Types of branchial cleft abnormalities

The Children's Hospital of Boston has an easy site on branchial cleft remnants.  There are four kinds of branchial cleft abnormalities, as described by the site:

1. First branchial cleft anomalies are rare, but do occur as cysts that lie in front, behind, or below the earlobe or under the jaw. A first branchial sinus has an external opening below the jaw and above the hyoid bone (a bone present in the neck just above the voice box).
   
2. Second branchial cleft sinuses occur as sinus tracts with an opening on the skin of the neck during the first 10 years of life, and as cysts during the second 10 years (see Figure 1). A skin tag or abnormal cartilage may occasionally be present at the opening of the sinus, and occasionally the tract may be felt as a band in the neck.
   
3. Third branchial cleft sinuses are extremely rare and are often located near the thyroid and along the front part of the muscle in the neck which attaches to the collar bone.
    
4. Fourth branchial cleft sinuses are also rare and are located low in the neck similar to the third cleft sinuses.

Dr. Green suspects Kate's is a second or third, likely second.  The ultrasound done on her at two weeks indicates it is suspected fourth, but Dr. Green is more experienced in branchial cleft abnormalities than the radiologists and doubts it is a fourth.  In fact, he said he had only seen one true fourth branchial cleft sinus in his lifetime and he said they are "a bear" to remove--they wrap down around the heart!  This would be a very grave prognosis and require (I am guessing) open chest cavity surgery.  We are prayerful it is not a fourth and perhaps even a very simple second that can be removed through the pin-hole opening only (no inch-long incision!). 

To determine where the tract goes, he will make a small cut on the opening and clamp the tract with a surgical clamp.  Then, he pulls!  He said you can see where the tract is by where it tugs on the skin.  This very low-tech method determines where and how he cuts next. 

Since we're discussing the rarity of the fourth type of branchial cleft abnormalities, it's worth discussing how rare the existence of any type at all is.  They do run in families (as ours does--my brother also has a long-closed mark on his neck!) but are only seen in a small percentage of children.  When she was diagnosed in the hospital at two weeks old, we had a contingent of medical students and residents tramp through wanting to examine our daughter's neck.  It seems that while branchial cleft abnormalities are something they all learn about, they rarely get to see one in person (lucky us!)  In fact, Dr. Green said he is referred cases from around the state of Michigan and the ENT department at U-M still only does about three or four branchial cleft cases a year!  Too bad we aren't as lucky in the lottery as we are in acquiring odd medical conditions...