Friday, December 19, 2008

Hunchbacks and Bony Variants

Photo by TCM Hitchhiker

The Hunchback of Notre Dame is a novel by Victor Hugo, set in 1482 in Paris, in and around the cathedral of Notre Dame de Paris. It has had numerous theatrical and movie interpretations. I'm no literary snob, and have to confess that my only real exposure to this story is via Walt Disney. One of the perils of having several children is unrelenting exposure to Uncle Walt and his minions.

There are hunchbacks in the medical world as well. The os styloideum was first described by the Frenchman Fiolle, in 1932. He termed this entity the "carpe bossu", which can be translated as "hunchback carpal bone". This anatomic variant is located on the dorsal side of the wrist, at the base of the third metacarpal. It is typically a separate ossicle, but can fuse with the adjacent bones, typically the second and third metacarpals, but sometimes with the trapezoid or capitate.

The carpe bossu is usually an incidental finding, but can cause symptoms in some patients, and can be confused with a ganglion cyst. When troublesome, patients will complain of focal dorsal pain, and a tender bone mass. The lesion usually becomes symptomatic in adulthood, but can rarely present in childhood.

In this case, a fourteen year old boy presented with wrist pain, and was discovered to have a scaphoid fracture on MRI. Review of the coronal images along the dorsal aspect of the hand reveals a carpal boss (red arrows) located between the bases of the second and third metacarpals:

The carpal boss is also well seen on this sagittal T1-weighted image:

The patient also had edema-like changes within the os styloideum and the base of the third metacarpal, seen on this coronal T2-weighted image:

Interestingly, the patient did not report any symptoms referable to this region. One wonders whether this area will eventually become symptomatic, given the degree of abnormal signal in this area.

Vic David MD

1 comment:

Roar said...

One of my secretaries at our radiological clinic has one of these os styloideum (in fact it is bilateral). Normally she has no symptoms, but when I have done a lot of MRI-studies and she has a lot to write - she gets symptoms form the os styolideum, probably from extending in the wrist and a lot of movement in the extensor tendons.
A good example of a selfperpetuating clinic, working so hard that the employees get symptoms that you can investigate with MRI and so on... ;-)