Slowly progressive cranial nerve palsies.

MJA • Volume 184 Number 12 • 19 June 2006 he ca wo T incidence of non-melanotic head and neck skin ncers in Queensland is among the highest in the rld. Perineural spread (PNS) from these lesions involves either small nerves, identified at pathological examination (incidental), or large nerves, presenting clinically as cranial nerve palsies. Basal cell carcinoma is the more common skin cancer, but incidental PNS is most frequently associated with squamous cell carcinoma. In 32 out of 34 patients over a 5-year period, isolated major nerve PNS was due to squamous cell carcinoma (unpublished data). PNS from melanoma and microcystic adnexal carcinoma has also been described. Because many clinicians are not familiar with PNS involving large cranial nerves, the diagnosis can easily be missed or delayed. The disease is associated with high treatment morbidity and poor prognosis once clinical or radiological evidence becomes apparent, with a 5-year survival rate of 20%–30%. Early detection of PNS in large cranial nerves is essential, as the condition is often unsalvageable once the tumour has spread through the skull base. The facial and trigeminal nerves are most commonly affected, although forehead tumours can gain access to the orbit via the ophthalmic nerve. Symptoms of trigeminal nerve infiltration include formication, dysaethesia, paraesthesia, numbness and pain (often severe and “electric shock-like” in nature). Slowly progressive facial nerve palsy may represent seventh cranial nerve infiltration or infiltration within the parotid, whereas diplopia and visual impairment indicate advanced orbital disease. These symptoms can mimic other diagnoses, such as Bell’s palsy or trigeminal neuralgia, but almost always manifest as slowly progressive and irreversible palsies. Close follow-up of patients to ensure resolution of symptoms is mandatory. The four patients we have described illustrate delays between clinical presentation and diagnosis. These delays could have been avoided by establishing the link between unresolving cranial nerve palsies and excision of cutaneous lesions from the head and neck. Patients 2 and 3 had a history of aggressive squamous cell carcinoma of the face treated with radical excision and postoperative radiotherapy. Advanced, recurrent skin squamous cell carcinomas have a higher incidence of PNS, particularly when located close to a cranial nerve, and should alert the clinician to the possibility of neural metastasis. Tumour size before excision, postoperative defect size, subclinical extension and Moh’s micrographic surgery levels are significantly larger in patients with PNS than in patients without PNS. Clinical records