Improving Recognition for Risk of Iatrogenic Skull Base Injury in Endoscopic Sinus Surgery Using the Gera and Thailand- Malaysia-Singapore (TMS) Classifications

A 31-year-old man diagnosed with type 2 chronic rhinosinusitis with nasal polyps, initially presenting with a 1-year history of nasal blockage and anosmia, was refractory to medical therapy and had been advised to undergo endoscopic sinus surgery (ESS). Bilateral frontal sinusotomy and complete ethmoidectomy were needed to ensure adequate delivery of post-operative topical steroids. During this portion of ESS, the anterior skull base would be vulnerable to iatrogenic injury. How could the surgeon prepare pre-operatively to avoid such a complication? Despite advances in imaging technology, instrumentation and surgical techniques for ESS, complications may still happen. Iatrogenic injury to the anterior skull base causing a cerebrospinal fluid (CSF) leak is one of the dreaded complications of ESS. The anterior skull base is composed of the cribriform plate and the fovea ethmoidalis or ethmoid roof. These bony structures are connected by the lateral lamella of the cribriform plate (LLCP) which delineates the lateral border of the olfactory fossa. The LLCP is known as the most vulnerable structure of the anterior skull base during ESS especially during ethmoidectomy and frontal sinusotomy.