**Question:** Cavernous sinus thrombosis can occur due to spread of odontogenic infection via:

**Core Concept:** Cavernous sinus thrombosis (CST) is a rare but potentially life-threatening condition characterized by the formation of blood clots (thrombi) within the cavernous sinus, a group of veins located in the skull base, separating the intracranial contents from the extracranial structures. Odontogenic infections, such as those originating from teeth or periapical tissues, can spread along the course of the inferior alveolar nerve and mandibular branches of the trigeminal nerve to reach the cavernous sinus and cause thrombosis.

**Why the Correct Answer is Right:** Cavernous sinus thrombosis can occur due to spread of odontogenic infection via option D, the inferior petrosal sinus (IPS). The IPS is a vein that connects the cavernous sinus to the internal jugular vein, allowing for the transmission of infections and pathogens from the oral cavity to the cavernous sinus. Infections originating from teeth or periapical tissues can spread along the inferior alveolar nerve and mandibular branches of the trigeminal nerve, then reach the cavernous sinus through the IPS, ultimately leading to thrombosis.

**Why Each Wrong Option is Incorrect:**

A. Spread via the superior petrosal sinus (SPS) is incorrect because the SPS is located superior to the cavernous sinus and does not directly connect to the IPS or the cavernous sinus.

B. Spread via the internal carotid artery is incorrect because the internal carotid artery is a blood vessel and does not serve as a pathway for infections to reach the cavernous sinus.

C. Spread via the internal jugular vein is incorrect because the internal jugular vein is a venous pathway for returning blood from the head and neck to the heart and does not serve as a direct route for infections to reach the cavernous sinus.

**Clinical Pearl:** Recognizing the correct route of spread (D) is essential in differentiating between odontogenic infections and non-odontogenic causes of cavernous sinus thrombosis, such as head and neck tumors, infections, or trauma. This understanding helps guide appropriate diagnostic and therapeutic interventions, including imaging studies and antibiotic regimens tailored to odontogenic infections.