2012 Radiology Exam - CT/MRI Case 2

History

A 9 year old, spayed female Labrador presented to the emergency room for a seizure characterized by full body muscular contractions and facial tremors.

Images

Sequences provided in several planes included: Spin echo T1-W and T2-W, GRE, FLAIR and T1-W +Gd. Only 4 selected images (post contrast t1-W and transverse T1-W) are presented here due to space constraints.

Observations
 
There is a large inhomogeneous, extra-axial mass extending into the left ethmoidal turbinates. The lesion is displacing the falx cerebri to the right, especially rostrally where there is marked compression of the left olfactory and left frontal brain lobes. The mass is also impinging unto the rostral aspect of the left lateral ventricle. The caudal aspect of the lesion has a large, well-defined cystic component. Lysis of the cribriform plate is present. There is mild peripheral enhancement in the white matter tracts at the medial and mid aspect of the mass. The lesion is of heterogenous contrast enhancement. There is also contrast enhancement of the meninges surrounding the mass and the rostral aspect of the falx cerebri.  
 
Synthesis
 
There is a large left-sided extra-axial mass with a large cystic component. As the mass extends through the cribriform into the ethmoidal turbinates, a process such as an esthesioneuroblastoma or a cystic meningioma should be considered. Other differentials such as nasal adenocarcinoma, histiocytic sarcoma and even fungal granuloma were considered less likely. Candidates that did well in this case generated a specific list of differential diagnoses, described well the location of the lesion, identified with clarity the association of the mass with the cribriform plate and ethmoidal turbinates and also the behaviour of the abnormal tissue on the different sequences provided. Candidates that did not do well had difficulty recognizing the axial versus extraaxial characteristics of the mass and hence generated a poor list of differential diagnosis. Points were earned by recommending biopsy of the lesion and collection of cerebrospinal fluid. This is a case in which all candidates are expected to identify a large lesion. However, candidates with the ACVR "day one skills" are expected to be specific with the list of differentials in light of the association of a cystic mass with the cribriform plate and nasal cavity.