The \'zebra sign\'

Clinical History

A routine brain CT follow-up was performed in a 39-year-old male patient after a supra-tentorial craniotomy for surgical resection of a relapsing frontal glioblastoma.

Imaging Findings

Pre-surgical brain magnetic resonance imaging demonstrated an expansive intra-axial lesion in the right frontal hemisphere with extension to the contralateral side, hyperintense on FLAIR, determining compression of the frontal horns of the lateral ventricles and effacement of the regional sulci (Fig. 1).
Post-operative follow-up CT depicted signs of supra-tentorial craniotomy with formation of a hygroma in the right subgaleal space (Fig. 2). A pattern of curvilinear cortical and subarachnoid haemorrhage in the superior surface of the vermis and cerebellar hemispheres with moderated oedema and reduced mass effect was also seen (Fig. 3). Incipient enlargement of the temporal horns was appreciated as well, without evidence of transudation (Fig. 3).

Discussion

Remote cerebellar haemorrhage (RCH) is a rare complication of supratentorial surgery [1-4], with an incidence of less than 1% of all procedures [2, 3]. Aneurysm clipping [2-4], temporal lobe ressection [2-4] and tumour surgery [2] are the most common procedures complicated with RCH. Recently, it has also been reported in association with spinal surgery [2-4].
The exact physiopathology of this entity is not well known [1-4], but most authors believe it has a venous origin and is a consequence of peri-operative cerebrospinal fluid (CSF) loss [1-4].
Some of other minor risk factors implicated in the RCH are blood coagulation disturbance [1, 2, 4] preoperative usage of antiplatelet agents [1-3], arterial hypertension [1-4], drain insertion [2, 4], head rotation with direct venous compression [1-4] or severe arteriosclerosis [3].
Patients may remain asymptomatic [1-3] with incidental detection of the abnormality on routine postoperative brain imaging or may present with neurological signs or symptoms (decreased level of consciousness, delayed awakening from anesthesia, motor deficits or gait ataxia) [1, 2].
Brain CT studies reveal a spontaneous cerebellar hyperdensity, which may be unilateral (ipsilateral or contralateral to the craniotomy) or bilateral [1, 4]. The haemorrhagic component typically occurs in the cerebellar cortex and in the adjacent subarachnoid space over the folia of the superior surface of the cerebellum vermis and hemispheres [1-4]. Usually, there is no significant oedema or mass effect in association with the haematic component [1]. These features configure a characteristic streaked pattern to the cerebellum that has been called in the literature the "zebra sign” [3, 4].
RCH is considered a self-limited benign condition, although the associated mortality rate is not consensual in previous studies [1, 2, 4]. A conservative treatment with close CT follow-up is usually recommended [1], being surgical intervention indicated in case of acute hydrocephalus [1, 2, 4].
The typical cerebellar bleeding pattern in the appropriate context is usually an indicator of acute CSF over-drainage and the correct and prompt radiologic diagnosis helps in the prevention of the complications of this entity [2, 4].

Differential Diagnosis List

Final Diagnosis

Remote cerebellar haemorrhage

URL:	https://www.eurorad.org/case/9719
DOI:	10.1594/EURORAD/CASE.9719
ISSN:	1563-4086