Opsoclonus

Amrita Choudhury, M.Optom

Senior Optometrist, I Care Eye Hospital-Noida

Saptarshi Mukherjee, M.Optom

Senior Optometrist, Centre for Sight, New Delhi, India

 

Opsoclonus is rare oculomotor disorder ,commonly known as dancing eye. It is defined as chaotic, multi-directional, rapid, involuntary, conjugate ocular movements without any intersaccadic interval. Specially Opsoclonus is categorised in two forms, Organic and Functional. Organic category is also manifested even during sleep or lid closure. However, functional category is associated in frequent blinking.

The exact etiology of opsoclonus remains uncertain, but proposed mechanisms include impaired omnipause cell function leading to lack of saccadic inhibition, or instability of the burst neurons and malfunctioning Purkinje cells in the vermis leading to disinhibition of the cerebellar fastigial nucleus.⁽¹⁾

Opsoclonus as a paraneoplastic disorder is more common in children than in adults. In adult organic opsoclonus is often manifested in carcinoma cases.

Organic Opsoclonus can occur due to paraneoplastic disorders, autoimmune, infectious, metabolic, and toxic disorders. Some studies ⁽²⁾ say, the most common malignancy associated with Opsoclonus is lung cancer.

In the other way functional Opsoclonus can be distracted with any secondary motor task. In this scenario, saccadic oscillations varies its amplitude.

Opsoclonus is mostly increased in attempting fixation, up gaze, convergence, smooth pursuit movement or vestibular nystagmus.

Limb myoclonus is often associated with acquired opsoclonus. It is most common in children. Its manifestation of occult malignancies, in particular, neural crest tumors (neuroblastoma, ganglioneuroblastoma, ganglioneuroma).

Acquired opsoclonus is probably immune arbitrate. Its neural component remains a mystery, and there may be no single site involved in the causation of opsoclonus. Opsoclonus in neonate form has been associated with visual disturbance, Para-infectious cerebellitis, and encephalitis. In this case some children can still be left with some permanent neurologic abnormalities, including ataxia and defective cognition. ⁽³⁾

Opsoclonus is rare disorder, it affects 1 in 10 lakhs in population. There is no perfect evidence of genetical or gender-based manifestation. Commonly it is presented in children between age of 1 to 3 years. Once opsoclonus is confirmed for a child, then child should be referred for oncologic investigations.

For adults’ cases, commonly opsoclonus and may be postinfectious, be drug induced e.g., amitriptyline, lithium, phenytoin, cocaine. Infections are encephalitis, human immunodeficiency virus. Although 14% cases are from cancer related. Opsoclonus may also occur from cerebellar, brainstem or diffuse cerebral injury.

Opsoclonus is quite similar with nystagmoid eye movements, but nystagmus is presence with slow phase during ocular movement which may or may not be fast re-fixating movements. Opsoclonus is a burst of back-to-back saccades with no intersaccadic interval. There is no slow phase and consists rapid movements. Sometimes opsoclonus is misdiagnosed with ocular flutter but it can be differentiated by multi-directional movements. So, it is possible that ocular flutter transfer to opsoclonus. Thus, ocular flutter is alarmed for suspicion of Opsoclonus- Myoclonus syndrome. It can be differentiated with good clinical observation as well as high contest clinical features.

 

References

1. Daniel R. Gold,17 – Eye Movement Disorders: Nystagmus and Nystagmoid Eye Movements,Neuro-Ophthalmology (Third Edition),2019,Pages 585-610,
2. Rishi P. Singh, Arun D. Singh, CHAPTER 63 – Ocular paraneoplastic diseases, Clinical Ophthalmic Oncology,W.B . Saunders 2007,Pages 378-384,
3. Grant T. Liu, Nicholas J. Volpe, Steven L. Galetta, CHAPTER 17 – Eye movement disorders: Nystagmus and nystagmoid eye movements. Saunders,2010,Pages 587-610,