CT/MRI Society Case of the Month
April 2006
Sponsored by Eklin Medical Systems
Patient Identification Number: CTMRSOC1
Patient Surname Code: CTMRSOC
Patient First Name Code: SHIROMA
Accession Number: APR06
Contributor: Jon Shiroma
Contributor’s Affiliation: MedVet, Worthington, Ohio
Species: Canine
Breed: Akita
Age at exam: 8 years
Gender: M
Presenting signs and pertinent history:
Rapid onset of right sided weakness 2 weeks prior. No pain associated with onset. Slightly improved strength since episode. Eating and drinking normally. No weight loss.
Clinical/Neuro exam findings:
Mental status: Alert and appropriate
Head posture and coordination: normal
Gain and stance: Mild, right hemiparesis, primarily characterized by slight scuffing of the toes on the right side. No significant dysmetria or ataxia.
Cranial nerve examination: Normal
Limb Examination: No changes other than hemiparesis
Proprioceptive positioning: Diminished, right side
Strength: Mild weakness, right side.
Muscle tone: Normal
Coordination: Normal
Flexor reflex: Normal
Crossed extensor reflex: Absent
Tendon reflexes: Brisk, both right pelvic and right thoracic limbs
Cutaneous trunci reflex: Normal
Anal reflex: Normal
Sensory exam: Normal
The patient re-presented 3 weeks later to the emergency service for acute worsening of right sided paresis and disorientation.
Relevant Laboratory data: None
Primary clinical rule-out pre imaging:
Two possible locations: left forebrain or deep intramedullary, ventral funiculus lesion of the cord (e.g. FCE).
Modality: MRI
Manufacturer: GE
Model/Field Strength: 1.0 T
Sequences Acquired:
T1 transverse, PD/T2 transverse (one sequence more T2 weighted), T1+C transverse, sagittal and dorsal, FLAIR transverse.
CT/MR Findings:
Non-enhancing mass effect at the right parietal lobe that is isointense to slightly hypointense on T1 images and mixed signal intensity (hyper- and hypointense) on T2 and FLAIR sequences is present. Part of the hyperintense region is presumed to represent peritumoral edema. Mass effect evidenced by displacement of falx towards the left side, and compression and slight ventral displacement of the right lateral ventricle. An ovoid area with low signal intensity is present at the dorsal aspect of this mass effect on the T2 and FLAIR sequences. A similar ovoid hypointense area is noted at the left parietal lobe (Se 4/Im 8). Hyperintense tissue (likely peritumoral edema) is present at the ventral border of this mass. A lesion is identified at the left midbrain that is hypointense on T1 and hyperintense on T2 suggestive for necrosis and/or cavitation. Focal contrast enhancement is seen at the ventral aspect of this lesion.
CT/MR Assessment:
Non-enhancing masses at bilateral parietal lobes. Necrotic and/or cavitated lesion at the left midbrain. Differentials include neoplasia and encephalitis.
Outcome:
The patient’s status declined acutely three weeks after the MRI. Owner elected euthanasia.
Final Diagnosis based on all diagnostic tests and outcome:
Necropsy and histopathology performed. Diagnosis: hemangiosarcoma. The necropsy was performed by the referring veterinarian. Accurate correlation of the post mortem lesions with the MRI was not possible
Comments:
In retrospect, the hypointense lesions (T2W and FLAIR sequences) at the dorsal aspects of the parietal lobes likely represented hemorrhage associated with tumor. Deoxyhemoglobin formation within hemorrhage can persist for several days and is hypointense on T1 and very hypointense on T2. Encephalitis was considered a differential based on multiple lesions and lack of contrast enhancement. However, lesions seen with encephalitis are generally uniformly hyperintense on T2 and FLAIR sequences. In addition, encephalitis is usually characterized by a progressive course. The acute episodes and varying neurologic signs in this case are presumed to have been due to hemorrhage from the neoplasm.
Hemorrhage in MRI of the Brain (www.strokecenter.org/education/ct-mri_criteria/#hemo)
|
|
Age |
T1
Weighted
|
T2
Weighted
|
|
Hyperacute |
Hours old, mainly oxyhemoglobin with surrounding edema |
Hypointense |
Hyperintense |
|
Acute |
Days old, mainly deoxyhemoglobin with surrounding edema |
Hypointense |
Hypointense, surrounded by hyperintense margin |
|
Subacute |
Weeks old, mainly methemoglobin |
Hyperintense |
Hypointense, early subacute with predominantly intracellular
methemoglobin. Hyperintense, late subacute with predominantly extracellular
methemoglobin |
|
Chronic |
Years old, hemosiderin slit or hemosiderin margin surrounding
fluid cavity |
Hypointense |
Hypointense slit, or hypointense margin surrounding
hyperintense fluid cavity |
