Easily detected signs of perineural tumour spread in head and neck cancer

Abstract

Perineural tumour spread (PNTS) in head and neck oncology is most often caused by squamous cell carcinoma. The most frequently affected nerves are the trigeminal and facial nerves. Up to 40% of patients with PNTS may be asymptomatic. Therefore, the index of suspicion should be high when evaluating imaging studies of patients with head and neck cancer. This review describes a "quick search checklist" of easily detected imaging signs of PNTS. TEACHING POINTS: • A distinctive feature of head and neck tumours is growth along nerves. • Perineural tumour spread is most often caused by squamous cell carcinoma. • There are several key findings for the detection of perineural tumour spread.

Keywords: Head and neck; Imaging; Oncology; Perineural tumour spread.

Fig. 1

Coronal (a) and oblique sagittal (b) reformatted CT images, as well as coronal (c) T1-weighted images illustrate the normal fat pad (arrows) around the ophthalmic nerve (V1) at the orbital apex (a) and superior to the levator palpebrae muscle (b–c). Axial CT image (d) demonstrates small normal fat pads anterior to the superior orbital rim (arrows) which can be also well-appreciated on (b) the oblique sagittal CT (arrowhead)

Fig. 2

Axial CT (a) and coronal reformatted CT (b) images show obliteration of the fat pad anterior to the superior orbital rim (arrow in a) and superior to the levator palpabrae muscle (white arrow in b) when compared to its normal appearance (black arrow in b). The coronal (c) and sagittal (d) T1 weighted images in a different patient reveal obliteration of the fat pad superior to the left levator palpebrae muscle (white arrows in c and d) in the expected location of V1, compared to the normal fat pad on the right side (black arrow in c). Notice also the obliteration of the fat pad anterior to the supraorbital foramen (arrowhead in d). These signs are indicative of PNTS along V1 in both of these patients with a history of excised skin cancer on the forehead and V1 numbness

Fig. 3

Axial CT (a and b) and axial T1-weighted (c and d) images show obliteration of the preantral fat pad on the left (long white arrow in a and c) when compared to its normal appearance on the right (short white arrow in a and c). In addition, note the enhancing soft tissue within the maxillary sinus (black arrow in a) as well as the obliteration of the fat pad in the left pterygopalatine fossa (long white arrow in b and d) compared to its normal appearance on the right (short white arrow in b and d). The obliteration of the fat pad in the left pterygopalatine fossa (long white arrow) can also be well appreciated on coronal images (e). These signs are indicative of PTNS along V2 in this patient with history of left cheek skin cancer presenting with V2 numbness

Fig. 4

Axial (a and b) CT images demonstrate a normal prominent fat pad at the mandibular foramen (arrow in a) as well as a markedly smaller fat pad anterior to the mental foramen (arrow in b). Axial T1 weighted image illustrates the normal fatty bone marrow in the mandible (arrow in c) that is typically observed in older adults, after red bone marrow normally has converted to fatty bone marrow

Fig. 5

Axial CT image (a) in a patient with lower face numbness reveals obliteration of the fat pad at the right mental foramen at the expected location of the mental nerve (long arrow in a) with a large primary tumour seen at the right retromolar trigone (arrowhead in a). This is an example of antegrade PNTS. Axial CT (b) and T1-weighted (c) images in a different patient illustrate a more subtle obliteration of the fat pad anterior to the right mental foramen (arrow in b and c). This becomes more apparent when a comparison to the normal left-sided fat pad (arrowheads in b and c) is made. This patient was asymptomatic and had a history of lip cancer removal

Fig. 6

Axial T1-weighted image (a) shows obliteration of the fatty bone marrow in the left mandible (arrow in a). The axial CT image (b) of the same patient reveals obliteration of the fat pad at the mandibular foramen (long arrow in b), compared to the normal fat pad on the right (short arrow in b). These signs are indicative of PTNS along V3 in this patient with history of gingival cancer and V3 numbness

Fig. 7

Coronal contrast-enhanced T1-weighted image (a) shows marked enhancement of left pterygoid muscles (between arrows in a) indicative of acute denervation of the muscles supplied by the motoric branch of V3. On an axial T2 weighted image in a different patient (b), the denervated muscles show marked hyperintensity (arrow in b) due to oedema in the acute phase and due to fatty replacement in the chronic phase. Muscular volume loss is usually the only distinguishing feature between the two on T2-weighted images with atrophy present in the chronic phase. Muscular atrophy and fatty replacement, as reflection of chronic denervation, can also be easily identified on axial T1 sequence (arrow in c). These findings can indicate the presence of (motoric) V3 malfunction due to PNTS

Fig. 8

Axial CT composite image shows obliteration of the fat pad at the left stylomastoid foramen (long arrow), compared to the normal fat pad on the right (short arrow). This finding is suggestive of PNTS along CN VII in particular in a patient with history of skin or parotid malignancy