Optic Neuritis Lecture Notes

Introduction

• Presenter: Dr. Amrit
• Topic: Optic Neuritis

Definition of Optic Neuritis

• A demyelinating inflammation of the optic nerve
• Key Term: Demyelinating
• Types based on affected part of optic nerve:
  • Papillitis: Inflammation of the optic nerve head
  • Retrobulbar Neuritis: Inflammation of the intraorbital part of the optic nerve
  • Neuroretinitis: Inflammation involves both optic nerve and retina

Pathophysiology

• Demyelination: Central process in optic neuritis
• Causes:
  • Breakdown of Blood-Brain Barrier
  • Autoimmune Attack
  • Inflammation
• Mechanism:
  • T-cells infiltrate nervous tissue, attack oligodendrocytes
  • Leads to formation of demyelinating plaques
  • Inflammatory processes aggravate damage

Types of Optic Neuritis Associations

• Isolated (Clinical Isolated Syndrome)
• Multiple Sclerosis (MS): Most common association
• Neuromyelitis Optica (Devic's Disease): Includes transverse myelitis
• Acute Disseminated Encephalomyelitis (ADEM): Often post-viral or post-vaccination
• Antibodies in Optic Neuritis:
  • AQP4-IgG: Aquaporin-4 water channel antibody
  • MOG-IgG: Myelin Oligodendrocyte Glycoprotein antibody

Infections as Causes

• Local (endophthalmitis, orbital cellulitis, etc.) and Systemic (Viral, Bacterial)
  • Viral: Influenza, Measles, Mumps, etc.
  • Bacterial: Tuberculosis, Syphilis
  • Fungal, Protozoan, Parasitic

Autoimmune Conditions as Causes

• Systemic Lupus Erythematosus (SLE), Polyarteritis Nodosa

Metabolic Causes

• Rarely: Anemia, B12 deficiency, Diabetes, Starvation, Pregnancy

Clinical Features

• Visual loss (mild to profound)
  • Typically unilateral and quick onset
• Age: 18-45 years
• Pain: Orbital/Retro-orbital pain aggravated by eye movement
• Other Features: Loss of color vision (red desaturation), Pulfrich phenomenon, Uhthoff's sign
• Course:
  • Rapid deterioration in 1 week, improvement starts in 2nd week
  • Full recovery in 4-5 weeks possible

Typical vs. Atypical Optic Neuritis

• Typical: Ages 18-45, mild pain, normal/mild disc edema, improvement within weeks
• Atypical: Outside typical age range, severe/no pain, persistent poor vision, bilateral, more severe disc edema

Risk of Multiple Sclerosis (MS)

• Higher in younger patients, women, Caucasians, northern latitudes
• Clinical features: Retrobulbar involvement, mild papillitis

Diagnostic Criteria (for MS)

• MRI: Assessing optic nerve and cerebral demyelination
• Criteria:
  • Dissemination in Space: Lesions in multiple CNS locations
  • Dissemination in Time: New lesions over time
• CSF Analysis: Presence of oligoclonal bands, high IgG index
• Antibodies: AQP4-IgG, MOG-IgG for atypical cases

Imaging and Diagnosis

• MRI findings: Short segment involvement in typical cases
• CSF Analysis: Oligoclonal bands for MS correlation
• Diagnosis of NMO: Based on history, imaging, antibody presence

Optic Neuritis Treatment

• To be detailed in next lecture

Summary

• Optic neuritis involves demyelination and inflammation of the optic nerve.
• Typical and atypical forms vary in symptoms, prognosis, and associations.
• Important links with MS and other autoimmune conditions.
• Diagnosis involves clinical signs, imaging, antibody testing, and CSF analysis.
• Upcoming lecture will cover treatment details. [Music]