Squamous cell carcinoma of the head and neck occurs in approximately 40,000 patients annually in the United States and is often treated with radiation therapy. Radiological studies are obtained following treatment for head and neck malignancies to assess for recurrent tumor, posttreatment changes, and associated complications. Radiation treatment creates a difficult clinical picture for oncologists, head and neck surgeons, neuroradiologists, and neuropathologists. As post-treatment imaging studies are often discussed at radiology/pathology working conferences, knowledge of the imaging appearance of radiation-associated changes in the head and neck and the terminology used by neuroradiologists may not only aid in interpretation of the pathologic specimen, but also assist in communications with neuroradiologists and referring clinicians.
Squamous cell carcinoma of the head and neck is diagnosed annually in approximately 40,000 patients in the United States [
There are a variety of complications following radiation treatment to the neck and it is important for neuropathologists involved with head and neck cancer to be aware of these complications. This paper reviews treatment-related changes including osteoradionecrosis of the mandible, hyoid bone, and skull base, discusses the imaging appearance of soft tissue ulceration and fistulous tract formation, as well as intracranial radiation injury and radiation-associated lesions. Knowledge or the imaging appearance of radiation-associated changes in the head and neck and the terminology used by neuroradiologists may aid in interpretation of the pathologic specimen and will assist in communications with neuroradiologists, head and neck surgeons, and referring clinicians.
Within the first two weeks of treatment, mucosal irritation and edema may occur. In the pharynx and larynx, mucositis and submucosal edema result in prominent mucosal contrast enhancement with thickening of the epiglottis and aryepiglottic folds (Figure
Postradiation changes of the oropharynx: Axial postcontrast CT demonstrates mucositis of the oropharynx characterized by enhancement (large arrow), and edema/swelling, or the epiglottis (small arrow).
Osteoradionecrosis, a known complication of radiation therapy for head and neck malignancies [
Risks for osteoradionecrosis related to the radiation therapy include total radiation dose, photon energy, brachytherapy, field size, fractionation [
A study by Curi and Lauria [
The clinical presentation of osteoradionecrosis includes pain, drainage, and fistula formation between the mucosa or skin, and related to bone in the radiation field. Other symptoms include otalgia, pain localized to the face, jaw, or throat. Long-term complication includes dry mouth, loss of taste, progressive periodontal attachment loss, dental caries, microvascular alternation, soft tissue necrosis, less commonly osteoradionecrosis, and limitation of mouth opening [
Mandibular osteoradionecrosis (ORN) is a serious complication of radiation therapy for neoplasms of the oral cavity, oropharynx, nasopharynx, and parotid gland, with a varying reported incidence of 5% to 22% [
The clinical diagnosis of mandibular osteoradionecrosis is based on symptoms and signs of ulceration or necrosis of the overlying mucous membrane with exposure of necrotic bone [
Mandibular osteoradionecrosis: (a) Axial contrast-enhanced CT of the mandible (bone window) shows destruction of the mandible, including along the lingual cortex and loss of the normal trabecular pattern (arrow). (b) Axial contrast-enhanced CT (soft tissue window) shows no evidence of an enhancing soft tissue mass. Linear enhancement (arrow) represents mucositis.
The hyoid bone is located inferior to the oral cavity and oropharynx and above the thyroid cartilage. The musculature of the floor of the mouth and the tongue are attached to the hyoid bone, providing assistance in tongue movement and swallowing. Tumor adjacent to the hyoid bone before radiation therapy is a factor that should be considered as putting the hyoid at risk [
Hyoid bone osteoradionecrosis: (a) Axial contrast enhanced CT of the mandible bone (bone window) shows destruction of the right hyoid bone with soft tissue air (arrow). (b) Axial contrast-enhanced CT (soft tissue window) shows soft tissue ulceration without evidence of an enhancing soft tissue mass (arrow).
Osteoradionecrosis of the skull base may be suggested by destruction of the bone and may be extensive and symmetric or localized. The most common locations are the sphenoid bone, followed by the clivus, internal carotid canal, and temporal bone. Destruction of bone is present with sequestra present within or surrounding necrotic bone and small collections of air within the soft tissue adjacent to the necrotic bone [
Radiation necrosis of the skull base with fistulous tract: Sagittal contrast-enhanced CT of the mandible bone (bone window) shows irregularity of the skull base (small arrow). In addition, there is a fistulous tract extending towards the oral cavity (large arrow).
The larynx includes the thyroid, arytenoid, and cricoids cartilages and is involved in speech and swallowing. Computed tomography can have a role in the evaluation of patients showing signs of laryngeal edema and/or necrosis after radiation. The diagnosis of chondronecrosis of the larynx can be strongly suggested in cases of sloughing of the arytenoid cartilage, fragmentation and collapse of the thyroid cartilage, and the presence of gas bubbles around the cartilage [
Chondronecrosis of the thyroid cartilage: (a) Axial contrast-enhanced CT of the thyroid cartilage (bone window) shows destruction of the left side of the cartilage (arrow). (b) Axial contrast-enhanced CT (soft tissue window) shows no evidence of an adjacent enhancing soft tissue mass (arrow).
Ulceration is defined as a defect, or excavation, of the surface of a tissue or organ, which is produced by the sloughing of inflammatory necrotic tissue [
Benign and malignant soft tissue ulceration: (a) Axial contrast-enhanced CT of the oral cavity (soft tissue window) shows a benign ulceration (arrow) without an associated soft tissue mass. (b) Axial contrast-enhanced CT (soft tissue window) shows recurrent tumor characterized by irregular enhancement along the floor of the ulceration (arrows).
A fistulous tract is an abnormal pathway between an internal cavity or organ and the surface of the body. These may be caused by infection, tumor, or radiation. Orocutaneous fistulas (Figure
Orocutaneous fistula: (a
Seventy percent of congenital neck masses are thyroglossal duct cysts [
Enlarging thyroglossal duct cyst: (a
Radiation necrosis to the temporal lobes of the brain can occur following radiation treatment of head and neck tumors, notably for lesions of the nasopharynx. The incidence has been reported to be 3% [
Temporal lobe radiation necrosis: (a) Axial contrast-enhanced MR examination of the brain demonstrates a peripherally enhancing focus in the right temporal lobe. (b) Axial fast spin echo T2 sequence shows edema around the focus of radiation necrosis characterized by signal hyperintensity (arrow).
Abscess formation after radiation may be related to surgery or be odontogenic in origin. Abscesses will present as a rim enhancing fluid collection with a surrounding edema, characterized by soft tissue swelling and reticulation (Figure
Left facial abscess: (a) Axial contrast-enhanced CT (soft tissue window) shows an abscess (arrow) of the left face. This is characterized by a peripherally enhancing fluid collection with a small focus of air and adjacent soft tissue swelling.
Sarcomas are a known complication [
Radiation-associated osteosarcoma of the mandible: (a) Axial contrast-enhanced CT of the mandible (bone window) shows an osteoid matrix (arrow) within the tumor.
Interpretation of the posttreatment neck can be difficult, with the appearances of complications sometimes mimicking recurrent tumor. A basic understanding of the findings commonly seen after radiation therapy may aid the neuropathologist in interpreting pathologic specimens. Neuropathologists will be aided by familiarity with the imaging appearances of the posttreatment neck, including changes to bone and soft tissue structures and features differentiating expected complications from recurrent tumor.