Ocular neuromyotonia: an unusual case after radiotheraphy for nasopharyngeal carcinoma.

Ocular neuromyotonia (ONM) is an infrequent disorder characterised by recurrent episodes of binocular diplopia caused by paroxysmal contraction of one or several extraocular muscles innervated by the same cranial nerve. It can be triggered spontaneously or caused by prolonged contraction of specific eye muscle(s) and is usually related to a local intracranial radiotherapy antecedent. We report the case of a 46-year-old woman who developed intermittent episodes of binocular diplopia eight years after radiotherapy for a nasopharyngeal carcinoma. After a complete neuro-ophthalmic assessment we diagnosed the case as an abducens nerve neuromyotonia. Although it is infrequent, radiotherapy to the nasopharynx is a possible cause of ONM, due to the proximity to the base of the skull and extraocular motor nerve pathways, especially that of the VI cranial nerve, as is the case presented in this article, about a patient whose history is a nasopharyngeal carcinoma treated with local radiotherapy.

Thyroid peroxidase antibodies may induce demyelination and oculomotor neuromyotonia in the absence of thyroid eye disease.

INTRODUCTION: The first report of oculomotor neuromyotonia (ONM) in a child induced by thyroid peroxidase antibodies (anti-TPO) in the absence of thyroid eye disease (TED). CASE: 14-year-old girl complained of left eye (LE) paroxysmal upper lid fluttering and ptosis precipitated by hyperventilation or sustained left gaze. On sustained left gaze, right eye (RE) upper lid retraction and LE upper lid fluttering with ptosis ensued. RESULTS: Diagnostic work-up revealed markedly elevated anti-TPO (> 600 IU/ml) and no TED. Brain MRI was normal with no signs of tortuous vessels presenting focal demyelination. We hypothesized that anti-TPO directly induced demyelination and set the ground for right ONM with ephaptic transmission between neurons supplying right medial rectus and levator muscle. CONCLUSIONS: Plethora of theories try to decode the ONM. TED associated ONM is not reported in children but is the second most common cause of ONM in adults, advocated to be of compressive origin. Conversely, this case holds true for cross talk hypothesis. All extraocular muscles must be tested to determine the triggering one. ONM should not be overlooked due to its positive response to carbamazepine.

Ocular Neuromyotonia in Children and Adolescents Following Radiation Treatment of Pediatric Brain Tumors.

PURPOSE: To report five cases of ocular neuromyotonia in children and adolescents following radiation therapy for a variety of pediatric brain tumors. Notably, three cases occurred in children younger than 11 years. METHODS: Case series of five patients with ocular neuromyotonia following proton beam therapy or conventional radiation. RESULTS: Five cases of ocular neuromyotonia were identified following radiation treatment of various pediatric brain tumors. Onset ranged from 5 to 142 months after radiation treatment. The abducens nerve/lateral rectus muscle was affected in three patients, and the trochlear nerve/superior oblique muscle was affected in two patients. Ages at symptom presentation were 4 years (intermittent head tilt), 9 years (intermittent blurry vision and head tilt), 10 years (intermittent blurry vision progressing to intermittent diplopia), 15 years (intermittent diplopia), and 17 years (intermittent diplopia). One patient improved with gabapentin. Two patients experienced spontaneous resolution. One patient died due to meta-static disease, and one patient has planned follow-up. CONCLUSIONS: Ocular neuromyotonia occurs most commonly following radiation to the brain and skull base. Clinicians need to be aware that ocular neuromyotonia presents differently in children (who may not report diplopia) than in adults or adolescents (who typically report diplopia). Two children in this series never reported diplopia, only intermittent head tilt and blurry vision. Ocular neuromyotonia requires a high index of suspicion to diagnose, especially in children. Membrane stabilizers can be used effectively, but observation may be a valid option in children because spontaneous resolution was seen. [J Pediatr Ophthalmol Strabismus. 2022;59(5):338-343.].

Post-surgical left oculomotor nerve neuromyotonia: Cause or coincidence?

Ocular neuromyotonia (ONM) is characterized by episodes of binocular diplopia usually triggered by an eye movement requiring contraction of the affected extraocular muscle. It consists of an involuntary, sometimes painful contraction of one or more extraocular muscles. It is most often secondary to radiotherapy of the para-sellar region, although other aetiologies have been reported. Some cases do not have a clearly identified aetiology and are classified as idiopathic. Most cases of ONMs are unilateral but bilateral ONMs have also been described.1-4 We report a case of left ONM in a 55-year-old female patient, several weeks after simultaneous surgical resection of two meningiomas, situated on the right side (Simpson II). The particularity of this case is linked to its puzzling presentation, its similarity with spasm of the near reflex and the putative mechanism through which surgery might have precipitated the symptoms.

Morvan Syndrome Converted from Isaacs' Syndrome after Thymectomy with Positivity for Both Anti-LGI1 and Anti-CASPR2 Antibodies.

Anti-voltage-gated potassium channel complex antibodies-mediated disorder includes Isaacs' syndrome, which is characterized by neuromyotonia, and Morvan syndrome, which is characterized by neuromyotonia, encephalopathy and autonomic dysfunction. We herein report a patient with Morvan syndrome that converted from Isaacs' syndrome after thymectomy. The patient first presented with myospasm in all extremities and positivity for both anti-leucine-rich glioma inactivated 1 (LGI1) and anti-contactin-associated protein like 2 (CASPR2) antibodies and subsequently developed encephalopathy after thymectomy, which was successfully improved by immunotherapy. This is the first case of Morvan syndrome wherein thymectomy worsened Isaacs' syndrome, suggesting that immunotherapy should be considered for Isaacs' syndrome accompanied by positivity for both anti-LGI1 and anti-CASPR2 antibodies to prevent worsening to Morvan syndrome.

Mercury poisoning complicated by acquired neuromyotonia syndrome: A case report.

RATIONALE: Acquired neuromyotonia syndrome is a rare form of peripheral nerve hyperexcitability syndrome. It is characterized by spontaneous and continuous muscle contractions. Acquired neuromyotonia syndrome is mainly observed in patients with autoimmune diseases or tumors, but it is a rare neurological clinical manifestation in patients with mercury poisoning. PATIENT CONCERNS: A 56-year-old woman presented with continuous and involuntary muscle twitching in her legs for 2 months; it was accompanied by a burning sensation in the lower limbs, insomnia, fatigue, and night sweats. These symptoms did not disappear during sleep. DIAGNOSES: Toxicological blood analysis via atomic fluorescence spectrometry revealed that the level of mercury was 0.07 µmol/L (normal level: <0.05 µmol/L). Her urinary mercury level measured using the cold atomic absorption method was 217.50 µmol/mol creatinine, which was considerably higher than the reference range (0-2.25 µmol/mol creatinine for people not in contact with mercury, 0-20 µmol/mol creatinine following long-term exposure). Upon further testing, a high level of mercury (10,572 mg/kg) was detected in the patient's cream. Accordingly, this patient was diagnosed with mercury poisoning. INTERVENTIONS: Treatment with 2,3-dimercapto-1-propanesulfonic acid (DMPS) was initiated. Her urinary mercury level decreased to 9.67 µmol/mol creatinine, and her neuromyotonia syndrome and hyponatremia were relieved, with urine protein completely disappearing after 3 months of treatment. OUTCOMES: After DMPS treatment, the clinical manifestations of the nervous system disappeared and electrolyte parameters returned to normal levels. LESSONS: Acquired neuromyotonia syndrome is a rare disorder caused by the hyperexcitability of peripheral nerves, resulting in spontaneous and continuous muscle contraction. Mercury poisoning should be considered in patients with neuromyotonia syndrome. Early detection of mercury poisoning can prevent unnecessary examinations and treatments.

Childhood onset of acquired neuromyotonia: association with vitamin D deficiency.

Purpose/Aim: Acquired neuromyotonia or Isaacs syndrome is a type of peripheral nerve hyperexcitability of autoimmune origin. It may occur as an isolated, paraneoplastic or accompanied with some autoimmune diseases. This report describes acquired neuromyotonia in a child with a new reported association with vitamin D deficiency. Case report: A 9-year-old child, in whom the diagnosis of acquired neuromyotonia was made by clinical and typical electromyographic findings. All paraneoplastic and autoimmune workup was normal, except for a vitamin D deficiency state. A dramatic improvement was recorded on both clinical and electrophysiological base after vitamin D replacement. Conclusion: An in-depth future analysis of vitamin D status in patients with neuromyotonia will help to establish whether the association of neuromyotonia with vitamin D deficiency is casual or whether these two conditions may be causally related.

Bilateral oculomotor ocular neuromyotonia: a case report.

BACKGROUND: Ocular neuromyotonia (ONM) is characterized by episodic diplopia, which is usually triggered by prolonged eccentric gaze of the affected extraocular muscles. The spell is characterized by involuntary, occasionally painful, sustained contraction of one or more extraocular muscles innervated by the oculomotor, trochlear, or abducens nerve. ONM usually occurs as a late consequence of radiotherapy around the parasellar area, although idiopathic cases have been reported. Most cases are unilateral; however, bilateral ONM has occasionally been described. CASE PRESENTATION: A 60-year-old woman presented with a 4-month history of episodic, painful, horizontal binocular diplopia. She underwent external beam radiotherapy to the skull base for treatment of nasopharyngeal carcinoma. The tumor was well controlled. General neurological examination findings were unremarkable. Neuro-ophthalmic examination revealed normal visual acuity, visual fields, pupils, and fundi. Ocular alignment showed orthotropia with normal ocular motility. Myasthenic eyelid signs were absent. However, she developed episodes of involuntary sustained contraction of the medial rectus muscle following prolonged eccentric gaze toward the affected medial rectus muscle, which resulted in esotropia upon returning to the primary position. The esotropic episodes spontaneously resolved after approximately 2 min. These spells affected both medial rectus muscles. Both pupils remained normal throughout the examination. Magnetic resonance imaging revealed neither brain parenchyma/brain stem lesions nor tumor recurrence. Her symptoms were successfully treated with carbamazepine. CONCLUSIONS: Episodic esotropia in the adducting eye following prolonged horizontal eccentric gaze is a significant characteristic of ONM affecting the bilateral medial rectus muscles (i.e., bilateral oculomotor ONM). In spite of its extreme rarity, ONM should be considered as a differential diagnosis of episodic diplopia, especially in patients with a history of radiotherapy around the parasellar area. Careful examination with prolonged eccentric gaze should be performed to achieve a correct diagnosis and avoid an extensive unnecessary workup.

Ocular Neuromyotonia: Case Reports and Literature Review.

Ocular neuromyotonia (ONM) is a rare eye movement disorder, presenting as a paroxysmal involuntary spasm of one or more extra-ocular muscles, that can persist for a few seconds up to several minutes. The phenomenon is caused by the contraction of an extra-ocular muscle, excited by a damaged nerve, which leads to delayed muscle relaxation. We present eight patients with this rare condition together with an overview of the literature on all published ONM cases. One of the presented cases is possibly secondary to hypovitaminosis D. This association has not been reported previously in the literature. A possible underlying mechanism is given.

Isaacs' syndrome in a patient with dermatomyositis: case report and review of the literature.

This is a case report of Isaacs' syndrome in dermatomyositis. The patient presented with proximal muscle weakness, rash, elevated muscle enzyme, myopathic electromyograph and typical muscle biopsy. Ultimately he developed typical symptoms of Isaacs' syndrome which is an autoimmune channelopathy from voltage gated potassium channel antibody (anti-VGKC) leading to dysfunction of axonal discharge at neuromuscular junctions. It shares some similar characteristics with dermatomyositis such as autoimmunity, its association with malignancy and the response to treatment.

Extensive Postradiation Ocular and Diffuse Cranial Neuromyotonia Mimicking Myasthenia Gravis.

BACKGROUND: Ocular neuromyotonia is a rare, but well-recognized, complication of cranial irradiation. CASE REPORT: Using figures and videos, we report a 52-year-old man with extensive ocular, brainstem, and lower cranial nerve neuromyotonia postradiation therapy for a fourth ventricle glioma who, in the context of an apparently positive edrophonium test, was initially misdiagnosed with myasthenia gravis. CONCLUSIONS: This is the first case of postirradiation neuromyotonia to be reported with such extensive cranial nerve and brainstem involvement.

Abducens ocular neuromyotonia as a delayed complication of oropharyngeal carcinoma treated with radiation.

BACKGROUND: Ocular neuromyotonia (ONM) is a disorder characterized by periodic involuntary extraocular muscle contraction that occurs almost exclusively in the setting of prior radiation to the sella or skull base. We present the first case of abducens neuromyotonia associated with oropharyngeal carcinoma. METHODS AND RESULTS: We report a case of a 63-year-old patient with abducens ONM occurring 16 years after radiation treatment for oropharyngeal squamous cell carcinoma. A literature review was performed using Medline and PubMed databases to search for all documented cases of abducens neuromyotonia. Our review found 20 cases of abducens neuromyotonia but none after radiotherapy (RT) to the oropharynx. CONCLUSION: Abducens ONM can occur because of disease at anatomic locations remote from the course of the sixth cranial nerve, most likely because of the irradiated area exceeding the intended field. Our case also supports the fact that RT can significantly precede symptom onset. © 2016 Wiley Periodicals, Inc. Head Neck 38: E2428-E2431, 2016.

Use of botulinum toxin type A for the treatment of radiation therapy-induced myokymia and neuromyotonia in a dog.

CASE DESCRIPTION A 5-year-old castrated male Maltese was evaluated for intermittent clinical signs of muscle cramping and abnormal movements of the skin of the right pelvic limb at the site where an infiltrative lipoma had twice been resected. After the second surgery, the surgical field was treated with radiation therapy (RT). The clinical signs developed approximately 14 months after completion of RT. CLINICAL FINDINGS When clinical signs were present, the right biceps femoris and semitendinosus muscles in the area that received RT were firm and had frequently visible contractions, and the skin overlying those muscles had episodic vermiform movements. Electromyography of those muscles revealed abnormal spontaneous activity with characteristics consistent with myokymic discharges and neuromyotonia. Magnetic resonance imaging of the affected leg revealed no evidence of tumor regrowth. The myokymia and neuromyotonia were considered secondary to RT. TREATMENT AND OUTCOME 4 U of Clostridium botulinum toxin type A (BoNT-A) neurotoxin complex was injected into the affected muscles at each of 6 sites twice during a 24-hour period (ie, 48 U of BoNT-A were administered). The clinical signs were completely resolved 10 days after BoNT-A treatment and were controlled by repeated BoNT-A treatment every 3 to 4 months for > 1 year. CLINICAL RELEVANCE To our knowledge, this is the first report of myokymia and neuromyotonia secondary to RT in a dog. For the dog of this report, injection of BoNT-A into the affected muscles was safe, effective, and easy to perform.