Neuro-ophthalmic Manifestations of Intracranial Lesions

Papilledema & ICP - Pressure Cooker Eyes

• ICP Pathophysiology: Monro-Kellie doctrine: Cranial volume (brain, blood, CSF) is constant. ↑ one component → ↓ others or ↑ICP (normal <15 mmHg).
• Papilledema: Optic disc swelling due to ↑ICP.
  • Causes: Tumors, hydrocephalus, idiopathic intracranial hypertension (IIH), meningitis.
  • Clinical: Headache, transient visual obscurations (TVOs), N/V; acuity initially preserved.
  • Frisen Scale: 0 (normal) to 5 (severe).
• Differentiate:
  • Pseudopapilledema (e.g., optic disc drusen): No ↑ICP, anomalous elevation.
  • Papillitis/Optic Neuritis: Pain on eye movement, early ↓vision.

⭐ Idiopathic Intracranial Hypertension (IIH) classically affects young, obese females, presenting with headache and papilledema.

Visual Pathway Lesions - Sight Stealers Central

Anatomy: Retina → Optic Nerve (ON) → Chiasm → Optic Tract (OT) → LGN → Radiations → Cortex.

• ON: Ipsilateral blindness, central scotoma.
• Chiasm: Bitemporal hemianopia. Junctional scotoma (Traquair) if anterior.
• OT: Contralateral incongruous homonymous hemianopia.
• LGN: Contralateral homonymous hemianopia (sectoranopia/quadrantanopia).
• Optic Radiations:
  • Meyer's Loop (Temporal): Contralateral superior quadrantanopia ('pie in the sky').
  • Parietal Lobe: Contralateral inferior quadrantanopia ('pie on the floor').
  • 📌 PITS: Parietal-Inferior, Temporal-Superior.
• Visual Cortex (Occipital): Contralateral congruous homonymous hemianopia, often with macular sparing (PCA territory).
• Optic Atrophy Types: Primary, secondary, consecutive, glaucomatous.

⭐ Bitemporal hemianopia classically indicates a pituitary adenoma compressing the optic chiasm.

Ocular Motility Disorders - Wobbly Gaze Woes

Intracranial lesions (nuclear/infranuclear) cause CN palsies. 📌 LR6SO4R3 (LRVI, SOIV, Rest III).

• CN III (Oculomotor): Eye 'down & out', ptosis.
  • Pupil involved (mydriasis): PCOM aneurysm (compressive).
  • Pupil spared: Diabetes (ischemic).
• CN IV (Trochlear): Vertical diplopia (worse downgaze, contralateral head tilt - Bielschowsky's test). Hypertropia, head tilt away from lesion.
• CN VI (Abducens): Horizontal diplopia (worse ipsilateral gaze). Failure of abduction (eye turned in).

Pupillary Pathways & Key Syndromes - Pupil Power Plays

• Relative Afferent Pupillary Defect (RAPD/Marcus Gunn Pupil): Sign of optic nerve/tract lesion.
• Horner's Syndrome: Ptosis, miosis, anhydrosis (sympathetic pathway lesion).
• Light-Near Dissociation: Pupils constrict to near stimulus, poorly to light (e.g., Argyll Robertson, Parinaud's).

Key Syndromes:

High‑Yield Points - ⚡ Biggest Takeaways

• Pituitary adenomas often cause bitemporal hemianopia by compressing the optic chiasm.
• CN III palsy with pupil dilation suggests a compressive lesion, like a PCOM aneurysm.
• CN VI palsy can be a non-localizing sign of raised intracranial pressure (ICP).
• Foster Kennedy syndrome (optic atrophy, contralateral papilledema, anosmia) indicates a frontal lobe tumor.
• Internuclear ophthalmoplegia (INO) points to a medial longitudinal fasciculus (MLF) lesion.
• Homonymous hemianopia localizes to retrochiasmal pathways (optic tract to occipital cortex).
• Papilledema is bilateral optic disc swelling from ↑ICP, with initial visual sparing.