Site of lesion of internuclear ophthalmoplegia – Medicine MCQ

Which of the following is the site of lesion of internuclear ophthalmoplegia?
A. Medial longitudinal fasciculus
B. 6th nerve nucleus
C. Pontine paramedian reticular formation
D. A and C

Correct answer: A. Medial longitudinal fasciculus

Explanation:

Supranuclear gaze pathway:

To look towards the right side, the left Frontal Eye Field (FEF) sends impulses to the right Pontine Paramedian Reticular Formation (PPRF) which in turn sends impulses to the right Abducens nucleus. Abducens nucleus sends impulses to the right lateral rectus as well as the left Oculomotor nucleus via left Medial Longitudinal Fasciculus (MLF) for activating the left medial rectus.

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Internuclear ophthalmoplegia

It occurs in lesions of the MLF. When the person tries to look towards the right side, the impulses from the right Abducens nucleus does not reach the left Oculomotor nucleus resulting in failure of adduction of the left eye. It is also associated with nystagmus of the right eye.

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Other options:

  • Lesion of the Abducens nucleus: Results in the failure of abduction of the ipsilateral eye and failure of adduction of contralateral eye – conjugate gaze palsy.
  • Lesion of MLF and PPRF: Failure of abduction and adduction of ipsilateral eye; failure of adduction of contralateral eye. Only movement possible is abduction of contralateral eye – One and a half syndrome.

 

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