyotonia is a rare disorder characterized by episodic diplopia occurring either spontaneously or after a sustained eccentric gaze ( 1). It may be idiopathic, but some patients have had compressive or inflammatory lesions and others have had radiation to the parasellar and sellar regions months to years earlier ( 1,2). Abnormal electromyographic activity of the extraocular muscles suggests that this phenomenon may result from spontaneous Departments of Neurology ( KDC, SHP, JSK) and Ophthalmology ( JMH), College of Medicine, Seoul National University, Seoul, Korea; and Department of Neurology ( KDC), Pusan National University Hospital, Pusan National University School of Medicine and Medical Research Institute, Pusan, Korea. This work was supported by Korea Research Foundation Grant ( KRF- 2004- 003- E00202). Address correspondence to Ji Soo Kim, MD, Department of Neurology, Seoul National University Bundang Hospital, 300 Gumi- dong, Bundang- gu, Seongnam- si, Gyeonggi- do, 463- 707, Korea; E- mail: jisookim@ snu. ac. kr discharges of the ocular motor nerve axons with unstable cell membranes ( 3). There are reports of patients with aberrant regeneration as an isolated or main sign between the spells of ocular neuromyotonia ( 4- 6). However, the association of aberrant regeneration and neuromyotonia has received little attention. There are no reports of isolated infraduction deficit and lid retraction on downgaze between episodes of neuromyotonia. We describe a 52- year- old woman who had signs of aberrant regeneration of the third cranial nerve with superimposed episodes of ocular neuromyotonia. CASE REPORT A 52- year- old woman was referred for evaluation of intermittent diplopia that had been present for 6 months. The diplopia was mixed horizontal and vertical and often was associated with an inward pulling sensation of the right eye. The diplopia lasted for 3- 4 minutes and resolved after prolonged right gaze or repeated voluntary blinking. She denied having accompanying oscillopsia or headache. She had no history of migraine, cranial radiation, or other medical illnesses. The general medical and neurologic examinations were normal. Visual acuity, visual fields, pupils, and fundi were normal. Between the episodes, she was orthotropic without ptosis or lid retraction in the primary position. However, infraduction of the right eye was mildly impaired, and right upper lid retraction was noted on downgaze ( Fig. 1). There was no widening of the palpebral fissure with adduction of the right eye or pupillary changes with adduction or infraduction of the right eye. On resuming the primary position after prolonged left gaze, she developed 18 prism-diopters of right esotropia and reduced abduction, supraduction, and infraduction of the right eye ( Fig. 2). Sustained right gaze or upgaze did not induce this phenomenon. The esotropia and reduced ductions were eliminated by attempted right gaze. Results of routine chemical analyses and thyroid function tests were normal. Review of the outside MRI showed no abnormalities, especially in the midbrain. The patient reported markedly reduced episodes after taking 200 mg carbamazepine twice a day. In addition, the 248 J Neuro- Ophthalmol, Vol. 26, No. 4, 2006 Primary Aberrant Regeneration and Neuromyotonia J Neuro- Ophthalmol, Vol. 26, No. 4, 2006 FIG. 1. Extraocular movements during the quiescent period. A. The range of eye movements is full except for slightly reduced infraduction in the right eye. B. Upper lid retraction on the right is evident on downgaze. interictal infraduction deficit and lid retraction on down-gaze improved with the medication. However, she could not continue the medication because of elevated liver enzyme levels. Five months later, the neuromyotonia almost resolved without medication. However, mild lid retraction on downgaze remained. DISCUSSION We believe that our patient had neuromyotonia in the setting of primary aberrant regeneration of the third cranial nerve. Ocular neuromyotonia is characterized by brief, episodic contractions of muscles innervated by the oculomotor, trochlear, or abducens nerves, which result in an episodic ocular motility disorder ( 1,4). The episodes may develop spontaneously or after sustained eccentric gaze ( 1,4). Between the episodes, patients may show signs of ophthalmoplegia ( 4). Ocular neuromyotonia has been described in 45 patients and has involved the third cranial nerve in 28 ( 62.2%), the fourth cranial nerve in 4 ( 8.9%), and the sixth cranial nerve in 13 ( 28.9%) ( 1,7- 12). Ocular neuromyotonia may be idiopathic ( 1). However, most of the previously reported patients had identifiable causes including cranial irradiation ( n = 22, 48.9%) ( 4,7,13,14), neurovascular compression ( n = 3, 6.7%) ( 2,9,15), dysthyroid orbitopathy ( n = 3, 6.7%) ( 16,17), previous intracranial surgery ( n = 2, 4.4%) ( 18,19), compression by Paget disease ( n = 1,2.2%) ( 6), cavernous sinus thrombosis due to mucormycosis ( n = 1) ( 20), previous myelography ( n = 1, 2.2%) ( 21), and brainstem stroke ( n = 1, 2.2%) ( 10). Ocular neuromyotonia involving the third cranial nerve usually manifests with episodes of horizontal or vertical diplopia, lid retraction, or pupillary disorder ( 1,4,19). Previously, features of aberrant regeneration ( widening of FIG. 2. Extraocular movements during a neuromyotonic episode. On resuming primary gaze after sustained left gaze, the patient has esotropia and reduced abduction, supraduction, and infraduction of the right eye. 249 J Neuro- Ophthalmol, Vol. 26, No. 4, 2006 Choi et al the palpebral fissure on downgaze or pupillary synkinesis) had been described between the episodes in only 7 patients with third cranial nerve neuromyotonia ( 4- 6). Five of these patients also had a baseline partial third nerve palsy consisting of mild ptosis ( n = 2), ptosis with elevation deficit ( n = 1), ptosis with pupillary dilatation ( n = 1), and impaired all ductions ( n = 1) ( 4- 6). Four of the 7 patients with third cranial nerve neuromyotonia and interictal signs of aberrant regeneration had a history of cranial radiation due to parasellar tumor ( 4,5), one showed an aneurysm of the internal carotid artery, and another one exhibited severe remodeling of the skull base along with third and sixth cranial nerve palsy due to Paget disease ( 6). 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