fluorodeoxyglucose positron emission tomography/computed tomography findings in a patient with...

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Asian Journal of Surgery (2014) xx, 1e5

Available online at www.sciencedirect.com

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CASE REPORT

Fluorodeoxyglucose positron emissiontomography/computed tomography findingsin a patient with cerebellar mutism afteroperation in posterior fossa

Gonca Kara Gedik a,*, Oktay Sari a, Ender Koktekir b,Gokhan Akdemir b

a Department of Nuclear Medicine, Faculty of Medicine, Selcuk University, Konya, Turkeyb Department of Neurosurgery, Faculty of Medicine, Selcuk University, Konya, Turkey

Received 25 June 2013; received in revised form 16 September 2013; accepted 14 January 2014

KEYWORDScerebellum;FDG;mutism;PET/CT

Conflicts of interest: The authorsfinancial or non-financial conflicts of inmatter or materials discussed in the m* Corresponding author. Department

of Medicine, Selcuk University, 42075E-mail address: goncakara@yahoo.

Please cite this article in press as: Gea patient with cerebellar mutism aj.asjsur.2014.01.004

http://dx.doi.org/10.1016/j.asjsur.201015-9584/Copyright ª 2014, Asian Su

Summary Cerebellar mutism is a transient period of speechlessness that evolves after pos-terior fossa surgery in children. Although direct cerebellar and brain stem injury and supraten-torial dysfunction have been implicated in the mediation of mutism, the pathophysiologicalmechanisms involved in the evolution of this kind of mutism remain unclear. Magnetic reso-nance imaging revealed dentatothalamocortical tract injuries and single photon emissioncomputed tomography showed cerebellar and cerebral hypoperfusion in patients with cere-bellar mutism. However, findings with 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in this group of patients have not been documented pre-viously. In this clinical case, we report a patient who experienced cerebellar mutism after un-dergoing a posterior fossa surgery. Right cerebellar and left frontal lobe hypometabolism wasshown using FDG PET/CT. The FDG metabolism of both the cerebellum and the frontal lobe re-turned to normal levels after the resolution of the mutism symptoms.Copyright ª 2014, Asian Surgical Association. Published by Elsevier Taiwan LLC. All rightsreserved.

declare that they have noterest related to the subjectanuscript.of Nuclear Medicine, FacultyKonya, Turkey.com (G.K. Gedik).

dik GK, et al., Fluorodeoxyglucosfter operation in posterior foss

14.01.004rgical Association. Published by E

1. Introduction

Posterior fossa syndrome consists of transient cerebellarmutism, cognitive symptoms, and neurobehavioral abnor-malities.1 It was first reported in 1985 as a complication ofposterior fossa surgery.2 Although a transient nature wasrecognized as the hallmark of this type of mutism,

e positron emission tomography/computed tomography findings ina, Asian Journal of Surgery (2014), http://dx.doi.org/10.1016/

lsevier Taiwan LLC. All rights reserved.

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2 G.K. Gedik et al.

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development after the resection of a cerebellar masslesion, delayed onset after intervention, and associationwith other neurological, emotional, and behavioral distur-bances were described as core features of this syndrome.3

The incidence of postoperative cerebellar mutismranges between 11% and 29%.4 It is more commonlyobserved after the resection of posterior fossa tumors inchildren; however, trauma, vascular incidents, or infectionsmay also be followed by this complication.4 Patients withmedulloblastomas and/or brain stem invasion are at agreater risk of experiencing this condition compared withthose who have pilocytic astrocytoma or ependymoma.5

After the first description of this syndrome appeared,more than 400 cases with cerebellar mutism have beenreported, and several hypotheses have been suggested toexplain the clinical features of this complex syndrome.Because surgery is the primary event, surgical injury todentate nuclei of the cerebellum has been proposed as theprimary cause of the initiation of mutism. However, thedelayed onset of mutism after surgery and the presence ofconcomitant neurological symptoms have raised questionsabout the association of supratentorial structures to thisclinical picture. On one hand, there were some studies withsingle photon emission computed tomography (SPECT)showing cerebellar hypoperfusion in mute patients withnormalization of blood flow after mutism had resolved6,7;on the other hand, SPECT studies linking mutism to hypo-perfusion of contralateral frontal cortex or other supra-tentorial targets were also reported.1,8 This asymmetricblood flow in cortical areas contralateral to a remote

Figure 1 Preoperative (A) axial and (B) sagittal T1-weighted magthe fourth ventricle (arrow) with significant brain stem and cerebeare shown on (C) postoperative computed tomography. T1-weightformed 3 months after surgery reveal a decrease in cyst size (arro

Please cite this article in press as: Gedik GK, et al., Fluorodeoxyglucosa patient with cerebellar mutism after operation in posterior fossj.asjsur.2014.01.004

cerebellar lesion, which is described previously as crossedcerebello-cerebral diaschisis, is a well-known phenomenon,and injury to the dentatothalamocortical pathway is sug-gested as the cause.3

We describe a patient who underwent cerebellar surgeryand developed mutism after the procedure. Metabolic im-aging with 18F-fluorodeoxyglucose positron emission to-mography/computed tomography (FDG PET/CT) wasperformed at both mutistic and postmutistic phases. TheFDG metabolism of the primary surgical site and thecortical areas is discussed, and the literature is reviewed.

2. Case report

A 17-year-old male patient was admitted to the hospitalcomplaining of a headache. His history showed that he hasbeen suffering from headaches and vomiting for 4 monthsand 3 weeks, respectively. His Glascow Coma Scale was 15,and his neurological examination yielded completelynormal results. Cranial magnetic resonance imaging (MRI)showed a large arachnoid cyst formation (47 � 36 � 61 mm)at the fourth ventricle with significant brain stem andcerebellum compression accompanied with mild tetraven-tricular hydrocephalus (Fig. 1A and B). The patient under-went an operation at the neurosurgery department. Theoperation was performed with the patient placed in asitting position, and a midline suboccipital approach wasused. After the suboccipital craniotomy, the dura wasopened and both cerebellar hemispheres were retracted

netic resonance imaging show large arachnoid cyst formation atllum compression. Pneumocephalus and ventricular dilatationed (D) axial and (E) sagittal magnetic resonance imaging per-w) as well as compression of the cerebellum and brain stem.


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laterally. After the splitting of the vermis, under micro-scopic visualization, the thickened membrane of the largearachnoid cyst, which was located at the floor of the fourthventricle, was perforated (cystoventriculostomy). Theanterioreinferior part of the arachnoid cyst was alsofenestrated into the cerebellomedullary cisterns (cystocisternostomy).

The early postoperative neurological examination wasuneventful until the 2nd postoperative day. Twenty-fourhours after the surgery, results of his neurological exami-nation showed that his condition had deteriorated. Cere-bellar mutism-like symptoms such as speechlessness,cerebellar ataxia, and apathia developed.

The patient was imaged anatomically and metabolicallyat the mutistic phase. His CT scan (Fig. 1C) revealed dila-tation and pneumocephalus in all ventricles including rightand left lateral ventricles and the fourth ventricle. How-ever, no structural abnormality was noted.

Metabolic imaging with dual modality PET/CT examina-tion was obtained 60 minutes after the intravenous

Figure 2 (A, D) PET, (B, E) CT, and fused (C, F) PET/CT images othe right cerebellar hemisphere [(C) thick arrow, fused PET/CT imimage] is shown. (G, J) PET, (H, K) CT, and (I, L) fused PET/CT imimages showed symmetric FDG metabolism in the frontal lobeshemispheres [(L) thick arrows, fused PET/CT image]. CT Z computeemission tomography.


administration of 7 mCi FDG, using an integrated scanner(Biograph mCT, Siemens, Germany; Fig. 2AeL). The patientwas kept at rest in a silent room after the injection of aradiopharmaceutical. CT was performed without intrave-nous contrast injection, with 120 kV, 35 mA, a pitch of 1.5,a section thickness of 5 mm, and a field of view of 70 cm.The PET scan was started immediately after the unen-hanced CT. Standardized uptake value (SUV) was calculatedusing the “region of interest” technique. Relative hypo-metabolism was shown both in the right cerebellar hemi-sphere (Fig. 2A and C) and the left frontal lobe (Fig. 2A, C,D and F) with PET/CT at the mutistic phase. Whereas theratio of SUV mean values of right to left cerebellar hemi-sphere was calculated as 0.82, the ratio of SUV mean valuesof left to right frontal lobe was calculated as 0.80 at themutistic phase. Ventricular dilatation and pneumocephalusfindings were also noted. Physologic FDG biodistributionwas seen in the remaining parts of the body.

Regression in mutism symptoms was observed 3 monthsafter the surgery. The patient recovered spontaneously;

btained at the mutistic phase. Relative FDG hypometabolism inage] and left frontal lobe [(C, F) thin arrows, fused PET/CTaging are repeated at the postmutistic phase. Fused PET/CT[(I) thin arrows, fused PET/CT image] and in the cerebellard tomography; FDGZ 18F-fluorodeoxyglucose; PETZ positron


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headache and vomiting symptoms were controlled. PET/CTexamination was repeated at the postmutistic phase underthe same physical conditions, and it revealed that FDGmetabolism of the frontal lobes (Fig. 2G and I) and thecerebellum (Fig. 2J and L) were symmetric; no relativehypometabolism was observed. At the postmutistic phase,the ratio of SUV mean values of right to left cerebellarhemisphere was calculated as 1.03, and the ratio of SUVmean values of left to right frontal lobes was calculated as1.01. The cranial MRI, which was performed 3 months afterthe surgery, showed a marked decrease in cyst size(37 � 29 � 54 mm) as well as compression findings in thecerebellum and the brain stem (Fig. 1D and E).

3. Discussion

Posterior fossa syndrome and cerebellar mutism may occurafter the resection of cerebellar tumors. The pathophysi-ology and anatomic basis of this syndrome have not beenwell understood yet, but a variety of mechanisms havebeen suggested in previous studies. In some studies, thedevelopment of mutism was attributed to the transientdysfunction of the dopaminergic cell group in the mesen-cephelon.9 Postoperative vasospasm of cerebellar or brainstem territories, surgical manipulation of cerebellum,intraoperative coagulation of perforating vessels, andarterial embolic occlusion were also discussed in theevolving process of cerebellar mutism.10 Taking intoconsideration the association between the cerebellum andcognitive and linguistic functions, which depend on thefunctional connection of the lateral part of the right cer-ebellum to the left prefrontal area, the authors wonderedwhether cortical areas play a role in the generation of thissyndrome by trans-synaptic reflex mechanisms. This hy-pothesis carried the discussion to an area in which dia-schisis was reported as a conceivable explanation behindthis syndrome. In patients with cerebellar mutism, func-tional depression of cerebelloethalamoecerebral pathwaysand deprivation of cerebellar input have been implicated toinduce cerebral circulatory and metabolic hypofunction.8

Hypoperfusion of the cerebral hemispheres with SPECT ra-diotracers has been shown; however, the FDG metabolismof the cerebellum and the cerebrum during the course ofthis clinical picture has not been previously demonstratedwith PET/CT.

Neuroimaging of the central nervous system by scintig-raphy can be performed with SPECT or PET. SPECT was firstintroduced in the 1960s to detect breakdowns in thebloodebrain barrier, and PET with FDG was later developedto measure regional cerebral glucose metabolism.11 Bloodflow and metabolism are coupled in most pathological en-tities, and the changes seen on SPECT brain perfusionassociate with the corresponding abnormalities on FDGPET.11

The hallmark features of diaschisis are hypoperfusion,decreased oxygen consumption, and hypometabolism,which can be shown by MRI or with SPECT studies. In crossedcerebello-cerebral diaschisis, it is suggested that damageto the efferent cerebellar pathway, which is often invadedby posterior fossa tumors and prone to surgical damageduring resection, deprives the cerebral cortex of cerebellar


input. Significant decreases in cerebral blood flow withinthe frontal regions have been reported with contrast-enhanced perfusion MRI in patients with posterior fossasyndrome by Miller et al.8 Catsman-Berrevoets and Aarsen3

reported hypoperfusion of the frontal cortical regions inmost of the children they have studied with Tc-99m hex-amethylpropyleneamine SPECT in posterior fossa syndrome.A significant improvement of frontal perfusion deficits inparallel to the clinical remission of mutism was shown withSPECT by De Semet et al.1 In an adult patient who experi-enced cognitive, linguistic, and affective disturbances aftera right superior cerebellar artery infarction, relativehypoperfusion in the right cerebellar hemisphere and leftmedial frontal lobe was depicted with Tc-99m ethyl-cysteinate dimer SPECT study by Marien et al.12

In our case, relative FDG hypometabolism was shown inthe right cerebellar hemisphere and the left frontal lobe, andthe presence of hypometabolismdwhich, although alwayssuggested, was not previously demonstrated in posteriorfossa syndromedwas proven. No relative FDG hypo-metabolism was noted after the recovery of the symptoms.The SUVmean ratio of right to left cerebellar hemispherewas0.82 during themutistic phase,which thenchanged to 1.03 atthe recovery stage. Similarly, the left to right SUVmean ratioof frontal lobes was 0.80 and 1.01 at the mutistic and post-mutistic phases, respectively. Because, in our case, theoperation was performed through the cerebellar vermianlobe, we thought that FDG hypometabolism was generatedsecondary to cerebellar manipulation during surgery. Vaso-spasm and edemamight have occurred during surgery, whichinduced hypoperfusion in the cerebellum or its outflow tract,which deprived the cerebral cortex from cerebellar input.This disconnection between the cerebellar projections tothalami and cerebral cortex resulted in metabolic hypo-function in the cerebrum. Hypometabolism in the left frontallobe may also evolve secondary to the compressive effect ofpneumocephalus and dilated ventricle, which was moreprominent in the left lateral ventricle. However, there wasalso dilatation in the fourth ventricle and although it was auniform dilatation, there was still relative hypometabolismin the right cerebellar hemisphere. Considering the presenceof right cerebellar and left frontal hypometabolism, wethought that hypometabolism, which resolved at the post-mutistic phase,was generated secondary to crossed cerebro-cerebellar diaschisis instead of the compressive effect ofdilatation.

The question why mutism manifests after a latencyperiod remains unanswered in the literature. The mostprobable explanation is the coexisting cerebellar andcortical dysfunction. Because cerebellar deficits should beapparent directly after cerebellar injury, they cannotexplain the delayed onset of mutism. Postmutistic symp-toms also show variability. Because vasospasm or edemaare the suggested primary effects of surgery (which initi-ates hypoperfusion and hypometabolism), normalization ofblood flow provides perfusion, thereby allowing metabolismof the affected region to return to the normal level. Thefact that hypometabolism was observed both in the cere-bellum and the cerebrum and eventually resolved after therecovery period, also supports the idea that cerebellarinjury alone cannot fully explain the cognitive andemotional deficits observed in posterior fossa syndrome.


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Our case also shows that unilateral cerebellar and cerebralhypometabolism may be observed in this syndrome insteadof bilateral involvement. Because full recovery without anysequela was observed in our patient, we thought that uni-lateral involvement may be associated with reduced post-operative morbidity.

We report the reduced FDG metabolism in the cere-bellum and the cerebrum with PET/CT in a patient withcerebellar mutism for the first time in the literature. Themetabolic depression of frontal lobe strengthens the hy-pothesis that mutism in posterior fossa syndrome is aspeech apraxia, rather than a simple dysarthria.

References

1. De Semet HJ, Baillieux H, Wackenier P, et al. Long-termcognitive deficits following posterior fossa tumor resection: aneuropsycological and functional neuroimaging follow-upstudy. Neuropsychology. 2009;23:694e704.

2. Rekate HL, Grubb RL, Aram DM, Hahn JF, Ratcheson RA.Muteness of cerebellar origin. Arch Neurol. 1985;42:697e698.

3. Catsman-Berrevoets CE, Aarsen FK. The spectrum of neuro-behavioural deficits in the posterior fossa syndrome in childrenafter cerebellar tumour surgery. Cortex. 2010;46:933e946.


4. Gudrunardottir T, Sehested A, Juhler M, Schmiegelow K.Cerebellar mutism. Child Nerv Syst. 2011;27:355e363.

5. Kuper M, Timmann D. Cerebellar mutism. Brain Lang. 2013;127:327e333.

6. Nishikawa M, Komiyana M, Sakamoto H, Yasui T, Nakajima H.Cerebellar mutism after basilar artery occlusiondcase report.Neurol Med Chir. 1998;38:569e573.

7. Ersahin Y. SPECT in cerebellar mutism. Child Nerv Syst. 1998;14:611e613.

8. Miller NG, Reddick WE, Kocak M, et al. Cerebello-cerebraldiaschisis is the likely mechanism of postsurgical posteriorfossa syndrome in pediatric patients with midline cerebellartumors. Am J Neuroradiol. 2010;31:288e294.

9. Catsman-Berrevoets CE, Van Dongen HR, Zwetsloot CP. Tran-sient loss of speech followed by dysarthria after removal of aposterior fossa tumour. Dev Med Child Neurol. 1992;34:1102e1117.

10. Ferrante L, Mastronardi L, Acqui M, Fortuna A. Mutism afterposterior fossa surgery in children. Report of three cases. JNeurosurg. 1990;72:959e963.

11. Alavi A, Hirsch LJ. Studies of central nervous system disorderswith single photon emission computed tomography and posi-tron emission tomography: evolution over the past 2 decades.Semin Nucl Med. 1991;21:58e81.

12. Marien P, Baillieeux H, De Semet HY, et al. Cognitive, linguisticand affective disturbances following a right superior cerebellarartery infarction: a case study. Cortex. 2009;45:527e536.


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