Cavernous Sinus Thrombosis (CST)
Ocular Emergency: NEET PG High-Yield
1. Pathophysiology
CST is a life-threatening, septic thrombosis of the cavernous sinus, usually originating from an infection in the “danger triangle” of the face (nose, lips, and medial canthus) via the ophthalmic veins.
2. Clinical Hallmark Features
- Severe Bilateral Signs: Often begins unilaterally but rapidly becomes bilateral due to the inter-cavernous sinus connections.
- Ophthalmoplegia: Total paralysis of eye movements (CN III, IV, and VI are inside the sinus).
- Sensory Deficit: Anesthesia or severe pain in the distribution of CN V1 and V2.
- Proptosis & Chemosis: Secondary to venous congestion and orbital congestion.
3. Key Cranial Nerve Involvement
| Nerve | Clinical Note |
|---|---|
| CN VI (Abducens) | Usually, the first nerve affected (which runs centrally through the sinus). |
| CN III, IV, V1, V2 | Involved later (runs along the lateral wall of the sinus). |
4. NEET PG High-Yield Pearls
- Diagnosis: MRI with MR venography (MRV) is the investigation of choice.
- Etiology: Staphylococcus aureus is the most common causative organism.
- Management: Requires high-dose, intravenous, broad-spectrum antibiotics and potentially systemic anticoagulation.
- Differential: Must differentiate from orbital cellulitis (which is usually unilateral and lacks the rapid progression to bilateral involvement seen in CST).