18f-fdg pet/ct findings of perineural involvement in head...

Perineural invasion (PNI) is the process of neoplastic

invasion of nerves and is an under-recognized route of

metastatic spread. It is emerging as an important

pathologic feature of many malignancies, particularly in

head and neck cancers, associated with decreased

survival, increased and earlier recurrence. PNI status

often significantly affects surgical strategies and

adjuvant treatments in head and neck cancers. MRI has

been the gold standard imaging modality for the

evaluation of PNI. FDG PET/CT has been increasingly

used for staging and restaging head and neck cancers.

Beyond locoregional disease and lymph node metabolic

characterization, different PET imaging patterns

suggesting PNI can also be identified. Our goal is to

demonstrate different examples of PNI visualized by

PET/CT and the correlation with other cross sectional

imaging modalities, such as CT and MRI.

• PNI is a poor prognostic indicator in head neck

malignancies.

• Asymmetric FDG uptake in the head and neck should

be always evaluated in all 3 planes and MIP on PET-

only images.

• FDG PET/CT patterns can suggest PNI and could be

described as such.

• Increased awareness of such patterns can be helpful in

the evaluation and cross sectional correlation of cases

suggestive of PNI.

• Review of the MIP of the head and neck

• Review of PET-only images in the axial, coronal and sagittal

plane. Asymmetries are noted.

• Foci of asymmetric FDG uptake get also identified in the other

planes and their pattern is recognized (focal, linear etc.)

• Findings are correlated with CT portion of PET/CT and other

available modalities

Introduction - Aim

Proposed Algorithm

Key points

References

Case 2: Hypoglossal n.

Case: 54 yo male with history of

squamous cell carcinoma of the right

tongue base, status post definitive

chemoradiation more than 1 year

before. PET/CT for evaluating

recurrence showed a large focus of

FDG uptake in the right tongue base,

suspicious for tumor recurrence, as well

as a linear focus of uptake extending

from the base of the tongue to the base

of the skull, concerning for perineural

spread along the hypoglossal n.

Perineural involvement was confirmed

with subsequent biopsy.

MIP, sagittal view Source: Wikipedia

Source: Radiology Anatomy Atlas Viewer

Case 4: Trigeminal Ganglion

Case: 76 y/o female with history of

SCCA of the right lower lip, extending

into mental nerve and foramen ovale,

status post surgical resection and

combined chemoradiation, referred for

restaging 4 months afterwards.

PET/CT shows linear extension of

FDG activity through the trigeminal

nerve, foramen ovale and petrous apex

to the mesencephalus (trigeminal

ganglion).

MRI: Perineural spread in the same

location, progression of disease.

Case: 49 yo male with radiation-induced malignant

histiocytoma of the right jaw and skull base, status post

right hemimandibulectomy, and remote history of

squamous cell carcinoma of the tongue 13 years before,

treated with primary external beam radiation without

chemotherapy.

PET/CT study performed for restaging shows an FDG-avid

right masticator space mass involving the mandible, as

well as a linear focus of uptake in the ramus of the

remaining right mandible, suspicious for perineural spread.

MRI was in accordance and also suggestive for perineural

spread through the foramen ovale and rotundum. These

findings were subsequently confirmed by biopsies twice.

Case 1: Inferior Alveolar n.

Case: 54 y/o male

with recent diagnosis

of large B-cell

lymphoma of the

mandible, stage IB.

PET/CT shows a focus

of increased uptake in

the ramus of the right

mandible along the

course of the right

inferior alveolar nerve,

highly suspicious for

lymphomatous

involvement.

CECT of the head

confirmed these

findings showing the

nerve foramina

expansion and bony

erosion.

Case 5: Mandibular n. Case 6: Mental n.

Case 3: Maxillary n.

Case: 79 yo female with biopsy proven meningioma of the skull base and

infratemporal fossa. She underwent PET/CT for staging, which showed a linear

focus of moderate uptake (SUVmax =3.67)

Corresponding to a soft tissue mass along the right foramen ovale and 2nd and 3rd

branch of the trigeminal n. MRI showed gross involvement of the right V3 foramen

ovale with no significant enlargement of the foramen, but a large amorphous

component of the mass is seen contiguous in the right infratemporal fossa.

Case 7: Inferior Alveolar n.

Source: Wikipedia

Source: Wikipedia

1. Gandhi, D., S. Gujar, et al. (2004). "Magnetic resonance imaging of

perineural spread of head and neck malignancies." Top Magn Reson

Imaging 15(2): 79-85.

2. Caldemeyer, K. S., V. P. Mathews, et al. (1998). "Imaging features and

clinical significance of perineural spread or extension of head and neck

tumors." Radiographics 18(1): 97-110; quiz 147.

3. Radiology Anatomy Atlas Viewer

(http://web.mac.com/rlivingston/RAAViewer/)

4. Wikipedia (www.wikipedia.org)

Materials and Methods

We identified cases of head and neck cancer patients

from our institution with suspected or established

perineural involvement. All patients underwent a whole

body PET/CT study and afterwards a separate head and

neck component, 90 mins after IV injection of 481 – 555

MBq (13-15 mCi) of 18F-FDG, in a Philips Gemini TF-

16 Time of Flight PET/CT scanner. Oral or IV contrast

was not used and low-dose CT was acquired for

attenuation correction and anatomical localization only.

Our algorithm for interpreting the head and neck part of

the PET/CT studies included careful review of PET only

images in all three planes and in maximum intensity

projection (MIP), and correlation with CT images.

Source: Radiology Anatomy Atlas Viewer

MIP, coronal and sagittal view

Case: 76 yo female with history of

SCCA of the right lower lip, with

involvement of the mental nerve

and intracranial progression (same

patient as case 4). PET/CT shows

the extension along the mandibular

nerve. MRI: Same findings.

Case: Again, the 76 y/o female with

history of SCCA of the right lower lip and

perineural extension along the mandibular

ramus of the trigeminal nerve. PET/CT

shows the initial extension to the mental

ramus of the mandibular nerve in the site

of the primary tumor in the right lower lip.

MRI: Focal area of low signal in the right

lip, suspicious for mental nerve

involvement.

Source: Radiology Anatomy Atlas Viewer

Source: Radiology Anatomy Atlas Viewer

Source: Radiology Anatomy Atlas Viewer

Source: Radiology Anatomy Atlas Viewer

Source: Wikipedia

Source: Wikipedia

18F-FDG PET/CT Findings of Perineural Involvement in Head and Neck

Malignancies Fabio Paes MD, Dimitrios Kalkanis MD, Osama Gomaa MD and Aldo Serafini MD

Department of Radiology, Division of Nuclear Medicine, University of Miami, Miami, Florida

Contact email: fpaes@med.miami.edu