Sea saw nystagmus is seen in –
**Core Concept**
Sea saw nystagmus, also known as pendular nystagmus, is a type of ocular motor disorder characterized by a rhythmic oscillation of the eyes in multiple planes. This condition is often associated with disorders of the brainstem, particularly those affecting the cerebellum or its connections.
**Why the Correct Answer is Right**
Sea saw nystagmus is typically seen in patients with multiple sclerosis (MS), a chronic autoimmune disease that affects the central nervous system. The exact mechanism of sea saw nystagmus in MS is not fully understood, but it is thought to involve damage to the cerebellar connections within the brainstem. This damage disrupts the normal coordination of eye movements, leading to the characteristic pendular oscillations.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because sea saw nystagmus is not typically associated with peripheral vestibular disorders, such as benign paroxysmal positional vertigo (BPPV).
**Option B:** This option is incorrect because while ocular motor apraxia can cause eye movement disorders, it is not characteristically associated with the pendular oscillations seen in sea saw nystagmus.
**Option C:** This option is incorrect because congenital nystagmus is a type of nystagmus that is present at birth and typically involves a different type of eye movement abnormality.
**Clinical Pearl / High-Yield Fact**
Sea saw nystagmus is often seen in patients with multiple sclerosis, and its presence can be a useful clinical clue in diagnosing this condition. However, it's worth noting that sea saw nystagmus can also be seen in other conditions, such as trauma, stroke, and certain types of tumors.
**Correct Answer: D. Multiple sclerosis.**