Presentation
Acute severe headache and dizziness. Background of hypertension and diabetes mellitus.
Patient Data
Near-symmetrical hypodensity areas are seen involving both inferior cerebellar hemispheres with effacement of the cerebellar folia, confined to both medial branches of posterior inferior cerebellar artery territories.
No evidence of intra- or extra-axial hemorrhage.
No evidence of midline shift.
Normal ventricular system, basal cistern, Sylvian fissures, and convexity sulci.
The right vertebral artery and proximal basilar artery, as well as both distal internal carotid arteries, show atherosclerotic changes.
IMPRESSION:
Bilateral inferior cerebellar hypodensities. Infarctions in both posterior inferior cerebellar artery territories have to be considered for clinical correlation, further assessment by MRI DWI/MRA/MRV, and urgent neurological consultation.
Bilateral hyperintense areas on T2/FLAIR and ADC and DWI show an acute infarction involving bilateral cerebellar hemispheres at the territory of posterior inferior cerebellar arteries.
A small area of altered signal is noted in the right internal capsule, which may indicate old ischemic insult.
Bilateral periventricular white matter hyperintense foci are noted, likely indicating chronic white matter ischemic changes.
No evidence of hemorrhage, mass or midline shift.
Normal ventricular system, basal cistern, Sylvian fissures, and convexity sulci.
MRA:
- the right posterior inferior cerebellar artery is not visualized, but there is a well developed left posterior inferior cerebellar artery arising from the left vertebral artery (seen in 3D and axial source images of the time-of-flight MRA)
- a well developed right anterior inferior cerebellar artery and moderately developed left one
- patency of both vertebral, basilar, posterior cerebral, and both superior cerebellar arteries
- the internal carotid arteries and their branches are normal in appearance
- there is no evidence of narrowing, dissection, irregularity, aneurysm or occlusion
MRV shows a normal flow signal noted in the superior sagittal, straight, transverse and sigmoid sinuses bilaterally, denoting patency. Normal course and caliber of internal cerebral veins, as well as vein of Galen.
Case Discussion
Cerebellar infarcts are now seen well by CT and especially MRI. MRI demonstrates precise anatomic localization of these lesions. Some infarcts involve the full territory supplied by a cerebellar artery and others involve partial territory infarcts, which are more common than full territory infarcts. Few patients suffering from bilateral cerebellar infarction could survive with a good functional recovery.
Physicians (neurologists in particular) and radiologists should be aware of the possibility of simultaneous bilateral medial cerebellar infarcts. Familiarity with these similar radiologic findings of the cerebellar anatomy, its vascular territories, and patterns of infarctions of the posterior fossa depicted with MRI can make the radiologist help in saving the patient survive.
Our case is a good example of bilateral cerebellar infarction and needs meticulous effort to know the vascular anatomical variants that can be the cause of infarctions. Our patient came a day before with non-specific symptoms, took medication, and then went home. The patient then came a day after (on the day of diagnosis) and underwent head CT, which showed edema and mass effect in the medial aspect of both cerebellar hemispheres. MRI brain from the same day (about 10 hours apart) as the CT scan confirms acute infarction in the medial posterior inferior cerebellar artery territories bilaterally (confined to the territory of the medial branches of the posterior inferior cerebellar arteries).
An astute radiologist should look at all images, search for the cause, and help the physician manage the patient. The cause of simultaneous bilateral cerebellar infarct is probably related to an anatomical variant of the PICAs in this case. We believe that our patient has an absent right posterior inferior cerebellar artery and had a dominant single left PICA which supplied medial branches of both PICAs and hence caused the bilateral stroke. This caused infarction in the territory of the medial branches on both sides without remaining brainstem signs.
Case courtesy: Dr Kamel Ahmed Kamel, Dr Mohammed Habib Radhi Al Ayous, and Dr Safwatal Moghazi.