British Journal of Radiology (2005) 78, 1042-1046
© 2005 British Institute of Radiology
doi: 10.1259/bjr/97374075
Pseudotumoural hemicerebellitis: imaging findings in two cases
J L F de Mendonca, MD1,2,
H Barbosa, MD3,
S L Viana, MD2,
F M O Freitas, MD2,
M A C B Viana, MD3 and
A C L Ferreira, MD3
1 Radiology Unit, Hospital de Base do Distrito Federal, SMHS 101, Bloco A, Subsolo, CEP 70335-900, Brasilia, DF – Brazil, 2 Magnetic Resonance Department, Clinica Radiologica Vila Rica, SHLS 716, Centro Clinico Sul, W423/431, CEP 70390-907, Brasilia, DF – Brazil and 3 Pediatric Neurology Unit, Hospital de Base do Distrito Federal, SMHS 101, Bloco A, 7° andar, CEP 70335-900, Brasilia, DF – Brazil
Correspondence: Dr Sergio Lopes Viana
 |
Abstract
|
|---|
Pseudotumoural hemicerebellitis is exceedingly rare. It may closely resemble a tumour either clinically or on imaging, and a high index of suspicion is required to avoid unnecessary surgical procedures. MRI is the most useful diagnostic tool, and reveals a swollen cerebellar hemisphere, hyperintense in T2 weighted images. A pattern of predominantly pial contrast enhancement, absence of a well-defined mass and regression of the abnormalities in follow up examinations help to rule out malignancy. We report two cases of pseudotumoural cerebellitis (an 11-year-old girl and a 9-year-old boy) studied with CT and MRI.
|
Introduction
|
|---|
Although acute cerebellitis is one of the main causes of cerebellar dysfunction in children, unilateral presentations (hemicerebellitis) are rare. Pseudotumoural hemicerebellitis is even rarer and to our knowledge, was previously reported only once. We report two new cases of pseudotumoural hemicerebellitis, stressing the role of MRI as a non-invasive diagnostic tool for differentiation between inflammatory and tumoural aetiologies of unilateral cerebellar enlargement.
|
Case reports
|
|---|
Case 1
An 11-year-old girl was admitted to the hospital with a history of severe headache and vomiting of sudden onset 1 week previously, without fever. Her personal and family morbid history were unremarkable, and there were no recent viral illnesses or vaccination. She was not on any medication. No abnormalities were found at physical examination and there were no signs of meningeal irritation. Her blood chemistry was normal, and a lumbar puncture to study the cerebrospinal fluid (CSF) was not performed at that time. Intravenous analgesics and hydration were prescribed at the emergency room and remission of the symptoms was achieved within a few hours. Non-enhanced CT revealed an ill-defined hypodensity in the right cerebellar hemisphere; the fourth ventricle was hardly seen (Figure 1
). MRI was performed and showed a swollen right cerebellar hemisphere, diffusely hypointense on T1 weighted images and hyperintense on T2 weighted images and fluid attenuated inversion recovery (FLAIR) weighted images (Figure 2). There was mild mass effect over the fourth ventricle and the brainstem, without hydrocephalus. After intravenous gadolinium infusion, a distinct pial contrast enhancement was observed along the cerebellar folia in the affected hemisphere. A hypothesis of acute hemicerebellitis was proposed, and the patient was put on intravenous Acyclovir for 2 days and oral Acyclovir over the following 6 days. She remained asymptomatic, except for mild sporadic headaches. A follow up MRI performed 2 weeks later revealed regression of the swelling and of the mass effect of the right cerebellar hemisphere, without significant atrophy (Figure 3). Signal abnormalities were much less intense, as was the pial enhancement. Diffusion-weighted imaging (DWI) did not show restricted diffusion. She was discharged clinically well 16 days after admission.
View larger version (92K):
[in this window]
[in a new window]
|
Figure 1. Case 1. Non-enhanced CT at the level of the posterior fossa showing an ill-defined hypodensity affecting the right cerebellar hemisphere.
|
|
View larger version (85K):
[in this window]
[in a new window]
|
Figure 2. Case 1. MRI of the posterior fossa. (a) Axial T2 weighted image and (b) fluid attenuation inversion recovery (FLAIR) images and (c) coronal T1 weighted image image after infusion of gadolinium demonstrating a swollen right cerebellar hemisphere, hyperintense in T2 weighted image and FLAIR, distorting the fourth ventricle and exerting mild mass effect over the brainstem. A pial pattern of gadolinium enhancement can be seen.
|
|
View larger version (131K):
[in this window]
[in a new window]
|
Figure 3. Case 1. Follow up MRI (axial fluid attenuation inversion recovery (FLAIR) and T2 weighted fast spin echo (FSE) images (a, b) and (c, d) axial and coronal T1 weighted images after infusion of gadolinium) showing important regression of the swelling, of the contrast enhancement and of the mass effect. Residual hyperintensity in long repetition time images can be seen.
|
|
Case 2
A 9-year-old boy was referred to the emergency department for persistent headache and vomiting beginning 2 weeks previously, without fever. There was no relevant personal or family medical history, no use of medications and no history of recent viral illnesses or vaccination could be elicited. At physical examination, moderate neck stiffness was found, without evidence of cerebellar dysfunction or other findings. Blood chemistry was normal and a lumbar puncture was not performed. Non-enhanced CT showed hypodensity in the vermis and the right cerebellar hemisphere, with a slightly deformed fourth ventricle (Figure 4). At MRI, his right cerebellar hemisphere was swollen, exhibiting diffuse low-intensity signal in T1 weighted imaging and high signal intensity in T2 weighted imaging and FLAIR (Figure 5). Similar findings were seen in the superior vermis. The fourth ventricle was deformed, with compression of the right vallecula, without hydrocephalus. Marked pial enhancement was seen along the right cerebellar folia after intravenous gadolinium infusion. A hypothesis of hemicerebellitis was made and he was put on supportive measures, with quick improvement of the symptoms. A follow up MRI performed 26 days later showed marked improvement of imaging abnormalities, with only a mild hyperintensity remaining in T2 weighted imaging and FLAIR; no contrast enhancement was discernible (Figure 6). He was discharged asymptomatic 30 days after admission.
View larger version (89K):
[in this window]
[in a new window]
|
Figure 4. Case 2. Non-enhanced CT showing hypodensity of (a) the right cerebellar hemisphere and (b) of the superior vermis. Blunting of the right vallecula is evident.
|
|
View larger version (83K):
[in this window]
[in a new window]
|
Figure 5. Case 2. MRI with (a) axial T2 weighted imaging and (b) fluid attenuation inversion recovery (FLAIR) images and (c) coronal T1 weighted image after infusion of gadolinium revealing a swollen right cerebellar hemisphere, with high signal intensity in long repetition time sequences and hypointensity in T1 weighted imaging affecting both the cortex and the white matter. The superior vermis is also affected. There is mass effect over the fourth ventricle.
|
|
View larger version (81K):
[in this window]
[in a new window]
|
Figure 6. Case 2. Follow-up MRI ((a) axial T2 weighted image and (b) fluid attenuation inversion recovery (FLAIR) images and (c) coronal T1 weighted image after infusion of gadolinium) demonstrating almost complete remission of the abnormalities previously observed, with only mild hyperintensity remaining on long repetition time sequences.
|
|
|
Discussion
|
|---|
Acute cerebellitis is one of the main causes of cerebellar dysfunction in children, and may be infectious, post-infectious or post-vaccination. Its aetiology is usually viral and a large number of viruses have been implicated (varicella-zoster, measles, mumps, coxsackie, Epstein-Barr, rubeola, pertussis and diphtheria, among others), although in most cases a definite aetiology remains undetermined [1, 2]. It presents a highly variable clinical course, and while some patients may be almost asymptomatic, others may follow a fulminant downhill course [1, 3]. Typically, patients present with truncal ataxia, wide-based gait, nystagmus, dysartria, dysmetria, tremor and altered mental state, mostly in early childhood. Headache, mild or high-grade fever, vomiting, seizures and meningeal signs may also be present [4–6]. The cerebrospinal fluid examination may be normal or reveal pleocytosis, and the diagnosis is based mainly on clinical criteria [6, 7]. The disease is usually benign and self-limiting, its prognosis is habitually good, and recovery with a few or no sequelae is the usual outcome. Surgical intervention for posterior fossa decompression may rarely be necessary [2]. Steroids and antiviral agents may be used, chiefly in severely symptomatic individuals, but most patients would recover without any specific treatment.
Cerebellitis is typically a bilateral and symmetric disease, and neuroimaging is especially useful in this condition. Whenever it is available, MRI is the study of choice. In a recent article, De Bruecker et al [2] have found only 29 reports of MRI findings in cerebellitis in the absence of cerebral or brainstem lesions (including their own four cases). Although in some patients the imaging studies may be entirely normal, the most common imaging findings are bilateral hemispheric abnormalities [2, 5]. Signal abnormalities in the cerebellar grey and white matters are seen as low-signal in T1 weighted imaging and, mainly, hyperintense signal in T2 weighted imaging; findings may be confined to the cortex, which may appear swollen (the most characteristic pattern) [1, 4, 7]. When the white matter is affected, lesions may be patchy or diffuse. Contrast enhancement is predominantly pial, along the cerebellar folia, and may be variably seen in acute and subacute phases. When mass effect exists, obstructive hydrocephalus may result from compression over the fourth ventricle [8]. When the process resolves, the cerebellum may return to its normal appearance or there may be signs of cerebellar atrophy; in some cases, residual T2-hyperintensity may remain for many months, and MRI is not useful to predict the prognosis [2]. Our first case seems to be one of the first to report findings of DWI in this condition, which showed no signs of restricted diffusion. Jaggi et al [9] have recently reported one case of bacterial cerebellitis studied by DWI and proton MRI spectroscopy, which showed restricted diffusion and signs of anaerobic infection, respectively. Our data suggest that this is not true for non-bacterial cerebellitis; however, we must emphasise that DWI was performed in the subacute phase in our patient. Discordant results were reported with single-photon emission computed tomography (SPECT, cerebellar hypoperfusion in two studies [5, 10] and increased perfusion in one [11]), and its role in acute cerebellitis is not yet established.
CT may be entirely normal or show low-density areas in the cerebellar hemispheres; it may be also useful to detect acute hydrocephalus, cerebellar oedema or brainstem compression [1, 2, 4]. However, due to its inherent limitations in the study of the posterior fossa and to its inferior contrast resolution when compared with MRI, it is not the preferred method in these patients.
The differential diagnosis of classical bilateral cerebellitis includes acute intoxication, posterior fossa tumours and demyelinating processes [1]. A careful history might be taken to rule out recent exposure to drugs and alcohol. Posterior fossa tumours are usually unilateral and obvious at imaging studies. Demyelination, by its turn, takes place predominantly in the white matter, which is not the case with cerebellitis. Sometimes, when a history of recent viral illness or vaccination is present, acute cerebellitis may be indistinguishable clinically and from the imaging standpoint from acute disseminated encephalomyelitis (ADEM) confined to the cerebellum [2, 5]. In an appropriate setting, lead poisoning may present in a similar manner at imaging as well. Another possible differential diagnosis is Lhermitte-Duclos disease (LDD), but enhancement after gadolinium infusion and recovery of symptoms are against LDD.
Unilateral involvement in cerebellitis (hemicerebellitis) is very rare, and was previously reported in seven patients [2, 6, 7, 12–15], with unilateral imaging findings similar to classic bi-hemispheric cerebellitis in most cases; reasons for unilateral involvement are as yet unknown. Unilateral pseudotumoural presentation is even rarer, and to our knowledge, was reported only once, by Jabbour et al [12]. This previous report and our two cases have similar features, namely a swollen cerebellar hemisphere (with vermian involvement in one of our patients), diffusely hyperintense in T2 weighted images, with mass effect over the fourth ventricle and showing pial enhancement along the cerebellar folia. Due to their atypical appearance, acute cerebellitis may be unwarily not considered in the differential diagnosis in cases like these. Patients may be severely symptomatic due to increased intracranial pressure or acute hydrocephalus (caused by compression of the fourth ventricle), urging surgical decompression, and a tumoural condition may be erroneously diagnosed. Imaging clues to a correct diagnosis include the absence of a well-defined nodular lesion and the predominantly pial enhancement, along the cerebellar folia. Whenever unilateral cerebellitis is suspected, surgical procedures should be deferred for some weeks, if possible, when a follow up MRI should be performed. Clinical improvement and partial or full regression of the imaging findings will exclude a neoplastic process. However, surgical decompression may be necessary in some cases refractory to treatment, as was performed in the case of Jabbour et al [12]. Our cases were atypical cerebellitis as long as there were no signs of cerebellar dysfunction (as well as the previous one), no history of recent viral illnesses or vaccination could be elicited and the patients were only mildly symptomatic in spite of the mass effect observed; the pseudotumoural appearance of the cerebellar hemisphere was highly surprising. The stable clinical picture allowed for a watchful waiting in both cases.
In conclusion, pseudotumoural hemicerebellitis seems to be exceedingly rare. Clinical presentation is variable and may not suggest cerebellar involvement. MRI is crucial in its evaluation, avoiding unnecessary and risky surgical interventions. Although a swollen cerebellar hemisphere, diffusely hyperintense in T2 weighted imaging, exerting mass effect over the adjacent structures may closely resemble an infiltrative tumour, a correct diagnosis can be suggested by demonstrating (1) a mostly pial enhancement instead of nodular, (2) absence of a well-delimited mass and (3) partial or full regression of these findings in follow up examinations.
|
Acknowledgments
|
|---|
The authors would like to express their gratitude to Philippe Demaerel, MD (Leuven, Belgium), Angels García-Cazorla, MD (Barcelona, Spain), Maria Augusta Montenegro, MD (Campinas, Brazil) and Fabio Marinho do Rego Barros, MD (Recife, Brazil) for their help during the preparation of this manuscript.
Received for publication April 8, 2005.
Accepted for publication April 22, 2005.
|
References
|
|---|
- Montenegro MA, Santos SL, Li LM, Cendes F. Neuroimaging of acute cerebellitis. J Neuroimaging 2002;12:72–4.[Medline]
- De Bruecker Y, Claus F, Demaerel P, Ballaux F, Sciot R, Lagae L, et al. MRI findings in acute cerebellitis. Eur Radiol 2004;14:1478–83.[Medline]
- Levy EI, Harris AE, Omalu BI, Hamilton RL, Branstetter BF 4th, Pollack IF. Sudden death from fulminant acute cerebellitis. Pediatr Neurosurg 2001;35:24–8.[CrossRef][Medline]
- Ciardi M, Giacchetti G, Fedele CG, Tenorio A, Brandi A, Libertone R, et al. Acute cerebellitis caused by herpes simplex virus type 1. Clin Infect Dis 2003;36:e50–4.[CrossRef][Medline]
- Nagamitsu S, Matsuishi T, Ishibashi M, Yamashita Y, Nishimi T, Ichikawa K, et al. Decreased cerebellar blood flow in postinfectious acute cerebellar ataxia. J Neurol Neurosurg Psychiatry 1999;67:109–12.[Abstract/Free Full Text]
- Garcia-Cazorla A, Olivan JA, Pancho C, Sans A, Boix C, Campistol J. Infectious acute hemicerebellitis. J Child Neurol 2004;19:390–2.[Medline]
- Usano A, Torres J, Jadraque R, Avilla JM, Collado E. Acute unilateral cerebellar ataxia: a case report. Rev Neurol 2000;30:698–9.[Medline]
- Dogulu F, Onk A, Kaymaz M, Kardes O, Baykaner MK. Acute cerebellitis with hydrocephalus. Neurology 2003;60:1717.[Free Full Text]
- Jaggi RS, Husain M, Chawla S, Gupta A, Gupta RK. Diagnosis of bacterial cerebellitis: diffusion imaging and proton magnetic resonance spectroscopy. Pediatr Neurol 2005;32:72–4.[CrossRef][Medline]
- San Pedro EC, Mountz JM, Liu HG, Deutsch G. Postinfectious cerebellitis: clinical significance of Tc-99m HMPAO brain SPECT compared with MRI. Clin Nucl Med 1998;23:212–6.[CrossRef][Medline]
- Gruis KL, Moretti P, Gebarski SS, Mikol DD. Cerebellitis in an adult with abnormal magnetic resonance imaging findings prior to the onset of ataxia. Arch Neurol 2003;60:877–80.[Abstract/Free Full Text]
- Jabbour P, Samaha E, Abi Lahoud G, Koussa S, Abadjian G, Nohra G, et al. Hemicerebellitis mimicking a tumour on MRI. Childs Nerv Syst 2003;19:122–5.[Medline]
- Sekhara T, Christophe C, Christiaens F, Dan B. Postinfectious hemicerebellitis. Rev Neurol (Paris) 2001;157:84–6.[Medline]
- Iester A, Alpigiani MG, Franzone G, Cohen A, Puleo MG, Tortori-Donati P. Magnetic resonance imaging in right hemisphere cerebellitis associated with homolateral hemiparesis. Childs Nerv Syst 1995;11:118–20.[CrossRef][Medline]
- Omeis IA, Khoshyomn S, Braff SP, Maugans TA. Idiopathic lymphocytic cerebellitis. Pediatr Neurosurg 2002;36:52–3.[CrossRef][Medline]
Top
Abstract
Introduction
