Normal Variant: Cervical Rib

Note the corresponding transverse process points caudally => Cervical origin

Incidental finding of Cervical rib.
Can be unilateral or bilateral.
0.5 - 8% of population*
Usually asymptomatic, but occasionally may give rise to complications.
Think about the anatomical structures that goes through the thoracic outlet, and the attachment of the scalene muscle.

Complications:
- Usually in adulthood
- Thoracic outlet syndrome
- Subclavian artery aneurysm as a result of compression

DDx:
- Hypoplastic 1st rib (rudimentary 1st rib)
- Elongated transverse process of C7

Key to differentiate from the other DDx:
(1) Check transverse process. Cervical transverse process points down, 1st thoracic transverse process points up.
(2) Check presence of joint space between the rib and the transverse process. Absent joint space means it's a elongated transverse process.

Right cervical rib. Note the transverse process pointing down.

*Reference from: Guttentag AR, Salwen JK. Keep your eyes on the ribs: the spectrum of normal variants and diseases that involve the ribs. RadioGraphics 1999;19:1125-1142

Normal Variants: Paranasal Sinuses

Normal variants in the paranasal sinuses

Note listed are only the more common ones.
These are important in radiology report, as gives the endoscopist an idea what to look out for (Surgical planning).

Name	Location	Implication
Agger nasi cell	Ethmoid aircells. Located most anteriorly, infront of the cribriform plate where the middle turbinate attaches	If inflamed, patient may experience epiphora as it is close to the medial canthus	Agger nasi cell on the left side, just inferior to the frontal sinus
Haller cell (MaxilloEthmoidal cell, Infraorbital cell)	Aircells located along the margin of the orbital floor. Inferolateral to the ethmoidal bulla.	Presence of these cells may narrow the infundibulum and/or maxillary sinus ostium. Prone to obstruction and inflammation of the maxillary sinus.	Large right Haller cell
Onodi cell	Ethmoid aircells that extends into the sphenoid bone, located superior to the sphenoid sinus.	At risk of intracranial extension of the endoscope if surgeon (endoscopist) is not aware of the presence of Onodi cell.
Concha bullosa	Pneumatized middle turbinate. These cells usually communicates with the anterior ethmoid aircells.	Large concha bullosa enlarges the turbinate,  makes one prone to obstruction/ inflammation. Concha bullosa also makes endoscopic access more difficult.	Right concha bullosa. Notice the right middle turbinate is larger than the left (with absence of concha bullosa).

What normal variant(s) did you see here?

Saupe Classification

Saupe's Classification: Based on the position of the accessory ossification center

More about bipartite patella here

Type I (5%)	Accessory ossification center at the inferior pole
Type II (20%)	Accessory ossification center at the lateral margin
Type III (75%)	Accessory ossification center at the superolateral pole

Normal Variant: Bipartite Patella

Bipartite patella occurs due to presence of unfused ossification centre.
Other variants include

• Tripartite patella
• Multipartite patella

These normal variants can be classified using Saupe's classification.

Male : Female = 9 : 1

Occurs in 2% of population

Usually asymptomatic

Saupe type 3 Bipartite patella. About half of bipartite patellae are bilateral.

Ossification:

• Primary ossification begins at 5 - 6 years old
• 77% from one center
• 23% from two or three centers
• The ossification centers usually fuse mutually

Keros Classification

Keros Classification in CT scan of the paranasal sinuses

Measures depth of the olfactory fossa
Measurement: Distance from the lamina cribrosa to the roof of ethmoid (highest point) Note: Depth of the olfactory fossa can be asymmetrical Note the measurement (double-head arrow)
Keros type	Measurement	Illustration
1	1-3 mm	Keros type 1: notice relatively shallow olfactory fossa
2	4-7 mm	Keros type 2: Deeper olfactory fossa
3	8-16 mm	Keros type 3: Deep olfactory fossa
Implication: Stratifies the risk of intracranial penetration during ENT surgery