Volume 6, Issue 3 , Pages 128-130, September 2011
Recurrent meningitis in a child secondary to a parasellar arachnoid cyst: A case report
Article Outline
Abstract
We report a case of recurrent pneumoccal meningitis in an 8-year-old boy with an underlying congenital cerebrospinal fluid (CSF) fistula of the sphenoid sinus associated with a large parasellar arachnoid cyst. High resolution computed tomography (CT) scan showed no obvious skull base defects. A magnetic resonance imaging (MRI) scan revealed a large parasellar arachnoid cyst. He underwent obliteration of the right sphenoid sinus via an endoscopic transsphenoidal approach. Conclusion: Recurrent bacterial meningitis requires needs to be fully investigated with CT scan and MRI of the brain and skull base. Repair of these skull base defects are mandatory.
Keywords: Recurrent pneumococcal meningitis, CSF leaks, Congenital skull base defects, Arachnoid cysts
1. Introduction
Acute bacterial meningitis is an infection of cranial and spinal leptomeninges which is potentially life threatening and has a mortality rate of 10–25% [1]. A single episode of meningitis is often due to blood borne bacteria. However, in recurrent meningitis possible predisposing factors have to be investigated [2]. Immunological investigations to identify complement or antibody deficiency are required [3]. Hyposplenism is also a risk factor and can be detected by means of ultrasonography as well as radionucleotide scan [3], [4]. Children with congenital defects such as encephalocoele, cranial and spinal dermoid sinuses, dermoid cyst, fibrous bone dysplasia and persistent craniopharyngeal ducts are all susceptible to recurrent meningitis and consequently these abnormalities need to be excluded [5]. Otolaryngologic causes are also important to consider.
Cerebrospinal fluid fistulae of the anterior skull base in the paediatric population are very rare [4]. Suspicion would be raised in a child with recurrent meningitis and clear watery rhinorrhea [4]. We report a case of a congenital arachnoid cyst replacing the cavernous sinus and causing an associated CSF fistula in the sphenoid sinus. This has not been previously reported in the literature.
2. Case report
We present an 8-year-old boy who first developed bacterial meningitis in 2005. Prior to this he had had a 5-month history of clear watery rhinorrhea suggestive of a CSF leak. The causative organism was Streptococcus pneumoniae. The meningitis was complicated by cranial nerve paresis of the right VI and VII nerves, which subsequently resolved. Several months later he again complained of watery rhinorrhea and a post-nasal drip. He had no history of allergic rhinitis, and no history of head trauma. On examination no obvious CSF leak was demonstrated. Examination of his ears revealed intact and mobile tympanic membranes. A high resolution CT scan of the paranasal sinuses showed features of ethmoidal and maxillary sinusitis on the right (Fig. 1). The sphenoid sinus was clear (Fig. 2) and the frontal sinuses were rudimentary. A CT scan of the brain was normal. An MRI scan revealed a large arachnoid cyst replacing the area of the right cavernous sinus with the carotid artery within the cyst (Fig. 3). The child underwent endoscopic endonasal surgery obliterating the right sphenoid sinus via a transsphenoidal approach. At surgery the sphenoid mucosa was removed, the right lateral wall of the sphenoid was covered with Duragen® and fat used to obliterate the sinus. The anterior wall was repaired using a further layer of Duragen® and mucosal flap from the septum. This was covered with a final layer of fibrin glue. His postoperative recovery was uneventful.
Fig. 1.
Coronal CT scan of paranasal sinuses.
Fig. 2.
Coronal CT of sphenoid sinus.
Fig. 3.
MRI scan showing suprasellar arachnoid cyst.
3. Discussion
Drummond et al. assessed the etiology of recurrent meningitis in the paediatric population and found that 33% of patients had otorhinolaryngologic causes [4]. Similarly, Kiem showed that 32% of patients with meningitis and over 90% of those with recurrent meningitis were due to otorhinolaryngologic aetiologies. This highlights the importance of adequate otolaryngologic investigations [1].
In recurrent meningitis other mechanisms of spread of bacterial pathogens to the CSF has to be considered. These may be congenital or acquired pathways from the skull base and potential routes may be broadly divided into temporal bone and anterior skull base pathways. The most common infective organism in these cases is Streptococcus pneumoniae (70–80%) [2], [6]. The risk of meningitis from a CSF fistula ranges from 10 to 20% [2], [6]. Otogenic causes of CSF fistulae may present as a persistent middle ear effusion, otorrhea, or clear rhinorhea with drainage through the eustachian tube [7]. Otogenic causes may be associated with hearing loss therefore audiometry in these cases is an important investigation [7].
Our patient had a parasellar arachnoid cyst and had symptoms highly suggestive of a CSF leak, although this was not confirmed (beta-2 transferrin was negative). It is particularly difficult to make a diagnosis of CSF rhinorrhea in children as they are often unable to give a detailed history or the CSF leaks may be intermittent. In contrast to adults, developmental defects are a more common cause of CSF fistulae than trauma or iatrogenic causes [4]. Contrast enhanced CT scans of the head should be performed with thin section (2
mm) tomography of the anterior skull base (axial and coronal) as well as of the temporal bone, to exclude otogenic causes of CSF rhinorrhea or recurrent meningitis [8].
The patient in our case report had a CT brain as well as a CT of the paranasal sinuses which showed no hydrocephalus and no skull base defect. An MRI scan revealed a large parasellar arachnoid cyst which had replaced the right cavernous sinus resulting in an associated fistula into the sphenoid sinus.
Arachnoid cysts are space-occupying lesions filled with CSF content and surrounded by a membrane resembling arachnoid mater [9]. They are regarded as a development abnormality of the arachnoid, originating from a splitting or duplication of this membrane [9]. However, precise aetiology and natural history remain controversial. Different hypotheses have been developed including agenesis of brain structures, arachnoiditis, active fluid secretion, and pulsatile pump [9]. There are a few reported cases where a slit-valve mechanism was observed and cited as the underlying aetiology [9], [10]. Arachnoid cysts tend to be more common in males than females and occur in 15% of the paediatric population compared to 10% of the adult population. In a recent case series of 20 patients with arachnoid cysts; seventy percent of the cysts were supratentorial, 5% infratentorial, and 25% spinal. Symptoms at presentation included headache (41%), weakness (23%), seizure (14%), hydrocephalus (9%), scoliosis (4%), cognitive decline (4%), and visual loss (4%) [11]. Most arachnoid cysts are incidental and in these cases the management is conservative, however patients who have symptomatic arachnoid cysts require surgical intervention [11]. Treatment may include cystoperitoneal shunt placement, craniotomy, or endoscopic fenestration, and stereotactic aspiration [11].
In this case the only presenting feature of the arachnoid cyst was recurrent pneumococcal meningitis (2 episodes) due to a CSF fistula of the sphenoid sinus which was successfully repaired endoscopically.
4. Conclusion
Recurrent pneumococcal meningitis may be due to an underlying anatomical skull base defect and a multidisciplinary team which includes otolaryngology, neurosurgery and paediatrics is necessary to successfully treat these patients. This case highlights the importance of detailed imaging in the form of CT scan of both temporal bone and anterior skull base as well as the value of an MRI study if the CT scan is normal. Due to the high morbidity and mortality from complications such as meningitis and pneuomocephalus, it is mandatory that all skull base fistulae be repaired.
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PII: S1871-4048(10)00039-0
doi:10.1016/j.pedex.2010.05.005
© 2010 Elsevier Ireland Ltd. All rights reserved.
Volume 6, Issue 3 , Pages 128-130, September 2011
