Occult facial nerve palsy: Case of masquerading malignancy reported

The case study has been published in the Journal of Otolaryngology and Rhinology.

Peripheral facial nerve palsy is mostly attributed to Bell's palsy, however in 5-10% of cases it may be from an underlying malignancy. It can be difficult to distinguish initially, frequently leading to misdiagnosis and a delay in management, potentially compromising survival of these patients.

A common distinguishing feature is that facial palsy from malignancy is typically gradual onset and progressive as opposed to sudden in that of Bell's palsy, although other benign causes may also present similarly.

Magnetic resonance imaging is the imaging modality of choice, but it can be falsely negative, adding to the diagnostic difficulty.

The researchers studied case report of a patient who ultimately was diagnosed with a malignant cause for their facial palsy.

An 81-year-old man with a background of hypertension and no history of previous skin malignancies presented to the neurology department one year after onset of a progressive left lower motor neuron facial weakness. Magnetic resonance imaging (MRI) scan performed a year after onset showed no abnormality of the facial nerve. He received ectropion repair of the lower eye lid, brow lift, and tarsorrhaphy by an ophthalmologist. When seen by an otolaryngologist two years after onset, a repeat MRI with contrast showed oedema and hyperemia along the maxillary (V2) and mandibular (V3) divisions of the trigeminal nerve extending to involve the foramen ovale and the facial nerve up to the mastoid segment (Figure 1). It also showed enhancement of the parotid gland but without any discrete lesion. By now he had complete left facial palsy, numbness of lip, face, tip of tongue, and gums on left side. He subsequently had a non-targeted ultrasound-guided core biopsy of the parotid gland which demonstrated a primary salivary gland cancer, favoring salivary duct carcinoma. Multidisciplinary meeting recommended palliative radiotherapy, which he managed to only partially complete due to side effects, including neuropathic pain, lacrimation, hypersalivation, and fatigue. He also had facial reanimation with a static sling with tensor fascia lata, as well as gold weight to the upper eyelid. A year following diagnosis he was found to have metastasis to C6 vertebrae with associated paresthesia of the right arm and received radiation therapy to the lesion. He remains alive nearly four years following onset of symptoms.

Several factors have been associated with malignancy in the facial nerve. Although facial pain occurs in around 50% of cases with malignant involvement of facial palsy, the pain that occurs in Bell's palsy or Ramsay Hunt syndrome is usually present at the onset of the palsy and then improves. If the pain persists it should be investigated, especially if the facial weakness persists.

This case series and literature review highlights the importance of a high index of suspicion, especially with a progressive facial palsy, even in absence of positive imaging.

The authors recommend a more proactive approach whereby repeat imaging is performed at three months with operative exploration in patients with high-risk features, such as history of cutaneous SCC. Furthermore, in those without high-risk features a further period of observation may be undertaken, they added.

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DOI: 10.23937/2572-4193.1510102