If not attached to occipital bone, process is isolated rod-like bony element called massa paracondylica
Portions may be pneumatized from mastoid air cells
Top Differential Diagnoses
• Assimilation of C1 into occiput
Bony fusion across occipital condyles and lateral masses of C1
• Klippel-Feil syndrome
Variable fusions of multiple cervical vertebral bodies and posterior elements
• Proatlas segmentation abnormality
Shelf-like bony projection arising from ventral foramen magnum or occipital condyle
Clinical Issues
• Typically asymptomatic
• May cause limitation of neck movement and restricted range of motion
• Rare cases of chronic headache pain relieved by surgical resection of paracondylar process
• Rare reports of associated vertebral stenosis
(Left) Coronal NECT shows a large bony mass projecting off the right occipital condyle and merging with an enlarged right transverse process of C1 with a neoarticulation . The vertebral artery has a well-defined canal through the bony mass .
(Right) Axial NECT shows the junction of the right paracondylar process with the markedly enlarged right transverse process of C1 . The paracondylar process shows considerable variation, ranging from a small tubercle to a large bony process.
(Left) Coronal NECT shows a large, well-defined and corticated bony fusion that has occurred on a congenital basis connecting the mastoid region to the transverse process of C1 . This is usually asymptomatic, although there are rare reports of associated vertebral artery stenosis.
(Right) Sagittal NECT shows the paracondylar process as a large, cone-shaped, corticated bony mass extending inferiorly from the occipital condylar region .
TERMINOLOGY
Synonyms
• Paramastoid process, paroccipital process, jugular process, parajugular process
Definitions
• Enlarged bony process of cranial base projecting caudally to transverse process of atlas (C1)
• Epitransverse process is mirror image process and arises from transverse process of atlas and projects cephalad to occipital condyle
Only gold members can continue reading. Log In or Register to continue
and merging with an enlarged right transverse process of C1 with a neoarticulation 
. The vertebral artery has a well-defined canal through the bony mass 
.
. The paracondylar process shows considerable variation, ranging from a small tubercle to a large bony process.
. This is usually asymptomatic, although there are rare reports of associated vertebral artery stenosis.
.
