1. Imaging Evaluation of Cutaneous Symptoms in the Region of the Cheek
Gino J. Mongelluzzo, MD
Amit Mahajan, MBBS
Sarah W. Meng, DO
E. Leon Kier, MD
Department of Radiology and Biomedical Imaging
Yale University School of Medicine

2. The Infraorbital Nerve
The cheek is innervated by the infraorbital nerve, the continuation of the second (maxillary) division of the trigeminal nerve.

3. Anatomy
After emerging from the cavernous sinus, the maxillary (V2) division of the trigeminal nerve enters the pterygopalatine fossa via foramen rotundum, where it gives off many branches, before continuing through the inferior orbital fissure as the infraorbital nerve.
The nerve travels along the floor of the orbit within the bony infraorbital canal before exiting through the infraorbital foramen of the maxilla to provide sensation to the cheek and the upper teeth.

4. Axial Anatomy of Infraorbital Canal
superior
Axial Anatomy of Infraorbital Canal
inferior
Series of reformatted axial CT images, presented from superior to inferior, show the course of the right infraorbital bony canal.

5. Coronal Anatomy of Infraorbital Canal
posterior
anterior
Reformatted CT images in the coronal plane are often best to visualize the course of the canal and aid in comparing side-to-side, as shown above from posterior to anterior.

6. Normal Infraorbital Nerve
Coronal fat saturation C+ MRI images show the normal infraorbital nerve along the floor of the orbit and in the infraorbital foramen.

7. Reformatted sagittal CT images show the course of the infraorbital nerve as it passes from the inferior orbital fissure (orange arrow) to the infraorbital canal (yellow arrow) and normally descends slightly as it exits the infraorbital foramen (green arrow) to reach the cheek.

8. Sagittal T2-weighted MRI image shows the normal infraorbital nerve.
I made changes in this image
Sagittal T2-weighted MRI image shows the normal infraorbital nerve.

9. CT images CT images
CT images showing varying position of the infraorbital canal within the maxillary sinus
The infraorbital canal and nerve can protrude into the maxillary sinus in up to 10.8% of patients1.

10. Pathology Trauma: Nerve injury and post-traumatic neuroma
Perineural Spread of Tumor:
Cutaneous Malignancies
Sinonasal Tumors
Primary Tumors:
Benign - Nerve Sheath Tumors
Malignant - Neurofibrosarcoma, Lymphoma

11. Trauma
The location of the infraorbital nerve within the orbital process of the maxilla (aka orbital floor) makes the nerve vulnerable to injury in cases of maxillofacial trauma.
As the nerve provides sensory information, patients will report a numb or painful cheek on the side of injury.

12. Case 1:
This patient presented with facial numbness following a trauma. Fractures of the left maxillary sinus and orbital floor (yellow arrows) can damage the bony infraorbital canal. The normal canal is seen on the right (green arrow).

13. Case 2:
This patient presented with cheek pain 3 years following a trauma. Coronal CT images show deformity of the right orbital floor at the site of the infraorbital canal with slight enlargement and entrapment of the nerve (yellow arrows).

14. Coronal MRI images obtained 3 years later in the same patient shows further enlargement of the right infraorbital nerve, consistent with a post-traumatic neuroma.

15. Perineural Spread of Tumor
When evaluating a patient with cheek numbness of unknown cause, one of the most serious pathologies to be considered is perineural spread of a cutaneous or sinus malignancy.
Although MRI is generally preferred for evaluating perineural spread of malignancy, the unique anatomic considerations of the infraorbital nerve (being confined within a bony canal surrounded by the aerated maxillary sinus and fat-containing orbit) often provide for intrinsic contrast and lesion conspicuity on CT images.

16. Case 3:
53 year-old patient with 1 month of left facial numbness and pain. The infraorbital nerve is enlarged, and the canal is eroded (yellow arrows). Note soft tissue density obscuring the retromaxillary fat pad (dark orange arrow), and extending into the pterygopalatine fossa (light orange arrow).

17. MRI in the same patient shows further perineural spread with enhancement and enlargement of the infraorbital nerve(yellow arrow) that continues in a retrograde fashion through foramen rotundum and the cavernous sinus (green arrow) and continues inferiorly along V3 through foramen ovale (magenta arrow) into the masticator space.
CT-guided fine needle aspiration revealed poorly-differentiated squamous cell carcinoma. However, a primary site was not identified on imaging or clinical examination.

18. Case 4:
CT study of a 64-year old patient with cutaneous squamous cell carcinoma of the left cheek (light green arrow), enlargement of the infraorbital nerve (yellow arrow) is consistent with perineural spread of malignancy.
Soft tissue can also be seen in the left pterygopalatine fossa, which is widened (orange arrows).

19. Coronal and sagittal reformatted CT images in the same patient show spread along the infraorbital nerve (yellow arrows) extending to the pterygopalatine fossa (orange arrow).

20. Case 5:
MR images show a squamous cell carcinoma of the left (light green arrow) spreads along the infraorbital nerve (yellow arrows) and the maxillary nerve (V2) in the foramen rotundum (cyan arrow).

21. Case 6:
MR images of a different case of squamous cell carcinoma show involvement of the infraorbital nerve (yellow arrows), the cavernous sinus (green arrow), and Meckel’s cave (white arrow).

22. Case 7:
Perineural spread of tumor (yellow and light green arrows) is also seen by PET in this case of melanoma. The large primary lesion (light green arrow) is in the left nasolabial region on the sagittal MR image.
Although squamous cell carcinoma is commonly encountered, other neurotropic tumors with a propensity for perineural tumor spread include adenoid cystic carcinoma, melanoma, and lymphoma.

23. Case 8:
Axial MR images show perineural spread of a recurrent right nasal ala melanoma extending along the infraorbital nerve (yellow arrows) into the pterygopalatine fossa (orange arrow), through the cavernous sinus (green arrows), into Meckel’s cave (white arrow), and into the cisternal segment of the trigeminal nerve (red arrow).

24. Coronal images in the same patient again show spread along the infraorbital nerve (yellow arrows), the maxillary nerve within foramen rotundum (cyan arrow), through the cavernous sinus, into Meckel’s cave (white arrow), and into the cisternal segment of the trigeminal nerve (red arrow).

25. Sagittal image of the same patient demonstrates enlargement of the infraorbital nerve (yellow arrows).

26. Case 9:
MR images of a patient with B-cell lymphoma the left cheek (light green arrow) with perineural spread that involves the infraorbital nerve (yellow arrows), pterygopalatine fossa (orange arrow), and cavernous sinus (green arrow).

27. Case 10:
MR study of a patient with a left nasal pleomorphic sarcoma (light green arrow) spreading along the infraorbital nerve (yellow arrow) and the maxillary nerve in the foramen rotundum (cyan arrow).

28. Case 11:
MR study of a patient with an oral cavity squamous cell carcinoma with invasion of the maxillary sinus and the infraorbital nerve (yellow arrows) into the foramen rotundum (cyan arrow) , through the cavernous sinus (green arrows), into Meckel’s cave (white arrows), and into the cisternal segment of the trigeminal nerve (red arrows).

29. Primary Tumors
Primary tumors, both benign and malignant, can involve the trigeminal nerve and any of its branches.

30. Case 12:
MR study of a 64-year-old patient who presented with left face numbness and slowly progressive diplopia.
A lobular, enhancing mass is present in the left pterygopalatine fossa (orange arrows).

31. MR study in the same patient shows some central necrosis following Gamma Knife therapy of this presumptive trigeminal nerve schwannoma in the pterygopalatine fossa (orange arrows).

32. References:
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