Ring Enhancing Lesions

 

Although I'm supposed to be talking about orthopaedic surgery stuff on this blog, it's kind of hard to gather good material when you aren't actually seeing patients with musculoskeletal problems.  

This is a case that I saw during an off service rotation that I think almost everyone would find interesting.  It's the true House sort of mystery.  

I've been unfortunate enough to see two cases like this during my short medical career.  Each time, the patient presented the same way.  They were brought to the ED by a family member because of strange behavior.  They were both having trouble with memory and were acting strangely.  Neither was able to really communicate.  They would answer questions with short phrases.  One was getting confused and had become incontinent of both stool and urine.  One had a CT scan (without contrast) that was read as negative.  The other got a head CT with and without IV contrast which showed some ring enhancement.  Both ended up getting MRI scans that looked similar to the above picture, which I stole from the interweb.

One patient was found to have metastatic breast cancer.  The other, at least to the point I stopped taking care of them, remains a medical mystery.  Although, trust me, the neurologists, ID docs, and probably many other specialties by this point are on the case.

For those wondering, the differential diagnosis for ring enhancing brain lesions is not terribly long.  I found this case at Medscape as a good example of the presentation.  They provide the pnemonic MAGIC DR to help remember the DDx:  metastatic disease, abscess, glioma, infarction, contusion, demyelination, and resolving hematoma/radionecrosis.  

One of the most interesting categories is probably abscess.  Their are three classic infections tested on the boards:  toxoplasmosis and CMV in immunocompromised individuals and neurocysticercois. I think that cysticercosis is probably the most interesting, but that's just me.

Cysticercosis is an infection in which an individual (usually from Mexico in the test question) eats undercooked pork and then begins acting strangely.  The patients experiences these symptoms when the pork that they ingested is infected with tapeworm (Taenia solium) eggs.  The eggs hatch and the larvae burrow their way through the lining of the intestines.  They then find their way into the circulation and are then free to migrate throughout the body.  Their most common stomping grounds include the musculature, brain parenchyma and the eyes.  In the eye, if the larvae are alive, you may actually be able to see them moving around in the eye.  Treatment is with either antihelmenthic drugs like albendazole or surgical removal.

What lessons can we learn from this case?  1)  Always cook your pork.  2)  If a patient presents acting strangely, you should think about ordering your head CT with and without IV contrast.