Adenoid Cystic Carcinoma with Perineural Spread

Perineural spread (PNS) of head and neck malignancies is defined by the contiguous extension of tumoral cells along the potential space between the nerve and the surrounding sheath. Branches of the trigeminal and facial nerves are most frequently affected.

PNS is more common in adenoid cystic carcinoma (20–80%) and in squamous cell carcinoma (27–82%), especially when tumors are located in the midface region.

Perineural infiltration (PNI, diagnosed by histology) has been reported in the head and neck region in 2.5–5.0% of patients. PNS as diagnosed by macroscopic tumor extension occurs at a lower rate. Most histology is of squamous cell carcinoma, as it is by far the most common head and neck malignancy (up to 95% of all H&N cancers). Adenoid cystic carcinoma represents 1–3% of H&N malignancies, but presents with PNI in up to 50% of patients.  

PNS is considered an independent predictor of poor diagnosis, increases rates of local recurrence, and has repercussions for treatment because it requires more extensive resection and larger fields of radiation therapy.

Up to 40% may be asymptomatic.

Patients can complain of the insidious development of hypoesthesia, burning or pain, trigeminal neuralgia, facial palsy, or masticatory muscle weakness. 

Patterns of PNS of different primary tumors are indistinct by imaging and depend mainly on tumor location/extension. 

Nerve enlargement with homogeneous enhancement of the whole nerve circumference 

Obliteration of fat planes due to tumor growth and associated local inflammation

Foraminal and canal enlargement or destruction 

Muscle denervation

Spread to the intracranial compartment 

Tumors: Benign tumors like schwannomas and neurofibromas, which are more likely to be more focal, usually have more canal enlargement, but no bone erosion. Meningiomas and metastases can have hyperostosis and erosion of the adjacent bone, respectively. Meningiomas show dural tails.

Infections (mucormycosis, aspergillus): Search for infectious sinus involvement in patients who are immunocompromised or diabetic.

Inflammatory pseudotumors: Typical extension to the orbital vertex. Pain is almost a mandatory symptom. Good response to steroids. 

Inflammatory or meningeal carcinomatosis: More peripheral enhancement and multiple locations on the cisternal segments of the cranial nerves

PNS changes the treatment strategy from curative to palliative care.

Aggressive surgery with radical nerve dissection is proposed, especially in patients with extracranial PNS (better prognosis).

Our patient chose palliative radiation therapy.