642 J Neurol Neurosurg Psychiatry 2000;69:642–644 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.69.5.642 on 1 November 2000. Downloaded from

SHORT REPORT

Idiopathic ocular neuromyotonia: a neurovascular compression syndrome?

C Tilikete, C Vial, M Niederlaender, P L Bonnier, A Vighetto

Abstract specifically there was no history of radiation Ocular neuromyotonia in the muscles treatment. innervated by the right oculomotor nerve Neuro-ophthalmological examination was diagnosed in a patient without a showed normal visual acuity, visual field, and history of radiation therapy. Electromyog- fundi. Between episodes, the patient had mild raphy of the levator palpebrae showed ptosis, poorly reactive miosis, and slight limita- continuous motor unit activity. Brain MRI tion of infraduction and supraduction of the disclosed a close contact between the right right eye. Orthoptic measurements showed a third cranial nerve and a basilar artery small exophoria worsening on left gaze, a right dolichoectasia. The patient partly ben- hypophoria in primary and far up gaze, and a efited from carbamazepine therapy. This small right hyperphoria in far down gaze. unique finding suggests that neurovascu- There was no evidence of primary misdirection lar compression syndrome could be an phenomena. Her right pupil was 2.4 mm and hitherto unrecognised cause of ocular the left pupil was 2.8 mm diameter. Cocaine neuromyotonia. instillation resulted in a bilateral pupil dilation (J Neurol Neurosurg Psychiatry 2000;69:642–644) (RE=3.5 mm and LE=3.7 mm) ruling out oculosympathetic paresis. Ptosis and limitation copyright. Keywords: ocular neuromyotonia; neurovascular com- pression syndrome; carbamazepine of eye movements suggested a minimal right Neuro-ophthalmology third nerve palsy. Neurological examination Unit, Hôpital was otherwise normal. Neurologique et Diplopic paroxysms could occur spontane- Neurochirurgical P Ocular neuromyotonia is a rare paroxysmal Wertheimer, 59 Bd involuntary contraction of one or more ocular ously but were often triggered by holding the Pinel, 69003 Lyon, motor muscles resulting in paroxysmal diplopia eyes upwards for 20 to 30 seconds. During an France and strabismus. Among 29 patients reported in attack, the right eye showed mild esotropia, C Tilikete the literature, 16 had received radiation marked limitation of supraduction, and infra- A Vighetto therapy to the parasellar and sellar regions a duction with lid retraction, mild limitation of 1–6 Electromyography few months to 18 years before. In seven abduction, and no change in the pupil size. Unit, Hôpital cases, ocular neuromyotonia resulted from Paroxysmal diplopia could not be triggered by http://jnnp.bmj.com/ Neurologique et compressive lesions such as a clivus chordoma, hyperventilation. Neurochirurgical P a supraclinoid carotid aneurysm, a Paget bone Electromyography with a concentric needle Wertheimer, 59 Bd dystrophy, a mycormycosis of the cavernous (diameter=0.3 mm) was normal, showing no Pinel, 69003 Lyon, 3–5 7 spontaneous activity or myotonia in the first France sinus, arachnoiditis, and Graves’ disease. In C Vial the six remaining patients, no lesion was dorsal interosseus, the deltoid, and the orbicu- found.3589We document with EMG and MRI laris oculi. However, EMG was abnormal in Neuro-radiology Unit, a unique case of neurovascular compression the right levator palpebrae, disclosing sponta-

Hôpital Neurologique syndrome associated with idiopathic ocular neous continuous muscle unit activity, with on September 30, 2021 by guest. Protected et Neurochirurgical P neuromyotonia. brief bursts of motor unit potentials, firing at Wertheimer, 59 Bd high frequency. Voluntary contraction of this Pinel, 69003 Lyon, France muscle was normal and no afterdischarges M Niederlaender Case report were recorded. A 67 year old man presented with a 1 month Brain CT (GE, slice thickness=5 mm) with Radiology Unit, history of episodic diplopia. He reported spells and without contrast enhancement did not Clinique de la of horizontal or oblique double vision that show any brain stem lesion but disclosed a Sauvegarde, Av des sources, 69 009 Lyon, occurred spontaneously five or six times a day, dolichoectasia of the basilar artery displaying a France lasting less than 10 seconds. While complain- large right sided loop anterior to the mesen- P L Bonnier ing of diplopia, his wife noticed a transient cephalon. T2 MRI (Philips Gyroscan T5-NT; esodeviation of the right eye. He was symptom 0.5 tesla with head coil; TR=5000 ms, TE=450 Correspondence to: free between attacks. ms, TF=69; slice thickness=1 mm) of the brain Dr Caroline Tilikete [email protected] History disclosed abdominal aortic aneu- stem using fast spin echo high resolution rysm, lumbar sympathectomy for arteriopathy, (FSE-HR) in the plane of the third nerve was Received 6 December 1999 and asymptomatic 50% stenosis of the left performed. It showed a contact between the and in revised form 24 February 2000 carotid artery. There was no history of ocular loop of the dolichoectasic basilar artery and the Accepted 6 March 2000 motor, anisocoria, or neurological disorder and right oculomotor nerve in the premesen-

www.jnnp.com Idiopathic ocular neuromyotonia: a neurovascular compression syndrome? 643 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.69.5.642 on 1 November 2000. Downloaded from

FSE-HR T2 MRI of the brain stem in the plane of the third nerves showing a contact between the loop of the dolichoectasic basilar artery and the right oculomotor nerve (arrows) in the premesencephalic fossa, close to the root exit zone. cephalic fossa, close to the root exit zone paretic pupil dilation, rarely as transient pupil (figure). contraction occurring during the diplopic The patient was treated with 100 mg spells, and in one recent case as permanent carbamazepine daily. He subjectively reported tonic pupil.37Right miosis of our patient could a 50% decrease of spell frequency within a few either be related to unknown physiological ani- days. However, on examination, the same par- socoria or permanent tonic pupil related to copyright. oxysms of ocular spasms could still be triggered ocular neuromyotonia. Other permanent exci- by holding the eyes upward. Finally, car- tatory manifestations in the third nerve de- bamazepine was poorly tolerated even at the pendent muscles have been reported, such as low dose and was stopped. Spell frequency lid retraction and pupil synkinesis. then returned to its pretest level. Gabapentine Neuromyotonia (not limited to ocular neu- (300 mg three times a day) and acetazolamide romyotonia) is a syndrome of spontaneous (250 mg twice a day) trials yielded no benefit. muscle hyperactivity that can be triggered by Aftera1yearfollow up, the patient remained voluntary muscle contraction, due to abnormal medication free and still had the same eye excitability of peripheral nerve motor axons.10 movement disorder. Neuromyotonia belongs to the syndromes of continuous motor unit activity which encom- Discussion pass diVerent diseases that vary in their clinical http://jnnp.bmj.com/ The paroxysmal limitation of right eye move- presentation and associated electrophysiologi- ments that occurred in this patient was typical cal abnormalities, but have in common sus- of ocular neuromyotonia aVecting muscles tained involuntary motor unit activity.10 In innervated by the oculomotor nerve. Indeed, continuous motor unit activity, EMG shows the clinical hallmark of ocular neuromyotonia continuous hyperactivity such as neuromyot- is transient diplopia and strabismus that onic and myokimic discharges and fascicula- develop spontaneously and after holding ec- tions. Continuous motor unit activity is associ- centric gaze, due to a tonic contraction or ated with peripheral motor nerve diseases, on September 30, 2021 by guest. Protected spasm of ocular muscles.8 In this patient, either in a diVuse or a focal distribution.10 sustained upgaze induced spasms of the levator Ocular neuromyotonia is likely to be related to palpebrae and superior rectus of the right eye focal continuous motor unit activity. Indeed, in with resulting lid retraction and limitation of the first reported cases of ocular neuromyoto- infraduction. Concomitant spasms of inferior nia extraocular muscle EMG showed neuro- oblique, inferior rectus, and medial rectus best genic abnormalities.12 Since then, the disease explained the limitation of supraduction and has been clinically recognised without EMG abduction of the same right eye. This coactiva- investigation. In our patient, we were able to tion of muscles related to the same ocular record EMG activity in the levator palpebrae, motor nerve is a frequent symptom of ocular and we showed unambiguous signs of continu- neuromyotonia.3 Our case associated ocular ous motor unit activity. This result indicates neuromyotonia with a chronic third nerve defi- that ocular neuromyotonia, at least in our case, cit. Half of the reported cases of ocular neuro- meets diagnosis criteria for focal continuous myotonia have also a chronic ocular motor motor unit activity. nerve involvement. Involvement of pupil motil- Radiation induced plexus lesion is a well ity has been rarely reported in ocular neuro- established cause of focal limb continuous myotonia of the third nerve, as permanent motor unit activity. Many cases of ocular neu-

www.jnnp.com 644 Tilikete, Vial, Niederlaender, et al J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.69.5.642 on 1 November 2000. Downloaded from

romyotonia also occurred after cerebral radia- frequency with 50 mg carbamazepine twice a tion therapy. Focal continuous motor unit day. Unfortunately, the medication was poorly activity may involve other cranial nerves. tolerated and had to be stopped. Other Among them, hemifacial spasm usually results membrane stabilising agents such as gabapen- from neurovascular compression syndrome tine and acetazolamide were not eYcient in our and recently, a case of superior oblique case. myokimia has also been related to a neurovas- We suggest that some idiopathic ocular neu- cular compression.11 12 Brain MRI in our romyotonias might be explained by vascular patient clearly demonstrated a close contact compression of one ocular motor nerve, which between dolichoectasic basilar artery loop and might be identified by specific MRI investiga- the third nerve, near the root exit zone. Abnor- tion. mal enlargement and elongation of the basilar artery (vertebrobasilar dolichoectasia) is a well We thank Professor DS Zee for helpful commentaries, and Mrs recognised finding in brain imaging studies and M Bongrand for orthoptic assistance. aVects 1.7% of the population.13 This condi- tion is asymptomatic but in 6% of pqatients, it 1 Ricker VK, Mertens HG. Okulare neuromyotonie. Klin may cause rostral brain stem signs and Monatsbl Augenheilkd 1970;156:837–42. 2 Papst W. Zur diVerentialdiagnose der okularen neuromyot- symptoms, usually related to ischaemia or onie. Ophthalmologica 1972;164:252–63. compression. Compression by a dolichoectasic 3 Ezra E, Spalton D, Sanders MD, et al. Ocular neuromyoto- nia. Br J Ophthalmol 1996;80:350–5. basilar artery has already been involved in ocu- 4 Yee RD, Purvin VA. Ocular neuromyotonia : three case lar motor nerve paresis and in hemifacial reports with eye movement recording. J Neuroophthalmol 10 14 1998;18:1–8. spasm. Although we cannot rule out a coin- 5 Shults WT, Hoyt WF, Behrens M, et al. Ocular neuromyo- cidental finding, we suggest that it could tonia. A clinical description of six cases. Arch Ophthalmol 1986;104:1028–34. explain the oculomotor nerve ocular neuro- 6 Morrow MJ, Kao GW, Arnold AC. Bilateral ocular myotonia in our case. neuromyotonia: oculagraphic correlations. Neurology 1996; 46:264–6. Ephaptic neural transmission is the potential 7 Abdulla N, Eustace P. A case of ocular neuromyotonia with mechanism for hemifacial spasm, ocular neu- tonic pupil. J Neuroophthalmol 1999;19:125–7. 8 Frohman EM, Zee DS. Ocular neuromyotonia: clinical fea- romyotonia, and likely superior oblique neuro- tures, physiological mechanisms and response to therapy. myokimia. In our patient, as in hemifacial Ann Neurol 1995;37:620–6. 9 Safran AB, Magistris M. Terminating attacks of ocular neu- spasm, this ephaptic neural transmission could romyotonia. J Neuroophthalmol 1998;18:47–8. originate in a segmental demyelinated portion 10 Auger RG. Diseases associated with excess motor unit activ- ity. Muscle Nerve 1994;17:1250–63. of the nerve, where vascular compression 11 Milandre L, Bonnefoie B, Pestre P, et al. Dolichoectasies occurs.8 However, hyperventilation, which may artérielles vertébrobasilaires. Rev Neurol 1991;147:714–22. 12 Samii M, Rosahl SK, Carvalho GA, et al. Microvascular copyright. precipitate manifestations of demyelinating decompression for superior oblique myokimia: first experi- lesion on cranial nerves, did not trigger ocular ence. J Neurosurg 1998;89:1020–4. 15 13 Yu YL, Moseley IF, Pullicino P, et al. The clinical picture of neuromyotonia spells in our patient. On the ectasia of the intracerebral arteries. J Neurol Neurosurg Psy- other hand, sensitivity to carbamazepine (a chiatry 1982;45:29–36. 14 Moschner C, Moser A, Kömpf D. Bilateral oculomotor membrane stabilising agent), even at low doses nerve palsy due to dolichoectasia of the basilar artery. Neu- such as 100 mg twice a day in ocular roophthalmology 1997;17:39–43. neuromyotonia, is consistent with this concept. 15 Walker MF, Zee DS. The eVect of hyperventilation on downbeat nystagmus in cerebellar disorders. Neurology Our patient had decreased diplopic spell 1999;53:1576–9. http://jnnp.bmj.com/ on September 30, 2021 by guest. Protected

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