Perineural invasion resulting in leptomeningeal carcinomatosis is a rare, but well-recognized phenomenon in head and neck carcinomas. We report the rare case of a patient with a squamous cell carcinoma of the lip resulting in leptomeningeal carcinomatosis and review the relevant published work. A 51-year-old man presented with progressive facial paraesthesia after treatment for a recurrent squamous cell carcinoma of the lower lip. Cavernous sinus involvement was confirmed on MRI and he received stereotactic radiotherapy. He subsequently developed progressive lower limb neurological signs. An MRI showed multiple enhancing leptomeningeal nodules in the cervical and lumbar spine consistent with leptomeningeal carcinomatosis. Whole spine radiotherapy and dexamethasone resulted in short-term stabilization of symptoms only and he rapidly succumbed to progressive neurological disease. To our knowledge, this is the first published report of a squamous cell carcinoma of the lip resulting in leptomeningeal disease of the cauda equina. It illustrates the potential aggressive natural history of squamous cell carcinomas with perineural invasion.