Magical Doctor is the pneumonic that has been used to remember the causes responsible for ring enhancing lesions that can present on a radio contrast enhanced CT (Computed Tomograph). A ring-enhancing lesion is an abnormal radiological sign on contrast enhanced MRIs or CT scans. An area of decreased density is surrounded by a thicker brighter border or rim demarcating or encircling that area.
- Cerebral Abscesses
The above three are the most common causes for ring enhancing lesions. These three should be considered first i.e they would be at the top the differential diagnosis if such a case presents.
Infections especially toxoplasmosis in HIV can typically cause such lesions. Tuberculomas and neurocysticercosis are other infective causes.
Brain Contusions which are resolving have ring enhancement. Sub acute infarct and hemorrhage can also present as such.
Aneurysms which are thrombosed can present with ring enhancing lesion.
The other 3 causes are
- CNS Lymphoma
- Demyelinating disorders with Acute demyelinating plaque Multiple Sclerosis in particular
- Radiation Necrosis
Radiological Differentiating Points in relation to the above causes
The following are characteristic differentiating points for the different causes of ring enhancing lesions.
- Similar sized and rounded lesions present at the grey white matter interface would indicate metastases or abscesses
- exaggerated edema relative to the size of the lesion itself would point towards an abscess
- incomplete ring formation favors demyelination as the possible cause
- irregular lesion with no distinct boundary with finger like projections into the adjacent space would favor Glioblastom
- The enhancing wall of a Neoplastic lesion would be thick and nodular as compared to an abscess which would be thin and regular
So let us fit the pneumonic Magical Doctor with these causes to make it easier to remember them
- M METASTASES
- A ABSCESS
- G GLIOBLASTOMA
- I INFECTIONS (TOXOPLASMOSIS)
- C CONTUSION (RESOLVING)
- A ANEURYSM (THROMBOSED)
- L LYMPHOMA (CNS LYMPHOMA)
- D DEMYELINATING DISORDER (ACUTE DEMYELINATING PLAQUE M.S)
- R RADIATION NECROSIS