Type:
Educational Exhibit
Keywords:
Head and neck, CT, CT-High Resolution, Education, Neoplasia
Authors:
A. D. P. P. Borges, R. Murakoshi, C. Toyama, R. L. E. Gomes, H. Tames, E. Gil, E. M. M. Gebrim
DOI:
10.26044/ecr2023/C-18864
Findings and procedure details
Mehanna classification is a new risk stratification system for carotid body tumors, validated in a multicenter international cohort. It demonstrated better power for predicting complications following surgery, primarily neurological and neurovascular complications, than the widely used modified Shamblin classification system, which has a limited assessment in predicting the risk of neurological damage of cranial nerves.
Mehanna classification does not distinguish between the different types of paragangliomas, and it stands for all tumors classified as carotid body tumors involving the carotid bifurcation.
The authors hypothesized that cranial extension was the primary determinant of complications from carotid body tumor surgery, more critical than clinical and radiological risk factors, such as age, craniocaudal dimension, and volume.
They proposed that the cephalic extension of carotid body tumors is associated with an increased rate of nerve injury because the limited exposure to gain distal vascular control of high tumors required more retraction and manipulation of adjacent nerves.
The new classification system is based upon the highest anatomical landmark reached by the tumor's cranial extent, classified in types 1 to 4. The risk of complications increases significantly with increasing Mehanna type.
- Type 1 - extends up, but not above, the superior-most aspect of the body of the hyoid bone.
- Type 2 - extends up, but not above, the lower border of the angle of the mandible.
- Type 3 - extends up, but not above, the superior-most aspect of the body of the C2 vertebra.
- Type 4 - extends above the superior-most aspect of the body of the C2 vertebra. This is the type with the highest risk of neurological complications.
An additional subclassification to the type can be added for surgical planning:
- E: It is for carotid body tumors encircling bifurcation, internal or common carotid artery;
- F: It is for functional carotid body tumors, secreting catecholamines;
- S: It is for carotid body tumors reaching the skull base.