Internuclear Ophthalmoplegia

Internuclear ophthalmoplegia (INO) is an ocular movement disorder that affects the conjugate horizontal gaze, meaning the eyes are incapable of moving in a simultaneous and coordinated manner on the horizontal plane. This disorder is usually caused by a lesion in the brain stem Brain Stem The brain stem is a stalk-like structure that connects the cerebrum with the spinal cord and consists of the midbrain, pons, and medulla oblongata. It also plays a critical role in the control of cardiovascular and respiratory function, consciousness, and the sleep-wake cycle. Brain Stem involving the medial longitudinal fasciculus (MLF) and is characterized by impaired adduction ipsilateral to the MLF lesion and abduction nystagmus contralateral to the MLF lesion. Internuclear ophthalmoplegia is a clinical diagnosis. However, investigations involving neuroimaging, especially MRI, help establish the diagnosis. Management of INO varies depending on the cause. The prognosis mainly depends on the etiology. For instance, trauma patients do not have a very favorable prognosis, whereas patients with ischemic and demyelinating causes have a favorable recovery.

Last update:

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Table of Contents

Share this concept:

Share on facebook
Share on twitter
Share on linkedin
Share on reddit
Share on email
Share on whatsapp

Overview

Definition

Internuclear ophthalmoplegia (INO) is an ocular movement disorder that is due to a lesion of the medial longitudinal fasciculus (MLF), mainly in the brain stem Brain Stem The brain stem is a stalk-like structure that connects the cerebrum with the spinal cord and consists of the midbrain, pons, and medulla oblongata. It also plays a critical role in the control of cardiovascular and respiratory function, consciousness, and the sleep-wake cycle. Brain Stem tegmentum (dorsomedial pons or the midbrain).

Epidemiology

  • ⅓ of cases in adolescents due to multiple sclerosis Multiple Sclerosis Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease that leads to demyelination of the nerves in the CNS. Young women are more predominantly affected by this most common demyelinating condition. Multiple Sclerosis
  • ⅓ of cases in old age due to stroke/infarction
  • Rare in children

Etiology

Internuclear ophthalmoplegia is mainly due to autoimmune demyelinating disorder and infarction.

  • Autoimmune INO: due to a demyelinating disorder, such as multiple sclerosis Multiple Sclerosis Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease that leads to demyelination of the nerves in the CNS. Young women are more predominantly affected by this most common demyelinating condition. Multiple Sclerosis or Sjögren syndrome (bilateral)                                                                                                                           
  • Infarction INO: due to a brain stem Brain Stem The brain stem is a stalk-like structure that connects the cerebrum with the spinal cord and consists of the midbrain, pons, and medulla oblongata. It also plays a critical role in the control of cardiovascular and respiratory function, consciousness, and the sleep-wake cycle. Brain Stem infarction (unilateral)
  • Other causes:   
    • Head trauma Head trauma Head trauma occurs when external forces are directed to the skull and brain structures, resulting in damage to the skull, brain, and intracranial structures. Head injuries can be classified as open (penetrating) or closed (blunt), and primary (from the initial trauma) or secondary (indirect brain injury), and range from mild to severe and life-threatening. Head Trauma
    • Tumors ( medulloblastoma Medulloblastoma Medulloblastomas are malignant primitive neuroectodermal tumors that arise in the posterior fossa in children. Medulloblastomas are the most common malignant brain tumors in children. Patients with medulloblastoma present with symptoms of increased intracranial pressure and cerebellar signs, which both evolve and worsen over weeks to a few months. Medulloblastoma, glioma, lymphoma)
    • Arnold-Chiari malformation
    • Infection (HIV, syphilis Syphilis Syphilis is a bacterial infection caused by the spirochete Treponema pallidum pallidum (T. p. pallidum), which is usually spread through sexual contact. Syphilis has 4 clinical stages: primary, secondary, latent, and tertiary. Syphilis, cysticercosis, etc.)
    • Hydrocephalus
    • Brain stem hemorrhage

Pathophysiology

Normal physiology

The MLF has a very important role in controlling the direction of eye movements.

  • A pair of crossed fiber tracts surrounding the paramedian area of the midbrain and pons
  • Heavily myelinated
  • Mainly controls the horizontal gaze by interconnecting the cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. Overview of the Cranial Nerves III (oculomotor nerve), IV (trochlear nerve), and VI (abducens nerve) via interneuronal pathways:
    • The signal for saccadic eye movements (quick simultaneous movements) initiates in the frontal eye field which, in turn, activates the contralateral paramedian pontine reticular formation (PPRF). 
    • The PPRF innervates the ipsilateral cranial nerve (CN) VI nucleus, resulting in abduction of the ipsilateral eye through the action of the lateral rectus muscle. 
    • Signals from the activated abducens nucleus are also transmitted to the contralateral CN III nucleus via the MLF, resulting in adduction of the contralateral eye through the action of the medial rectus muscle.

Pathophysiology

Internuclear ophthalmoplegia occurs because of a lesion or dysfunction of the MLF, characterized by: 

  • Defective adduction on the same side as the lesion 
  • Abducting nystagmus on the contralateral side
  • Normal convergence of the eyes due to intact medial rectus innervation
Defect of horizontal gaze in internuclear ophthalmoplegia

Defect of horizontal gaze in internuclear ophthalmoplegia:
Note the ipsilateral defective adduction, contralateral abducting nystagmus, and normal convergence.
MLF: medial longitudinal fasciculus
III: nucleus of the oculomotor cranial nerve III
VI: nucleus of the abducens cranial nerve VI
PPRF: paramedian pontine reticular formation

Image by Lecturio. License: CC BY-NC-SA 4.0

Clinical Presentation

The presentation of patients with INO can vary but includes:

  • Changes in vision and eye movements:
    • Marked limitation of adduction in eye ipsilateral to the side of MLF lesion
    • Abduction nystagmus of contralateral eye
    • Blurry vision
    • Diplopia (sometimes vertical diplopia, mainly seen in unilateral INO)
    • Oscillopsia
  • Others:
    • Dizziness
    • Gait instability
    • Weakness
    • Headache

Diagnosis and Management

Diagnosis

  • Clinical: The diagnosis is mainly clinical, based on the assessment of the patient’s ability to perform conjugate eye movements.                  
  • Radiologic:
    • MRI and CT scans may be used (MRI is preferred).
    • Proton density imaging is also helpful for diagnosing underlying demyelinating lesions. 
    • Optokinetic tape is also highly sensitive for testing for INO.

Management

Management depends on the underlying cause.

  • Neurologic cause: treated after detailed neurology evaluation
  • Infectious/autoimmune cause: 
    • Corticosteroids are the treatment of choice.
    • Diframpadine (potassium channel blocker) has been used in patients with demyelinating disease.
  • Diplopia: can be treated with botulinum toxin injections or Fresnel prisms
  • Strabismus Strabismus Strabismus is the misalignment of the eyes while fixating the gaze on an object. Strabismus can be idiopathic, but it may also be caused by cerebral palsy, uncorrected refractive errors, and extraocular muscle or cranial nerve dysfunction. Strabismus: can be surgically treated in patients with wall-eyed bilateral INO

Differential Diagnosis

  • Lateral gaze palsy: due to a lesion in CN VI (abducens) resulting in impaired ipsilateral abduction. Lateral gaze palsy can be caused by trauma or microvascular ischemia or can be secondary to multiple other causes, including multiple sclerosis Multiple Sclerosis Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease that leads to demyelination of the nerves in the CNS. Young women are more predominantly affected by this most common demyelinating condition. Multiple Sclerosis, stroke, or increased intracranial pressure Increased Intracranial Pressure Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP).
  • One and a half syndrome: horizontal movement disorder of the eyes. One and a half syndrome is characterized by a conjugate horizontal gaze palsy in one direction and an internuclear ophthalmoplegia in the other. The syndrome is caused by a lesion of the PPRF and the MLF and is most commonly due to cerebrovascular diseases. 
  • Stroke: occlusion of distal penetrating arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries that leads to dorsal brain stem Brain Stem The brain stem is a stalk-like structure that connects the cerebrum with the spinal cord and consists of the midbrain, pons, and medulla oblongata. It also plays a critical role in the control of cardiovascular and respiratory function, consciousness, and the sleep-wake cycle. Brain Stem infarction and can present as INO, diplopia, or vision changes. Brainstem stroke can also present with diverse visual symptoms, including homonymous hemianopia or cortical blindness, skew deviation of eyes, nystagmus, and ocular or facial pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain.

References

  1. Rubin, M. (2020). Internuclear ophthalmoplegia. Merck Manual Professional Version. Retrieved May 28, 2021, from https://www.merckmanuals.com/professional/neurologic-disorders/neuro-ophthalmologic-and-cranial-nerve-disorders/internuclear-ophthalmoplegia
  2. Swisher, J., Kini, A., Lee, A.G. (2020). Internuclear ophthalmoplegia. American Academy of Ophthalmology. Retrieved May 28, 2021, from https://eyewiki.aao.org/Internuclear_Ophthalmoplegia

USMLE™ is a joint program of the Federation of State Medical Boards (FSMB®) and National Board of Medical Examiners (NBME®). MCAT is a registered trademark of the Association of American Medical Colleges (AAMC). NCLEX®, NCLEX-RN®, and NCLEX-PN® are registered trademarks of the National Council of State Boards of Nursing, Inc (NCSBN®). None of the trademark holders are endorsed by nor affiliated with Lecturio.

Study on the Go

Lecturio Medical complements your studies with evidence-based learning strategies, video lectures, quiz questions, and more – all combined in one easy-to-use resource.

Learn even more with Lecturio:

Complement your med school studies with Lecturio’s all-in-one study companion, delivered with evidence-based learning strategies.

User Reviews

0.0

()

¡Hola!

Esta página está disponible en Español.

🍪 Lecturio is using cookies to improve your user experience. By continuing use of our service you agree upon our Data Privacy Statement.

Details