Internuclear Ophthalmoplegia review |neet pg | USMLE Step 1 | Examples

Right & Left Internuclear Ophthalmoplegia (ino) review for neet pg and USMLE Step 1 is Explained with Examples with causes, test and treatment plan to ace international medical exams like neet pg, usmle, smle, DHA, HAAD and others.

Internuclear ophthalmoplegia (INO) is a neuro-ophthalmological disorder characterized by impaired horizontal eye movement due to dysfunction of the medial longitudinal fasciculus (MLF). The MLF is responsible for coordinating eye movements, particularly the conjugate movement of the eyes during lateral gaze. Here are some high-yield points regarding the causes, symptoms, signs, and treatment of internuclear ophthalmoplegia for USMLE and NEET PG preparation:

INO is commonly caused by demyelination or structural lesions affecting the MLF. Multiple sclerosis (MS) is the most frequent cause of INO, accounting for approximately 50% of cases. Other potential causes include stroke (e.g., brainstem infarction), brainstem tumors (e.g., glioma), trauma, infections (e.g., brainstem encephalitis), and vascular malformations.

Symptoms of Patient coming with INO typically present with double vision (diplopia) during lateral gaze, particularly when looking towards the side of the affected eye. The diplopia is often horizontal and occurs due to the impaired adduction of the affected eye. Vertical eye movements and convergence are generally preserved. Some individuals may also complain of oscillopsia, which refers to the perception of a visual oscillation or instability and patient can't track fastly moving objects.

On examination, there are specific signs that help diagnose INO. During lateral gaze towards the side of the affected eye, the affected eye fails to adduct properly, leading to dissociated nystagmus. Nystagmus is characterized by involuntary rhythmic oscillations of the eyes. In INO, nystagmus may be observed in the abducting eye, with horizontal oscillations away from the midline. The contralateral eye (the one not performing the abduction) shows normal adduction.

The management plan of INO primarily focuses on addressing the underlying cause. In cases where INO is caused by multiple sclerosis, disease-modifying therapies aimed at reducing inflammation and preventing further demyelination may be initiated. Corticosteroids, such as high-dose intravenous methylprednisolone, are commonly used as a short-term treatment option to manage acute exacerbations of MS-related INO. Physical therapy and prism glasses may be considered to help alleviate diplopia and improve visual function.

The prognosis of INO depends on the underlying cause. INO associated with multiple sclerosis tends to have a relapsing-remitting course, with periods of exacerbation and remission. However, it is important to note that the prognosis varies based on the severity and location of the lesion causing INO. INO caused by other etiologies, such as stroke or tumors, may have different outcomes depending on the extent of the damage and response to treatment.

In conclusion, internuclear ophthalmoplegia is characterized by impaired horizontal eye movement due to dysfunction of the medial longitudinal fasciculus. It is commonly caused by demyelination or structural lesions affecting the MLF, with multiple sclerosis being the most frequent cause. Symptoms include diplopia during lateral gaze, while examination reveals dissociated nystagmus with impaired adduction of the affected eye. Treatment focuses on addressing the underlying cause, and the prognosis varies depending on the etiology and response to treatment.

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