Case Author(s): M. Roarke, MD, F. Dedashti, MD , 11/2/95 . Rating: #D3, #Q5

Diagnosis: Crossed cerebellar diaschisis.

Brief history:

30-year old woman with history of brain tumor, now presenting with increasing right- sided weakness and emotional lability.


F-18 FDG PET axial images

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Full history/Diagnosis is available below

Diagnosis: Crossed cerebellar diaschisis.

Full history:

30-year old woman with history of recurrent anaplastic ganglioglioma status post surgery and intracavitary radiotherapy as well as external beam radiotherapy. The magnetic resonance imaging examination has been stable over the past year, but her clinical symptoms of right-sided weakness, memory loss, and emotional lability are worsening. This examination was requested to evaluate for evidence of residual tumor.


10.8 mCi F-18 fluorodeoxyglucose i.v.


Subtle increased FDG accumulation, less than that of normal gray matter, was seen corresponding to the rim enhancement at the tumor resection bed in the left parietal lobe seen on magnetic resonance imaging (not shown). There is diffusely decreased tracer accumulation throughout the left cerebral hemisphere, predominantly involving the frontal, parietal, and temporal lobes. Decreased activity also is seen in the left basal ganglia and thalamus. Decreased tracer accumulation is seen in the right cerebellar hemisphere, likely reflecting crossed cerebellar diaschisis. This diffusely decreased metabolism in the territories above is new since the patientıs prior PET imaging study performed 17 months ago. These findings are thought to be most consistent with the effects of radiation on the cerebral vessels and blood flow.


Crossed cerebellar diaschisis refers to hypometabolism in a cerebellar hemisphere contralateral to a cerebral hemispheric lesion. The location of the lesion is a critical factor in producing this effect as lesions located in the motor cortex, anterior corona radiata, and thalamus produce the most marked suppression of the contralateral cerebellar cortical metabolism. The cerebellar hemispheric hypometabolism is thought to be secondary to disconnection of cerebro-ponto-cerebellar pathways, which leads to decreased oxygen and glucose utilization and, hence, decreased CO2 production, which results in local arterial constriction (decreased cerebellar blood flow) and diminished uptake of tracer. The causes of crossed cerebellar diaschisis include stroke, brain tumor, and sickle cell disease. The ipsilateral hypometabolism in the pontine, thalamic, and basal ganglia in this patient was thought to be due to the known interval radiotherapy (stereotactic radiosurgery 11 months prior to the current study), although the presence of residual tumor also raises the possibility of tumor induced hypometabolism.

References: 1) Rumbaugh C, et al. Cerebrovascular disease: imaging and intervention. 1995 2) Rozental, et al. Cerebral diaschisis in patients with malignant glioma. J Neuro Oncol 1990; 8:153- 161

ACR Codes and Keywords:

References and General Discussion of PET Tumor Imaging Studies (Anatomic field:Skull and Contents, Category:Organ specific)

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Case number: pt006

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