Journal of Clinical Neuroscience 16 (2009) 603–604

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Journal of Clinical Neuroscience

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Short Communication

Crossed cerebellar hyperperfusion on ictal FDG PET in astrocytoma

Michael Lin a,*, Tracy Smith b, Roy G. Beran b

a Department of PET and Nuclear Medicine, Liverpool Hospital, University of New South Wales, 1 Elizabeth Drive, Liverpool, New South Wales 2170, Australiab Department of Neurology, Liverpool Hospital, University of New South Wales, Liverpool, New South Wales, Australia

a r t i c l e i n f o

Article history:Received 14 December 2007Accepted 13 July 2008

Keywords:FDGPETPositron emission tomographyIctalAstrocytoma

0967-5868/$ - see front matter Crown Copyright � 2doi:10.1016/j.jocn.2008.07.073

* Corresponding author. Tel.: +61 2 9828 3515; faxE-mail address: michael.lin@swsahs.nsw.gov.au (M

a b s t r a c t

Crossed cerebellar hyperperfusion (CCH) is a rare phenomenon and reflects the close anatomical andfunctional relationship between the frontal brain region and its mediated remote effect on the contralat-eral cerebellum via the corticopontocerebellar pathway. Although it is well documented on cerebral sin-gle photon emission tomography (SPECT) in patients with epilepsy, it is rarely observed in seizuresoriginating from brain tumours. We report a 41-y-old man who whilst undergoing 18F-fluorodeoxyglu-cose (FDG) positron emission tomography (PET) for investigation of suspected glioma, developed a gen-eralized seizure. The scan performed shortly after seizure onset demonstrated intense metabolic activityin the right superior frontal lobe and in the contralateral cerebellar hemisphere consistent with CCH.

Crown Copyright � 2008 Published by Elsevier Ltd. All rights reserved.

1. Introduction

A previously fit and well 41-y-old man presented to the emer-gency department in status epilepticus that evolved from a simplepartial seizure involving his left forearm while a passenger in a mo-tor vehicle. The seizures were terminated with 1 g of sodium val-proate administered rectally using the oral syrup administered asan enema. A CT scan of the brain demonstrated two focal lesionsin the right superior frontal lobe and MRI revealed a correspondingarea of diffuse hyperintensity (Fig. 1) suspicious for a low gradeglioma.

After the patient had been free of seizures for 15 d on oralsodium valproate, 18F-fluorodeoxyglucose (FDG) positron emissiontomography (PET) was performed. During the uptake period, at20 min after FDG injection, the patient again developed a simplepartial seizure involving his left forearm that evolved into a sec-ondarily generalized seizure lasting 2 min with termination fol-lowing intravenous diazepam. A PET scan performed shortly afterseizure onset demonstrated a moderately large area of intenseFDG accumulation at a degree greater than contralateral grey mat-ter in the right superior frontal lobe, and associated intense uptakein the contralateral cerebellar hemisphere consistent with crossedcerebellar hyperperfusion (CCH) (Fig. 2). A repeat PET scan per-formed on the following day, after the patient had been free of sei-zures for 12 h, showed metabolic activity in the right frontal lobethat was much less than that demonstrated of normal grey matterand at a level similar to presumed normal contralateral white mat-

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: +61 2 9828 3529.. Lin).

ter (Fig. 3). Subsequently we performed an excisional biopsy,which revealed increased cellularity and mitoses consistent witha World Health Organization (WHO) Grade 3 astrocytoma.

2. Discussion

FDG PET is utilized in grading brain tumours. A relatively simplevisual grading scale was devised by Meyer et al..1 In the case above,the lesion showed a degree of FDG uptake similar to that of whitematter on post-ictal PET scan, favouring a low grade glioma. How-ever, the final histologic grade was not consistent with the PETfindings. One possible contributing factor may be due to the rela-tively short time interval between seizure onset and PET scanning,which may have resulted in an underestimation of the level of met-abolic activity, hence the grade of the tumour. The post-ictal hypo-metabolism observed is similar to that seen during interictal PETscans for epilepsy. Although a post-ictal study should be delayedin order to circumvent this, the ideal time interval between seizureonset and FDG PET scan in brain tumours is unclear and hypome-tabolism has been observed for many days following initial seizureonset.2 While interictal patterns on PET are well described, ictalimaging, as a result of the short half life of the tracer, is a conse-quence of the serendipitous occurrence of seizure activity duringthe uptake period.3

CCH is a rare phenomenon and reflects the close anatomical andfunctional relationship between the frontal brain region and itsmediated remote effect on the contralateral cerebellum via the cor-ticopontocerebellar pathway.4 The corticopontine projection pro-vides an excitatory input in the contralateral cerebellarhemisphere. Activation of the corticopontocerebellar pathway,

ights reserved.

Fig. 2. A dedicated 18F-fluorodeoxyglucose (FDG) positron emission tomography(PET) of the brain was performed 30 min after intravenous administration of 361MBq of FDG using a Philips Allegro PET camera (Philips Medical systems, Milpitas,CA, USA) following a 6 h fasting period. Transmission data were acquired with a137Caesium line source followed by one 15-min emission scan of 17.8 cm in length.The data were reconstructed using three-dimensional Row Action MaximumLikelihood Algorithm (RAMLA) and oblique section analysis was performed.Following seizure onset during the tracer uptake period, the PET scan demonstrateda moderately large area of intense FDG accumulation in the right superior frontalregion and associated hypermetabolism in the contralateral cerebellar hemisphere.

Fig. 3. Post ictal positron emission tomography (PET) scan showing correspondinghypometabolism in the right superior frontal region and contralateral cerebellarhypometabolism, suggestive of a low grade glioma and associated crossedcerebellar diaschisis.

Fig. 1. MRI of the brain (Siemens Symphony 1.5T, Siemens Medical Systems,Erlangen, Germany) on T2-weighted sequences demonstrated an area of diffusehyperintensity in the right superior frontal lobe involving the cortex and adjacentwhite matter associated with local mass effect. There was no appreciable contrastenhancement and no evidence of restricted diffusion. There was minor effacementof the right frontal horn of the lateral ventricle. The overall appearances aresuggestive of an infiltrative process such as a low grade glioma.

604 M. Lin et al. / Journal of Clinical Neuroscience 16 (2009) 603–604

such as that during seizure activity, would also lead to contralat-eral cerebellar hyperperfusion, increased glucose demand andhypermetabolism on FDG PET scan.5

References

1. Meyer PT, Schreckenberger M, Spetzger U, et al. Comparison of visual and ROI-based brain tumour grading using 18F-FDG PET: ROC analyses. Eur J Nucl Med2001;28:165–74.

2. Kawai N, Kawanishi M, Tamiya T, et al. Crossed cerebellar glucosehypermetabolism demonstrated using PET in symptomatic epilepsy-Casereport. Ann Nucl Med 2005;19:231–4.

3. Barrington SF, Koutroumanidis M, Agathonikou A, et al. Clinical value of ‘‘ictal”FDG-positron emission tomography and the routine use of simultaneous scalpEEG studies in patients with intractable partial epilepsies. Epilepsia1998;39:753–66.

4. Allen GI, Tuskahara N. Cerebrocerebellar communication systems. Physiol Rev1974;54:957–1006.

5. Chugani HT, Rintahaka PJ, Shewmon A. Ictal patterns of cerebral glucoseutilization in children with epilepsy. Epilepsia 1994;35:813–22.