Opsoclonus myoclonus and ataxia syndrome with supraventricular tachycardia

Abstract

Pediatric opsoclonus-myoclonus and ataxia syndrome (OMAS) is a neurologic disorder characterized by disturbances in eye movement, muscle jerks, ataxia, sleep, and mood. In approximately 50% of cases, it is a paraneoplastic syndrome associated with a neuroblastoma. In the remaining cases, it is believed that the tumor is occult, has involuted, or there is a preceding immune-stimulating event. While neuroblastomas can be associated with other paraneoplastic syndromes, supraventricular tachycardia (SVT) is rarely reported in the literature, and to our knowledge, this is the first case of SVT secondary to idiopathic OMAS. Confounding treatment toxicity, including intravenous immunoglobulin and other immunomodulatory drugs, should be screened for possible cardiovascular side effects in OMAS patients. The development of cardiac arrhythmias during OMAS treatment is not a contraindication to therapy. In these patients, arrhythmias should be controlled with vagal maneuvers or antiarrhythmics as needed while OMAS treatment is completed.

Opsoclonus-myoclonus and ataxia syndrome (OMAS) is a rare movement disorder in children. Onset is usually between 1 and 3 years of age.¹ It is often associated with an underlying neuroblastoma or considered to be parainfectious. Diagnosis can be difficult and requires three of four criteria to be met: opsoclonus or ocular flutter, myoclonus or ataxia, behavioral or sleep disturbances, and neuroblastoma.² OMAS is treated with immunomodulatory drugs such as steroids, intravenous immunoglobulin (IVIG), and rituximab. Regardless of etiology, early recognition and treatment of OMAS is important to prevent permanent neurologic sequelae.² To better characterize the clinical profile of this syndrome and its associated conditions, we present a case report of a 9-month-old male experiencing supraventricular tachycardia (SVT) and OMAS without an associated neuroblastoma.

CASE DESCRIPTION

A 9-month-old male was born via cesarean delivery at 34 weeks’ gestation due to maternal preeclampsia and fetal heart rate decelerations. His past medical history was significant for macrocephaly and hypotonia. A month before presentation, he developed abnormal eye and body movements. He was noted to be more tired and to be eating less than usual. Upon examination, he was alert and had intermittent, rapid, low-amplitude, chaotic eye movements, abnormal jerking of the head and arms, and low truncal tone. Muscle bulk and reflexes were normal except for an exaggerated Moro reflex. An extensive initial workup included magnetic resonance imaging of his brain consistent with benign enlargement of subarachnoid spaces of infancy. Computed tomography of the neck, chest, abdomen, and pelvis and urinary vanillylmandelic acid (VMA) and homovanillic acid (HVA) levels were within normal limits and did not reveal a neuroblastoma.

An overnight electroencephalogram showed motion artifact due to near-constant myoclonus but otherwise normal brain activity. Lumbar puncture revealed no evidence of paraneoplastic, autoimmune, or infectious processes. Due to concern for a metabolic process, additional laboratory tests were sent out, including lactic acid, organic acids, plasma total and free carnitine, acylcarnitine, and cell pellet to bank DNA. The patient was then started on IVIG and dexamethasone. After his first infusion of IVIG, his abnormal movements worsened, his heart rate increased into the 300s, and telemetry showed an absence of P waves, consistent with SVT. He did not respond to ice or vagal maneuvers so his heart rate was controlled with adenosine. Follow-up electrocardiogram excluded Wolff-Parkinson-White syndrome and other pathologies. An echocardiogram showed no structural abnormalities. He was then started on propranolol. While in the pediatric intensive care unit, the patient experienced four episodes of SVT, two of which self-resolved and two of which resolved with vagal maneuvers.

After completion of treatment with IVIG and dexamethasone, the patient’s opsoclonus completely resolved. His myoclonus was no longer apparent when laying supine, but he did have infrequent, subtle jerks of his arms and trunk when held in a sitting position. After two more episodes of SVT, he was started on digoxin. The patient was discharged on propranolol and digoxin. Repeat urine VMA and HVA levels were slightly elevated secondary to suspected dilution. All metabolic laboratory tests that were sent out returned with normal results. An outpatient meta-iodobenzylguanidine scan revealed a normal distribution of radiotracer without uptake suspicious for a mass.

DISCUSSION

This 9-month-old infant had ocular flutter, myoclonus, and behavioral disturbances consistent with OMAS. While OMAS is often secondary to diagnosable neuroblastoma, this patient met the criteria for OMAS with symptoms alone.^3,4 No neuroblastoma has been detected in this patient to date. When no tumor is elucidated from OMAS patients, a viral etiology can usually be identified as the primary cause of OMAS. In extremely young patients like the infant in this case, a history of viral infection is not always obvious, and no known infection was present in this patient before symptom onset.

This patient was initially treated by IVIG. Four hours after his infusion, he experienced his first episode of SVT. While cases of SVT during IVIG infusion have been reported, these episodes typically occur exclusively during infusion.^5,6 This patient’s SVT occurred significantly after IVIG infusion and reoccurred multiple times with no relation to medication administration. For this reason, the patient’s SVT is likely a symptom of OMAS rather than a medication side effect. Currently, no literature associates OMAS with SVT. Only one other case report described SVT as the presenting symptom of neuroblastoma in a 12-week-old female patient, but she had no additional symptoms of OMAS.⁷