Perineural Tumor Spread - Patterns of Spread
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Hello everyone.
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Dr. Sidney Levy here, continuing our discussion on perineural
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tumor infiltration as part of our head and neck
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squamous cell malignancy diagnosis and staging series.
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In this vignette, I'd like to discuss some
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common pathways of perineural tumor infiltration.
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We have our case example here involving
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the right maxillary nerve or V2 division
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of the trigeminal nerve.
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If this is involved, as we've demonstrated, the infraorbital
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nerve is a common site of involvement, spreading posteriorly
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from cutaneous squamous cell carcinoma of the nose or cheek.
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If this spreads far enough, it may
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reach the pterygopalatine fossa, here.
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And from there, head further posteriorly
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via the maxillary nerve into the cavernous
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sinus and eventually to the brainstem.
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Other branches of the maxillary nerve that might be
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involved are the greater and lesser palatine nerves,
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in particular in the setting of palatine malignancy.
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If the mandibular division is involved, then this
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is often seen with malignancies of the oral cavity,
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uh, including those of the alveolar mucosa.
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In the example of alveolar mucosal squamous cell
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malignancy, it's very important to look at the
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inferior alveolar nerve within the mandibular canal.
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If the patient has a history of lip squamous cell
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malignancy, you need to look at the mental nerves,
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which come out the mental foramina of the mandible anteriorly.
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And if the patient has a parotid malignancy, you need to
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also look at the auriculotemporal nerve, which is a branch
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which can communicate with the facial nerve as well.
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If the mandibular nerve itself is involved,
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then that passes through foramen ovale.
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So it's important to look in the region of foramen
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ovale for loss of fat planes or nerve enlargement.
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And in the Meckel's cave as well, which
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is where the mandibular nerve travels
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approximately as far back as the brainstem.
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The ophthalmic division is rarely involved and, when involved,
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may relate to forehead squamous cell malignancy or melanoma.
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In which case, you need to look in the cavernous
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sinus, particularly on the coronal projection,
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for evidence of asymmetric enlargement
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of the ophthalmic nerve.
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The other cranial nerve which may be involved with
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perineural infiltration is the facial nerve,
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in particularly, in the setting of parotid malignancy.
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So it's worth keeping in mind, in that setting,
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that this can also become involved with tumor.
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In summary, perineural tumor infiltration most commonly
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involves the maxillary division of the trigeminal nerve.
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So think of the infraorbital nerve, the pterygopalatine
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fossa, and the cavernous sinus as places to look,
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as well as the greater and lesser palatine foramina on CT.
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57 00:03:20,715 --> 00:03:23,325 The mandibular nerve is the next most common
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involved division of the trigeminal nerve.
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So think of the mental nerves in the vicinity of the lips.
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Think of the inferior alveolar nerve within the mandibular
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canal in the setting of alveolar squamous cell carcinoma.
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And think of the mandibular nerve around foramen ovale
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as it heads back into Meckel's cave.
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And lastly, the ophthalmic division,
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or V1, very uncommonly involved.
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Think about it if the patient has a forehead squamous
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cell carcinoma, and have a look in the cavernous
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sinus or the supraomedial orbit for loss of fat
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planes or asymmetric nerve enlargement or enhancement.
Sidney Levy, PhD, MBBS
Radiologist and Nuclear Medicine Specialist
I-MED
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