Opsoclonus as a paraneoplastic manifestation is most commonly seen in
**Core Concept**
Opsoclonus is a rare paraneoplastic neurologic disorder characterized by chaotic, rapid, and irregular eye movements, often accompanied by myoclonus and ataxia. This phenomenon is thought to result from an autoimmune response against the cerebellar neurons, leading to the characteristic symptoms.
**Why the Correct Answer is Right**
The most common association of opsoclonus with a neoplasm is neuroblastoma, particularly in children. This is because the opsoclonus-myoclonus syndrome (OMS) is often seen in patients with neuroblastoma, and the presence of OMS can be an indicator of the underlying tumor. The pathophysiology involves an autoimmune response to the neuronal antigens released by the tumor, which leads to the activation of microglia and the release of pro-inflammatory cytokines, ultimately resulting in the characteristic symptoms of opsoclonus.
**Why Each Wrong Option is Incorrect**
**Option A:** Other paraneoplastic syndromes such as Lambert-Eaton myasthenic syndrome (LEMS) and paraneoplastic cerebellar degeneration (PCD) are more commonly associated with small cell carcinoma of the lung. While they can also present with neurological symptoms, they are not typically associated with opsoclonus.
**Option B:** Multiple sclerosis is an autoimmune disease of the central nervous system, but it is not typically associated with opsoclonus as a paraneoplastic manifestation.
**Option C:** Glioblastoma is a primary brain tumor that can cause neurological symptoms, but it is not typically associated with opsoclonus as a paraneoplastic syndrome.
**Clinical Pearl / High-Yield Fact**
When encountering a patient with opsoclonus, it is essential to consider the possibility of an underlying neoplasm, particularly neuroblastoma in children. A thorough evaluation, including imaging studies and tumor markers, is necessary to rule out an underlying malignancy.
**Correct Answer:** D. Neuroblastoma.