Cavernous Sinus Metastasis in Patients of Head & Neck Squamous Cell Carcinoma: A Series of Five Rare Instances and Review of Literature.

Head and neck squamous cell carcinoma (HNSCC) exhibits a higher degree of local aggressiveness as compared to a tendency for distant metastasis. Cavernous sinus metastasis from HNSCC is exceptionally rare, with only a handful of cases reported worldwide. This case series presents five instances showcasing an unusual metastatic pattern of HNSCC to the cavernous sinus, documented over one year in a single tertiary cancer care centre in Northeast India. Typically, the treatment of cavernous sinus metastasis involves radiotherapy and chemotherapy with a palliative intent. Unfortunately, the prognosis for this entity is grim, with survival typically measured in months. Notably, all five patients were diagnosed with cavernous sinus metastasis manifested within 6 to 18 weeks post-completion of their definitive treatment. Among these five patients, four patients developed left-sided cavernous sinus metastasis and had the primary disease on the left side with nodal positivity and extranodal extension. Given the rarity of metastasis in this region, maintaining a vigilant follow-up is imperative for the early identification and treatment of these patients, especially in patients with left-sided primary with nodal positivity and extracapsular extension.